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1
Tavakolikhaledi, Mohammadreza. "Vanadium : leaching and solvent extraction." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46814.
Full textAbstract:
The fundamental understanding of vanadium hydrometallurgy was developed in three phases: vanadium (V) leaching, vanadium (III) oxidative leaching, and solvent extraction of vanadium (V&IV).
In the first section, V₂O₅ leaching was studied in three steps. First, vanadium leaching and solubility of VO₂⁺ at different pH’s and temperatures were investigated in sulfuric acid. Secondly, the kinetics of vanadium leaching in pH 5 and pH 8 solutions, and the reductive leaching of vanadium pentoxide using sodium sulfite were studied. It was shown that the kinetics of acid leaching is rapid but suffers from low solubility of VO₂⁺ in solution. Thirdly, the shrinking sphere model was employed to analyze the kinetics of reductive leaching.
In the second step, V₂O₃ oxidative leaching was studied from 30°C to 90°C in sulfuric acid. This study has also been done in three different sections. First, the kinetics of oxidative leaching using oxygen was investigated. It was shown that this oxidative leaching is chemical reaction rate controlled with an activation energy of 69 kJ/mol. In the next step, it was shown that the presence of ferric enhanced kinetics significantly. Finally, oxidative leaching using a constant ferric-ferrous ratio from 1 to 300 was studied. The addition of KMnO₄ solution to the leach reactor was found to be a suitable oxidant for controlling solution potential. The oxidation rate using the constant ferric-ferrous ratio was very sensitive to temperature, with a large activation energy (38 kJ/mol) and the rate was proportional to the Fe(III)/Fe(II) concentration to the power of 0.47.
In the third part, purification of synthetic vanadium-containing solutions using the solvent extraction technique was investigated. Various solvent extractants have been tested for vanadium recovery from acid leachates. One of the biggest problems for purification of the vanadium solution is iron separation. Therefore, this research assesses selectivity of vanadium over iron. The extraction of vanadium (V&IV), iron (III&II) with phosphinic acid (CYANEX 272), phosphonic acid (IONQUEST 801), phosphoric acid (D2EHPA) and phosphine oxide (CYANEX 923) extractants is reported. In addition, the extraction reactions for vanadium (V) and (IV) extraction using CYANEX 923 and D2EHPA were also studied.
2
Muslim, Abrar. "Thiosulfate leaching process for gold extraction." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/896.
Full textAbstract:
Increasing environmental concerns over the use of cyanide for gold recovery has intensified the need to deeply understand gold thiosulfate leaching system. Therefore, experimental and modelling work for the kinetics and equilibrium adsorption of thiosulfate, polythionates, gold and copper onto strong based anion exchange resin have been conducted in this study, and the results are concisely discussed in the thesis. Experimental procedures, reaction mechanisms and novel dynamic models for the adsorption phenomena were also proposed.
3
Buyukakinci, Ergin. "Extraction Of Nickel From Lateritic Ores." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609291/index.pdf.
Full textAbstract:
The aim of this study was to extract nickel and cobalt from the lateritic nickel ores of Gördes region by hydrometallurgical methods under the optimum conditions. Limonitic and nontronitic types of Gö
rdes lateritic nickel ores were used during experiments. Agitative and column leaching experiments at atmospheric pressure were conducted with various parameters
these were duration, temperature and initial sulfuric acid concentration of leach solution. It was shown that in agitative leaching, under the optimum conditions that were determined as 24 hours of leaching at 95°
C with initial sulfuric acid concentration of 192.1 g/L for nontronite and 240.1 g/L for limonite, nickel and cobalt extractions were 96.0% and 63.4% for nontronite
93.1% and 75.0% for limonite, respectively. Overall acid consumptions of ores were calculated as 669 kg H2SO4/ton dry ore for nontronitic type nickel ore and 714 kg H2SO4/ton dry ore for limonitic type nickel ore. Column leaching experiments also showed that nickel and cobalt could be extracted from both ore types by heap leaching. Nontronite type of laterite was found to be more suitable for column leaching by sulfuric acid. In column leaching, the calculated nickel and cobalt extractions were 83.9% and 55.2% for nontronite after 122 days of leaching with 100 g/L sulfuric acid concentration. Acid consumption of nontronite was found to be 462 kg H2SO4/ton dry ore.
4
Goveli, Ahmet. "Nickel Extraction From Gordes Laterites By Hydrochloric Acid Leaching." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607738/index.pdf.
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Leaching is the most widely used process for extraction of nickel metal from lateritic ores.
In this study, nickel extraction from Manisa-Gördes region laterites by hydrochloric acid leaching is aimed. The mineralogical analysis of sample showed that hematite, goethite, dolomite, quartz and smectite are the main minerals in the ore. Attrition scrubbing, cycloning and magnetic separation with permroll were used as preconcentration processes but results were unsatisfactory. HCl leaching experiments were conducted both at room temperature and at elevated temperatures. The effects of various parameters such as leaching duration, particle size, concentration of HCl, pulp density, Cl- concentration and temperature on nickel recovery were examined. The results showed that under the optimised leaching conditions (particle size: 100 % -1 mm, HCl concentration: 3 N, leaching duration: 3 hours, leaching temperature: 100 oC, pulp density: 1/30 solid to liquid ratio by volume) it was possible to extract 87.26 % of nickel in the ore.
5
Fowler, Sandra Dee. "COPPER SOLVENT EXTRACTION FROM CHLORIDE-SULFATE MEDIA." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275369.
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Askari, Hallo Mustafa. "Studies of leaching, recovery and recycling of heavy metals." Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/5087.
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The leachability of cadmium, cobalt, copper, lead, nickel and zinc metals and their oxides, sulfides and carbonates by water, 0.5 mol dm-3 CH3COOH, 0.1 mol dm -3 HCl/NaCI (1: 1 mixture) and 2 mol dm -3 HNO3 is reported. The concentrations of the leached heavy metals are compared with the trigger levels set by World Health Organisation (WHO). Three leaching solutions (nitric, sulfuric and hydrochloric acids) were used to extract copper, zinc, cobalt, nickel, iron and lead from spent catalysts prior to the application of separation technologies. Leaching experiments were conducted using both traditional methods and a microwave-assisted extraction technique. Data are provided on the effects of leaching temperature, leaching time, solid to liquid ratio and acid concentration on the extraction of different metals. The use of 2 mol dm-3 sulfuric acid at 50°C for 60 minutes and at a solid/liquid (S/L) ratio of 1: 25 achieved more than 90% extraction for all the metals studied. A comparison of the results from traditional and microwave extraction techniques demonstrates that microwave heating reduced the time required to obtain maximum metal extraction. The kinetics for the traditional extraction procedure showed that diffusion was the ratecontrolling process, but it was not possible to conclusively establish the rate controlling process for the microwave leaching. The feasibility of using an electrodialysis process to separate metal ions, such as copper from zinc, was examined. A laboratory-scale three compartments membrane system was designed, constructed, used and optimised for the separation process. The separation of copper from zinc in the electrodialysis process exploited the greater stability of the Cu-EDTA complex compared with the Zn-EDTA complex. It was observed that Zn 2+ ions migrated through the cation-exchange membrane from central compartment to catholyte and, simultaneously, the negative Cu-EDTA complex transferred to the analyte compartment crossing the anion exchange membrane. The technique was successfully used to separate mixtures of Cu: Cd and Zn: Ni. The technique could not, however, be used for the separation of Zn from Cd. An adsorption process was used to prepare copper, iron, nickel and zinc oxides catalysts on y-A1203 as support. The materials prepared were used in a fixed bed reactor to assess the catalytic oxidation of volatile organic compounds (methane and ethane) in air. Cu/y- A1203 was found to be the most promising catalyst for the complete oxidation of methane and ethane at temperatures of 575°C and 525°C, respectively. Increasing the calcination temperature in the drying and pre-treatment of the catalysts resulted in a decrease in the catalytic activity.
7
Dakubo, Francis. "Sustainable Mining - Solving the Problem of Chalcopyrite Treatment/Processing - Leaching, Solvent Extraction & Flotation." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/604862.
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Chalcopyrite ore forms the significant fraction of copper deposits in the earth crust. However, it is also the most difficult to treat using conventional ferric leaching methods. Smelting and electro-refining are currently the methods used in treating chalcopyrite concentrate obtained from froth flotation. Due to the ever increasing environmental requirements on smelters by the Environmental Protection Agency, new smelters are scarce in the United States. The scarcity of smelters has led to the urgent need to find a novel leaching method for the abundant chalcopyrite deposits in the USA and the rest of the world. This chapter(one) of the dissertation, therefore, investigated the leaching of chalcopyrite ore at pH 2 using a newly discovered oxidant (peroxodisulfate). Our results show that chalcopyrite leaching using peroxodisulfate follows a surface reaction shrinking core model. The activation energy of chalcopyrite leaching using peroxodisulfate ion was calculated as 41.1 kJ mol⁻¹. We also report that the leaching of chalcopyrite ore is affected by particle size and that stirring hurts leaching of chalcopyrite. Additionally, we found that peroxodisulfate can produce from sulfuric ions electrochemically. Hydrogen peroxide, permanganate, peroxodisulfate and ferric ions are all strong oxidants that have been researched in production pregnant leach solution (PLS) from chalcopyrite ore leaching. Because, solvent extraction is the next step in the recovery of copper from pregnant leach solutions (PLS). The questions, therefore, arises as to the fate of the organic extractant used in solvent extraction coming in contact with strong oxidant residual in the PLS. In chapter two of the dissertation, we studied the effect of strong oxidant residual in PLS on the degradation of organic extractants during solvent extraction of copper. Exposed organic extractants were analyzed using interfacial tension(IFT), Fourier Transform Infrared (FTIR) spectroscopy and CG LS. The results obtained from IFT and FTIR analysis, show no effect on the organic extractants exposed to sunlight and PLS containing the residual strong oxidant. Finally in chapter 3, the dissertation exams alternative water source for the flotation of chalcopyrite. Mineral flotation is a water-intensive process in mining. In order to sustain mining operations such flotation, which rely heavily on water, chapter 3 of the dissertation looks at using alternative water sources (in this case reclaimed wastewater) in the flotation of chalcopyrite ores; this effort is to limit the mining industries dependence on fresh ground water particularly in the Southwest of United States where water is a scarce commodity. The research studied the effect of reclaimed waste water on chalcopyrite flotation via contact angle and surface energy measurements. Furthermore, atomic force microscopy (AFM) and flotation tests were used to supplement the findings from contact angle and surface studies. We conclude here that the contact angle of a pure chalcopyrite surface was determined to be 75.6 degrees. We also found that pure chalcopyrite mineral surface is slightly polar with surface energies γCuFeS2^(LW) = 41.4 mJ/m² (apolar), γCuFeS2^(AB) = 2.9 mJ/m² (polar). The high value of the surface energy indicates pure chalcopyrite surface is slightly hydrophobic.
8
Sedres, Grant. "Recovery of SiO₂ and Al₂O₃ from coal fly ash." University of the Western Cape, 2016. http://hdl.handle.net/11394/5651.
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>Magister Scientiae - MScMost of the world's energy production is still mainly achieved by the combustion of coal in power stations. Coal fly ash is the inevitable waste product that accumulates to metric ton volumes each year. These vast volumes pose a problem in the disposal of the coal fly ash which conventionally is loaded onto ash dumps located near the coal power stations. Alternatives need to be investigated for the use of the coal fly ash in applications that would make the coal fly ash useful and thereby help to mitigate the environmental strain imposed by conventional ash dump disposal. This study focussed on investigating the extraction of Si and Al from CFA. The investigation into the removal of the magnetic iron oxide content and calcium content from coal fly ash was also carried out to enhance the extraction of the Si and Al from CFA e.g. the removal of calcium was attempted to promote the leaching of aluminium from the ash. The rationale for this process was that by removing and recovering these major constituent elements from the ash, it would be easier to concentrate and isolate the trace elements especially the rare earth elements that are present in the CFA. Coal fly ash sourced from Matla coal power station was characterised using x-ray diffraction to determine the mineral phases present in the raw coal fly ash and elemental composition determined by x-ray fluorescence and laser ablation ICP-MS. The main mineral phases in coal fly ash were determined to be quartz, mullite, magnetite and lime (CaO). Magnetic extraction was initially carried out on the coal fly ash to remove the iron rich magnetic material. Extraction tests were then performed on the coal fly ash using alkaline and acidic media namely; NaOH, HCl and H₂SO₄. The extraction tests were assessed and a sequential extraction experimental procedure developed to achieve the highest extraction yield for Si, Al, Fe, Ca, and Mg from the coal fly ash. Lastly the rare earth element content in coal fly ash was tracked from the beginning till the end of the sequential extraction procedure to ascertain whether the rare earth elements partitioned to the leachates or the solid residues. The total element recoveries for Al, Si, Ca Fe, Mg were 53.36 %, 39.96 %, 93.8 %, 25.6 % and 67.3 % respectively using the sequential extraction procedure developed in this study. The rare earth elements contents were not affected by the sequential extraction procedure and on the whole remained in the solid residues at the completion of the sequential extraction, resulting in a residue with enriched levels of recoverable or extractable REE content after the removal of the major oxides from the CFA. The lowest enrichment being approximately 5 % for Thulium and the highest being approximately 76 % for Erbium.
9
Heckley, Philip Scott. "Extraction and separation of cobalt from acidic nickel laterite leach solutions using electrostatic pseudo liquid membrane (ESPLIM)." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/2188.
Full textAbstract:
Approximately 70% of the western world's known nickel reserves are contained in laterite ores, but only 30% of the world's nickel production comes from these ores. This is due to the lack of economically viable technology to extract the nickel from these ores. However, recent advances in pressure acid leaching technology have resulted in new commercial attempts to extract nickel and its valuable by-product, cobalt, from laterite ores. The commissioning of three nickel laterite projects in Western Australia in the late 1990s represents the first of these new generation nickel operations, with several other projects; in Australia and overseas, in various stages of development. Unfortunately, several technical issues have hindered full production in these new refineries. Some of these problems are directly attributable to the mixer-settler contactors used in the solvent extraction process. This has highlighted a need to develop alternative contactors for industrial use. Electrostatic Pseudo Liquid Membrane (ESPLIM) is an alternative, novel technique to conduct the solvent extraction process. It combines the basic principles of solvent extraction, liquid membrane and electrostatic dispersion into a simple, compact reactor that utilises many advantages of each technique. The aim of this study w as to develop a method of extracting and separating cobalt from an acidic nickel laterite leach solution using ESPLIM. Bench scale tests using synthetic and actual leach solutions have shown that: the design and construction materials of the baffle plate and electrodes have a significant effect on the performance of the reactor; an AC power supply provided better droplet dispersion than a DC power supply; an increase in the applied electric field strength above a critical value resulted in a decrease in the aqueous droplet size and an increase in residence tune.These effects increased the extraction efficiency and the concentration of the loaded strip solution. However, further increases in applied electric field strength decreased efficiency due to excessive levels of swelling and leakage; the known extraction isotherms for cobalt and nickel apply in the ESPLIM technique; salts of soluble organic acids influence extraction efficiency by changing the aqueous pH and interfacial tension; the use of ammonia was found to be effective as a replacement for salts of soluble organic acids; the ESPLIM reactor can cope with large changes in the flow rates of both feed and strip solutions. However, an increase in the feed flow rate should be accompanied by a relative increase in the ship flow rate to maintain high extraction efficiencies; the baffle design has a significant impact on the levels of swelling and leakage; provided the electrostatic field strength is maintained and flow rates are increased proportionately to the size of the reactor, no significant scale-up issues were observed, indicating that the data generated in bench scale studies could be applied to plant scale contactors. The optimum conditions, devised as a result of this investigation, to extract cobalt from an acidic nickel laterite leach solution using the ESPLIM technique are as follows: an applied electric field strength of 5.5 kV/cm. a raffinate pH of 5.5, a solvent containing 10% Cyanex 272 with 5% TBP in Solvent HF diluent, a feed to strip flow ratio of approximately 5 and a 1 M H[subscript]2S0[subscript]4 strip solution. At these conditions, almost complete cobalt extraction is achieved after only two extraction stages. A comparable extraction using conventional mixer-settlers could only be achieved after five stages.
10
Saba, Mojtaba. "The Extraction Behaviour of Zinc, Lead and Silver from Ores and Concentrates by Glycine Leaching Processes." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/81907.
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This research covers the fundamental aspects of the direct leaching of sphalerite by considering the dissolution of silver, lead, and copper contents and their effects on the process. The effects of independence variables such as sodium hydroxide, potassium permanganate, hydrogen peroxide, lead nitrate, sodium chloride, dissolved oxygen, temperature, glycine concentration, dissolution time, and particle size on the process were investigated. All the outputs have been modelled and optimised through the analysis of variance.
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劉偉藻 and Wai-cho Ivan Lau. "Removal of refractory chemicals in landfill leachate by UASB and advanced oxidation processes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31240471.
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Chen, Ting. "Physicochemical properties of nickel and cobalt sulphate solutions of hydrometallurgical relevance." Thesis, Chen, Ting (2003) Physicochemical properties of nickel and cobalt sulphate solutions of hydrometallurgical relevance. PhD thesis, Murdoch University, 2003. https://researchrepository.murdoch.edu.au/id/eprint/653/.
Full textAbstract:
Producing nickel and cobalt metal by high pressure acid leaching (HPAL) of nickel laterites is becoming one of Australia's largest mineral processing industries. However, the background chemical information for this process, including the fundamental physicochemical properties of acidic metal sulphate leachate solutions, is not well known. In order to improve the efficiency of current and future HPAL plants, high quality physicochemical and thermodynamic data will be necessary. This thesis reports measurements on the densities and heat capacities of nickel and cobalt sulphate solutions and their mixtures along with detailed studies of the nature of the species present and the thermodynamics of their interconversions.
Densities and heat capacities of nickel and cobalt sulphate and perchlorate solutions and their ternary mixtures were measured using a vibrating tube densimeter and a flow microcalorimeter respectively. These data were used to calculate the apparent molal volumes and heat capacities of these solutions. Standard partial molal quantities were then obtained by appropriate extrapolation procedures, along with the volume and heat capacity changes of ion pair formation. A comparison has been made between experimental densities and heat capacities with those predicted by Young's rule. Good agreement was obtained except when the degree of complexation varied significantly in the mixtures. The various ion pair species in nickel and cobalt sulphate solutions, along with those of magnesium sulphate (which is a major impurity in HPAL leachates), were reinvestigated by dielectric relaxation spectroscopy.
Doubly solvent separated ion pairs, solvent shared ion pairs and contact ion pairs were shown to exist simultaneously in solution and their concentrations were determined from dilute to near-saturated concentrations. Evidence for the possible existence of a triple ion, M2SO4 2+, was also obtained in highly concentrated solutions. The equilibrium constants of the stepwise reactions and the effective hydration numbers of ions and ion pairs were also calculated.
The heats of complexation of nickel(II) and cobalt(II) sulphate were determined at different ionic strengths in sodium perchlorate media by titration calorimetry. These data were fitted to a specific ion interaction model to obtain the standard state values. The corresponding entropies of complexation were calculated and were found to be the major contributor to the stability of the complexes.
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Chen, Ting. "Physicochemical Properties of Nickel and Cobalt Sulphate Solutions of Hydrometallurgical Relevance." Murdoch University, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040706.144034.
Full textAbstract:
Producing nickel and cobalt metal by high pressure acid leaching (HPAL) of nickel laterites is becoming one of Australia's largest mineral processing industries. However, the background chemical information for this process, including the fundamental physicochemical properties of acidic metal sulphate leachate solutions, is not well known. In order to improve the efficiency of current and future HPAL plants, high quality physicochemical and thermodynamic data will be necessary. This thesis reports measurements on the densities and heat capacities of nickel and cobalt sulphate solutions and their mixtures along with detailed studies of the nature of the species present and the thermodynamics of their interconversions.
Densities and heat capacities of nickel and cobalt sulphate and perchlorate solutions and their ternary mixtures were measured using a vibrating tube densimeter and a flow microcalorimeter respectively. These data were used to calculate the apparent molal volumes and heat capacities of these solutions. Standard partial molal quantities were then obtained by appropriate extrapolation procedures, along with the volume and heat capacity changes of ion pair formation. A comparison has been made between experimental densities and heat capacities with those predicted by Young's rule. Good agreement was obtained except when the degree of complexation varied significantly in the mixturesThe various ion pair species in nickel and cobalt sulphate solutions, along with those of magnesium sulphate (which is a major impurity in HPAL leachates), were reinvestigated by dielectric relaxation spectroscopy.
Doubly solvent separated ion pairs, solvent shared ion pairs and contact ion pairs were shown to exist simultaneously in solution and their concentrations were determined from dilute to near-saturated concentrations. Evidence for the possible existence of a triple ion,
M2SO4 2+, was also obtained in highly concentrated solutions. The equilibrium constants of the stepwise reactions and the effective hydration numbers of ions and ion pairs were also calculated.
The heats of complexation of nickel(II) and cobalt(II) sulphate were determined at different ionic strengths in sodium perchlorate media by titration calorimetry. These data were fitted to a specific ion interaction model to obtain the standard state values. The corresponding entropies of complexation were calculated and were found to be the major contributor to the stability of the complexes.
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Ince, Alev Emine. "Usage Of Microwave And Ultrasound In The Extraction Of Essential Oils And Phenolic Compounds." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612904/index.pdf.
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The objective of this study is to extract phenolic compounds from nettle and melissa by using microwave and ultrasound and to compare these methods with conventional extraction and maceration, respectively. Extraction of melissa essential oil was also studied.
In extraction of phenolics, effects of extraction time (5-20 min for microwave5-30 min for ultrasound) and solid to solvent ratio (1:10, 1:20, 1:30 g/ml) on total phenolic content (TPC) were investigated for microwave and ultrasound extractions. Different powers were also studied for ultrasound extraction. In addition, effect of solvent type (water, ethanol, ethanol-water mixture at 50:50 v/v) was analyzed and water was found as better solvent. Optimum conditions for microwave extraction of phenolics were determined as 10 min and 1:30 solid to solvent ratio for nettle, and as 5 min and 1:30 solid to solvent ratio for melissa. TPC at these conditions for nettle and melissa extracts were 24.6 and 145.8 mg GAE/g dry material, respectively. Optimum conditions for ultrasound extraction was 30 min, 1:30 solid to solvent ratio, and 80% power for nettle and 20 min, 1:30 solid to solvent ratio, and 50% power for melissa. TPC at these conditions for nettle and melissa were 23.9 and 105.5 mg GAE/g dry material, respectively. Major phenolic acids were determined as naringenin in nettle and rosmarinic acid in melissa. Major aromatic compounds in melissa essential oil were found as limonene, citral, and caryophyllene oxide. Yields of essential oil obtained by microwave and hydrodistillation were 4.1 and 1.8 mg oil/g dry sample, respectively.
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Ozdemir, Veysel. "Hydrometallurgical Extraction Of Nickel And Cobalt From Caldag Lateritic Ore." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607777/index.pdf.
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In this study, an attempt has been made to hydrometallurgical extraction of cobalt and nickel by atmospheric pressure sulphuric acid leaching and a pug-roast-leach process using two stage roasting for lateritic ore. The ore used in the study was obtained from Çaldag Lateritic Ore, Manisa, Turkey. The metal contents of the ore are 2.1 % Ni, 0.12 % Co, 32.45 % Fe, 1.01 % Mn, 2.58 % Cr, 0.78 % Mg and 1.01 % Al. The reserve of lateritic ore deposit is approximately 40 million tonnes. In the study, first sulphuric acid leaching was applied at atmospheric pressure for leaching the Ç
aldag lateritic ore. The effect of various parameters, such as leaching time, leaching temperature, particle size, pulp density and acid strength on Ni and Co extractions were determined. By leaching at 80oC for 40 wt % H2SO4 addition of ore, 1/3 pulp density, Ni and Co extractions were found 44.49 % and 53.03 % respectively, yielded a pregnant solution containing 3.11 g/L Ni and 0.12 g/L Co. But the result of atmospheric pressure sulphuric acid leaching was considered insufficient from the recovery point of view. In the pug-roast-leach process, which is consisted of a two stage roasting followed by water leaching, decomposition temperature differences of sulphates of cobalt, nickel and iron are exploited. In this process, amount of acid, sulphatization and decomposition temperature, sulphatization and decomposition time, leaching temperature and time, solid/liquid ratio, and the effect of water addition during pugging were optimized. Under the optimized conditions (sulphuric acid: 25 wt % of ore
moisture: 20 wt % of ore
sulphatization temperature: 450oC
sulphatization time: 30 minutes
decomposition temperature: 700oC
decomposition time: 60 minutes
leaching temperature: 70oC
leaching time: 30 minutes and solid-liquid ratio: 1/4 by weight), Co and Ni extractions were found 91.4 and 84.4 percent, respectively. A pregnant solution containing 3.084 g/L Ni and 0.185 g/L Co was obtained. These results were considered sufficient for the leaching of lateritic nickel ores.
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Heckley, Philip Scott. "Extraction and separation of cobalt from acidic nickel laterite leach solutions using electrostatic pseudo liquid membrane (ESPLIM)." Curtin University of Technology, Western Australian School of Mines, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14124.
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Approximately 70% of the western world's known nickel reserves are contained in laterite ores, but only 30% of the world's nickel production comes from these ores. This is due to the lack of economically viable technology to extract the nickel from these ores. However, recent advances in pressure acid leaching technology have resulted in new commercial attempts to extract nickel and its valuable by-product, cobalt, from laterite ores. The commissioning of three nickel laterite projects in Western Australia in the late 1990s represents the first of these new generation nickel operations, with several other projects; in Australia and overseas, in various stages of development. Unfortunately, several technical issues have hindered full production in these new refineries. Some of these problems are directly attributable to the mixer-settler contactors used in the solvent extraction process. This has highlighted a need to develop alternative contactors for industrial use. Electrostatic Pseudo Liquid Membrane (ESPLIM) is an alternative, novel technique to conduct the solvent extraction process. It combines the basic principles of solvent extraction, liquid membrane and electrostatic dispersion into a simple, compact reactor that utilises many advantages of each technique. The aim of this study w as to develop a method of extracting and separating cobalt from an acidic nickel laterite leach solution using ESPLIM. Bench scale tests using synthetic and actual leach solutions have shown that: the design and construction materials of the baffle plate and electrodes have a significant effect on the performance of the reactor; an AC power supply provided better droplet dispersion than a DC power supply; an increase in the applied electric field strength above a critical value resulted in a decrease in the aqueous droplet size and an increase in residence tune.These effects increased the extraction efficiency and the concentration of the loaded strip solution. However, further increases in applied electric field strength decreased efficiency due to excessive levels of swelling and leakage; the known extraction isotherms for cobalt and nickel apply in the ESPLIM technique; salts of soluble organic acids influence extraction efficiency by changing the aqueous pH and interfacial tension; the use of ammonia was found to be effective as a replacement for salts of soluble organic acids; the ESPLIM reactor can cope with large changes in the flow rates of both feed and strip solutions. However, an increase in the feed flow rate should be accompanied by a relative increase in the ship flow rate to maintain high extraction efficiencies; the baffle design has a significant impact on the levels of swelling and leakage; provided the electrostatic field strength is maintained and flow rates are increased proportionately to the size of the reactor, no significant scale-up issues were observed, indicating that the data generated in bench scale studies could be applied to plant scale contactors. The optimum conditions, devised as a result of this investigation, to extract cobalt from an acidic nickel laterite leach solution using the ESPLIM technique are as follows: an applied electric field strength of 5.5 kV/cm. a raffinate pH of 5.5, a solvent containing 10% Cyanex 272 with 5% TBP in Solvent HF diluent, a feed to strip flow ratio of approximately 5 and a 1 M H[subscript]2S0[subscript]4 strip solution. At these conditions, almost complete cobalt extraction is achieved after only two extraction stages. A comparable extraction using conventional mixer-settlers could only be achieved after five stages.
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Khalesi, Mohammad Reza. "Integrated modeling of grinding, liberation and leaching of gold ores." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27466/27466.pdf.
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Linde, Mats. "Trace metals in urban soils : Stockholm as a case study /." Uppsala : Dept. of Soil Sciences, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005111.pdf.
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Wen, Ying. "Approach to Arsenic and Selenium Removal from Fly Ash by Oxalate and Estimation of Calcium Effects on Both Elements." TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1046.
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An approach to arsenic and selenium removal from fly ash is studied. This research includes a comparison of the leaching ability of ammonium oxalate, ammonium citrate, ammonium nitrate and EDTA to extract arsenic and selenium; use of common agricultural waste as a source of oxalate anion to remove arsenic and selenium from fly ash and estimation of additional calcium effects on arsenic and selenium leaching behaviors. This research shows that extraction strength order is EDTA > ammonium oxalate > ammonium citrate > ammonium nitrate > water, achieving arsenic extraction efficiencies of 94.18%, 84.17%, 4.50%, 2.89% and 0.18%, respectively; achieving selenium extraction efficiencies of 96.14%, 96.26%, 84.34%, 26.60% and 0.71%,respectively, in single-stage extraction. Tall fescue is applied as a source of natural oxalate resource and is able to remove over 70% of arsenic and selenium from fly ash. Additional calcium is found to make 82.20% of total arsenic in free oxalate leachate drop to 1.65% of total arsenic in free oxalate and free calcium leachate. All samples were analyzed using HG-AFS. Hopefully, this research will be helpful when a large scale, cheap and sustainable fly ash clean-up approach is needed for power plants prior to landfilling. Also, calcium effects will enable arsenic and selenium to move to the solid phase and could possibly solve the problem of toxic wastewater generated from the clean-up process. The enriched toxic solid waste could be used for pesticide applications.
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Chestnutt, Sheryl A. "Comparison of the extraction procedure toxicity test (EP) and the toxicity characteristic leaching procedure (TCLP) for the analysis of trace organic compounds in land applied municipal wastewater sludges." Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/44626.
Full textAbstract:
The current Environmental Protection Agency (EPA) method utilized for analysis of trace organic chemicals and heavy metals leached from solid waste is the Extraction Procedure (EP) Toxicity Test. Because of various operational problems and limitations of the EP, the EPA has developed and plans to implement the Toxicity Characteristic Leaching Procedure (TCLP), which is an expanded version of the EP capable of analyzing more organic components, in particular volatile organic chemicals.
The purpose of this research was to investigate and compare the ability of the EP and TCLP test procedures to quantitatively recover added surrogate standards (1,2-dibromoethane, bromoform, 1â chlorooctane, fusarex, heptachlor, and DDT) and also qualitatively identify and evaluate unknown trace organic chemicals in domestic wastewater sludges. In order to meet the research objectives established, three small (approximately 1 MGD or less) municipal wastewater treatment plants that land applied their sludges were analyzed.
Master of Science
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Addo, Douglas Kweku. "OPERATION AND PROCESS CONTROL DEVELOPMENT FOR A PILOT-SCALE LEACHING AND SOLVENT EXTRACTION CIRCUIT RECOVERING RARE EARTH ELEMENTS FROM COAL-BASED SOURCES." UKnowledge, 2019. https://uknowledge.uky.edu/mng_etds/50.
Full textAbstract:
The US Department of Energy in 2010 has identified several rare earth elements as critical materials to enable clean technologies. As part of ongoing research in REEs (rare earth elements) recovery from coal sources, the University of Kentucky has designed, developed and is demonstrating a ¼ ton/hour pilot-scale processing plant to produce high-grade REEs from coal sources. Due to the need to control critical variables (e.g. pH, tank level, etc.), process control is required. To ensure adequate process control, a study was conducted on leaching and solvent extraction control to evaluate the potential of achieving low-cost REE recovery in addition to developing a process control PLC system. The overall operational design and utilization of Six Sigma methodologies is discussed. Further, the application of the controls design, both procedural and electronic for the control of process variables such as pH is discussed. Variations in output parameters were quantified as a function of time. Data trends show that the mean process variable was maintained within prescribed limits. Future work for the utilization of data analysis and integration for data-based decision-making will be discussed.
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Ngoie, Mpinga Cleophace. "The extraction of precious metals from an alkaline cyanided medium by granular activated carbon." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71787.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: A 2 stage heap leach process to extract base and precious metals from the Platreef ore is currently being investigated industrially. A first stage bioleach is used to extract the base metals. In the 2nd stage, cyanide is used as the lixiviant at high pH to extract the platinum group metals and gold. By analogy with current gold recovery practices, the present study investigates the preferential and quantitative adsorption of precious metals (Pt, Pd, Rh and Au) over base metals (Cu, Ni and Fe) from an alkaline cyanide medium, by means of granular activated carbon. Experiments were designed statistically to optimise the process parameters using synthetic alkaline cyanide solutions close in composition to those expected from plant leach solutions. The statistical approach allowed the development of a reliable quantitative approach to express adsorption as a response variable on the basis of a number of experiments. A 2IV(7-2) fractional factorial design approach was carried out in a batch adsorption study to identify significant experimental variables along with their combined effects for the simultaneous adsorption of Pt(II), Pd(II), Rh(III) and Au(I). The adsorbent was characterized using SEM-EDX, and XRF. Precious metals adsorption efficiency was studied in terms of process recovery as a function of different adsorption parameters such as solution pH, copper, nickel, free cyanide ion, thiocyanate, initial precious metal (Pt, Pd, Rh and Au) ion and activated carbon concentrations. It was shown that adsorption rates within the first 60 minutes were very high (giving more than 90% extraction of precious metals) and thereafter the adsorption proceeds at a slower rate until pseudo-equilibrium was reached. Among the different adsorption parameters, at 95% confidence interval, nickel concentration had the most influential effect on the adsorption process followed by the adsorbent concentration. Adsorption of Ni was found to proceed at approximately the same rate and with the same recovery as the precious metals, showing a recovery of approximately 90% in two hours. The kinetics of Cu adsorption were slower, with less than 30% being recovered at the 120 minute period. This suggests that the co-adsorption of Cu can be minimised by shortening the residence time. Adsorption of Fe was found to be less than 5%, while the recovery of Rh was negligibly small. The effect of thiocyanate ion concentration was not as important as the effect of free cyanide ion concentration but still had some influence. The correlation among different adsorption parameters was studied using multivariate analysis. The optimum experimental conditions resulted in a solution with pH of 9.5, [Cu(I)] of 10 ppm, [Ni(II)] of 10 ppm, [CN ] of 132.44 ppm, [SCN ] of 98.95 ppm, [PMs] of 2.03 ppm and [AC] of 10 g/L. Under these conditions, predicted adsorption percentages of Pt, Pd and Au were approximately 98, 92 and 100%, at the level of 95% probability within two hours as an effective loading time. The negative values of ΔG° for all ions under optimum conditions indicate the feasibility and spontaneous nature of the adsorption process. Chemisorption was found to be the predominant mechanism in the adsorption process of Pt(II), Pd(II) and Au(I). Based on their distribution coefficients, the affinity of activated carbon for metal ions follows the selectivity sequence expressed below. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Finally, it is important that additional research and development activities in the future should prove the economic viability of the process. Future work is also needed to investigate the adsorption of precious metals (PMs) by comparing the efficiencies and kinetics of adsorption when using sodium hydroxide (in this study) or lime, respectively, in order to control the pH.
AFRIKAANSE OPSOMMING: ʼn Tweefasige hooploogproses vir die ontginning van basis- en edelmetale van die Platrif-erts word tans industrieel ondersoek. ʼn Eerstefase-bioloog word gebruik om die basismetale te ontgin. In die 2de fase word sianied gebruik as die uitloog by hoë pH om die platinum-groepmetale en goud te ontgin. Na analogie van hedendaagse goudherwinningspraktyke het die huidige studie die voorkeur- en kwantitatiewe adsorpsie van edelmetale (Pt, Pd, Rh en Au) bo basismetale (Cu, Ni en Fe) vanuit ʼn alkaliese sianiedmedium met behulp van korrelrige geaktiveerde koolstof ondersoek. Eksperimente is op statistiese wyse ontwerp om die parameters van die proses te optimaliseer deur van sintetiese alkaliese sianiedoplossings wat in hulle samestelling nou ooreenstem met dié wat van oplossings van plant-loog verwag word, gebruik te maak. Die statistiese benadering het die ontwikkeling van ʼn betroubare kwantitatiewe benadering om adsorpsie as ʼn responsveranderlike op grond van ʼn aantal eksperimente uit te druk, moontlik gemaak. ʼn 2IV(7-2) -Fraksionele faktoriale ontwerp-benadering is tydens ʼn lot-adsorpsiestudie gevolg om beduidende eksperimentele veranderlikes tesame met hulle gekombineerde uitwerkings vir die gelyktydige adsorpsie van Pt(II), Pd(II), Rh(III) en Au(I) te identifiseer. Die adsorbeermiddel is met behulp van SEM-EDX en XRF gekenmerk. Adsorpsiedoeltreffendheid van edelmetale is bestudeer ten opsigte van proseskinetika en herwinning as ʼn funksie van verskillende adsorpsieparameters soos oplossing-pH, koper, nikkel, vry sianiedioon, tiosianaat, aanvanklike edelmetaal (Pt, Pd, Rh en Au)-ioon en geaktiveerde koolstofkonsentrasies. Daar is aangetoon dat adsorpsietempo‟s binne die eerste 60 minute baie hoog was (het meer as 90% ekstraksie van edelmetale opgelewer) en daarna het die adsorpsie teen ʼn stadiger tempo voortgegaan totdat pseudo-ekwilibrium bereik is. Onder die verskillende adsorpsieparameters, by 95%-vertroubaarheidsinterval, het nikkel-konsentrasie die grootste invloed op die adsorpsieproses gehad, gevolg deur konsentrasie van die adsorbeermiddel. Daar is bevind dat die adsorpsie van Ni teen nagenoeg dieselfde tempo en met dieselfde herwinning as die edelmetale voortgegaan het, wat ná twee uur ʼn herwinning van nagenoeg 90% getoon het. Die kinetika van Cu-adsorpsie was stadiger, met minder as 30% wat teen die 120-minute-tydperk herwin is. Dit dui daarop dat die ko-adsorpsie van Cu tot die minimum beperk kan word deur verkorting van die verblyftyd. Daar is bevind dat die adsorpsie van Fe minder as 5% is, terwyl die herwinning van Rh onbeduidend klein was. Die uitwerking van die konsentrasie van die tiosianaatione was nie so belangrik as die uitwerking van die konsentrasie van vry sianiedione nie maar het steeds ʼn mate van invloed gehad. Die korrelasie tussen verskillende adsorpsieparameters is met behulp van meerveranderlike analise bestudeer. Die optimale eksperimentele toestande het gelei tot ʼn oplossing met ʼn pH van 9.5, [Cu(I)] van 10 dpm, [Ni(II)] van 10 dpm, [CN] van 132.44 dpm, [SCN] van 98.95 dpm, [EM‟e] van 2.03 dpm en [AC] van 10 g/L. Onder hierdie toestande was die voorspelde adsorpsiepersentasies van Pt, Pd en Au nagenoeg 98, 92 en 100%, op die vlak van 95%-waarskynlikheid binne twee uur as ʼn doeltreffende laaityd. Die negatiewe waardes van ΔG° vir alle ione onder optimale toestande dui op die uitvoerbaarheid en spontane aard van die adsorpsieproses. Daar is bevind dat chemiesorpsie die deurslaggewende meganisme by die adsorpsieproses van Pt(II), Pd(II) en Au(I) is. Gebaseer op hulle distribusiekoeffisiënte volg die affiniteit van geaktiveerde koolstof vir metaalione die selektiwiteitsvolgorde soos hieronder voorgestel. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Laastens, dit is belangrik dat addisionele navorsing en ontwikkelingsaktiwiteite in die toekoms die ekonomiese haalbaarheid van die proses bewys. Werk in die toekoms is nodig om die adsorpsie van edelmetale (EM‟e) te ondersoek deur vergelyking van die doeltreffendhede en kinetika van adsorpsie wanneer natriumhidroksied (in hierdie studie) of kalk, onderskeidelik, gebruik word ten einde die pH te beheer
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Alderman, Lori A. "The evaluation and comparison of the extraction procedure toxicity test and the toxicity characteristic leaching procedure for the analysis of municipal wastewater sludges." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44103.
Full textAbstract:
A viable sludge management alternative is land application of waste sludge. However, it is necessary to implement efficient monitoring and analysis of land applied sludges in order to assess potential health risks associated with this means of disposal.
The State of Virginia is considering a proposal that requires land-applied wastewater sludges to undergo analysis by EPAâ s Toxicity Characteristic Leaching Procedure (TCLP) (EPA, 1986b) to determine if the sludge exhibits hazardous characteristics, which preclude land application as a management alternative. The method currently used for the analysis of hazardous wastes is the Extraction Procedure (EP) Toxicity Test. Both of these test methods analyze for trace organic chemicals and heavy metals. However, the TCLP is designed to analyze for volatile organic chemicals to a greater extent than the EP. Because of the added complexity and the current expense of the TCLP, the State is concerned that the TCLP may not be warranted for the analysis of trace organic chemicals in land-applied sludges.
This research was designed to compare the abilities of the EP and TCLP for the analysis of trace organic chemicals in wastewater sludges. Samples from three municipal wastewater treatment plants that utilize secondary biological treatment, aerobic digestion and land-apply waste sludge were evaluated by both EP and TCLP methods. Both tests utilize a weak acid extraction to remove organic chemicals from the wastewater sample. The weak acid extract was subjected to liquid-liquid extraction (EPA Method 625) to partition and concentrate the organic chemicals into methylene chloride; this methylene chloride extract was then subjected to GC and GC/MS for quantitative analysis and qualitative identification of targeted and nontargeted organic chemicals.
In order to assess recovery and extractability efficiencies of each test, surrogate standards were added prior to the test procedure. These standards were bromoform, 1-chlorooctane, DDT, ethylene dibromide (EDB, a volatile fungicide), fusarex (tetrachloronitrobenzene), and heptachlor. Control samples were run for both EP and TCLP, in addition to a sludge samples with no surrogates added.
Analysis indicated that both the TCLP and EP tests showed high variability for the recovery of the sludge surrogates. The recoveries of the surrogate standards were low and varied between zero and 30 percent depending on the standard and the matrix. Surrogate recoveries were evaluated with respect to various physical/ chemical properties of the individual standard, the sample site, and the test method utilized. Although the TCLP recovered the volatile surrogate standards only slightly better than the EP, there was no statistically significant difference between the TCLP and EP for the recovery of the non- and semi-volatile surrogate standards.
Specific trace organic chemicals identified in the sludges included dimethylpentanol, dichlorodimethoxybenzene, 4-methylphenol, and tetrabutylphenol. Other chemicals, such as contaminants and artifacts resulting from laboratory processing and background contamination in the reagents, were also identified in the blank control samples as well as the sludge samples.
Master of Science
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Refifi, Jihen. "Extraction de la silice à partir d'un composé H₂SiF₆ pour la fabrication d'un bioverre." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S066.
Full textAbstract:
L'acide fluorosilicique (FSA) est la principale eau usée générée par la fabrication d'acide phosphorique en Tunisie. Actuellement, Une énorme quantité de cet acide est générée comme sous-produit de l'industrie des engrais phosphatés. En plus des pertes économiques, le rejet de cette industrie dans la mer, entraine également un véritable danger dans le cadre écologique pour le domaine marin. Par conséquent, notre attention s'est portée sur le développement d'un procédé de traitement par extraction de la silice de ces déchets fluorés, qui peut être utilisée dans plusieurs applications intéressantes comme la synthèse de biomatériaux. En effet, cette étude se concentre sur la récupération du fluor dans l'industrie des engrais phosphatés, la majeure partie de cette récupération étant basée sur la FSA. En fait, cette étude se concentre sur la récupération du fluor dans l'industrie des engrais phosphatés, la majeure partie de cette récupération étant basée sur la FSA. Le processus implique la réaction de FSA et d'hydroxyde de sodium pour générer la suspension aqueuse alcaline. Les particules de silice extraites ont une largeur moyenne de particule de 50 à 60 nm et une longueur à l'échelle microscopique. La seconde partie de ce travail de recherche porte sur la synthèse de verres bioactifs à partir de cette silice extraite pour une utilisation comme biomatériau osseux. Ils sont synthétisés par la méthode de fusion dans le système SiO₂-CaO-Na₂O-P₂O₅. L'ingénierie tissulaire est apparue comme une approche alternative pour créer du tissu osseux en cultivant des cellules sur des échafaudages 3D. Cette étude a pour objectif de synthétiser un composite verre / chitosane (BG-CH) en utilisant le procédé New Salt Leaching Using Powder (SLUP) afin de contrôler le taux de porosité puis la réactivité chimique du produit final. Le processus SLUP consiste à créer de cavités avec les tailles de pores souhaitées. Ce processus est basé sur la dissolution des particules de NaCl utilisées pour cela. Cela est dû à sa grande solubilité dans les milieux aqueux. Il ne nécessite pas de traitement thermique. Ce travail est basée sur l’élaboration, la caractérisation physico-chimique et l’évaluation biologique de bioverre pure et associé au chitosane. Une gamme de scaffolds avec différentes teneurs en verre bioactif / chitosane a été synthétisée. Différents tailles des particules du NaCl ont été utilisés dans le but d'optimiser le réseau de pores. Les résultats obtenus montrent que la surface spécifique et le volume des pores augmentent avec l'augmentation de la teneur en chitosane et en porogène (NaCl). Les mêmes observations pour le volume des pores ont été enregistrées. Les scaffolds obtenus avaient une porosité élevée (90%) avec une forte connectivité entre pores. Les images MEB ont révélé une forte dépendance des tailles et des formes des pores de rapports sel / compositeFluorosilicic Acid (FSA) is the main wastewater generated by the phosphoric acid manufacture in Tunisia. Currently, this effluent is wildly discharged into the sea, which is an ever more serious environmental stake for phosphoric acid production plants. Therefore, our attention has been focused on developing a treatment process by extracting silica from this fluorine waste, which can be used in several interesting applications such as the synthesis of biomaterials. In fact, this study focuses on fluorine recovery in the phosphate fertilizer industry, with most of this recovery based on FSA. To model and optimize the process conditions, response surface methodology and a full factorial design were employed in the extraction of silica from FSA. The process involves the reaction of FSA and sodium hydroxide to generate the alkaline aqueous slurry. Extracted silica particles were found to have an average particle width of 50-60 nm and length in the micronic scale. The second part of this research work focuses on synthesis of bioactive glasses based on this extracted silica for use as bone biomaterial. They are synthesized by the melting method in the system SiO₂-CaO-Na₂O-P₂O₅. Tissue engineering has emerged as an alternative approach to create bone tissue by growing cells on 3D scaffolding. The aim of this study was to synthesize a composite glass/chitosan (BG-CH) by using New Salt Leaching Using Powder (SLUP) process in order to control the porosity rate and then the chemical reactivity of the final product. SLUP process consists on the cavities creation with desired pore sizes. This process is based on the washing out the NaCl particles used for that. It is due to its high solubility in aqueous media. It does not require heat treatment. This work focuses on the elaboration, physicochemical and chemical reactivity studies of pure bioactive glass and bioactive glass associated with chitosan. A range of composite scaffolds with different bioactive glass/Chitosan contents has been synthesized. NaCl with a distinct range size was used with the aim of optimizing the pore network. Obtained results show that the specific surface area and pores volume increase with increasing of chitosan and porogen content. The same observations for pores volume were registered. The obtained scaffolds had high porosity (90%) with good pore connectivity. SEM images revealed strong dependence of sizes and shapes of pores on the salt/composite ratios
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Vincent, Laura A. "The Effect of Salinity Level upon the Yield, Root Growth, and Water Extraction of Contrasting Rooting Subpopulations of Alfalfa (Medicago sativa) Under Conditions of Zero Leaching." DigitalCommons@USU, 1996. https://digitalcommons.usu.edu/etd/6432.
Full textAbstract:
A major problem in irrigated agriculture in the Western U.S. is the gradual accumulation of salinity in the plant root zone. These nonuniformly saline soils contain increasing amounts of salinity with depth, and salt accumulation is accelerated in situations where leaching is minimized. Root growth and thus plant yield is limited in these soils due to decreased water uptake. We studied the root growth of two subpopulations of alfalfa differing in their ability to produce fibrous roots to determine if altering root morphology would increase plant yield and water extraction, in an irrigated saline soil.
Soil profiles for a control and three treatments with increasing salinity were packed in to PVC cylinders fitted with a flat window down one side for root measurements. A single alfalfa plant was grown from seed in each cylinder, and irrigated with water enriched primarily in sulfate salts. Alfalfa plants were grown for five successive harvests in a greenhouse, and water extraction was measured in the control and high Salinity treatment by time-domain reflectometry. Final electrical conductivities of the soil ranged from 3.0 to 23 dS m-1. The yield of the high fibrous root subpopulation was not reduced by the soil salinity by the fifth harvest, while that of the low fibrous subpopulation was reduced 22%. Root growth of the high fibrous subpopulation was significantly increased by as much as 54% in the upper 30 cm of the root zone, compared to that of the low fibrous subpopulation. Water extraction was higher in the upper, least saline portion of the root zone for the high fibrous root subpopulation. The results of this study support the use of alfalfa with increased fibrous root production under saline irrigation with minimal leaching.
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Marchant, P. Brad. "Continuous biological tank leaching of a refractory arsenical sulphide concentrate to enhance gold extraction by cyanidation : a pilot plant and feasibility study at Equity Silver Mines Limited." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26314.
Full textAbstract:
Bench and pilot scale testing has shown that biooxidation of a refractory arsenical sulphide concentrate enhanced gold and silver extraction by cyanidation. Direct cyanidation of Southern Tail bulk sulphide concentrate typically resulted in less than 10% gold and silver recovery. Biological pretreatment of the sulphide
concentrate resulted in 70% gold extraction and at least 30% silver extraction within economic process constraints.
Biooxidation of a low grade arsenical sulphide concentrate, 5.5 g Au/t, 80 g Ag/t, and 2-5% As, was economically attractive due to apparent preferential oxidation of the gold bearing suphide mineral assemblage(s). Selective sulphide oxidation minimized the bioleach residence time, the oxygen/CO₂ requirements, and the costs associated with neutralization of the acidic byproducts of sulphide oxidation. Approximately 15% total sulphide
oxidation was required to effect 70% gold extraction and 30-40% silver extraction. Additional sulphide oxidation improved gold extraction slightly and improved silver extraction significantly but was not economically
attractive. Complete batch and continuous laboratory bioleach facilities were constructed at Equity. A detailed
description of apparatus, methods, and operating data is presented. Critical variables that were studied included temperature, pH, pulp density, particle size, air/CO₂ requirements, nutrients, bioleachate recycle, inoculum source, degree of sulphide oxidation, cyanidation conditions, and bioleachate treatment. The laboratory data provided the design and operating criteria for a continuous bioleach pilot plant.
Operation of the continuous pilot circuit, with a nominal design capacity of 2 tonnes per day, showed there was no significant effect of scale on the biohydrometallurgy or resultant precious metals hydrometallurgy. A detailed description of the pilot equipment and steady state operating parameters is presented. Considerations for scaleup and for plant scale design and optimization are discussed.
A preliminary feasibility study, based on a conceptual design for an 800 tonne per day bioleach circuit, is detailed. The feasibility analysis showed that it is economically attractive to scavenge gold and silver values from Southern Tail flotation tailing using biooxidation to enhance the gold and silver extraction by cyanidation. The base case cash flow analysis showed a Net Present Value potential of $4,975 x 106 (1985) at 15% discount factor.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
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Correa, Monica Maria Jimenez. "Separação e purificação de metais presentes em placas de circuito impresso de computadores descartados utilizando-se extração por solventes." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-07032016-101348/.
Full textAbstract:
Com o transcorrer dos anos a problemática da geração de resíduos sólidos vem ganhando destaque no âmbito ambiental. Atualmente, várias tecnologias na área de tratamento de resíduos sólidos estão sendo estudadas com o objetivo de reduzir o volume de resíduos gerados e obter ganhos econômicos adicionais. As placas de circuito impresso (PCIs) descartadas são classificadas como resíduos sólidos e na sua composição, por vezes, possuem quantidades de metais maiores que as encontradas em minérios. O presente trabalho estudou a separação de metais não ferrosos encontrados em dois tipos de placas de circuito impresso de computadores descartados (placas mãe e placas de vídeo), visando a sua recuperação. O procedimento utilizado incluiu etapas de processamento físico e processamento hidrometalúrgico. O processamento físico foi iniciado com a cominuição das PCIs utilizando moinho de facas e moinho de martelos. Em seguida, foi retirada uma parte do resíduo moído para ser quarteado e encaminhado para os ensaios hidrometalúrgicos. As amostras obtidas após o quarteamento foram denominadas amostras da rota I. Com o restante do material moído foi realizada separação magnética, na qual foram obtidas amostras de material não magnético, denominadas: amostras da rota II, tais amostras seguiram também para tratamento hidrometalúrgico. A seguir foi realizada a caracterização dos materiais presentes nas PCIs e nas suas respectivas amostras (amostras da rota I e amostras da rota II). O processamento hidrometalúrgico foi então iniciado com a etapa de lixiviação. Nesta etapa, parâmetros como tempo, temperatura e concentração do ácido foram avaliados. O licor coletado na lixiviação das amostras da rota II seguiu para fase de extração por solventes (SSX), na qual os metais foram purificados e separados. Nos ensaios de SSX foram empregados os extratantes ácidos Cyanex 272, D2EHPA, TBP e suas misturas. Experimentos variando a relação aquosa/orgânica (A/O), a temperatura e a concentração de extratante foram desenvolvidos. Finalmente foram determinados o número de estágios teóricos de extração para purificar o licor obtido na lixiviação das amostras da rota II. Os resultados mostraram que as placas mãe possuem na sua composição 35,8% de metais; 38,4% de polímeros e 25,9 % de cerâmicos, já as placas de vídeo estudadas possuem 35,8 % de metais, 33 % de polímeros e 31,2 % de cerâmicos. Na etapa de lixiviação foi possível recuperar 100% do cobre contido nas amostras da rota II (fração não magnética da placa de vídeo e da placa mãe). A etapa de extração por solventes permitiu separar o alumínio e o zinco do licor obtido na lixiviação das amostras da rota II (fração não magnética da placa de vídeo e da placa mãe). A extração do alumínio e o zinco empregou 10% v/v D2EHPA, temperatura ambiente, tempo de reação de 10 min e pH igual a 3,5. Além disso, o cobre foi separado usando-se 20% v/v de D2EHPA, temperatura ambiente, tempo de reação de 10 min e pH igual a 3,5. Finalmente foi encontrado que este procedimento permite recuperar 82 % do cobre contido na placa mãe e 60 % do cobre da placa de vídeo.Over the years, the solid waste generation problem has been gaining strength in an environmental context. Currently, several technologies on the field of waste treatment are been studied aiming to reduce the volume of produced waste and gain additional economic value. Discarded printed circuit boards (PCBs) are classified as solid waste and in it composition, sometimes, they hold greater quantities of metal than ores. The present research studied the separation of non-ferrous metals from two types of printed circuit boards from discarded computers (motherboards and video boards) aiming its recovery. The overall process used physical treatment and hydrometallurgical treatment. The physical processing started with griding the PCBs using a knife mill and a hammer mill. Quartered samples from the grinded material were utilized on the hydrometallurgical process. Samples obtained after quartering were called samples from route l. The remained milled material was magnetically separated generating non-magnetic samples, called: samples from route ll, also followed by hydrometallurgical treatment. After, present materials on the PCBs and its respective samples were characterized (samples from route l and samples from route ll). Leaching those materials was the first step of the hydrometallurgical step. Leaching parameters time, temperature and acid concentration were evaluated. The resulting liquor from leaching samples from route ll followed to the solvent extraction (SSX) phase, in which metals were screened and purified. On the extraction phase there were utilized the acid extractants: Cyanex 272, D2EHPA, TBP and its mixtures. Experiments varying extraction parameters as organic/aqueous (O/A), temperature and extractant concentration were carried out during this phase. Finally, the number of theoretical stages of extraction were determined to purify the liquor obtained by leaching samples from route ll. The results showed that the mother PCBs are constituted by 35.8% of metals; 38.4% of polymers and 25.9% of ceramic, while the video PCBs are composed by 35.8% of metals, 33% polymer and 31.2% of ceramic. In the leaching step was possible to recover 100% of the copper contained in the route II samples (non-magnetic fraction of the video boards and motherboards). The solvent extraction step can separate aluminum and zinc from the liquor produced in leaching process of the Route II samples (non-magnetic fraction of the video board and motherboard). Aluminum and zinc extraction used 10% v/v of D2EHPA, room temperature, reaction time 10 min and pH 3.5. Moreover, copper was removed using 20% v/v of D2EHPA, room temperature, reaction time of 10 min and pH 3.5. Finally it was found that this procedure allows recovering 82% of the copper contained in the motherboard and 60% of the copper video board.
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Belfqueh, Sahar. "Développement d’un procédé éco-compatible de recyclage des terres rares issues des aimants permanents." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2022. http://theses.enscm.fr/interne/ENSCM_2022_BELFQUEH.pdf.
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Les terres rares (TRs) sont omniprésentes dans les objets technologiques du quotidien (téléphones mobiles, ordinateurs, …) et sont de plus en plus utilisées dans les technologies vertes (éoliennes, véhicules électriques, …). Ces métaux, de par leur importance, sont considérés comme critiques pour l’Europe qui détient très peu de gisements primaires. L’accès à ces TRs peut être envisagé au travers du recyclage de produits en fin de vie, en particulier par l’intermédiaire des aimants permanents de type NdFeB ou SmCo qui représentent environ 37%, en masse, du marché des TRs.Dans ce contexte, la présente thèse étudie le recyclage des TRs (Nd, Pr et Dy) provenant des aimants permanents de type NdFeB issus des disques durs d’ordinateurs par voie hydrométallurgique « éco-compatible » en considérant l’utilisation d’un acide organique lors du processus de lixiviation comme alternative aux acides minéraux, et un diglycolamide (N,N,N′,N′‐Tetraoctyl diglycolamide - TODGA) comme molécule extractante dans le processus d’extraction liquide-liquide comme alternative aux composés organophosphorés.Des études multiparamétriques ont été réalisées afin d’étudier la récupération sélective des TRs vis-à-vis des autres éléments présents dans ces aimants, en particulier le fer.Ainsi à partir des résultats obtenus, deux procédés alternatifs sont proposés.Le premier consiste en un grillage oxydant de la poudre d’aimants NdFeB suivi de deux lixiviations sélectives par l’acide acétique qui permettent, après les étapes de précipitation et de calcination, une séparation de l’oxyde Didymium (Nd2O3. Pr2O3), de l’oxyde de dysprosium (Dy2O3) et de l’oxyde de fer (Fe2O3) qui est non lixiviable dans l’acide acétique. La faisabilité de ce procédé a été démontrée sur des mélanges synthétiques d’oxydes ayant une composition identique à celle d’une poudre d’aimants NdFeB oxydée (lixiviation > 95%, pureté des oxydes >99,8%). Cependant, les conditions du grillage oxydant doivent être optimisés davantage pour reproduire les mêmes résultats sur la poudre d’aimant réelle.Le second procédé consiste en une lixiviation totale de la poudre d’aimant NdFeB brute par l’acide acétique suivi par une étape d’extraction liquide-liquide en utilisant le TODGA comme molécule extractante. Ainsi il a été montré que l’extraction quantitative de l’ensemble des TRs (Nd, Pr et Dy) avec une excellente sélectivité vis-à-vis des autres métaux présents dans le lixiviat (Fe, B, Co et Ni) est possible en deux étages d’extraction liquide-liquide. La désextraction quantitative de l’ensemble des TRs extraits a ensuite été possible en utilisant une solution d’EDTA. De plus, Une extraction multi-étagée en utilisant le TODGA suivi d’une désextraction à l’eau déionisée permet d’envisager la séparation du Didymium et du DyRare earth elements (REEs) are omnipresent in high technology devices (smartphones, computers…) and are increasingly used in green technologies (wind power turbines, electric vehicles…). Due to their importance, these metals are considered critical for Europe, which has very few primary deposits. Access to these REEs can be considered through the recycling of end-of-life products, in particular through NdFeB or SmCo permanent magnets, which represent 37%, by weight, of the REEs market.In this context, this thesis studies the recycling of REEs, especially Nd, Pr and Dy from NdFeB permanent magnets, found in hard disk drives, through “eco-compatible” hydrometallurgical routes considering the use of organic acids in the leaching process as alternatives to the mineral acids, and the use of a diglycolamide (N,N,N′,N′‐Tetraoctyl diglycolamide - TODGA) as the extracting molecule as an alternative to organophosphorus compounds.Multiparametric studies were realized in order to evaluate the selective recovery of REEs from other elements present in these magnets, in particular iron.Thus, from the results obtained, two alternative methods are proposed.The first process consists in an oxidative roasting of the NdFeB magnet powder followed by two selective leaching steps that allow, after the steps of precipitation and calcination, the separation of Didymium oxide (Nd2O3. Pr2O3), dysprosium oxide (Dy2O3) and iron oxide (Fe2O3) which is non-leachable in acetic acid. The feasibility of this process has been demonstrated on synthetic mixtures of oxides having the same composition as an oxidized NdFeB magnet powder (leaching> 95%, oxide purity> 99.8%). However, the oxidative roasting conditions must be further optimized in order to reproduce the same results on the real NdFeB magnet powder.The second process starts with the complete leaching of the non-roasted NdFeB magnet powder followed by a solvent extraction step using the extracting molecule TODGA. Thereby, a two-stage solvent extraction allowed the extraction of all REEs (Nd, Pr and Dy) with excellent selectivity against other elements present in the acetic acid leachate (Fe, B, Co and Ni). The quantitative stripping of all extracted REEs was possible using an EDTA solution. In addition, a multi-stage solvent extraction, using TODGA, followed by a stripping step using water allowed the separation of Didymium and dysprosium
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Elsayed, Nada H. "Leaching of active ingredients from blueberries and cranberries using supercritical carbon dioxide and ethanol as an entrainer and analyzing using GC/MS." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002933.
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Obón, Estrada Eleonora. "Towards the recovery of rare earth elements from end-of-life products : hydrometallurgical routes and mathematical modelling of extraction systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/669262.
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The rare earth elements (REEs) are essential ingredients for the development of modern industry and the transition to a more sustainable economy model. The unique physicochemical features of these elements, such as their magnetism and optical properties, are greatly expanding their application. They have become key elements for the manufacture of many ordinary consumer goods like hybrid cars, fluorescent lamps or electronic devices like mobile phones or tablets. The growing popularity of the rare earth elements derivatives is leading to an increase in the global demand and the price of these elements. Unfortunately, the current availability of these resources is limited due to three main factors: their heterogeneous geological location, their low concentration in the ores, and the environmental issues related with their mining.
All these disadvantages concerning the supply of the rare earth elements have led to the study of new techniques to obtain them, such as the recycling of end-of-life products. Recycling of REEs arises as a new secondary source of supply of REEs, especially in Europe where large amounts of technological waste are generated every year. Currently, the recycling of rare earth elements represents less than 1% of the global supply. Nevertheless, some studies in the literature assume that by 2050 the recovery rate of REEs will be 90% for wind turbines, 70% for electrical vehicles and 40% for the rest of derivative products.
The research presented in this thesis relies on experimental investigation of new hydrometallurgical routes, the majority of them involving the use of ionic liquids, which could eventually be applied for the recovery of rare earth elements from end-of-life products. Matemathical modelling of the reported extraction systems has been carried out in order to provide a computational instrument that can be easily tailored for prediction of other collecting processes requiring minor adjustments.Les terres rares son ingredients essencials per al desenvolupament de la indústria moderna i la transició cap a un model econòmic més sostenible. Les seves característiques físico-químiques úniques, com el seu magnetisme i propietats òptiques, han precipitat un increment accelerat en l’aplicació d’aquests elements. Les terres rares s’han convertit en elements clau per a la fabricació de molts articles d’ús diari com per exemple, cotxes elèctrics i dispositius electrònics com telèfons mòbils i tabletes. La creixent popularitat dels productes que contenen aquests metalls està provocant un escalat en la demanda global i el preu de les terres rares. Desafortunadament, en l’actualitat, la disponibilitat d’aquests recursos a la natura és limitada degut bàsicament a tres factors: heterogènia localització geològica, baixa concentració als minerals que els contenen i inconvenients mediambientals relacionats amb la mineria. Els inconvenients relacionats amb el subministrament de les terres rares a nivell mundial han propiciat l’estudi de noves tècniques per a la obtenció d’aquests elements mitjançant el reciclatge de productes que els contenen. El reciclatge sorgeix com una font secundària alternativa a la mineria per tal d’assegurar el provisionament de terres rares especialment a Europa, on generem grans quantitats de residus tecnològics cada any. Actualment, la taxa de reciclatge de terres rares se situa per sota l'1% del subministrament global. No obstant, alguns estudis publicats en la literatura assumeixen que l’any 2050, la taxa de recuperació haurà augmentat considerablement, de manera que es reciclarà fins a un 90% de les terres rares provinents d’aerogeneradors, 70% de vehicles elèctrics i 40% de la resta de productes que contenen aquests metalls. La recerca presentada en aquesta tesi es basa, principalment, en la investigació de noves rutes hidrometal·lúrgies, la majoria d’elles utilitzant líquids iònics, que puguin ser implementades en processos de recuperació de terres rares a partir de residus tecnològics. D’altra banda, s’han elaborat models matemàtics dels sistemes d’extracció reportats que pretenen convertir-se en una eina computacional, fàcilment adaptable, per a la predicció del comportament d’extracció en d’altres processos de recuperació amb diferents condicions experimentals.
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Souza, Ariane Gaspari Oliveira. "Recuperação de óxido de escândio de alta pureza de resíduos industriais da cadeia de produção do níquel." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-22082016-110903/.
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O Escândio é um elemento terra rara, utilizado principalmente em ligas de alumínio, células combustíveis de óxido sólido e na produção de lâmpadas de haletos metálicos. Apesar de ser o 31° elemento mais abundante na crosta terrestre, raramente é encontrado concentrado na crosta terrestre, e sua produção é sempre associada ao processamento de outros minerais na forma de um subproduto, ou a recuperação de sucata. Minérios de Níquel podem conter teores de Sc variando de 50 a 350ppm e resíduos gerados durante seu processamento pode concentrar o Sc acima de 1000ppm. A recuperação do Escândio de um resíduo da cadeia de produção do Níquel foi estudada, de modo a obter um óxido com pureza acima de 99,0% para aplicações industriais. O resíduo utilizado é um precipitado, na forma de hidróxido, e contém principalmente Fe, Cu, Ni e Co, sendo o teor de Escândio em base seca aproximadamente 1000ppm. O processo de recuperação proposto consiste na lixiviação atmosférica do resíduo, precipitação seletiva para concentração do escândio e extração por solventes. A lixiviação atmosférica em meio sulfúrico 2,0mol.L-1 a 70°C permitiu a recuperação de 92,5% do Escândio contido no resíduo. Entretanto, não foi seletiva, lixiviando também parte dos demais metais presentes. Após a lixiviação para concentrar o Escândio, antes da extração por solventes, foi realizada uma precipitação com NaOH. O intuito foi precipitar o Fe, principal contaminante presente no lixiviado, entretanto ocorreu a co-precipitação de 95,5% do Sc junto a 65,6% Fe em pH 2,0. O precipitado representou uma concentração do Escândio do resíduo em 5,6 vezes. Esse concentrado de Escândio obtido foi dissolvido em solução de H2SO4 para recuperação do Escândio por extração por solventes. O extrante escolhido foi o Cyanex 923, uma mistura de óxidos alquil-fósfinicos. O mecanismo de extração do Sc pelo Cyanex 923 observado foi a solvatação e a estequiometria da reação 1:2. Foi observado um aumento na extração do Sc com o aumento da concentração de H+. O processo de extração do Sc com o Cyanex 923 é exotérmico, sendo favorecido a temperatura ambiente. O teor de Fe na solução aquosa antes da extração é 35 vezes maior que o Escândio, e apesar do Cyanex 923 ser mais seletivo para o Sc do que para o Fe, parte do Fe é co-extraído. O Fe co-extraído foi removido da fase orgânica por meio de uma lavagem com H2SO4 3mol.L-1 com uma perda de Sc de 1,3%. A reextração do Sc na fase orgânica não foi efetiva utilizando ácidos fortes devido a formação de um complexo estável. Foi utilizado ácido oxálico, técnica consolidada para reextração de terras raras, para recuperação do Sc da solução orgânica e a recuperação do Sc foi de 84,3% para uma solução com 4,0% de ácido oxálico. O oxalato de Sc precipitado foi recuperado por filtração e calcinado a 600°C. O óxido obtido apresentou pureza mínima de 99,0%.Scandium is a rare earth element, used mainly in special aluminum alloys, SOFC\'s and metal halide lamps production. Despite of being the 31st element more abundant in Earth\'s Crust, it is rarely found concentrated in ores, and its production is always related to other minerals processing as a by-product or scrap recovering. Scandium content in Nickel ore may vary between 50 and 350ppm and residues produced during its processing can concentrate Sc above 1000ppm. Scandium recovery from a residue of Nickel processing was studied in order to obtain an oxide with purity higher than 99,0% for industrial applications. The residue used is a hydroxide precipitate, which contains mainly Fe, Cu, Ni and Co, Sc content is around 1000ppm (dry basis). The recovery process proposed consists in atmospheric leaching of the residue, selective precipitation to concentrate the Scandium and solvent extraction. The atmospheric leaching in sulfuric acid 2,0mol.L-1 at 70°C allowed the recovery of 92,5% of the Scandium present in the residue. However it was not selective and part of the other metals present in the residue were also leached. After leaching, in order to concentrate the Sc before solvent extraction, a precipitation with NaOH was performed. The initial aim was to precipitate the Iron - main contaminant present in the leach liquor - nevertheless it occurred the co-precipitation of 95,5% of the Sc besides 65,6% of Fe in pH 2,0. The precipitantion represented a concentration of the Sc in the residue of 5,6 times. The Scandium concentrate obtained was dissolved in a sulfuric acid solution to Sc recovery by solvent extraction. The extractant selected was Cyanex 923, a mixture of alkyl-phosphinic oxides. The mechanism of extraction of Scandium observed was solvation and reaction stechiometry was 1:2. It was observed an increase in Sc extraction rates by increasing the concentration of H+. The extraction of Scandium with Cyanex 923 is exothermic, and favorable at room temperature. The Iron content in aqueous solution before extraction is 35 times higher than that of Scandium, and even though Cyanex 923 being more selective for Sc than Fe, part of the Fe is co-extracted. The Fe co-extracted was removed of the organic phase by H2SO4 3mol.L-1 scrubbing with a Sc loss of 1,3%. The stripping of Scandium from organic phase was not accomplished by using strong acids due to formation of a stable complex. Afterwards, it was used oxalic acid - a technique consolidated for rare earths stripping - and the Sc recovery of organic phase was 84,3% with a solution of 4,0% oxalic acid. The Scandium oxalate precipitated was recovered by filtration and calcinated at 600°C. The Scandium oxide obtained presented 99,0% minimum purity.
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Fatoba, Ojo Olanrewaju. "Chemical interactions and mobility of species infly ash-brine co-disposal systems." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5672_1305271283.
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The primary aim of these coal fired industries for co-disposing fly ash and brine was to use the fly ash as a sustainable salt sink. It is therefore important to study the interaction chemistry of the fly ash-brine systems to fully understand the leaching and mobility of the contaminant species, and to determine the possibility of capturing the salts from the brine solution when fly ash and brine are co-disposed. In order to achieve the aims and objectives of this study, several leaching procedures such as batch reaction tests, long-term fly ash-brine interaction tests, acid neutralization capacity (ANC) tests, up-flow percolation tests and sequential extraction tests were employed. The geochemical modeling software was applied to predict the formation of secondary mineral phases controlling the release of species in the fly ash-brine systems. Several analytical techniques such as x-ray diffraction (XRD), x-ray fluorescence (XRF), scanning electron microscopy-energy dispersion spectroscopy (SEM-EDS), inductively coupled plasma-mass spectroscopy (ICP-MS) and ion chromatography (IC) were applied to characterize the fresh fly ashes, solid residues recovered from the fly ash-brine interaction tests, the brine sample used in this study and the leachate samples in order to determine the chemical and mineralogical compositions and speciation of the waste materials.
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Bíscaro, Thaís [UNESP]. "Avaliação da disponibilidade de boro em um latossolo de Mato Grosso/MT." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/86425.
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Em algumas condições não se têm obtido correlações entre os teores de B do solo, extraído com água quente, o teor de boro na planta e a produtividade da soja no Estado do Mato Grosso, mais precisamente na região de Campo Novo do Parecis. Sabe-se que o boro é um nutriente fortemente adsorvido nas partículas minerais do solo. Objetivou-se com este trabalho submeter amostras de solo de uma determinada área de estudo, na qual foi cultivada soja por três anos consecutivos e posteriormente cultivado algodão, a diferentes métodos de extração de boro, a fim de se estabelecer correlações entre a dose de boro na planta, a dose de nutriente aplicada e o teor de boro no solo disponível às plantas e, ainda, com a produtividade da soja. Amostras de solo, cultivadas com soja, coletadas por ocasião da condução do experimento no campo, foram analisadas quanto à concentração de B extraída pelos métodos: água quente modificado com solução de BaCl2 1,25 g L-1 (recomendado e chamado de método da água quente pelo IAC); água quente modificado com solução de CaCl2 0,01 mol L-1,a quente e água quente tradicional (o qual é preconizado por muitos autores como o método oficial) para dessa forma, tentar quantificar a real disponibilidade de boro neste solo, caracterizado como um LATOSSOLO VERMELHO AMARELO (LVA), possibilitando a determinação de um nível crítico. Ainda, durante o período de condução do trabalho, foi feito um estudo de adsorção de B nas amostras, e um estudo do comportamento da lixiviação do nutriente em colunas de solo, procurando verificar o efeito das adubações na dinâmica do nutriente. Em relação aos métodos de extração de boro no solo, o CaCl2 foi o que apresentou correlação positiva e significativa com o boro presente no tecido vegetal nos três anos agrícolas. Os métodos do BaCl2 e...
In some conditions, doesn't have obtained correlations among boron content in soil, boron extracted by hot water, boron content in plants and soybean productivity in a region (Campo Novo do Parecis) of the state of Mato Grosso/Brazil. This work was carried out to submit soil samples from determined area of study where was tillage soybean for three subsequent years and after tillage cotton, to differents extraction methods by boron with the aim to establish correlations among, amount of boron content in plants, amount of nutrient putted in soil, boron content in soil disponible to plants and the productivity. Soil samples obtained during the conduction of experiment on field were analyzed to predict the amount of boron in soil by the methods: hot water modified with BaCl2 solution (recommended and called by hot water from IAC - Instituto Agronômico de Campinas/SP-Brazil), hot water modified CaCl2 0,01 mol L-1 solution and hot water traditional (which is preconized by many authors like the official method) to this way try to quantify the real situation of boron disponibility in this soil, characterized like a Yellow Red Latossol, to take the determination of a critical level. During the conduction period of this work was made an adsorption study in the samples, and still a study of boron leaching behavior in soil columns, to verify fertilizer effect in nutrient dynamic. The extraction method with CaCl2 presented positive and significative correlation with boron present in soybean leaves on three subsequent farm work years. BaCl2 method and hot water traditional also presented positives and significatives correlations each one in two farm work years, this results were expected in function of similarity among three methods, it's an evidence that there is a method with capacity to predict boron disponibility in soils of Mato Grosso... (Complete abstract, click eletronic address below)
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Bíscaro, Thaís 1978. "Avaliação da disponibilidade de boro em um latossolo de Mato Grosso/MT /." Botucatu : [s.n.], 2005. http://hdl.handle.net/11449/86425.
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Orientador: Ciro Antonio RosolemBanca: Dirceu Maximino Fernandes
Banca: José Carlos Casagrande
Resumo: Em algumas condições não se têm obtido correlações entre os teores de B do solo, extraído com água quente, o teor de boro na planta e a produtividade da soja no Estado do Mato Grosso, mais precisamente na região de Campo Novo do Parecis. Sabe-se que o boro é um nutriente fortemente adsorvido nas partículas minerais do solo. Objetivou-se com este trabalho submeter amostras de solo de uma determinada área de estudo, na qual foi cultivada soja por três anos consecutivos e posteriormente cultivado algodão, a diferentes métodos de extração de boro, a fim de se estabelecer correlações entre a dose de boro na planta, a dose de nutriente aplicada e o teor de boro no solo disponível às plantas e, ainda, com a produtividade da soja. Amostras de solo, cultivadas com soja, coletadas por ocasião da condução do experimento no campo, foram analisadas quanto à concentração de B extraída pelos métodos: água quente modificado com solução de BaCl2 1,25 g L-1 (recomendado e chamado de método da água quente pelo IAC); água quente modificado com solução de CaCl2 0,01 mol L-1,a quente e água quente tradicional (o qual é preconizado por muitos autores como o método oficial) para dessa forma, tentar quantificar a real disponibilidade de boro neste solo, caracterizado como um LATOSSOLO VERMELHO AMARELO (LVA), possibilitando a determinação de um nível crítico. Ainda, durante o período de condução do trabalho, foi feito um estudo de adsorção de B nas amostras, e um estudo do comportamento da lixiviação do nutriente em colunas de solo, procurando verificar o efeito das adubações na dinâmica do nutriente. Em relação aos métodos de extração de boro no solo, o CaCl2 foi o que apresentou correlação positiva e significativa com o boro presente no tecido vegetal nos três anos agrícolas. Os métodos do BaCl2 e ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In some conditions, doesn't have obtained correlations among boron content in soil, boron extracted by hot water, boron content in plants and soybean productivity in a region (Campo Novo do Parecis) of the state of Mato Grosso/Brazil. This work was carried out to submit soil samples from determined area of study where was tillage soybean for three subsequent years and after tillage cotton, to differents extraction methods by boron with the aim to establish correlations among, amount of boron content in plants, amount of nutrient putted in soil, boron content in soil disponible to plants and the productivity. Soil samples obtained during the conduction of experiment on field were analyzed to predict the amount of boron in soil by the methods: hot water modified with BaCl2 solution (recommended and called by hot water from IAC - Instituto Agronômico de Campinas/SP-Brazil), hot water modified CaCl2 0,01 mol L-1 solution and hot water traditional (which is preconized by many authors like the official method) to this way try to quantify the real situation of boron disponibility in this soil, characterized like a Yellow Red Latossol, to take the determination of a critical level. During the conduction period of this work was made an adsorption study in the samples, and still a study of boron leaching behavior in soil columns, to verify fertilizer effect in nutrient dynamic. The extraction method with CaCl2 presented positive and significative correlation with boron present in soybean leaves on three subsequent farm work years. BaCl2 method and hot water traditional also presented positives and significatives correlations each one in two farm work years, this results were expected in function of similarity among three methods, it's an evidence that there is a method with capacity to predict boron disponibility in soils of Mato Grosso... (Complete abstract, click eletronic address below)
Mestre
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Ferreira, Marcos Manoel. "Estudo da mobilidade e da biodisponibilidade do arsênio em solos e sedimentos de Paracatu-MG." Niterói, 2016. https://app.uff.br/riuff/handle/1/1666.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ
Este estudo buscou avaliar a contaminação, a mobilidade e a bioacessibilidade do As na água subterrânea e em solos e sedimentos superficiais, em uma área de mineração de ouro no município de Paracatu-MG. O As apresentou valores abaixo do limite estabelecido pela legislação brasileira (< 10 g.L-1) em todas as amostras de águas subterrâneas. As avaliações realizadas indicam que as condições físicoquímicas encontradas, juntamente com as características geológicas da região são fatores preponderantes para estes baixos teores. Nas amostras de solos e sedimentos, a concentração de As total variou de 32,9 a 1280 g.g-1 e de não detectável a 4727 g.g-1, respectivamente. Os maiores teores de As nos sedimentos e solos foram encontrados na bacia do córrego Rico, mostrando a influência direta dos processos oriundos da área de mineração em sua nascente. As demais áreas apresentaram teores inferiores a esta área, mas acima da média mundial e do folhelho médio, podendo estar sob a influência de alguns processos, tais como, a ciclagem biogeoquímica natural deste elemento, deposição de sedimentos por erosão hídrica, descarga de águas subterrâneas, e dispersão atmosférica de material particulado enriquecido em As, oriundo da área de mineração. Todos estes processos proporcionam em maior ou menor proporção o enriquecimento de As na região. De acordo com os ensaios de extração sequencial utilizados, em todas as amostras de solos e sedimentos, as frações solúvel e trocável exibiram valores extremamente baixos, correspondendo a menos de 2 % do teor total de As contido nestas amostras, mostrando baixa disponibilidade do As para o ambiente nos solos e sedimentos em Paracatu. A mobilidade do As trocável nos solos de Paracatu foi avaliada através de experimentos de lixiviação em coluna. Os resultados mostraram uma associação do As com os óxidos e hidróxidos de Fe que favorecem a retenção deste metaloide nos solos mesmo na fração trocável. Segundo os resultados deste e de outros estudos, a adição de Ca a solos contaminados favorece o processo de retenção do As, mostrando grande potencial na utilização de compostos deste elemento em estratégias que visem a remediação de áreas contaminadas.
This study aims to evaluate the mobility and inaccessibility of As in groundwater and in surface soils and sediments in a mining area of gold in the Paracatu municipality- MG. The Arsenic concentrations in all the groundwater samples showed below the established limits by the Brazilian legislation (< 10 μg.L-1). The evaluations were indicating that the physical-chemical conditions encountered together with the geological characteristics of the region are predominant factors responsible to these lower values. In the soil and sediment samples, the concentration of As varied from 32,9 to 1280 μg.g-1 and to below detection limit to 4727 μg.g-1 respectively. The higher values of As in the sediments and soils were found in the Rico stream, showing the direct influence of the processes coming from its source of the mining area. The other areas showed inferior values to this area, but above world average and of the shale values, which may be under the influence of some processes, such as the natural biogeochemical cycling of this element, deposition of sediment by hydrological erosion, groundwater discharge and atmospheric dispersion of particulate material originated by mining. All these processes provide in proportions more or less the As enrichment in the region. According to the sequential extraction tests utilized, in all the soils and sediments samples, the soluble and exchangeable fractions exhibited extremely lower values corresponding less than 2% of the total As in these samples. These results showed low availability of As to the environment by the soils and sediments in Paracatu. The mobility of the exchangeable As in the soils of Paracatu was assessed through column leaching experiments. The results showed an association of the As with the Fe oxides and hydroxides which favors to retain this metalloid even in the exchangeable fraction in the soils. According to the results of this and other studies, an addition of Ca to the contaminated soils favors the process of the As retention, showing great potential in the use of compounds of this element in strategies that aimed at the remediation of contaminated areas
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Soukeur, Abderraouf. "Valorisation des éléments de terres rares par procédés membranaires (ETR lourds)." Electronic Thesis or Diss., Rennes 1, 2022. http://www.theses.fr/2022REN1S073.
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Cette thèse intègre le cadre général de la thématique de recherche scientifique du laboratoire d’hydrométallurgie et chimie inorganique moléculaire ex valorisation des minerais de l’USTHB. Le travail concerne la valorisation des éléments de terres rares lourds (ETRLs) contenus dans les ressources secondaires notamment les sous-produits miniers et les équipements électroniques en fin de vie par des procédés innovants et peu coûteux. Ce travail porte sur la faisabilité des techniques de séparation pour la valorisation des éléments de terres rares lourds (ETRLs) à partir d'un déchet industriel issu de l'exploitation des minerais de phosphate de "Djebel Onk" dans la région de Tébessa à l’Est de l’Algérie et les déchets électroniques après lixiviation menant à des solutions enrichies en éléments de terres rares suivie d’une extraction en utilisant des extractants organophosphorés et/ou des procédés membranaires. Des échantillons libellés de T1 jusqu’à T7 du minerai d'apatite provenant de Djebel Onk (Tébessa, Algérie) ont été fournis par la société Somiphos. D’après les analyses qui ont été effectuées sur tous les échantillons, l'échantillon T1 a été sélectionné dans cette étude car contenant la plus forte teneur en ETRs. Les résidus solides ont été d'abord lixiviés avec trois différents acides inorganiques (HNO3, H2SO4 et H3PO4) à des concentrations et des temps de lixiviation variés dans le but d’atteindre les paramètres optimaux. Les résultats des essais de lixiviation montrent un rendement très élevé d’ETRs avec l’acide HNO3 de concentration 3N durant 24h, ensuite une extraction liquide-liquide a été mise en œuvre avec deux exctactants TOPO et D2EHPA et des essais de micro flottaison en utilisant l’oléate de sodium et l’alkylhydroxylamine comme collecteurs dans différentes conditions. D’importants taux de récupération des phosphates ont été obtenus. Par ailleurs, une série de membranes ont été synthétisées ou modifiées (NF270, NF90, NP030 et SB90) dans la perspective d’être utilisées pour la séparation entre terres rares. Toutes les membranes élaborées ont été caractérisées. Les résultats obtenus permettent de proposer un protocole valorisant les ETRs contenus dans les ressources secondaires. La membrane NF90 modifiée par PEI/PDA pendant 48h a permis l’obtention des meilleurs rendements de purificationThis thesis integrates the general framework of the scientific research theme of the laboratory of hydrometallurgy and molecular inorganic chemistry ex valorization of ores of the USTHB. The work concerns the valorization of heavy rare earth elements (HREE) contained in secondary resources, in particular mining by-products and end-of-life electronic equipment, by innovative and low-cost processes. This work deals with the feasibility of separation techniques for the recovery of heavy rare earth elements (HREE) from an industrial waste resulting from the exploitation of phosphate ores of "Djebel Onk" in the eastern region of Tebessa in Algeria and electronic waste after leaching leading to solutions enriched in rare earth elements followed by an extraction using organophosphorus extractants and/or membrane processes. Samples labelled T1 to T7 of apatite ore from Djebel Onk (Tébessa, Algeria) were provided by the company Somiphos. Based on the analyses that were performed on all samples, sample T1 was selected in this study as containing the highest content of REEs. The solid residues were first leached with three different inorganic acids (HNO3, H2SO4, and H3PO4) at various concentrations and leaching times in an attempt to achieve the optimal parameters. The results of the leaching tests show a very high yield of REEs with HNO3 acid of 3N concentration during 24h, then a liquid-liquid extraction was implemented with two exctactants TOPO and D2EHPA and micro flotation tests using sodium oleate and alkylhydroxylamine as collectors under different conditions. Significant phosphate recovery rates were obtained. In addition, a series of membranes were synthesized or modified (NF270, NF90, NP030 and SB90) with the prospect of being used for rare earth separation. All the elaborated membranes have been characterized. The results obtained allow us to propose a protocol to valorize the REEs contained in the secondary resources. The NF90 membrane modified by PEI/PDA for 48h allowed the best purification yields to be obtained
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Sharma, Shekar. "Evaluating Leachability of Residual Solids Generated from Unconventional Shale Gas Production Operations in Marcellus Shale." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50514.
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Hydraulic fracturing operations utilized for shale gas production result in the generation of a large volume of flowback and produced water that contain suspended material, salts, hydrocarbons, metals, chemical additives, and naturally-occurring radioactive material. The water is impounded at drilling sites or treated off-site, resulting in significant generation of residual solids. These are either buried on site or are disposed in lined landfills. The objective of this study was to determine the levels of heavy metals and other elements of concern that will leach from these residual solids when placed in typical disposal environments.
For this purpose, laboratory leaching experiments were employed wherein representative samples were brought into contact with a liquid to determine the constituents that would be leached by the liquid and potentially released into the environment. The samples used included sludge resulting from the physicochemical treatment of process water (TS), sludge solidified with cement kiln dust (SS), raw solids obtained by gravity separation of process water (RS), and drilling mud (DM). The samples were subjected to both single extraction (i.e. Shake Extraction Test, SET) and multiple extraction (i.e. Immersion Test, IT) leaching tests. For the shake extraction test, samples were mixed with a specific amount of leaching solution without renewal over a short time period. In the immersion test, samples were immersed in a specific amount of leaching solution that was periodically renewed over a longer period of time. For both these tests, analyses were performed on the filtered eluate. The tests were performed as per standards with modifications. Distilled de-ionized water, synthetic acid rain (pH ~ 4.2), weak acetic acid (pH ~ 2.88), and synthetic landfill leachate were used as leaching solutions to mimic specific disposal environments.
Alkali metals (Li, K, Na), alkaline earth metals (Ba, Ca, Mg, Sr) and a halide (Br), which are typically associated with Marcellus shale and produced waters, leached at high concentrations from most of the residual solids sample. The SS sample, due to its stabilization with CKD, had a lower extraction efficiency as compared to the unconsolidated TS and RS samples. In EF 2.9 and EF SLL, the leaching took place under acidic conditions, while for EF DDI and EF 4.2, the leaching occurred in alkaline conditions. EF 2.9 and EF SLL were determined to be the most aggressive leaching solutions, causing the maximum solubility of most inorganic elements. Thus, high amounts of most EOCs may leach from these residual solids in MSW landfills disposed under co-disposal conditions. Agitation, pH and composition of the leaching solution were determined to be important variables in evaluating the leaching potential of a sample.
The results of this study should help with the design of further research experiments being undertaken to develop environmentally responsible management/disposal strategies for these residual solids and also prove useful for regulatory authorities in their efforts to develop specific guidelines for the disposal of residuals from shale gas production operations.Master of Science
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Santos, Wdson Costa. "Contribuição para avaliação de influência do tratamento preliminar de amostra sobre a confiabilidade das informações analíticas." reponame:Repositório Institucional da UFBA, 2012. http://www.repositorio.ufba.br/ri/handle/ri/11728.
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CAPES
No presente trabalho foram investigados os efeitos sobre a recuperação de elementos causados por modificações em processos prévios a amostragem laboratorial e lixiviação dos analitos das polpas de abóbora e batata. Inicialmente, foi avaliado o efeito da inversão na ordem de operações do procedimento de tratamento preliminar das amostras brutas das polpas sobre as recuperações dos elementos. As amostras das polpas foram secas para posterior trituração (PA) ou as amostras foram trituradas antes de serem submetidas à secagem (PB). Os resultados obtidos empregando ambos os procedimentos foram comparados para 95% de confiança e eles mostraram diferenças significativas para alguns elementos determinados na amostra de batata. As concentrações de K, P e Mn, na polpa de batata, determinadas aplicando o primeiro procedimento de pré-tratamento (PA) foram 13,6±0,4 mg K g-1, 1,95±0,04 mg P g-1 e 5,7±0,2 μg Mn g-1, enquanto 12,2±0,3 mg K g-1, 1,62±0,03 mg P g-1 e 2,6±0,2 μg Mn g-1 foram determinadas quando a mesma amostra bruta foi submetida ao pré-tratamento PB para a obtenção da amostra teste. Em contraposição, no caso da amostra bruta de polpa de abóbora, os resultados para os elementos (K, P, Mn, Mg) foram maiores quando a polpa foi previamente esmagada antes da secagem. Em um estudo independente, a eficiência da extração de metais de amostras de polpas trituradas de abóbora ou batata para soluções diluídas de HNO3 foi avaliada variando o modo (agitação mecânica ou irradiação ultrassônica) e o período (de 10 a 30 min) de agitação, bem como a concentração da solução de HNO3 na solução de lixiviação (de 0,7 a 2,1 mol L-1). Os resultados foram também comparados com aqueles obtidos nas digestões assistidas por micro-ondas das amostras teste v em meio nítrico-peróxido. Foi observado que para ambas as amostras teste (abóbora e batata) e independentemente do modo ou período de agitação que a eficiência de extração de Ca, K, Mg e Mn foi diminuída para solução para 2,1 mol L-1 HNO3. Uma melhora no nível de recuperação de P foi obtida quando a lixiviação foi realizada com soluções diluídas de HNO3 (0,7 e 1,4 mol L-1) e sob irradiação ultrassônica. Esse efeito foi relacionado à presença de átomos de fósforo em moléculas estruturais de células de abóbora e batata, bem como à cominuição (ou fragmentação) das partículas submetidas a um campo ultrassônico intenso. Contudo, efeitos indesejados foram também observados para alguns elementos quando submetidos às lixiviações assistidas com ultrassom, como exemplificado pelo teor de cálcio determinado após a lixiviação da amostra teste de batata ter atingido valor 2,3 vezes maior que o valor obtido após a mineralização da amostra em micro-ondas. Muitos desses efeitos foram relacionados à erosão da superfície interna frascos irradiados.
Salvador
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Gilligan, Rorie. "The extractive metallurgy of brannerite: Leaching kinetics, reaction mechanisms and mineralogical transformations." Thesis, Gilligan, Rorie (2017) The extractive metallurgy of brannerite: Leaching kinetics, reaction mechanisms and mineralogical transformations. PhD thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/36793/.
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Brannerite, ideally UTi2O6 is a refractory uranium mineral found in many uranium and rare earth element ore deposits around the world, including many in Australia. As brannerite is refractory, ores containing brannerite require more intense leaching conditions than typical uranium ores. Brannerite is the most common refractory uranium mineral, and the most important uranium ore mineral after uraninite (UO2) and coffinite (U(SiO4)1-x(OH)4x).
Several high-brannerite uranium deposits in Australia remain un-developed, despite being discovered as early as the 1950s. The aim of this study was to understand the leaching chemistry of brannerite in a variety of systems, starting with the conventional acidic ferric sulphate system and alternatives including the ferric chloride-hydrochloric acid system and the alkaline-carbonate system. The principal assumption is that an improved understanding of the leaching chemistry of brannerite will lead to more effective extraction processes, improving the extractions at existing mines, and enabling the development of new ones.
Brannerite was found to undergo congruent dissolution in acid, contrary to the often-reported mechanism in which a titanium oxide coating forms on the surface. Phosphate released by gangue minerals such as apatite can cause the formation of this layer however. When leaching with acidic ferric solutions, sulphate media is superior to chloride media. Alkaline carbonate leaching was also found to be effective for brannerite leaching, albeit much slower than acid leaching. These same alkaline leaching conditions were applied to a sample of refractory uranium ore from Queensland high in acid soluble gangue and shown to be effective. These findings are discussed in detail below.
A sample of brannerite from the Dieresis deposit in the Sierra Albarrana region of Spain was characterised in detail by XRD and SEM-EDX methods. The brannerite was found to be altered and metamict (rendered amorphous by self-irradiation), as is typical for brannerite. Many brannerite particles contained linear zones of titanium oxide surrounded by silicon enriched and uranium depleted brannerite, consistent with descriptions of naturally altered brannerite. These altered zones were more susceptible to leaching, regardless of the leaching conditions. All leached residues were analysed by the same methods to understand the changes taking place in the solid phase during leaching. This suggests that the extent of natural alteration influences the leachability of a particular brannerite.
The leaching of brannerite was studied in acidic ferric sulphate media (0.05 mol/L or 2.8 g/L Fe3+) over a range of temperatures (25-96°C) and acid concentrations (10-200 g/L H2SO4) for five hours. Leached brannerite was pitted and corroded. The rate of leaching was strongly dependent on temperature and weakly dependent on acid concentration. At lower temperatures, brannerite dissolved incongruently in the early stages of leaching. At higher temperatures brannerite dissolved congruently for the entirety of the leaching experiment. The transition between these two mechanisms happened at lower temperatures when the acid concentration was higher. In the incongruent dissolution reaction, the activation energies for uranium and titanium release were 36 and 48 kJ/mol respectively. In the congruent dissolution process, the activation energy was 23 kJ/mol for both uranium and titanium dissolution.
At high temperatures (>75°C) and low acid concentrations (<25 g/L H2SO4), the concentration of titanium dropped after the first hour of leaching and some secondary anatase (TiO2) formed. This anatase was distinct from the anatase in the original material in that it contained iron and did not contain uranium, confirming that it formed during leaching.
Ferric chloride and cupric sulphate lixiviants were studied over a similar range of temperatures and acid concentrations. As with the ferric sulphate leaching tests, the oxidising cation concentration was kept constant at 0.05 mol/L. The leaching behaviour of brannerite in cupric sulphate media was quite similar to what was observed in ferric sulphate media; the rate of leaching was slightly lower than what was observed in ferric sulphate media under comparable conditions. In chloride media, the rate of leaching was slow compared to sulphate media at the same temperature and acid concentration. This suggests that the formation of stable uranium complexes is an important part of the dissolution process. Uranyl sulphate complexes are much stronger than uranyl chloride complexes.
Certain leaching experiments were repeated with the addition of minerals commonly associated with brannerite to gain a clearer understanding of the effects of deleterious gangue. These experiments were run at the extremes and middle of the range of temperatures and acid concentrations studied. Ilmenite accelerated the precipitation of anatase while fluorite significantly increased the rate of uranium and titanium dissolution. Fluorapatite greatly reduced the rate of brannerite dissolution. These results showed a previously unknown interaction between phosphorus and titanium. Phosphate helped to initiate the formation of a titanium oxide coating on the leached brannerite, inhibiting the leaching reaction. Higher concentrations of sulphuric acid reduced these negative effects. Interestingly, phosphate improved the rate of leaching in chloride media, suggesting that chloride leaching may be a viable option when processing high-phosphate refractory uranium ores.
Alkaline leaching may be an effective alternative processing option. While it is often reported that brannerite and similar minerals will not readily dissolve in alkaline media, leaching experiments with sodium carbonate based lixiviants showed that alkaline leaching of brannerite is possible. Compared with acid leaching, it is slow however. Uranium extractions of 83% were achieved over 24 hours of leaching at 90°C in sodium carbonate media. These leaching experiments were repeated with a high-carbonate refractory uranium ore from Queensland and resulted in comparable extractions. Alkaline leaching is a viable alternative when dealing with high-acid consuming ores that contain brannerite.
This study has shed more light on the reaction mechanisms involved in brannerite leaching in typical industrial leaching systems, resulting in a much clearer understanding of brannerite leaching chemistry, potentially enabling the extraction of uranium from overlooked ore deposits. Mineral texture and alteration were also found to influence brannerite leaching. The negative and positive effects of certain gangue minerals have been understood in greater detail, and ways of mitigating or utilising these effects have been devised. Finally, alkaline leaching has been tested and shown to be effective for the leaching of brannerite and refractory uranium ores. Further work is needed to establish the most effective range of conditions and reagent dosages for the leaching of refractory uranium ores and develop economically viable processes based on this new information.
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Mwase, James Malumbo. "An investigation of cyanide-based heap leaching for extracting precious metals from Platreef ore." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/28335.
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Cyanide heap leaching had been proposed as an alternative to the classic crush-mill-loatsmelt-refine route for processing platinum group metals (PGMs) from the Platreef ore body. Overall the process includes two stages of leaching. The first stage involves the thermophile bioleaching of the base metal (BM) sulphide minerals and acts as a form of pre-treatment to oxidise sulphur compounds and recovery valuable metals such as Cu, Ni and Co. The second stage focuses on cyanide-based heap leaching for the recovery of precious metals (PGMs +gold) from the solid residue of the first stage. Exploration and optimisation of this second stage in the context of a whole ore Platreef material is the focus of the present study. The first part of the study used a series of laboratory tests simulating heap leaching, conducted on coarse ore. The initial tests showed high recoveries of base metals (Cu, Ni and Co) could be achieved in a pre-treatment bioleach process, while in the second stage cyanide leach high levels of Pd and Au were extracted, but only 58% of the Pt after 60 days from the whole ore. It was observed that during the 60 day leaching period the rate of Pt leaching decreased considerably after 35 days. From the trajectory of the Pt leach curve from the 35 day mark onwards, it was observed that the leaching would not cease even after 60 days but would likely proceed but at that slow pace which indicated further Pt extraction would not be commercially viable in the long run. Mineralogical analysis has indicated that a significant component of the Pt in the ore is in the form a mineral sperrylite (PtAs2), which appears to leach slowly in cyanide as compared to other mineral forms such as certain tellurides and sulphides in the ore. Subsequently, efforts were made to investigate methods to improve the second stage leach process, in terms of Pt leaching from sperrylite, through further work on a pure mineral sample. The key focus was on finding a suitable oxidant that can be used in cyanide solutions, from among air, oxygen and ferricyanide, to facilitate the dissolution. Various tests using sperrylite mineral samples micronized to 5 μm in batch stirred tank reactors (BSTR) at 50°C were conducted. It was found that a combination of ferricyanide with cyanide extracted as much as 16 times more Pt than tests using only cyanide. The presence of air or pure oxygen did not contribute significantly to the amount of Pt leached in this system and made no difference at all in the leach tests using only cyanide. Further bench-scale studies focused on characterising the leaching mechanism of sperrylite in cyanide-ferricyanide solutions. It was found that the reaction, after proceeding at appreciable rates initially, tended to cease after 1 day, indicating some form of surface passivation, tentatively related to some form of solution equilibrium being achieved. However after re-leaching the sample with fresh solution, the Pt dissolution improved tremendously. This was further investigated in continuous leaching of a sample of the mineral using a small bed of sperrylite fixed in mini-columns. The results from the minicolumns showed the same leaching pattern as the experiments using BSTRs. It was eventually revealed that a suitable wash of the sperrylite sample using water removes the inhibiting layer and facilitates further and improved leaching. Unlike the cyanide-only system where the passivation was attributed to As build-up at the surface, in the cyanide-ferricyanide system it was attributed to adsorption of unknown reaction products on the mineral surface. Residual samples from batch leach experiments were analysed using X-ray photoelectron spectroscopy and showed samples from the cyanide-ferricyanide tests had less As on the surface than the untreated sample and the sample leached in cyanide. To some degree this supported the hypothesis that Pt leaching is eventually hindered by As passivation in a cyanide system. The presence of ferricyanide serves to oxidise As and thereby release more Pt in solution. Additionally, electrochemical techniques using a sperrylite electrode were employed to further understand the redox reaction under varying oxidation conditions. While the tests indicated a weak current under mildly oxidising conditions in cyanide solutions, this became rapidly limiting at potentials expected in a ferricyanide solution, indicating a form of surface passivation. An attempt was made to determine the number of electrons transferred during Pt dissolution to indicate the primary reaction mechanism through a long-term test held at constant potential, but dissolution rates were too small to be conclusive. Hence the study has shown that the cyanide-based heap leaching of PGMs from Platreef type ores is feasible in principle, but the dissolution of PtAs2 remains limited. While the study has given valuable pointers to understanding this observation, the conclusion is that PtAs2 is refractory in the given context and further development of this process remains promising through further investigation into the use of the cyanide-ferricyanide combination.
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Migeon, Valérie. "Application des isotopes du molybdène en traçage des matériaux du cycle nucléaire." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN008/document.
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Au cours de ces dernières décennies, des études ont étés menées pour identifier plusieurs traceurs des matériaux du cycle du combustible nucléaire, dans le cadre de la lutte contre la prolifération nucléaire. Ces matériaux sont généralement collectés lors d’inspections dans des installations nucléaires, ou saisis lors de contrôles de trafics illicites. Les informations fournies par ces traceurs sont parcellaires et ne permettent pas de déterminer avec exactitude la provenance et l’historique industriel de ces matériaux.Le but de ce travail de thèse est de démontrer le potentiel de l’utilisation des isotopes du molybdène pour le traçage des matériaux du cycle du combustible nucléaire. Le choix s’est porté sur le molybdène car en raison de la similarité de leurs propriétés chimiques, le molybdène et l’uranium sont étroitement associés dans les minerais d’uranium et tout au long de la chaîne de purification de l’uranium. L’étude s’est focalisée sur une partie de l’amont du cycle du combustible, depuis l’extraction des minerais d’uranium jusqu’à la production des concentrés miniers d’uranium : divers procédés physiques et chimiques sont appliqués, à la fois pour purifier l’uranium et abaisser la concentration en molybdène.Au cours de cette étude, une nouvelle méthode de séparation du molybdène a été développée pour caractériser sa composition isotopique dans des minerais, minéraux et concentrés miniers d’uranium. La variabilité des compositions isotopiques du molybdène dans un gisement d’uranium est principalement due aux mécanismes d’adsorption et/ou de précipitation du molybdène. Les gisements magmatiques et sédimentaires ont des compositions isotopiques différentes, ce qui permet ainsi leurs distinctions. Les concentrés miniers d’uranium produits à partir de ces deux types de gisements ont des compositions isotopiques similaires aux minerais. Ces résultats soulignent ainsi le potentiel des isotopes du molybdène comme traceur des origines des concentrés miniers d’uranium. Cependant, un fractionnement des isotopes du molybdène a été établi lors de la production des concentrés miniers d’uranium pour deux usines au Niger. Les procédés de purification de l’uranium tels que la lixiviation, l’extraction par solvant et la précipitation ont été reproduits en laboratoire sur des échantillons réels pour expliquer le fractionnement isotopique du molybdène lors de la production des concentrés miniers. Au cours de ces procédés, le fractionnement peut être positif (lixiviation), négatif (extraction par solvant, précipitation à l’eau oxygénée) ou nul (précipitation à l’ammoniaque). Dans le cas des échantillons du Niger, la somme de ces procédés est négative, dans le sens des données expérimentales que nous avons obtenues, démontrant ainsi également le potentiel de l’utilisation des isotopes du molybdène comme traceur des procédés de transformations des matériaux du cycle du combustible nucléaireNuclear forensics aims at determining the age, provenance as well as industrial or storage history of uranium ores and uranium ore concentrates that are part of the nuclear fuel cycle. Several potential tracers have already been identified for this purpose. However, these tracers are not providing always unambiguous information. This study is focused on establishing Mo isotopes as a new tracer of uranium ore provenance and of ore processing for its application in nuclear forensics. Molybdenum and uranium share a number of common geochemical properties. In the nuclear fuel cycle, molybdenum is an impurity that is difficult to separate during uranium extraction and purification processes, while its concentration is required to be lower than some specification limits. We focused this study on the first part of the nuclear fuel cycle, from the uranium ores extraction to the production of uranium ore concentrates.We developed an enhanced separation method for Mo from a uranium-rich matrix (uranium ores, uranium minerals, uranium ore concentrates) in order to analyze the mass fractionation induced by processes typical of the nuclear fuel cycle. Molybdenum isotopic compositions in uranium ores depend of adsorption and precipitation processes. The δ98Mo values of sedimentary uranium ores is shifted to negative values relative to magmatic ores. This provides a means of distinguishing these types of uranium ores. Uranium ores concentrates produced from both uranium ore natures (magmatic and sedimentary) have Mo isotope compositions similar to the uranium ores. These results suggest that molybdenum isotopes have a strong potential of as a tracer for identifying the origin of the uranium ore concentrates. However, Mo isotopes fractionations were established during the production of uranium ore concentrates in the both Niger mills. We reproduced in laboratory the lixiviation, solvent extraction and precipitation processes to explain these observations. The Mo isotopes fractionation is positive for the lixiviation process, negative for the solvent extraction and precipitation with hydrogen peroxide, and null for ammonia precipitation. In the case of the Niger samples, the sum of these processes is negative and agrees with our experimental data. Mo isotopes have a strong potential as a tracer for identifying the origin and transformation of uranium in the nuclear fuel cycle, in the framework of nuclear forensics
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Haddadin, Jamal. "Études microbiologiques et cinétiques de la lixiviation bactérienne en réacteurs : effet de différents paramètres physico-chimiques, développement d'un procédé en réacteurs air-lift et lit-fluidisé et application à l'extraction de l'antimoine." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL063N.
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La lixiviation bactérienne est l'application biotechnologique la plus importante dans l'industrie métallurgique, celle-ci est utilisée pour la récupération des métaux par lessivage, utilisant les capacités que possèdent certains micro-organismes à solubiliser les métaux. Ce travail est divisé en quatre sections: premièrement, nous avons identifié la composition microbiologique de la culture mixte en notre possession. Cette culture mixte est composée de trois populations bactériennes. Deuxièmement, nous avons étudié l'influence de certains paramètres physico-chimiques tels que le pH, la température, la concentration en CO2, le taux de solides et l'ajout de Fe3+ au milieu réactionnel sur la cinétique de la biolixiviation, en culture discontinue. Ces études ont notamment conduit à la détermination d'un pH (1. 75), d'une température (32-37°C) et d'une concentration en CO2 (0,03 et 2% v/v) optimaux pour ce procédé. Troisièmement, nous avons comparé différents systèmes réactionnels (air-lift, lit fluidisé et mécaniquement agité) pour aider au choix d'une future technologie alternative. Notre dernière contribution a porté sur l'étude de la capacité de la culture mixte à oxyder des déchets industriels contenant de l'antimoine, en culture discontinue. Nous avons étudié le rôle important de l'interaction galvanique entre la pyrite et les résidus antimoniés sur la récupération de l'antimoine
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Tshibanda, Kabumana Dieudonne. "Contribution à la recherche d'un modèle de gestion d'un passif envronnemental issu d'un traitement métallurgique des minerais sulfurés cuivre zinc en République Démocratique du Congo." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209618.
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Ce travail traite d’un problème de pollution liée à la présence de métaux de base dans des passifs environnementaux issus d’un traitement métallurgique des minerais sulfureux cuivre – zinc provenant de la mine de Kipushi en République Démocratique du Congo. L’objectif principal de ce travail a été d’arriver à proposer des scénarios de gestion durable au passif environnemental de la filière présentant les risques environnementaux les plus élevés. Pour cela, on a d’abord procédé à une identification des différents problèmes environnementaux tout au long de la filière de traitement sur les quatre sites d’exploitation. Ensuite on a prélevé des échantillons puis procéder par des tests de disponibilité à la lixiviation à l’eau déminéralisée pour évaluer les fractions solubles des métaux de base présents et aussi par des tests de conformité de mise en décharge afin de classer ces rejets conformément à la directive européenne 2003-33-CE. Ainsi, les rejets Ex – UZK ont été identifiés comme les plus dangereux de la filière au regard de cette directive, car les quantités lixiviées de cuivre et de zinc dans ces rejets ont dépassé largement les limites fournies par la directive, et donc ils ne peuvent même pas être mis en décharge de classe I sans traitement métallurgique préalable pouvant permettre leur dépollution. Par contre, les autres rejets de la filière, en l’occurrence les rejets de flottation de Kipushi et les scories de fusion pour matte de cuivre, peuvent eux être acceptés en décharge de classe I, sans traitement préalable au regard des limites fournies par la même directive. Les procédés de lixiviation acide chaude et de digestion ont été proposés et retenus comme scénarios de gestion durable à appliquer à ces rejets Ex – UZK, car ils se réalisent tous deux en milieu acide sulfurique d’une part et d’autre part leur application et surtout leur faisabilité en République Démocratique du Congo reste possible ;en outre ils aboutissent à des nouveaux rejets contenant le fer sous forme d’hématite, pouvant être stocké aisément et durablement dans la nature, ce qui est conforme au principe du développement durable. Nous avons tenté de modéliser ces deux scénarios en discutant et comparant la circulation des flux de matière dans les deux procédés, d’abord autour de chaque opération métallurgique unitaire, et ensuite sur l’ensemble du procédé. Ainsi nous avons pu chiffrer tous les flux entrant et sortant dans le système étudié, en considérant 1000 kg de rejets Ex –UZK alimentés. Cette quantification nous a permis de comparer les coûts opératoires de ces deux procédés. Les résultats obtenus dans la présente étude sont encourageants et nous ont permis de formuler des recommandations pour les études ultérieures éventuelles dont les résultats pourront l’enrichir davantage, notamment sur les aspects technologiques, économiques et environnementaux, de manière à faciliter les applications sur terrain.
This work deals with environmental liabilities consisting of base metals pollution due to metallurgical processing of copper – zinc sulphide ores in Kipushi mine in Democratic Republic of Congo. The main objective of this work was to propose sustainable management scenarios for the most important environmental liabilities from metallurgical sector. For this purpose, liabilities were first identified on four metallurgical plants. Then, leaching tests with deionized water were carried out to assess the soluble fractions of base metals. These effluents were also classified according to the test described in european decision 2003-33-EC, which determines the conformity of waste to landfill. Ex – UZK effluents are the most dangerous from this sector, according to this directive, since the quantities of leached copper and zinc were far beyond the limits :they cannot be sent to class I landfill without prior metallurgical processing. However, other effluents like flotation wast and Lubumbashi slag originating from melting for copper matte, are acceptable without prior treatment. Hot acid leaching and digestion were proposed as sustainable management scenarios for to these Ex – UZK waste because :both can be performed in sulfuric acid and they are feasible in Democratic Republic of Congo. They also lead to an iron – rich waste consisting of hematite that can be stored easily and sustainably in nature, which is consistent with the principle of sustainable development. We have modeled these two scenarios by discussing and comparing the flows in both processes, first for each individual metallurgical unit process, and then for the whole chain of value. So we could assess all the inputs and outputs of the studied system, expressed per ton of Ex – UZK waste. The operating costs of both processes were calculated and compared. The results are encouraging. Recommendations were proposed for further studies, in order to investigate more deeply the technological, economical and environmental aspects, to facilitate the final application.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Tchoumou, Martin. "Hydrometallurgie du cuivre en milieu chlorure : attaques de minerais dosages polarographiques des solutions resultant de l'attaque et depot cathodique du cuivre." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13154.
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Etude dans le cadre de l'extraction de cu des minerais de type chalcopyrite. Lors de l'attaque des minerais de type chalcopyrite par des solutions de cu(ii) en milieu fortement chlorure, les metaux presents dans le minerai sous forme de sulfures passent en solution soit partiellement soit en totalite, et s elementaire precipite. Mise au point du dosage polarographique des ions cu, pb, zn et fe dissous. L'electrolyse de solutions a teneur elevee en cu(i) et contenant pb(ii), zn(ii) ou fe(ii) a mis en evidence un phenomene de codeposition de pb avec cu lorsqu'on opere a des densites de courant elevees, tandis que ni zn ni fe ne se codeposent avec cu
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Adipuri, Andrew Materials Science & Engineering Faculty of Science UNSW. "Chlorination of Titanium Oxycarbide and Oxycarbonitride." Publisher:University of New South Wales. Materials Science & Engineering, 2009. http://handle.unsw.edu.au/1959.4/44405.
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The project undertook a systematic study of chlorination of titanium oxycarbide and oxycarbonitride with the aim to develop further understanding of kinetics and mechanisms of the chlorination reactions. The project studied titania, ilmenite ores, and synthetic rutile reduced by carbon in argon and nitrogen and chlorinated at different temperatures, gas flow rates and compositions. Chlorination of titanium suboxides, iron and impurities in ilmenite was also examined. Chlorination of titanium oxycarbide Ti(O,C) or oxycarbonitride Ti(O,C,N) can be implemented at 200 to 400 deg.C, while the commercial chlorination process in the production of titanium metal or titania pigment requires 800 to 1100 deg.C. This makes chlorination of Ti(O,C) or Ti(O,C,N) an attractive technology in processing of titanium minerals. Chlorination reaction is strongly exothermal, which increased the sample temperature up to 200 deg.C above the furnace temperature. The chlorination of Ti(O,C) or Ti(O,C,N) was ignited at 150 deg.C to 200 deg.C depending on the sample composition. Their chlorination at 235 deg.C to 400 deg.C was close to completion in less than 30 min. The chlorination rate of titanium oxycarbide or oxycarbonitride increased with increasing gas flow rate. Sample composition had a significant effect on the extent of chlorination. The optimum results were obtained for titanium oxycarbide or oxycarbonitride produced with carbon to titania molar ratio of 2.5; these samples contained no detectable excess of carbon or unreduced titanium suboxides. In chlorination of reduced ilmenite ores and synthetic rutile, Ti(O,C) or Ti(O,C,N), metallic iron and Ti2O3 were chlorinated. The rate and extent of chlorination of titanium increased with increasing carbon to TiO2 ratio. Chlorination of Ti2O3 was slow relative to Ti(O,C) or Ti(O,C,N) and iron; chlorination of impurity oxides such as MgO, SiO2 and Al2O3 was not observed. The project also examined chlorination of Ti(O,C) or Ti(O,C,N) in ilmenite ore and synthetic rutile after removal of iron, which was achieved by aerated leaching of reduced samples in heated flask containing 0.37 M of ammonium chloride solution. Iron removal from the ilmenite ore or synthetic rutile resulted in higher rate and extent of chlorination of titanium oxycarbide or oxycarbonitride.
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Mocellin, Julien. "Ressources secondaires de métaux, valorisation par voie hydrométallurgique de résidus de sidérurgie pour la valeur en zinc, en manganèse et plomb." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0211/document.
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Entre le milieu du XIXème et du XXème siècle, le secteur sidérurgique a été l’une des principales sources de richesse en France. Toutefois, la production de ferromanganèse a généré une quantité considérable de déchets, notamment lors du lavage des fumées des hauts fourneaux. Ces boues d’épuration, riches en zinc (Zn), manganèse (Mn) et plomb (Pb) (5 à 40% en masse), ont été déposées dans des bassins de décantation en périphérie des sites sidérurgiques. Depuis la fermeture des usines, ces terrains sont restés en l’état et certains, comme à Pompey (Lorraine), ont été progressivement colonisés par la végétation. Compte tenu des risques sanitaires liés aux concentrations en métaux, une décontamination semble inévitable. Néanmoins, on prend conscience aujourd’hui de l’épuisement des ressources, et ces bassins apparaissent comme un gisement de ressources secondaires. Ce travail vise à développer un procédé hydrométallurgique pour extraire Zn, Mn et Pb de ces résidus, dans l’optique de récupérer ces métaux sous forme pure et revalorisable, tout en décontaminant ces sites. Tout d’abord, les expériences ont permis déterminer les conditions optimales (quantité d’acide, temps, température, ajout de réactifs, densité de pulpe) pour parvenir à extraire sélectivement Zn et Mn contenus dans les boues et former un résidu riche en Pb. Le Zn a été ensuite récupéré sous forme de ZnO ou ZnS par précipitation ou sous forme métallique par électrodéposition. Enfin, le Mn a été précipité sous forme de MnCO3 avec une concentration acceptable en impuretés. Une étude technico-économique a été réalisée pour évaluer l’intérêt de l’industrialisation du procédéDuring the XIXth and XXth centuries, steel industry has been one of the main sources of wealth in France. However, ferromanganese manufacturing has produced huge quantities of wastes, for instance after blast-furnace gas washing. The residual sludge, containing high concentrations of zinc (Zn), manganese (Mn) and lead (Pb) (5 to 40 wt %), has been deposited in ponds, in the vicinity of steel-making plants. Since plant closure, these fields have been left untouched; some of them, like in Pompey (Lorraine) have been colonized by vegetation. These sites may be considered as a threat to health and environment and should be cleaned up. Nevertheless, with awareness of metal shortage, these ponds may be considered as deposits of secondary resources. This works aims at designing a hydrometallurgical process to extract Zn, Mn and Pb from these residues and recover them in a valuable form, while decontaminating the sites. At first, experiments have enabled us to determine the optimal conditions (acid concentration, duration, temperature, reactant addition, pulp density) to extract selectively Zn and Mn from the sludge and leave a Pb-rich residue. Then, Zn was recovered as ZnO or ZnS after precipitation or as Zn after electrowinning. Mn was recovered as MnCO3 at an acceptable purity. A technico-economic study has been done to assess the industrial interest of the process
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Pires, Eduardo José Andrade Guimarães. "Recovery of metals from MSW fly ash by leaching and liquid-liquid extraction." Master's thesis, 2009. http://hdl.handle.net/10216/58676.
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Pires, Eduardo José Andrade Guimarães. "Recovery of metals from MSW fly ash by leaching and liquid-liquid extraction." Dissertação, 2009. http://hdl.handle.net/10216/58676.
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Rushwaya, Mutumwa Jepson. "Purification of coal fly ash leach solution by solvent extraction." Thesis, 2016. http://hdl.handle.net/10539/21055.
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A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering (Metallurgy and Materials Engineering), May 2016The solvent extraction of iron and titanium from solution generated by the two-step sulphuric acid leaching of coal fly ash by Primene JMT was investigated. The influence of hydrogen ion concentration, Primene JMT concentration, aqueous to organic volume phase ratio and temperature on the extraction of iron and titanium was determined by the use of Design of Experiments. Hydrogen ion concentration and the interaction between the aqueous to organic volume phase ratio with Primene JMT concentration had a significant effect on the extraction of iron while temperature did not. Hydrogen ion concentration and temperature did not have a significant effect on the extraction of titanium, while the interaction between Primene JMT concentration and aqueous to organic volume phase ratio had a significant effect. Extraction improvement tests showed that at a hydrogen ion concentration of 0.28M, 88% iron and 99% extraction of titanium from coal-fly ash leach solution could be achieved. Construction of a McCabe-Thiele diagram showed that a four-stage solvent extraction system with Primene JMT could reduce the iron and titanium concentration in the coal fly ash leach solutions to below 0.05g/L
GS2016
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Fosso-Kankeu, Elvis. "Ni²⁺ extraction from low grade leachate of tailing dumps materials using cloned indigenous bacterial species." Thesis, 2012. http://hdl.handle.net/10210/8033.
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