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1

Vinichenko, N. O. "Acid rain. Problems and solutions." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45158.

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Анотація:
Acid rain refers to a relatively new phenomenon, a form of precipitation that is acidic in nature. The result of human-induced emissions, acid rain has grave effects on the planet's flora and fauna and different ecosystems. The precipitation occurs when exhaust emissions of sulfur and nitrogen compounds react in the atmosphere.
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2

Magalhães, Júnior Antonio Irineudo. "Recovery of itaconic acid from aqueous solutions." reponame:Repositório Institucional da UFPR, 2015. http://hdl.handle.net/1884/44013.

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Анотація:
Orientador : Prof. Dr. Julio Cesar de Carvalho
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia de Bioprocessos e Biotecnologia. Defesa: Curitiba, 27/03/2015
Inclui referências : f. 79-83
Área de concentração: Agroindústria e biocombustíveis
Resumo: Ácido itacônico (AI) é um produto químico promissor que tem uma ampla gama de aplicações e pode ser obtido em grande escala por processos fermentativos. A separação de AI a partir do caldo fermentativo tem um impacto considerável no custo total da produção. Por conseguinte, a procura de processos para a recuperação de ácidos orgânicos com alta eficiência e baixo custo é um dos passos chave para a substituição de produtos de base petroquímica. Apesar dos avanços biotecnológicos em frente aos processos fermentativos, o principal obstáculo ainda é a separação e purificação. Uma revisão sobre os principais métodos de separação foi realizada nesse trabalho e fomentou as diretrizes dessa investigação. Um dos métodos mais comuns para a separação de ácidos orgânicos envolve a precipitação e ressolubilização (regeneração). Os estudos sobre a precipitação de AI são dificilmente encontrados na literatura, embora estejam bem desenvolvidos. Neste estudo, os dados da solubilidade de itaconato de cálcio foram determinados de modo a avaliar o potencial de precipitação de AI. O processo foi muito dependente da temperatura, com recuperação de 88 a 97% na faixa de 20 a 80°C. A separação de AI a partir de soluções aquosas usando resinas comerciais de troca iônica fortemente básicas foi outra investigação realizada. A adsorção foi investigada para determinar os efeitos da concentração inicial de AI, pH e temperatura. As isotermas clássicas de Freundlich e Langmuir e a cinética de pseudo-segunda ordem foram utilizadas para calcular os parâmetros de adsorção. Um modelo matemático simplificado foi desenvolvido e validado com dados experimentais de uma coluna de leito fixo. Durante os experimentos, um método analítico foi desenvolvido para a determinação da concentração de AI em solução aquosa. Palavras-chave: Recuperação de Ácidos Orgânicos, Ácido Itacônico, Análise, Precipitação, Adsorção.
Abstract: Itaconic acid (IA) is a promising chemical product, which has a wide range ofapplications and can be obtained in large scale by fermentative processes. Theseparation of IA from fermented broth has a considerable impact in the total cost ofproduction. In that way, the search for high efficiency and low cost processes oforganic acids recovery is one of the key steps to the replacement of petrochemicalbasedproducts. Despite the important biotechnological advances in fermentativeprocesses, the biggest remaining obstacles remain being the separation andpurification. In this work, a review of the main separation methods has been doneshowing that the most common methods of organic acids separation involvesprecipitation and regeneration. Studies about IA precipitation are rare in the literature.In this study, the data about calcium itaconate solubility were determined as a meansto evaluate IA precipitation potential. The process is dramatically dependent oftemperature, with recovering yields ranging from 88 to 97% at temperatures of 20 to80ºC. Another investigation made was the IA separation from aqueous solutionsusing strongly basic commercial ion-exchange resins. This adsorption method wasinvestigated in order to determine the effects of IA initial concentration, pH andtemperature. The classical isotherms of Freundlich and Langmuir and a pseudosecondorder kinetics were used to calculate the adsorption parameters. A simplifiedmathematical model was developed and evaluated with experimental data obtainedfrom a fixed bed column. During the experiments, an analytical method wasdeveloped to determine the concentration of IA in aqueous solution.Key words: Organic Acids Recovery, Itaconic Acid, Analysis, Precipitation,Adsorption.
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3

Fangelow, M. "Dimerisation of aleic acid in ionic solutions." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419519.

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4

Marti, Mustafa Esen. "Reactive Extraction Of Pyruvic Acid From Aqueous Single And Mixed Acid Solutions." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612261/index.pdf.

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Interest in recovery of carboxylic acids from their aqueous solutions and production media has been growing with the improvements in the production techniques. Reactive extraction is proposed as a promising method to achieve high distribution coefficients with good selectivity. In the present study, equilibrium and kinetic studies, needed for the design of a recovery unit were carried out. Reactive extraction of pyruvic, acetic and lactic acids from their single and mixed acid solutions were carried out with tertiary amines, Alamine 336 and trioctylamine, dissolved in diluents, 1-octanol and oleyl alcohol. The kinetic parameters such as reaction order and rate constant were calculated by using the aqueous solution of pyruvic acid with 1-octanol solution of trioctylamine. The distribution coefficient of pyruvic acid was obtained as 0.30 and 0.07 with 1-octanol and oleyl alcohol respectively. The trend did not change after the addition of the extractants to the diluents. As expected, the more polar diluent extracted more acid than the less polar one. The extractant was observed to be the limiting reagent of the reversible complexation reaction in the organic phase. It was seen that loading ratio was not affected by the concentration of the extractant in the organic phase but increased with the equilibrium concentration of the acid in the aqueous phase. The results showed that mainly (1-1) acid-amine reaction occurred in the organic phase. Because tertiary amines can react with only undissociated acids, the increase in the initial pH of the aqueous phase caused a decrease in the distribution coefficients of the carboxylic acids studied. The effect of the concentration of the organic phase disappeared when the initial pH of the aqueous phase was 4.0 and a distribution coefficient value of 0.1 was achieved for all concentration levels of organic phase. Similar results were obtained for acetic and lactic acids and this behavior was used to propose a selective recovery of the acids from their mixed acid solutions. The presence of acetic acid prevented the extraction of pyruvic acid. The increase in the concentration of the extractant in the organic phase caused an increase in the distribution coefficient of pyruvic acid. During the extraction process, lactic acid could not be recovered from ternary acid solutions because of its high hydrophilicity. The results of reactive extraction of lactic and pyruvic acids from their binary acid solutions showed that at higher concentration of lactic acid, the distribution of pyruvic acid was negatively affected. On the other hand, the presence of lactic acid at a low concentration level did not affect the distribution of pyruvic acid. It was found that the reaction between pyruvic acid and trioctylamine in 1-octanol was first order with respect to the reactants with a second order rate constant of 0.94 L mol-1 s-1. The enhancement factor of the system was obtained as 25.
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5

Trownson, Glenn. "The high temperature corrosivity of radiolysed nitric acid solutions." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/the-high-temperature-corrosivity-of-radiolysed-nitric-acid-solutions(56c0514a-718b-4bc6-9cf5-e3b968acf715).html.

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Currently in the UK, spent nuclear fuel is reprocessed using the PUREX (Plutonium Uranium Reduction Extraction) process. This process generates large amounts of aqueous nitric acid based waste which is reduced in volume by evaporation before being stored in stainless steel tanks pending eventual disposal to a repository after conversion into a solid wasteform. The corrosivity of nitric acid solutions towards these stainless steel storage tanks is strongly affected by the presence of oxidants that can form in situ if certain dissolved metals such as cerium, chromium, ruthenium and neptunium are present, which is invariably the case in nuclear reprocessing plant liquors. Such liquors are, however, subject to radiolysis leading to the formation of nitrous acid and NOx species in equilibrium with nitric acid and water. The redox chemistry of irradiated reprocessing plant liquors is therefore complex, depending on a large number of factors including acidity, nitrate ion concentration, temperature, pressure, radiation dose rate and the nature/concentration of dissolved species. High acidities, high temperatures and low dose rates favour the oxidation of species such as Ce(III). For example, when Ce(IV) forms, the corrosion rate of stainless steel is strongly increased since the reduction of Ce(IV) forms a kinetically-favoured path way. Furthermore, the presence of nitrous acid (which is radiolytically formed from nitrate/nitric acid) can act to reduce potential corrosion accelerators (e.g. Ce(IV)) to their non-oxidising valency states. These dependencies are only semi-quantitatively understood at present, hampering useful prediction of actual effects when conditions are changed. The research presented within this thesis is divided between two experimental campaigns which are interrelated by their applicability to highly active storage tank conditions; I. An investigation into the conditions which effect the radiolytic production of nitrous acid in nitric acid based solutions was undertaken. This included the quantitative measurement of the steady state concentration of nitrous acid experienced under different conditions. The conditions investigated include temperature, dose rate, gaseous headspace and liquor composition in order to elucidate which factors are of importance in estimating the concentration of nitrous acid which can be expected at the base of a highly active storage tank. The major result of this campaign was that nitrous acid data collected could be used to formulate a g-value of nitrous acid formation (which was found to be 0.71) and this value was used to calculate the nitrous acid production rate expected within a highly active storage tank which is a pre-requisite of underpinning the corrosion chemistry within. II. Investigation into the potential formation of in situ corrosion accelerators in a reprocessing liquor simulant was undertaken. For this, a bespoke experimental rig has been designed, built and operated in order to identify the valency of potential corrosion accelerators at high temperatures while closely representing the conditions expected at the base of a highly active storage tank. This included the simulation of nitric acid radiolysis by means of an appropriate nitrite addition underpinned by the radiolysis studies described above in (I). It was found that none of the conditions investigated were oxidising enough to promote the generation of Ce(IV), which is contrary to the current understanding and should be favourable with regards to the storage tank remnant life expectations. Results reported in this thesis provide insight into the corrosivity of reprocessing liquors under representative storage tank conditions at various temperatures (up to the local liquor saturation temperature) and this knowledge will help improve remnant life predictions of the highly active storage tanks on the Sellafield site.
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6

Bengraine, Karim. "Ozonation de solutions aqueuses : role de l'eau oxygenee." Paris 7, 1988. http://www.theses.fr/1988PA077176.

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Contribution a la meilleure connaissance des phenomenes impliques dans une filiere de traitement de l'eau, avec un interet plus particulier au role de l'eau oxygenee au cours de l'ozonation de solutions aqueuses. Etude de l'ozonation de molecules organiques (acides salicylique, phtalique et oxalique), des mecanismes mis en jeu et comparaison des produits obtenus par ozonation et par reaction de fenton
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7

Principe, Frank T. "Separation of iron(III) from zinc sulphate-sulphuric acid solutions using organophosphoric acid extractants." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/MQ55025.pdf.

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8

Österdahl, Kerstin. "Crystallization of iron fluoride trihydrate from mixed acid solutions /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-347.

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9

Liu, Jingyi. "Acetic acid separation from aqueous solutions using ionic liquids." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.679212.

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A series of hydrophobic ionic liquids (ILs) have been employed to extract acetic acid from aqueous solutions at 101.3 KPa. This study was carried out using tetradecyltrihexylphosphonium cation ([P666, 14]+) combined with two series of anions: benzoate and long-chain carboxylate based anions. For comparison, the extraction of organic solvent MTBE was also investigated. The long-chain carboxylate based ILs showed a larger two phase region and high extraction efficiency. [The performance of a selection of inorganic salts, organic salts, and ILs in the extractive distillation for the (HOAc + H20) system was analyzed by vapour-liquid equilibrium under atmospheric pressure. The results indicate that the inorganic salts showed a salting-out effect of acetic acid while all the organic salts and ILs presented salting-out effect of water. All the ILs investigated showed a notable salting-out effect of wate which implied that an IL might be a promising additive in extractive distillation processes. Supported materials were investigated in extractive distillation for the (HOAc + H20) system. The performance of a selection of organic and ILs functionalized supports was analyzed by vapour-liquid equilibrium at 101.3 kPa. Leaching problem of the imidazolium based IL tethered support, blockage problem of the powder support and the saturation of the support during continuous distillation are still the challenging parts in this work. The UNIFAC method was employed to correlate and predict the LLE and VLE data for IL/salt modified systems. The results illustrated that the UNIF AC model has the ability to correlate and predict both VLE and LLE in mixtures containing ILs or salts with satisfactory accuracy. In addition, the ability of a commercial process simulator (Aspen Plus), to model phase equilibrium for the ternary systems of (HOAc + H20 + IL/salt) was examined. The physico-chemical properties of the investigated ionic liquids were characterized as a function of temperature.
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10

Forsberg, Kerstin. "Crystallization of metal fluoride hydrates from mixed acid solutions /." Stockholm : Skolan för kemivetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10619.

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11

Li, Guangming 1965. "Electrochemical investigation of copper deposition onto silicon from hydrofluoric acid and buffered hydrofluoric acid solutions." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282657.

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For the fabrication of ULSI circuits, the silicon surface should be free of metallic and particulate contamination and be atomically smooth. Heavy metal contaminants have detrimental effects on the yield of microelectronic processing and reliability of solid state devices by increasing the junction leakage current, degrading the integrity of gate oxide and reducing the oxide breakdown voltage. It has been demonstrated that the contamination level for most metals has to be controlled below 10¹⁰ atoms/cm² for sub-quarter micron processing. Some transition and noble metal ions such as copper, silver and gold are known to deposit on silicon surfaces in acidic fluoride based solutions. Among them, copper has been the focus of most research due to the widespread use of copper in microelectronic industry. To investigate the mechanisms by which copper deposits on silicon surfaces in HF and BHF solutions, different electrochemical techniques were used, including dc polarization and ac impedance spectroscopy (EIS). The results of electrochemical measurements, in conjunction with various surface characterization techniques, such as TXRF, AFM and TEM, reveal the rates of reactions that occur at silicon/solution interface can be affected by many factors, such as silicon dopant type and doping levels, ionic strength of electrolytes, illumination conditions and the use of additives. For example, under darkness, the amount of copper deposition is nearly one order of magnitude less than that under illumination for p-type silicon in both HF and BHF solutions and n-type silicon in HF solutions. In BHF solutions, n-type silicon is very close to its flat band condition where illumination plays little role. The addition of copper ions in BHF solutions not only causes metal contamination, but also generates severe surface roughness due to the masking effect of copper on the anisotropic etching of silicon in BHF solutions. Local etching rate of 1nm/min was measured on the silicon sample prepared in 100 ppb Cu²⁻ BHF solutions. Some additives such as surfactants and hydrochloric acid can effectively reduce the reaction rates of silicon corrosion and copper deposition by either blocking the active reaction sites or form copper ion complexes.
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12

Qi, Fei. "Carboxylic acid and formaldehyde separation from aqueous solutions using ionic liquids." Thesis, Queen's University Belfast, 2017. https://pure.qub.ac.uk/portal/en/theses/carboxylic-acid-and-formaldehyde-separation-from-aqueous-solutions-using-ionic-liquids(56aa0414-73e4-4f2e-9622-a9d3cd88ff4e).html.

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A series of hydrophobic ionic liquids (ILs) have been employed to extract acetic acid (AcOH) or formaldehyde (HCHO) from aqueous solutions at atmosphere pressure. The ILs, mainly trihexyl(tetradecyl)phosphonium ([P6,6,6,14]+) carboxylate based ILs, were tested as a function of the anion chain length, which ranges from isobutyrate ([IB]-) to dodecanoate ([D]-). Most of these ILs show a large two-phase region and high extraction efficiency. Furthermore, tetraoctylphosphonium ([P8,8,8,8]+) and trihexyl(tetradecyl)ammonium ([N6,6,6,14]+) based ILs were also investigated to study the effect of the cation on extraction performance. Besides pure IL extraction, the mixture of IL and other chemicals, such as matched carboxylic acid, alkane and ester, were also investigated on extraction. The matched carboxylic acid could enhance the extraction performance and thus could be called ‘enhancer’. A balance point could be found for the ratio IL/enhancer to obtain a better extraction in each {H2O + AcOH + IL/enhancer} system, compared with the corresponding pure IL liquid-liquid equilibrium (LLE). Several ILs, including [P6,6,6,14]+ based ILs and imidazolium based ILs, were investigated on extraction of HCHO. Among these ILs, the imidazolium based ILs performed better than the [P6,6,6,14]+ based ILs in terms of two-phase region, hydrophobicity of IL-rich phase and partition coefficient/relative selectivity. The UNIQUAC method was employed to correlate the LLE data for pure IL systems. Some physical property data, such as density and viscosity, of ILs were correlated. The Joback group contribution method was used to predict the heat capacities of some ILs in this work. These correlations with low deviations made it possible for ILs to be further studied in Aspen process modelling.
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13

N'guessan, Job. "CORROSION INHIBITION OF 1018 STEEL IN CARBONIC ACID SOLUTIONS (THIOUREA)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291227.

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14

Ketusky, Edward. "Remediation of spent oxalic acid nuclear decontamination solutions using ozone." Thesis, Lancaster University, 2018. http://eprints.lancs.ac.uk/123625/.

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Анотація:
The Savannah River Site (SRS) has forty-three remaining very large underground tanks containing significant quantities of nuclear waste generated primarily from cold-war radiochemical separations. All of the tanks eventually must be closed. As part of decommissioning/closing the nuclear waste tanks, even residual quantities of the waste must be removed. Although most sludge can be removed mechanically, chemically cleaning (i.e. decontamination) with oxalic acid is used to aid in the removal of residual quantities. Although oxalic acid works for cleaning the tanks, its downstream impacts are considered detrimental. To better understand and quantify the impacts, detailed models were developed to account for different potential processing strategies for handling the spent oxalic acid nuclear decontamination slurries. Although the results vary, the models show that regardless of the oxalate handling strategies: 1) significant washing to decrease sodium concentration/solids concentration in vitrification feed will be required, and 2) the creation of copious future additions of feed for salt processing will be unavoidable. Using a Theory of Inventive Problem Solving (TRIZ) approach, a modified form of the Chemical Oxidation Reduction Decontamination (CORD) ultraviolet (UV) light was identified as being used with an analogous but already resolved problem that could be adapted to SRS HLW tank cleaning. A novel preliminary process called Enhanced Chemical Cleaning (ECC) was envisioned. As part of maturing the technology, the literature review identified three possible oxalate decomposition mechanisms associated with ECC. They are: 1)A heterogeneous non-Advanced Oxidation Process (AOP) mechanism where the target organic adsorbs onto the surface of a solid, often particulate, metal oxide at a so-called active site, followed by ozone attack on the sorbed organic; 2)A homogeneous non-AOP mechanism that operates under low pH acidic conditions and which involves complexation of the catalysing metal ion with the oxalate followed by ozone attack on the complex; and, 3)A homogeneous AOP mechanism that operates at a high basic pH and which involves metal ions catalysing the formation of hydroxyl radicals from ozone, with the said hydroxyl radicals then driving the oxalate decomposition. Process testing was conducted using slurries made from simulants designed to be chemically similar to real High-Level Waste (HLW) sludge types. Testing using slurries made from real HLW sludge was also performed, but because of safety limitations associated with handling HLW, only a much smaller scale test apparatus could be used. With the much smaller scale test apparatus, the purpose of the real HLW based testing was confirmatory. Each of the simulant decomposition test slurry was created using an Fe-rich or an Al/Mn-rich sludge simulant using either 1 wt% or 2.5 wt% oxalic acid. The real HLW based slurries were formed using 2 wt% oxalic acid. As part of the main postulate of this effort, both the simulant decomposition test slurries and real HLW based slurries demonstrate that UV light increased the decomposition rate. Even without UV, by adding only ozone, the oxalate decomposition was completed on an industrially relevant timescale. Also using simulant based testing, the overall oxalate decomposition exhibited four distinct stages related to the metal catalysts: Stage One – At short ozonation times, ozone decomposes Fe oxalates and solubilise Fe from ozone action on the metal oxide constituents of the sludge. Stage Two – At intermediate ozonation times, as a result of the loss of the solution capacity to complex (and so solubilise) Fe, Mn, and Ni ions due to O3 driven oxalate decomposition, as well as the pH increase that accompanies that decomposition, Fe begins to precipitate. Oxalate decomposition is still primarily catalysed by Fe ions during this stage. Stage Three – At intermediate ozonation times, Fe precipitation is near complete, and oxalate decomposition is now driven by ozone and Mn catalysis – Mn playing a major role in determining the final time to process endpoint of 1.1 × 10-3 M oxalate in solution. Stage Four – At long ozonation times, the process endpoint with Mn precipitation now near completion with Ni being the dominant metal ion in solution. Constructed plots compare the pH and remaining oxalate concentration, both as a function of time, suggesting some relationship. Regression analysis of the negative log of the oxalate concentration shows the R2 values are all greater than 0.80, confirming correlation. Thus, pH can be used as a field measure for confirming when oxalate decomposition is complete. As a principal hypothesis of this effort, using simulant based testing, both the scavenging effects of “all-ready present” nitrite (a soluble component of the sludge simulants) and oxalate mineralisation-derived carbonate are advantageously used in lieu of introducing hydroxyl radical probe compounds to the process. Specifically, differing nitrite concentrations between slurries showing no impact on the decomposition rates, and the build-up of carbonate not inhibiting the decomposition process strongly suggest that the decomposition is not the result of radicals. Instead, the oxalate decomposition is likely the result of a direct reaction of ozone with metal complexed oxalate (i.e. mechanism 2 discussed above).
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15

Garaix, Guillaume. "Radiolyse alpha de solutions aqueuses d'acide nitrique." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20136.

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Анотація:
L'acide nitrique est largement utilisé dans le procédé de retraitement du combustible nucléaire usé, le procédé PUREX (Plutonium and Uranium Refining by EXtration). Ce procédé est fondé sur l'extraction liquide-liquide de l'uranium et du plutonium aux degrés d'oxydation (+VI) et (+IV) respectivement. Le plutonium est ensuite désextrait, et ainsi séparé de l'uranium par ajout d'uranium (+IV) stabilisé en milieu acide nitrique par des ions hydrazinium (N2H5+). Or, la radiolyse de l'acide nitrique, inhérente à la présence d'émetteurs α dans ces solutions, génère des espèces radicalaires et moléculaires susceptible de modifier, d'une part, le comportement redox des actinides et, d'autre part, de réagir avec les ions hydrazinium. Le but de ce travail est de mieux maîtriser les paramètres chimiques et physico-chimiques susceptibles de modifier les degrés d'oxydation de l'uranium et du plutonium dans les solutions d'acide nitrique. Parmi ces paramètres, le rôle de l'acide nitreux et du peroxyde d'hydrogène, générés par radiolyse de l'acide nitrique, est primordial. L'objectif est de repréciser les cinétiques de formation du peroxyde d'hydrogène et de l'acide nitreux par radiolyse alpha des milieux acide nitrique / nitrate de sodium en fonction des paramètres : acidité, concentration des ions nitrate et transfert d'énergie linéique du rayonnement ionisant.Il a été montré que la formation de peroxyde d'hydrogène diminue avec l'augmentation de la concentration des ions nitrate et augmente fortement avec l'acidité de la solution, jusqu'à atteindre une valeur stationnaire pour une acidité proche de 0,2 mol L-1. Pour sa part, la formation de l'acide nitreux est favorisée par l'augmentation de la concentration des ions nitrate. Il a été observé que G(HNO2) évolue selon deux tendance distincte, la première dans les solutions diluées d'ions nitrate et la seconde dans les solutions concentrées d‘ions nitrate. Ces deux variations traduisent des phénomènes radiolytiques directs et indirects modifiant les mécanismes de formation de HNO2. L'étude de l'acidité des solutions irradié a montré que la formation de H2O2 et de HNO2 est favorisé avec l'augmentation de la concentration des ions hydronium, jusqu'à atteindre une valeur stationnaire pour une acidité proche de 0,2 - 0,5 mol L-1.Par ailleurs, les effets induits par la nature du rayonnement ionisants (,,,…), sur les rendements de formation de H2O2 et HNO2, ont été étudiés. Il a été montré que le transfert d'énergie linéique (TEL), compris entre 0,2 keV µm-1 (caractéristique d'un rayonnement gamma) et 130 keV µm-1 (caractéristique d'un rayonnement alpha émis par la décroissance radioactive d'un actinide), a une influence significative sur les rendements de formation de H2O2 et de HNO2. Il a été observé que l'impact des ions nitrate sur le rendement de formation de H2O2 devient plus marqué, lorsque le TEL augmente. A contrario, l'impact des ions nitrate favorisant le rendement de formation de HNO2, diminue lorsque le TEL augmente. Sur la base des résultats acquis durant cette étude et des données présentes dans la littérature, deux équations paramétriques ont été développées. L'intérêt de cette paramétrisation des effets est de prédire les rendements radiolytiques de formation de H2O2 et de HNO2 selon les conditions chimique du milieu ([NO3-] ≤ 4 mol L-1 et 10-5 mol L-1 ≤ [H+] ≤ 4 mol L-1) et selon la nature du faisceau (TEL compris entre 0,2 – 130 keV µm-1).La finalité de cette étude serait de prédire les quantités de H2O2 et de HNO2 formés par radiolyse de HNO3/NaNO3 dans les étapes du procédé de retraitement des combustibles nucléaires
Nitric acid is widely used in spent nuclear fuel reprocessing, especially in PUREX process (Plutonium and Uranium Refining by Extraction). This process is based on liquid-liquid extraction of Uranium (+VI) and Plutonium (+IV). Plutonium is separated from Uranium by addition of Uranium (+IV) in nitric acid, stabilized by hydrazinium ion (N2H5+). However, the radiolysis of nitric acid, result of the presence of alpha emitting radionuclides, generates in solutions free radicals and molecular species. These species are capable of modifying the redox state of actinides and reacting with hydrazinium ions.The aim of this work is to reveal the chemical and physical-chemical parameters that may modify the oxidation states of Uranium and Plutonium in nitric acid solutions. Among these parameters, the role of nitrous acid and hydrogen peroxide, generated by radiolysis of the nitric acid, is very important. The objective is to redefine the kinetics of formation of hydrogen peroxide and nitrous acid during alpha radiolysis of nitric acid / sodium nitrate, as a function of three parameters: acidity, nitrate concentration and the linear energy transfer of ionizing radiation.It was shown that the formation of hydrogen peroxide decreases with increasing nitrate ions concentration and increases greatly with the acidity of the solution (until it reaches a stationary value for an acidity of 0.2 mol L-1). The formation of nitrous acid is promoted by the increase the nitrate ions concentration. It was observed that G(HNO2) varies according to two trends. The first one in dilute nitrate solutions and the second in concentrated nitrate solutions. These two trends reflect the direct and indirect radiolytic phenomena, modifying the mechanisms of formation of HNO2. The study of acidity has showed that the formation of H2O2 and HNO2 is promoted by increasing the concentration of hydronium ions, until it reaches a steady state value for an acidity close to 0.2-0.5 mol L-1.Furthermore, the effects induced by ionizing radiation (,,,…) on formation yields of H2O2 and HNO2 were studied. It has been shown that the linear energy transfer (LET), between 0.2 keV µm-1 (characteristic of a gamma radiation) and 130 keV µm-1 (characteristic of the alpha radiation emitted by radioactive decay of actinides), has a significant influence on formation yield of H2O2 and HNO2. It was observed that the impact of nitrate ions on the formation yield of H2O2 becomes more pronounced when the LET increases. Conversely, the impact of nitrate ions which promote the formation of HNO2, decreases when the LET increases.Based on these results, two parametric equations were developed. The advantage of this parameterization is to predict the radiolytic yields formation of H2O2 and HNO2 according to chemical conditions ([NO3-] ≤ 4 mol L-1 and 10-5 mol L-1 ≤ [H+] ≤ 4 mol L-1) and the nature of the beam (LET between 0.2 to 130 keV µm-1).The purpose of this study is to predict the quantity of H2O2 and HNO2 formed by radiolysis of HNO3/NaNO3, during the different steps of the nuclear fuel reprocessing
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16

Acar, Ebru. "Oxidation Of Acid Red 151 Solutions By Peroxone (o3/h2o2) Process." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605527/index.pdf.

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Анотація:
Wastewaters from textile industry contain organic dyes, which cannot be easily treated by biological methods. Therefore, pretreatment by an advanced oxidation process (AOP) is needed in order to produce more readily biodegradable compounds and to remove color and chemical oxygen demand (COD) simultaneously. In this research, ozone (O3) is combined with hydrogen peroxide (H2O2) for the advanced oxidation of an azo dye solution, namely aqueous solution of Acid Red 151, which is called as &ldquo
Peroxone process&rdquo
. The aim of the study is to enhance the ozonation efficiency in treating the waste dye solution. The effects of pH, initial dye and initial ozone concentrations and the concentration ratio of initial H2O2 to initial O3 on color and COD removals were investigated. Also, the kinetics of O3-dye reaction in the presence of H2O2 was approximately determined. As a result of the experimental study, it was seen that an increase in the initial dye concentration at a constant pH and initial ozone concentration did not change the COD % removal significantly, from a statistical analysis of the data. The results obtained at pH values of 2.5 and 7 gave higher oxidation efficiencies in terms of color and COD removals compared to those at pH of 10. The best initial molar ratio of H2O2 to O3 was found to be 0.5, which yielded highest treatment efficiency for each pH value studied. The results of the excess dye experiments suggest that the ozonation of Acid Red 151 follows an average first order reaction with respect to ozone at pH=2.5 and pH=7 whereas it is around 0.56 at pH=10. By Initial Rate Method, the orders with respect to individual reactants of O3 and dye were determined as one, the total order of the reaction being two for all the studied pH. As a conclusion, a further study of the peroxone process at a pH of 10 can be recommended to determine the reaction kinetics and mechanism at this pH, where radicals play an important role.
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17

Basaran, Tolga Yener. "Ion Exchangers In The Recovery Of Tartaric Acid From Aqueous Solutions." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607367/index.pdf.

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Анотація:
Tartaric acid is a dicarboxylic acid naturally present in grapes, and has many application areas with its salts. It can be produced synthetically, manufactured as a by-product in wine industry, or can be recovered by electrodialysis and solvent extraction methods. Since, ion exchange is one of the oldest processing techniques for the recovery and purification of valuable materials, it can be applied to obtain this valuable organic acid. In this study it is aimed to investigate the effects of resin basicity, initial concentration, and initial pH of the solution on ion exchange equilibrium. The model tartaric acid solutions were prepared for the equilibrium analysis with two different anion exchange resins in a batch type system. A shaker bath at 28 oC with 300-rpm agitation rate was used. The weakly basic resin Lewatit MP62, and strongly basic resin Lewatit M511, which are in polystyrene structure, was obtained from the producer Bayer AG. In the analysis, Shimadzu PDA Detector at 210 nm with Waters Atlantis dC18 column was used. 20 mM NaH2PO4 at pH = 2.7 was introduced to the HPLC as the mobile phase at 0.5 ml/min flow rate. In the investigation of the resin basicity, MP62 presented better performance than M511. The equilibrium experiments were performed at three different initial acid concentrations (0.01, 0.02, and 0.10 M) for both resin, and in the pH ranges pH <
pKa1, pKa1 <
pH <
pKa2, and pKa2 <
pH for weakly basic resin, and in the pH ranges pH <
pKa1, pKa1 <
pH <
pKa2 for strongly basic resin at each concentration. Results show that the pH of the solution is a more important parameter than the initial concentration that affects the ion exchange equilibrium. Also, Langmuir and Freundlich isotherms were plotted, and it was shown that they were in good agreement with the experimental data especially for the systems that are at low total ion concentrations.
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18

Bartholomew, Richard J. "Raman spectral studies of solutions of formic acid and methyl formate." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21409.pdf.

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19

Schnitzer, Cheryl. "Sum frequency generation of water on inorganic acid and salt solutions /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1999.

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Анотація:
Thesis (Ph.D.)--Tufts University, 1999.
Adviser: Mary Jane Schultz. Submitted to the Dept. of Chemistry. Includes bibliographical references (leaves 134-136). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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20

Bryce, Christine. "The kinetics of copper etching in ferric chloride-hydrochloric acid solutions /." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61225.

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Анотація:
The kinetics of copper etching were studied using a ferric chloride-hydrochloric acid etchant in a stirred-tank reactor. At a constant acid molarity of about 0.84 and FeCl$ sb3$ concentrations varying from 0 to 3 M, the etch rate was found to reach a maximum at about 2 M FeCl$ sb3$. The use of a ferric nitrate-nitric acid solution yielded similar results but substantially reduced etch rates.
Since the nitrate ion is essentially non-complexing with the ferric ion, the presence of chloro complexes of the ferric ion in FeCl$ sb3$-HCl etchant solutions was investigated. The FeCl$ sb2 sp+$ and FeCl$ sb3 sp0$ complex ions were found to constitute the majority of ferric species at all concentrations, and their respective enhancing and inhibiting effects incorporated into a rate equation: = A {m sb{FeCl sbsp{2}{-}} over 1 + 0.25m sb{FeCl sbsp{3}{0}}} here m$ sb{ rm i}$ is the molality of species i. The rate constant, A, was found to fit an Arrhenius plot for a temperature range of 30-50$ sp circ$C.
Experiments performed with etchants containing both the chloride and nitrate ions showed etch rates increasing uniformly as the chloride fraction of total anion increased. The FeCl$ sb2 sp+$ complex continues to exhibit an enhancing effect in these solutions, but at the conditions chosen the concentration of FeCl$ sb3 sp0$ remains constant. The FeCl$ sp{2+}$, however, appears to inhibit the etch rate.
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21

Swinyard, B. T. "Multiple phase equilibria in polar polymer solutions containing poly(acrylic acid)." Thesis, University of Stirling, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370518.

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22

Gaw, Daryl Corbin. "Manganese Removal from Sulfuric Acid Leach Solutions of Nickel Laterite Ores." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/81026.

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Анотація:
An oxidative precipitation technique using potassium permanganate was explored for the removal of manganese from pregnant leach solution (PLS) generated from the pressure acid leaching (PAL) of nickel laterite ores. The results revealed that the right combination of pH and molar ratio is important in order to achieve maximum removal of manganese (II) with minimum nickel (II) and cobalt (II) losses.
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23

Lam, Luk Sang. "Flow conductivity of solutions of hyaluronic acid : effects of concentration and molecular weight." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28494.

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Анотація:
Hyaluronic acid plays an important role in regulating the transport of fluid and solutes in the interstitium. The concentration and molecular weight of hyaluronic acid in different connective tissues are different. These factors influence the hydraulic flow conductivity, K', of connective tissues. An experimental study of the effect of concentration and molecular weight of hyaluronic acid on the hydraulic flow conductivity is the subject of this work. Hyaluronic acid of different molecular weights were obtained by fractionating commercially available hyaluronic acid using ion-exchange column chromatography. The results were not reproducible, partly because of the elution process was not continuous. Nevertheless, three molecular weight fractions (6.99 to 11.1 X 10⁵ ) were obtained. Hyaluronic acid of lower molecular weights (0.454 to 1.65 X 10⁵) were obtained by acid hydrolysing some of the chromatographed fractions for 15 min., 1 hour and 2 hours. A more homogeneous hyaluronic acid fraction (M.W. = 1.96 X10⁵) was obtained by fractionating hyaluronic acid materials acid hydrolysed for 15 min. The hydraulic flow conductivity of solutions of hyaluronic acid can be calculated from the sedimentation coefficient of the solutions at 20°C, S₂₀‚ measured by ultracentrifugation. Centrifugation experiments determining the S₂₀ of the molecular weight fractions of hyaluronic acid at various concentrations were therefore undertaken. The results showed that S₂₀ decreased with increased concentration of hyaluronic acid. Also, the curves of as a function of hyaluronic acid concentration, c, converged at high concentration, indicating that a three dimensional molecular network is formed at high concentration and the extent of entanglement between molecules is the same for the high and low M.W. fractions. At lower concentrations, for the acid hydrolysed fractions, S₂₀ increased with M.W., which is in agreement with past sedimentation data. For the non-acid hydrolysed fractions, the difference in S₂₀ between two higher M.W. fractions is small, and the lowest M.W. fraction has consistently higher S₂₀ than the higher M.W. fractions. This finding does not agree with past literature results, and the difference in results is most probably due to experimental errors. However, when the fractionated non-acid hydrolysed fractions are taken as a high M.W. group (M.W. = 6.99 to 11.1X10⁵) and the acid hydrolysed fractions as a low M.W. group (M.W. = 0.454 to 1.96X10⁵), the curves of S₂₀ as a function of c of the low M.W. group fall below those of the high M.W. group, which is in agreement with past sedimentation data. The hydraulic conductivities (K'), calculated from S₂₀ data, for all the HA fractions varied inversely with concentration. The log-log plots of K' versus c compared well with the results of Ethier (1986). The K' versus c relationships for all the fractions converged at high concentrations. At low concentrations, the HA molecules of the high M.W. group has a higher K' than those of the low M.W. group.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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24

Vielma, T. (Tuomas). "Thermodynamic properties of concentrated zinc bearing solutions." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223193.

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Abstract Zinc is a common metal, and has a central role in the production of galvanised bulk products, battery applications and fertilisers. Its production relies mainly on the leaching of zinc minerals with sulfuric acid, followed by purification and electrowinning. In this thesis an internally consistent thermodynamic model for the industrially important ZnSO₄-H₂SO₄-H₂O system was developed. Model parameters were optimised using available literature data and new experimental freezing point and density data determined in this work. With Gibbs energy minimisation algorithms embedded in commercial software, such as ChemSheet and FactSage, the developed model can be used to calculate easily phase equilibria and thermodynamic properties of aqueous zinc sulfate solutions and solid zinc sulfate phases, including activity coefficients, enthalpy changes, heat capacities, densities and solubilities, in a wide range of temperature, pressure and sulfuric acid concentrations. Solution non-ideality was treated with the original Pitzer model with electrostatic mixing terms included. Applicability of thermodynamic approach and the developed model was demonstrated by two separate case studies on the hydrometallurgical zinc process. Precipitation of amorphous silica during hot acid leach was studied experimentally. Its solubility in the process solution was also successfully predicted using the thermodynamic approach. To study crystallisation of gypsum during the gypsum precipitation stage, the model was expanded by addition of the Ca²⁺ ion. The model calculations showed good agreement with the experienced Ca²⁺ levels. The results of this thesis have found immediate use in understanding the various stages of the electrolytic zinc process. The obtained results also form a basis on which new, more advanced tools for managing and studying the process can be developed
Tiivistelmä Sinkki on yleinen metalli, ja sillä on keskeinen rooli sinkittyjen terästuotteiden, paristojen ja jopa lannoitteiden valmistuksessa. Sen tuotanto perustuu sinkkipitoisten mineraalien rikkihappoliuotukseen, muodostuneen prossessiliuoksen puhdistukseen ja lopulta metallisen sinkin elektrolyysitalteenottoon. Tässä työssä kehitettiin termodynaaminen malli teollisesti tärkeälle ZnSO₄-H₂SO₄-H₂O -systeemille. Malliparametrit määritettiin kirjallisuudessa esitetyistä tuloksista ja tässä työssä tehdyistä uusista jäätymispiste- ja tiheysmittauksista. Käyttämällä kaupallisia Gibbsin energian minimointialgoritmiin perustuvia ohjelmistoja, kuten ChemSheet tai FactSage, tässä työssä kehitetyllä mallilla voidaan helposti kuvata sinkkisulfaattipitoisten vesiliuosten faasitasapainoja ja laskea systeemin termodynaamisia ominaisuuksia. Malliin sisällytettyihin ominaisuuksiin kuuluvat systeemin komponenttien aktiivisuudet, entalpiamuutokset, lämpökapasiteetit sekä tiheydet laajalla lämpötila-, paine- ja rikkihapon pitoisuusalueella. Liuoksen epäideaalisuutta kuvattiin Pitzerin ioniaktiivisuusmallilla. Työssä sinkkisulfaattiliuoksille kehitettyä mallia testattiin kahdessa sinkintuotannon kannalta keskeisessä tapaustutkimuksessa. Amorfisen piidioksidin saostumista vahvahappoliuotuksen aikana tutkittiin kokeellisesti ja laskennallisesti. Amorfisen piidioksidin liukoisuus prosessiliuokseen ennustettiin onnistuneesti. Kipsinpoistoprosessin tutkimusta varten mallia laajennettiin lisäämällä siihen Ca²⁺-ioni. Mallilla laskettiin kipsin liukoisuus prosessiliuokseen. Saadut tulokset vastasivat hyvin käytännössä havaittuja arvoja. Tutkimuksen tuloksia on suoraan hyödynnetty sinkintuotantoprosessin ymmärtämisessä. Ne myös mahdollistavat jatkossa edistyneempien työkalujen kehittämisen niin prosessin hallintaan kuin tutkimukseenkin
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25

Mihaylov, Indje O. (Indje Ognianov). "Gallium solvent extraction from sulphate solutions using organophosphoric acid reagents (D2EHPA, OPAP)." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70338.

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Анотація:
The subject of this work is gallium extraction from sulphate solutions--an additional source of this metal from hydrometallurgical zinc production--with organophosphorus acid reagents: di-2-ethyl hexyl phosphoric acid (D2EHPA) and OPAP, a mixed extractant consisting of mono- and di-octyl phenyl phosphoric acids. Extraction proceeds via cation-exchange and Ga$ sp{3+}$ is the reacting species. Gallium is extracted with D2EHPA mostly as GaR$ sb3$ - HR. The results for OPAP suggest existence of four reactions, which form GaM$ sb3,$ GaM$ sb2$D, GaMD$ sb2,$ and GaD$ sb3;$ this explains and allows prediction of behaviour over a wide range of OPAP compositions. Sulphate complexation causes decrease in concentration of the reacting species, and thus lower $D sb{ rm Ga}$ values and extraction rates. Prior knowledge on gallium aqueous complexes is used, and an algorithm developed, to allow quantitative prediction of complexation effects on extraction. The model of mass-transfer with chemical reaction, verified with several known criteria for reaction site determination, describes well the kinetic data for the Ga-D2EHPA system. The model is further developed to account for the stronger acidity and the monomer/dimer equilibria typical for the kind of extractants used. A detailed reaction mechanism is proposed and the first organic ligand addition is found as rate-limiting. The model parameters, estimated from extraction kinetic data, are reasonable, when compared with those obtained for other metals elsewhere. The model's predictions agree with the results from stripping kinetics; the equilibrium conditions (zero rate) can also be satisfactorily predicted, as found by comparisons with the equilibrium data. Ga-D2EHPA and Ga-OPAP systems are compared with an emphasis given to the potential for metal separation; the importance of the ligand exchange rate constant is illustrated with the example of Ga and Al extraction/stripping and their separation based on different rates with
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26

Kerr, Helen Rosemary. "The surface properties of hyaluronic acid solutions in relation to joint lubrication." Thesis, University College London (University of London), 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308428.

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27

Jayasekera, Sunil. "Study of the electrochemistry of gold telluride in acid and alkaline solutions." Thesis, Jayasekera, Sunil (1989) Study of the electrochemistry of gold telluride in acid and alkaline solutions. PhD thesis, Murdoch University, 1989. https://researchrepository.murdoch.edu.au/id/eprint/51563/.

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The work described in this thesis was undertaken to obtain a better understanding of the dissolution behaviour of gold tellurides which comprise a significant proportion of the gold found at Kalgoorlie, Western Australia and at other localities such as Fiji and Colorado. It deals mainly with a fundamental electrochemical study of synthetic calaverite (AuTe2). The electrochemical techniques of linear potential sweep voltammetry, cyclic voltammetry, controlled potential coulometry, controlled potential electrolysis and potentiometry were employed. To support and confirm the electrochemical results. the surface products formed during the reaction of AuTe2 were examined and identified using optical and scanning electron microscopy. In order to identify the features observed on the AuTe2 voltammograms resulting from electrochemically active tellurium species, the electrochemical behaviour of elemental tellurium was also investigated under similar experimental conditions as an integral part of this study. The anodic decomposition potentials of AuTe2 were determined as a function of pH and the results compared with potential-pH diagrams constructed using thermodynamic data. The initial oxidation products of AuTe2 in relatively strong acid perchlorate solutions have been shown to be metallic gold and soluble HTeO2+. This is in accord with the thermodynamic predictions, but the situation is complicated at higher anodic potentials due to the accumulation of sparingly soluble tellurous acid (H2TeO3). This species is also responsible for the passivation of the reacting surface at pH values above 2. The rate of dissolution of AuTe2 in chloride media is enhanced at higher chloride concentrations and lower pH. At low acid concentrations, the surface is passivated by the formation of a film of H2TeO3. The initial oxidation of AuTe2 in alkaline perchlorate solutions proceeds via formation of metallic gold and H2TeO3. Since H2TeO3 is readily dissolved in alkaline solutions the reacting surface remains active. The rate of dissolution increases with increasing pH. The rate of dissolution of AuTe2 in alkaline cyanide media increases with both cyanide concentration and pH. Using the appropriate Evans' diagrams, it was shown that under conventional cyanidation conditions the rate of dissolution is extremely slow. Ways of improving the dissolution rate are suggested. Alternatively, the feasibility of leaching AuTe2 in acid chloride media using oxidants such as Fe3+ was also demonstrated. The implications of the results obtained on likely hydroraetallurgical routes for the direct leaching of AuTe2 are discussed.
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28

Cader, Mohamed Shah Roshan. "The intercalation of bromine- and iodine fluorosulfate derivatives in solutions of fluorosulfuric acid." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25853.

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Анотація:
The oxidative intercalation of halogen fluorosulfate derivatives such as I(SO₃F) ₃, Br(SO₃F)₃, BrSO₃F, K[I(SO₃F)₄] and K[Br(SO₃F)₄] from solutions in fluorosulfuric acid into graphite (SP-1 and to a lesser extent HOPG) is studied. In addition, the intercalation of solvated cations of the type I₂₊ and NO⁺ is included in this research as well. The results, supported by microanalysis, X-ray powder diffraction data, Raman frequency shifts, Solid state -¹⁹F-NMR spectroscopy and UV-visible optical spectra of the supernatant solutions support three different courses of the intercalation reactions: a) At very high intercalant concentrations (about a five fold excess over the stoichiometrically required quantity) Hal (SO₃F)₃ and the anion [Hal(SO₃F)₄], with Hal - I or Br, intercalate without noticeable solvent cointercalation. b) At intermediate concentrations, solvent intercalation is observed. c) When low intercalant concentrations are used, the only intercalate is found to be the solvent HSO₃F. In all the intercalation reactions except the NO⁺ (solv) promoted synthesis, first stage compounds are formed. These stage one GIC's with c-axis layer repeat distance I[sub c] - 8.0 A are found for the intercalants I₂₊(solv), I(SO₃F)₃, BrSO₃F and Br(SO₃F)₃ with compositions C₃₂SO₃F.₃HSO₃F.0-2I, C₂₂l(SO₃F)₃, C₁₁HSO₃F.0•5SO₃F.xBrSO₃F (x ≤ 0.025) and C[sub 26.8] Br.4SO₃F respectively. K[Hal(SO₃F)₄] (Hal - Br, I) in HSO₃F gave first stage products with formulae C₈₄Br.11•22SO₃F and C₈₆I.10-51SO₃F. The NO⁺ (solv) induced reaction leads to a stage two compound with I[sub c] - 10.6 A, and a general composition of C[sub n] x SO₃F-yHSO₃F is proposed for the product which is compositionally inhomogeneous. In addition, the basal plane electrical conductivity enhancements are measured for the graphite-I₂₊(solv) and graphite-I(SO₃F)₃systems employing a contactless radio frequency induction method.
Science, Faculty of
Chemistry, Department of
Graduate
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29

Zhang, Lifeng. "Crew-cut aggregates of polystyrene-b-poly(acrylic acid) diblock copolymers in solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0008/NQ30429.pdf.

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30

Zhang, Lifeng. "Crew-cut aggregates of polystyrene-b-poly (acrylic acid) diblock copolymers in solutions." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34489.

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The morphological characteristics of highly crew-cut micelle-like aggregates of asymmetric polystyrene-b-poly(acrylic acid) copolymers PS-b-PAA, was studied by transmission electron microscopy and light scattering. The insoluble PS block contents in the copolymers ranged from 80 to 98 wt. %. The aggregates were formed by the water addition to the copolymer solution in N,N-dimethylformamide, and then were isolated in aqueous solutions.
Spherical micelles were formed when the PAA content in the copolymers was relatively higher. The PS core radii scaled as R$ sb{ rm core} sim$ N$ sb{ rm PS} sp{0.4}$ N$ sb{ rm PAA} sp{-0.15}$, where N$ sb{ rm PS}$ and N$ sb{ rm PAA}$ are the lengths of the PS and PAA blocks, respectively. The PAA corona shell dimensions were also studied. As the PAA content in block copolymers decreased, the morphology of the aggregate changed progressively from spheres to cylinders, to vesicles and lamellae, and eventually to compound micelles. The effects of the initial copolymer concentration and the addition of homopolystyrene on the aggregate morphology were also examined. The aggregate morphology appears to be controlled by a force balance mainly involving three aspects, i.e. the stretching of the PS chains in the core, the surface tension between the PS core and the solvent, and the inter-corona chain interactions.
The aggregate morphology can be controlled by adding ions in micro-molar (HCl, NaOH, CaCl$ sb2$ or Ca(Ac)$ sb2$) or milli-molar (NaCl) concentrations. In addition to the various morphologies obtained by changing the copolymer composition, large compound vesicles, a new morphology, can be obtained from a single block copolymer. The morphogenic effect of different added ions on the crew-cut aggregates can be ascribed to the changed inter-corona chain repulsive interactions, due to neutralization, protonation, ion-binding, and screened electrostatic field, etc. The range of morphologies obtained in this study is believed to be unprecedented for a block copolymer self-assembly system in low molecular weight solvents.
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31

Jurczyk, S. "A novel interpretation of reaction kinetics in aqueous solutions of concentrated sulphuric acid." Thesis, Swansea University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637744.

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The rates of hydrolysis of model sulphonate esters in aqueous solutions of concentrated sulphuric acid were studied. Data for these compounds were used to calculate the solvent parameters YOTs and NOTs in 0-60% w/w sulphuric acid using the Grunwald-Winstein approach. The small increases in hydrolysis rates of sulphonate esters were found to be due to medium effects with no acid catalysis occurring below 50% w/w sulphuric acid. The product distribution of 6-octyn-2-ol benzene sulphonates were predicted from YOTs and NOTs parameters in sulphuric acid solution. Phosphonate esters were found to be sensitive to acid catalysis in dilute acid solution. Phosphonate rate data in dilute acid solution were dissected into the contributions arising from solvolytic and acid-catalysed reaction pathways. The rates of hydrolyses of phosphonate esters in 0-98% w/w sulphuric acid solution were measured and discussed in terms of acidity function theory. A novel approach, using an extension of the Grunwald-Winstein method, to correlate reaction kinetics of protonated substrates in concentrated acid solution was developed. The similarities between this novel approach and the more traditional acidity function method are discussed. The relevant background in the preparation and use of phosphonic acid containing compounds as intermediates for reactive dyestuffs is briefly discussed and the dyeing of cotton fabrics is outlined.
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32

Larsson, Jesper. "Acid neutralization using steel slags : Adsorption of fluorides in solutions using AOD slags." Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171235.

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Surface treatment processes of stainless steel, such as pickling, produces acidic waste water consisting of Na⁺, Cl⁻, F⁻, NO⁻3, SO42-, PO43-, Fe3+, Cr6+ and Ni2+. At Sandvik ABs steel works in Sandviken, this waste water is treated and neutralized using slaked lime before being released into the lake Storsjön. The aim of this report was to make a literary review of previous work in using slag as a neutralizing agent for acidic waste water. Furthermore, to see if it’s possible to replace some or all of the slaked lime in the neutralization process with slag and to study what slag that might be suitable to use. Since the waste water contains HF acid, the focus of this report was on different materials used for fluoride adsorptions. The literary study showed that the fluoride adsorption process with BOF slag, quick lime and magnesium oxide as adsorbents were endothermic. Therefore, it benefitted from an increased temperature. Furthermore, the literature study showed that many materials follow a pseudo-second-order kinetic model as well as a Langmuir or Freundlich isotherm for a fluoride adsorption. A previous experiment showed that a mixture of BF slag and slaked lime had the best HF acid neutralization among the tested materials. A fluoride adsorption experiment was made at different temperatures (25 – 55 °C) by using a slag from an aluminium reduced steel melt and a slag from a silicon reduced steel melt from the AOD converter in Sandviken. The silicon reduced steel melt slag showed an increase of fluorides in the solution, due to the presence of calcium fluoride in the slag. This was observed for all temperatures. The aluminium reduced steel melt slag also increased the fluoride content in the solution at 25 and 30 °C. At higher temperatures the fluoride content in the solution decreased with 93.6 to 94.9 %. Na⁺, Cl⁻, F⁻, NO⁻3, SO42-, PO43-, Fe3+, Cr6+, and Ni2+
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33

Cross, Peggi. "Aqueous alpha-lipoic acid solutions for removal of arsenic and mercury from materials used for museum artifacts." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195574.

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Recorded use of pesticides in the conservation of artifacts dates back to the 16th century. Museums today are faced with a tremendous task of identification and remediation of pesticides from artifacts in order to protect museum workers and the general public. In addition, artifacts are being repatriated by Native American tribes for use in cultural ceremonies which may subject the practitioner to health risks. Arsenic and mercury salts are among the pesticides that were used that are highly persistent and toxic. The primary challenge lies in removing these hazardous and persistent metals without damaging the materials or pigments on the objects.Concentrated aqueous alpha-lipoic acid solutions were developed for removing arsenic and mercury pesticides from materials commonly used in museum artifacts. The alpha-lipoic acid solutions were reduced using natural sunlight or laboratory ultraviolet lamps to enhance the binding of arsenic. The solubility of alpha-lipoic acid in various organic and inorganic solutions was determined and environmental parameters that impact the reduction and solubility, such as pH and temperature, were examined. The kinetics of the reaction of arsenic (III) with reduced lipoic acid was examined by varying the reduced lipoic acid, base and arsenic concentration as well as temperature and stirring conditions. The results indicated that the reaction occurs at a moderate rate primarily within 8 seconds in air. The reaction is chemically rate limited enhanced at higher temperatures and lower pH. Aerobic conditions significantly decreased the extent of the reaction with increased stirring rate. This impact was minimized by using a nitrogen environment or by limiting agitation during the reaction step.The methods developed were capable of removing up to 1000 µg/cm2 arsenic (of sodium arsenite) from simulated artifacts to levels near the lower detection limit of the X-ray Fluorescence Spectrometer (1 µg/cm2) without leaving detectable residues according to Attenuated Total-Reflection Fourier Transform Infrared Spectroscopy. Similar results were achieved in removing mercury (of mercuric chloride) from non-sulfur containing materials; however, the solutions and processes developed were not capable of removing mercury from sulfur-containing materials such as wool and feathers.
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34

Dolgikh, O. V., N. V. Sotskaya, and L. V. Sapronova. "The Kinetic Characteristics of Nickel Electrodeposition From Solutions with Amino Acids." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34881.

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Kinetics of nickel electrodeposition from electrolytes containing glycine, alanine, serine and asparaginic acid was studied. It was shown, that the process occurs irreversibly under mixed kinetics conditions with dominant control by charge transfer and is complicated by adsorption. All the complexes present in the baths are electroactive and reduce simultaneously. The process rate and kinetic characteristics sufficiently depend on the nature of amino acids. Namely, the more stable complexes are formed, the larger charge transfer coefficient and the less heterogeneous rate constant of charge transfer. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34881
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35

Adhikari, Benu Prasad. "Drying kinetics and stickiness studies of single drop of sugar and acid-rich solutions /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17136.pdf.

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36

Hempel, Sascha [Verfasser]. "Force Field Development for Activity Coefficient Calculations in Aqueous Amino Acid Solutions / Sascha Hempel." München : Verlag Dr. Hut, 2015. http://d-nb.info/1069020559/34.

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37

Dahlstrøm, Morten. "Effect of Copper Content on etching Response of Aluminum in Alkaline and Acid Solutions." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19593.

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Copper are used as an alloying element in aluminum alloys to increase the strength of the material. By mixing copper and aluminum the good corrosion resistance of the pure aluminum decreases giving the alloy a lower corrosion resistance. After years of investigation on corrosion of aluminum alloys several results have shown increasing corrosion rates of aluminum that have been alloyed with both copper and zinc, giving a “grainy appearance” on the surface of the alloy. By adding copper to the aluminum increased intergranular corrosion and preferential etching of surface grains has been found after heat treatment and etching of the alloy.Before etching the aluminum alloys in alkaline and acidic environments, Glow Discharge Mass Spectroscopy (GDMS) measurements was done for all the alloys to determine the correct amount of alloying elements and impurities in each alloy. Preliminary etching trials have been performed on pure aluminum (Al 5N), aluminum containing 10 ppm copper (AlCu10), aluminum containing 100 ppm copper (AlCu100), and aluminum containing 1000 ppm copper (AlCu1000), as well as corrosion potential tests. Further, the surface of all the etched test specimens has been investigated in light microscope, Scanning Electron Microscope (SEM), Electron Backscattered Diffraction (EBSD), Confocal Microscope (IFM), Energy Dispersive Spectroscopy (EDS),and Glow Discharge Optical Electron Spectroscopy (GD-OES). These methods have been used to determine height differences between etched neighboring grains, the crystallographic orientation of grains, surface roughness, detecting elements occurring on the surface of etched specimens, and giving a depth profile of the etched specimens.For the alkaline etching trials, an increasing etching rate was found by increasing the amount of copper in the alloys, however the AlCu10-alloy showed little or no difference from the pure aluminum both in the etching trials and the corrosion potential tests. By increasing the copper amount in the aluminum the corrosion potential increased drastically for AlCu100-alloy and the AlCu1000-alloy. Further an increasing etching rate of grains having close to [111] crystallographic orientation could be seen in alkaline environment, a difference in the surface roughness between grains with different crystallographic orientations could also be seen for the alkaline etched test specimens. The GD-OES investigations done on test specimens that had been alkaline etched revealed differences in their depth profiles dependent on the etching temperature and how the specimens was treated after being etched. AlCu1000-alloys etched in acidic environment showed a different type of etching and surface after etching than the other alloys etched in the same environment. A clear difference could also be seen between the alkaline and the acidic etched AlCu1000 specimens.
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38

Kimweri, Henry Tegani H. "Solubility of oxygen in aqueous sulphuric acid-metallic salt solutions under pressure leaching conditions." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5551.

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The densities and equilibrium solubilities of oxygen were determined in aqueous sulphuric acid containing different amounts of dissolved zinc and ferric sulphate at conditions that simulated the conditions used for pressure leaching of zinc sulphide ores. A two-stage absorption-desorption process was used in the determination of the oxygen solubilities. The solutions were saturated with oxygen at high temperatures and pressures and then, the volume of gas desorbed at 101.3 kPa and 323 K, was measured. The solubilities of oxygen in these solutions are closely expressed by Henry's law. The oxygen solubilities were found to be very low, in the order of 10$\sp{-5}$ mole fraction at an oxygen partial pressure of 101.3 kPa. The addition of the sulphuric acid and the metal salts was found to significantly decrease the oxygen solubilities. However, the oxygen solubilities increase with an increase in the partial pressure of oxygen and an increase in temperature. At all temperatures, the densities of these solutions were higher than those of water. The densities of the solutions decreased with an increase in temperature. (Abstract shortened by UMI.)
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39

Kish, Joseph R. "Active-passive corrosion of Fe-Cr-Ni alloys in hot concentrated sulphuric acid solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0022/NQ50995.pdf.

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40

Kish, Joseph J. "Active-passive corrosion of Fe-Cr-Ni alloys in hot concentrated sulphuric acid solutions /." *McMaster only, 1999.

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41

Chung, Mi Young 1972. "Activity coefficients of glycylglycine and DL, -aminobutyric acid in electrolyte solutions ar 298.15 K." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32956.

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The activity coefficients of glycylglycine and DL, alpha-aminobutyric acid in four aqueous electrolyte solutions (+NaCI, +NaBr, +KCI and +KBr) were obtained at 298.2K. The mean ionic activity coefficient of the electrolyte in aqueous solutions containing these biomolecules was determined from measurements of the potential differences of a cation and an anion ion-selective-electrodes, each measured versus a double junction reference electrode.
For systems containing glycylglycine, the results show that the nature of the anion has a major effect on the activity coefficients of glycylglycine. Comparison of activity coefficient data for glycylglycine with literature data for glycine, both in aqueous NaCl solutions, indicates that the effect of the electrolyte is larger for the peptide than for the amino acid. For the peptide, in all cases, the effect of the electrolyte is more important at low molalities of the electrolyte. The Wilson equation was used to correlate the activity coefficient data obtained. The correlation results were satisfactory for the region of concentrated electrolyte. For systems of DL, alpha-aminobutyric acid in electrolyte solutions, the cation was found to have a significant effect on the activity coefficients of DL, alpha-aminobutyric acid. There exists a distinctively different tendency of the activity coefficients in the dilute and in the concentrated regions of electrolyte in the presence of DL, alpha-aminobutyric acid.
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42

Ciriello, Carmine. "Nickel solvent extraction from dilute acidic sulphate solutions using octyl phenyl acid phosphate (OPAP)." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69789.

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The subject of this work is nickel extraction from dilute, acidic sulphate solutions through the use of organophosphorous acid reagents. The focus is primarily on OPAP, a mixed extractant consisting of mono- and di-octyl phenyl phosphoric acids, as well as on di-(2-ethyl hexyl) phosphoric acid (D2EHPA). The effects of certain parameters on the extraction of nickel, both quantitative and qualitative, have been studied. The parameters include: modifier presence, concentration and type; OPAP concentration; phase ratio; aqueous environment; age of organic solution; and mono-/di-OPAP ratio. The ability to strip nickel from the organic solution as well as selectivity and kinetic tests were carried out.
The use of 10% isodecanol as a modifier was found to be essential for the purpose of OPAP solubility in kerosene and phase separation. Furthermore, the cation exchange reaction proceeds very quickly, attaining equilibrium within 10 minutes. Unlike other phosphoric acid reagents, OPAP is able to extract significant amounts of nickel in the acidic pH range of 1 to 2. As well, nickel is easily stripped using a 1.0 M sulphuric acid solution.
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43

Willmer, Richard Franklin. "Mechanistic studies of nitrations and oxidations in solutions of dinitrogen pentaoxide in nitric acid." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305757.

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44

Jabit, Nurul Ain. "Chemical and electrochemical leaching studies of synthetic and natural ilmenite in hydrochloric acid solutions." Thesis, Jabit, Nurul Ain (2017) Chemical and electrochemical leaching studies of synthetic and natural ilmenite in hydrochloric acid solutions. PhD thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/36360/.

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The research interest for upgrading ilmenite to synthetic rutile has increased over the years due to the increasing demand for titanium dioxide white pigment and titanium metal. Sulfate and chloride leaching processes in the absence or presence of reducing agents are the most commonly tested leaching routes. However, chloride leaching is more economical and hence the preferred option. It allows relatively easy treatment of waste solutions and therefore the regeneration and recycling of hydrochloric acid. Despite the many attempts to develop chloride processes to upgrade ilmenite to synthetic rutile, systematic kinetic and mechanistic studies based on chemical and electrochemical dissolution are lacking in the literature. In addition, no comparison has been made between flat natural or synthetic ilmenite surfaces and particles of ilmenite concentrates of different origin and composition in chloride solutions. The main objective of this thesis is to bridge this gap and improve the understanding of the kinetics and reactions for the dissolution of synthetic ilmenite and natural ilmenite concentrates of different compositions, under non-reducing and reducing conditions. The measured dissolution rates of flat surfaces of synthetic ilmenite were found to decrease with time and obey a parabolic rate law, due to the blockage of the surface by an insoluble product. The dissolution rates of both iron and titanium were higher in the presence of tin(II) chloride as a reducing agent and remained unaffected over time. The reductive role of tin(II) ions appears to be that of inhibiting the formation of surface blocking solids, which can be used to propose a reaction sequence for ilmenite leaching. In electrochemical studies the measured rest potential of an ilmenite electrode in hydrochloric acid solutions was found to be lower compared to that measured in sulfuric acid solutions, indicating higher dissolution rates in the former case, due to reducing conditions. The measured potentials and surface characterisation studies indicated the reductive dissolution of titanium(IV) in the solid phase to titanium(III) in the aqueous phase, which facilitates the reductive leaching process by removing the insoluble product layers. Hematite mineral, which is found associated with weathered ilmenite, was also found to have a higher dissolution rate under the cathodic conditions which facilitated leaching. The leaching of three ilmenite samples of different compositions collected from local producers over the years, labelled as North Capel, Iluka and Tiwest, gave different results with regards to the iron and titanium dissolution as a result of different degrees of alteration. The leaching efficiency appeared to be in the descending order of North Capel > Iluka > Tiwest, which appeared to be inversely proportional to the degree of alteration. The highest extraction in hydrochloric acid alone was obtained from North Capel ilmenite (99% Ti and ~100% Fe) under conditions of 11 M HCl, pulp density of 4 g/L, 80 -110 °C and 2 h of leaching time. However, in the presence of a reducing agent, dissolution rates of iron and titanium increased in solutions of low acid concentrations and temperature. The initial rate of ilmenite dissolution in hydrochloric acid under reducing conditions was found to be half order with respect to the concentration of reducing agent, which suggests the involvement of an electrochemical reaction. However, the chemical/electrochemical leaching studies of rotating flat surfaces of ilmenite, based on the parabolic rate law and kinetic study revealed the same diffusivity of protons through the product layer. The batch leaching of ilmenite particles obeyed a shrinking core kinetic model, supporting the view that the proton diffusion through a product layer is the rate controlling step. The magnitude of proton diffusivity obtained using chemical leaching studies of rotating flat surfaces of synthetic or natural ilmenite or batch leaching studies of different ilmenite concentrates agree reasonably well despite the difference in mineral composition.
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45

Virtanen, Vesa. "Determination of clodronate and clodronic acid esters in aqueous solutions and urine using different analytical methods." Oulu, Finland : Dept. of Chemistry, University of Oulu, 1993. http://catalog.hathitrust.org/api/volumes/oclc/34155043.html.

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46

Große, Daldrup Jan-Bernd [Verfasser]. "A Contribution to the Crystallization of Aqueous Multisolute Amino Acid Solutions / Jan-Bernd Große Daldrup." München : Verlag Dr. Hut, 2012. http://d-nb.info/102582136X/34.

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47

Baraka, Ahmad. "Removal of heavy metals from aqueous solutions by novel melamine-formaldehyde-polyaminopolycarboxylic acid chelating adsorbents." Thesis, University of Strathclyde, 2006. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21660.

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The contamination of water recourses by heavy metals is a serious worldwide environmental problem. Industrial activities, mining and coal combustion are typical contamination sources. Removal of these metals from wastewater effluents is crucial as this contamination is non-biodegradable and highly toxic. Extensive research has been carried out to introduce new materials which alleviate these metals from wastewater effluents before their discharge into water bodies such as rivers and lakes. Conventional methods to remove heavy metals from wastewater include chemical precipitation, ion-exchange and chelation-adsorption. Adsorption is an important and developing research area because of the new material types available according to the application. Furthermore, it is standard process to place the adsorbent in a column and pump the wastewater through in a continuous system. It is also a cost-effective process. Chelating adsorbents are typically characterised by functional groups containing 0, N, S, and P donor atoms which coordinate to different heavy metal ions. It is necessary that the adsorbent has a high capacity and that the kinetics of adsorption is sufficiently fast. Polyaminepolycarboxylic (PAPC) acids are strong chelating agents and form stable chelates with different types of metals: transition, lanthanides and actinides. In spite of its exceptional chelating power, many of the PAPC compounds - such as DTPA (8-coordinations), CDTA (6-coordinations) and NTA (4-coordinations) - have not been thoroughly studied for use as active sites in adsorbent materials for heavy metal remediation from contaminated water effluents. Furthermore, the effect of the number of coordination groups on the adsorption behaviour has not been investigated. Use of these strong chelating agents (PAPC) for heavy metal removal by a polymeric adsorbent is presented in this study, with discussion of the chelation mechanism and affinity. The PAPC chelating agents were anchored on melamineformaldehyde (MF) gel. Although MF gel has suitable chemical and physical properties allowing the production of an adsorbent for heavy metal removal, it has not been studied. MF gel is porous and its matrix has a suitable platform to functionalize with some chelating compounds. PAPC-modified melamine-formaldehyde matrix is easy to produce compared to conventional chelating resins based on styrene/divinylbenzene. In this work, melamine-formaldehyde-polyaminepolycarboxylic acid (MF-PAPC) chelating adsorbents were synthesised by anchoring polyaminepolycarboxylic acids (PAPC) to melamine by the reaction of the carboxylic group of PAPC with a primary amine group of melamine forming a covalent amide bond during MF matrix formation. A series of samples of these adsorbents were prepared by varying water content, acidity of water and temperature as parameters to control the properties of the product. Samples of MF-DTPA, MF-NTA and MF-CDTA were chemically characterized using IR, elemental analysis, TPD-MS, 13C-NMR and 15N-NMR. Physical characterisation was carried out using BET, FE-SEM, and XRD techniques. Elemental analysis and BET results were used to select optimum samples for adsorption experiments. Selected MF-PAPC adsorbent samples are hydrophilic, amorphous and rigid. The content of PAPC in the dry adsorbent samples ranges from 1.08 to 2.28 mmole g⁻¹. The MF-PAPC adsorbents have reasonable surface areas (ranges from 159 to 179 m² g⁻¹) and a mesoporous structure (average pore diameter: 19 - 130 Å). The adsorption performance of MF-PAPC adsorbents was investigated against environmentally problematic divalent metal ions, namely, Cu(II), Co(II), Cd(II) and Zn(II). The adsorption behaviour of these adsorbents was characterised using mixture solutions of these four ions. The effects of different controlling parameters (solution initial pH, temperature, metal ions initial concentration and contact time) on adsorption were considered. Experimental data was fitted to the selected kinetic and isotherm models to suggest the best models to represent the adsorption process on MF-PAPC adsorbents. The thermodynamic parameters (adsorption free energy, enthalpy and entropy) were also calculated and a mechanism of adsorption is suggested according to the evaluation of the results. It was found that MF-PAPC adsorbents follow reversible first order and pseudo second order models to represent the adsorption kinetics. The Langmuir isotherm model gives the best representation of the adsorption processes. These findings indicate the chemical and reversible nature of the adsorption process. Thermodynamically, the adsorption was found to be spontaneous and exothermic. The entropy change shows that adsorption is not favourable. The results indicate that chelation and ion exchange are the mechanisms of adsorption with chelation the dominant type especially at lower temperatures and higher initial pH values. The PAPC type controls the affinity order of the four heavy metals. MF-PAPC adsorbents are distinguished by chelation-adsorption. The adsorption can be universal, or selective according to the PAPC type. Moreover, the selectivity order is different and depends on the PAPC type. MF-PAPC adsorbents can be used for metal-separation applications due to the higher affinity towards transition elements, lanthanides and actinides with respect to alkali and alkaline earth metals. The elution of the adsorbed metal ions was successfully accomplished using a solution of EDTA due to its high chelation power. The MF-DTPA adsorbent was used in a packed column for removal of the Cu(II) ion in a continuous up-flow system. The parameters of the study were: Bed height, flow rate and initial concentration. The Thomas model was used to fit the kinetic data. The BDST model was used to examine the possibility of scaling-up the laboratory set-up to industrial scale. The capacity of dsorption was found to be sensitive to bed height (positive: due to mass transfer), initial concentration (positive: due to concentration driving force) and flow rate (negative: due to contact time). It was found that the adsorption zone moves up the column at a constant speed for different bed heights. Hence, the process can be scaled-up for practical use using a BDST model.
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48

Kavi, Parthiv. "The preparation and characterisation of highly selective adsorbents for fission product removal from acid solutions." Thesis, University of Central Lancashire, 2016. http://clok.uclan.ac.uk/16576/.

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Nuclear fuel reprocessing of fissile materials is carried out in order to provide recycled fuel for existing and future nuclear power plants. One aim of reprocessing is to recover unused uranium (U-238 and U-235) and plutonium isotopes thereby preventing them from being wasted. This can save up to 30% of the natural uranium that is required each year for the fabrication of new nuclear fuel. A second aim is to reduce the volume of high-level radioactive waste. Along with the separation of uranium and plutonium there has been a significant interest in the extraction of short-lived fission products such as caesium and strontium, which play critical role during high-level waste handling and disposal. The PUREX process for reprocessing of irradiated fuel has been unchallenged for more than half a century even though it has several deficiencies such as flexibility, non-specificity of Tri-Butyl Phosphate (TBP), degradation of the extractant, TBP, and diluent. This project addresses the development of an alternative separation process to either replace and/or complement the PUREX process. Our process is based on the chromatographic separation of fission products from U and Pu. This research focuses on the synthesis of highly stable and selective materials which could be used as a stationary phase in a continuous chromatographic separation for short lived fission products (Cs, Sr); a technique patented by UCLan. The objectives of this project were to synthesis highly selective adsorbents for fission products (primarily Cs and Sr) capable of extracting these cations from acidic liquor (up to 3 M HNO3). In addition to selectivity (specificity) and acid stability, the materials under investigation would require fast cation uptake and high capacity. The research explored three key approaches for ion sorption: (1) Creating charge imbalance into ordered mesoporous MCM-41 structure (chapter 4), (2) Examination of molecular sieves based on their size exclusive property (chapter 5), and, (3) Preparation of ammonium phosphomolybdate (AMP) encapsulated polymeric composites (chapter 6). Various physical and chemical properties of the materials were characterised by XRD, SAXS, surface area, pore volume, pore size distribution, SEM, TEM, ATR-IR, 29Si NMR and TGA techniques. The cation uptake performance of the materials were evaluated for single ion and mixed ions against various nitric acid conditions. The study was further extended to rate of uptake in the best performing AMPPAN composites and identified area of improvement. Insertion of heteroatom e.g. boron into silicate structures, did not produce the desired effect; selectivity and capacity for the target fission products (Cs and Sr) were negligible compared with the required criteria. The incorporation of a mesoporous shell around zeolite structure was effective but the uptake of fission products from nitric acid solutions was again disappointing. The uptake of fission products from slightly acid solutions (pH value ~5) was more encouraging but not specific to any single ion (e.g. Cs or Sr) and this approach could form the basis of further studies. The preparation of AMP composites addressed both inorganic and organic substrates; AMP alumina composites in a suitable form i.e. spheres/beads was challenging and produced materials that were unsuitable and incorporated low AMP concentrations. This produced composites with low Cs uptake. The use of an organic substrate such as polyacrylonitrile (PAN) produced a composite that had a high selectivity for Cs, near specific, from nitric acid solutions but with comparatively low capacity and rate of uptake compared to pure AMP. These properties could be improved by manipulation of the composite structure; future work in this area is recommended.
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49

Chen, Yingying, and Yingying Chen. "Removing Phosphonate Antiscalants from Membrane Concentrate Solutions using Ferric Hydroxide Adsorbents." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/624128.

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Phosphonate antiscalants are commonly used in nanofiltration and reverse osmosis water treatment to prevent membrane fouling by mineral scale. In many circumstances it is desirable to remove these phosphonate compounds before concentrate disposal or further treatment. This research investigated the removal of phosphonate compounds from simulated membrane concentrate solutions using ferric hydroxide adsorbents. Two phosphonate antiscalants were investigated, Permatreat 191® (PT191) and nitrilotrimethylphosphonic acid (NTMP). Batch adsorption isotherms and column breakthrough and regeneration experiments were performed on two commercial adsorbents and a ferric hydroxide loaded polyacrylonitrile fiber adsorbent prepared in our laboratory. The best performing adsorbent was Granular Ferric Hydroxide® (GFH) obtained from GEH Wasserchemie. Adsorption isotherms measured after 24-hour equilibration periods showed initial concentration effects, whereby the isotherms were dependent on the initial adsorbate concentration in solution. Significant differences in adsorption behavior were observed between the PT191 and the NTMP adsorbates. Differences in adsorption behavior between NTMP and PT191 are all consistent with the PT191 containing fewer phosphonate functional groups per molecule than NTMP. Desorption rates were bimodal, with 40-50% of the adsorbed phosphonate being released on a time scale of 10-24 hours, while the remaining fraction was released approximately one order of magnitude more slowly. The slow desorbing fraction primarily resulted from equilibrium effects resulting from significant phosphonate adsorption, even in 1.0 mol/L NaOH solutions. Complete regeneration could not be achieved, even after eluting the adsorbent columns with more than 300 bed volumes of 1.0 mol/L NaOH. However, the incomplete regeneration had only a minor effect on phosphonate uptake in subsequent column breakthrough experiments.
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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.

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Анотація:
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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