Dissertations / Theses on the topic 'Platinum Group Metals (PGM)'
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Zhang, Jingshu Ph D. Massachusetts Institute of Technology. "A bottom-up prospective dynamic materials flow assessment for platinum group metals (PGM) global demand forecast." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93048.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-77).
by Jingshu Zhang.
S.M.
Machado, Norma Maria Pereira. "Rheological study of nuclear glass melts containing Platinum Group Metal aggregates." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0018.
In France, borosilicate glass is used as a matrix to immobilize nuclear fission products resulting from spent fuel reprocessing. In the high-temperature vitrification process (1200 °C), most of elements to be contained react chemically with the vitrification additives to form a homogeneous glass melt. Platinum Group Metal (PGM) particles are not soluble in the melt and therefore are present as suspended particles of few microns. These particles exhibit an intense aggregation tendency and consequently the suspensions may present an anomalously high apparent viscosity. These systems are characterized by a shear-thinning and a thixotropic behaviors. The present study aims to provide important inputs for the overall rheological behavior of this system and its features through the characterization of a simulated nuclear glass melt containing 3.0 wt% (1.02 vol%) of PGM particles. A mathematical modeling of the thixotropic behavior of glass melts containing PGM particles is presented for the first time using a model similar to that proposed by Houska (Houska, 1981). This predictive model allow to describe experimental results obtained both in steady state and transient conditions. The impact of the shear stress and time on PGM aggregation degree and sedimentation kinetics is determined using an imposed-stress rheometer at high temperature and imaging analyses via Scanning Electron Microscopy (SEM). For the first time, the interplay between the rheological behavior of the system and the aggregation degree is provided, as well as the link with the particles settling. Based on the acquired experimental data, a force balance computation is executed to illustrate the different aggregation scenarios. The work provides a new input for the modeling and control of the vitrification process
Alshana, Usama Ahmed. "Separation And Quantitation Of Some Platinum Group Metals By Rp-hplc." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12605760/index.pdf.
-benzoylthiourea (DEBT). With the aim of reducing the number of steps in treating the samples, the method developed does not require the elimination of excess chelating reagent before the analysis of metal chelates. The different physical and chemical parameters affecting separation were examined in details. The whole analysis was completed on a C18 column in 16 min at 280 nm, with the mobile phase of acetonitrile-methanol-water (80:10:10, v:v:v) containing 0.20 mol l-1 pH 5.0 acetate buffer at a flow rate of 0.8 ml min-1. Detection limits of the method, based on 3s, were found as 14.2 ug l-1 for Pd and 0.77 mg l-1 for Pt using a 20-ul sample loop. Reproducibility of the method for ten repeated measurements was found as 2.36 % for 0.60 mg l-1 Pd and 2.58 % for 10.0 mg l-1 Pt as % RSD. The proposed method is a rapid, simple and highly selective method for the simultaneous determination of Pt and Pd by HPLC without the need for any interference elimination process.
Kriek, R. J. "Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5611.
Includes bibliographical references (leaves 74-79).
Historically the platinum group metals (PGMs) have been, and are still being dissolved by means of rather aggressive methods, e.g. aqua regia. Limited research has been conducted into the dissolution of the PGMs using different oxidizing agents. The dissolution of gold on the other hand has been afforded extensive research, and numerous papers and review articles have been published on the subject. The last number of years has seen the biggest application by volume of the PGMs as part of autocatalysts towards the degradation of harmful motor vehicle exhaust gases. This has subsequently sparked research into the recovery of specifically platinum, palladium, and rhodium from spent autocatalysts. Currently pyrometallurgical recovery of PGMs is being employed predominantly. A hydrometallurgical process on the other hand is, based on current technology, still a rather aggressive process that makes for high maintenance costs and an unpleasant environment. Gold has traditionally been dissolved by making use of cyanide, which is still the major route for gold dissolution. Due to environmental concerns lixiviants such as thiosulphate (S2O3 2-), thiourea (H2NCSNH2), and thiocyanate (SCN-) are gaining acceptance due to them being more environmentally friendly and giving good recoveries. These ‘softer’ alternatives have however not been tested on the PGMs. It is therefore the aim of this study to obtain an improved understanding of the leaching of the PGMs using lixiviants less aggressive than aqua-regia. These lixiviants include (i) SCN-, (ii) S2O3 2-, (iii) H2NCSNH2, and (iv) AlCl3/HCl. A thermodynamic study highlighted the fact that thermodynamic data for platinum-, palladium- and rhodium complexes are basically non-existent. To therefore obtain a clearer thermodynamic understanding of the leaching of the platinum group metals by means of these alternative lixiviants, future detailed speciation and thermodynamic investigations need to be conducted. An exploratory electrochemical investigation focusing on open circuit potentials and potentiodynamic scans, showed AlCl3 / HCl / NaOCl to be a good candidate for the leaching of the platinum group metals followed by SCN- / Fe3+ and CS(NH2)2 / Fe3+. Actual leach results, employing virgin autocatalysts as sample material, again highlighted the potential of AlCl3 / HCl / NaOCl as being a good lixiviant system. The surprise package, however, has been SCN- / Fe3+ that rendered very good results for Pd and Pt.
Aiglsperger, Thomas Hans. "Mineralogy and geochemistry of the platinum group elements (PGE), rare earth elements (REE) and scandium in nickel laterites." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/396340.
Van, der Horst Charlton. "Development of a bismuth-silver nanofilm sensor for the determination of platinum group metals in environmental samples." University of the Western Cape, 2015. http://hdl.handle.net/11394/4451.
Nowadays, the pollution of surface waters with chemical contaminants is one of the most crucial environmental problems. These chemical contaminants enter rivers and streams resulting in tremendous amount of destruction, so the detection and monitoring of these chemical contaminants results in an ever-increasing demand. This thesis describes the search for a suitable method for the determination of platinum group metals (PGMs) in environmental samples due to the toxicity of mercury films and the limitations with methods other than electroanalytical methods. This study focuses on the development of a novel bismuth-silver bimetallic nanosensor for the determination of PGMs in roadside dust and soil samples. Firstly, individual silver, bismuth and novel bismuth-silver bimetallic nanoparticles were chemically synthesised. The synthesised nanoparticles was compared and characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transformed infrared spectroscopy (FT-IR), Raman spectroscopy, and transmission electron microscopy (TEM) analysis to interrogate the electrochemical, optical, structural, and morphological properties of the nanomaterials. The individual silver, bismuth, and bismuth-silver bimetallic nanoparticles in the high resolution transmission electron microscopy results exhibited an average particle size of 10-30 nm. The electrochemical results obtained have shown that the bismuth-silver bimetallic nanoparticles exhibit good electro-catalytic activity that can be harnessed for sensor construction and related applications. The ultraviolet-visible spectroscopy, Fourier-transformed infrared spectroscopy, and Raman spectroscopy results confirmed the structural properties of the novel bismuth-silver bimetallic nanoparticles. In addition the transmission electron microscopy and selected area electron diffraction morphological characterisation confirmed the nanoscale nature of the bismuth-silver bimetallic nanoparticles. Secondly, a sensitive adsorptive stripping voltammetric procedure for palladium, platinum and rhodium determination was developed in the presence of dimethylglyoxime (DMG) as the chelating agent at a glassy carbon electrode coated with a bismuth-silver bimetallic nanofilm. The nanosensor further allowed the adsorptive stripping voltammetric detection of PGMs without oxygen removal in solution. In this study the factors that influence the stripping performance such as composition of supporting electrolyte, DMG concentration, deposition potential and time studies, and pH have been investigated and optimised. The bismuth-silver bimetallic nanosensor was used as the working electrode with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. The differential pulse adsorptive stripping peak current signal was linear from 0.2 to 1.0 ng/L range (60 s deposition), with limit of detections for Pd (0.19 ng/L), Pt (0.20 ng/L), Rh (0.22 ng/L), respectively. Good precision for the sensor application was also obtained with a reproducibility of 4.61% for Pd(II), 5.16% for Pt(II) and 5.27% for Rh(III), for three measurements. Investigations of the possible interferences from co-existing ions with PGMs were also done in this study. The results obtained for the study of interferences have shown that Ni(II) and Co(II) interfere with Pd(II), Pt(II) and Rh(III) at high concentrations. The interference studies of Cd(II), Pb(II), Cu(II) and Fe(III) showed that these metal ions only interfere with Pd(II) and Pt(II) at high concentrations, with no interferences observed for Rh(III). Phosphate and sulphate only interfere at high concentrations with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. Based on the experimental results, this bismuth-silver bimetallic nanosensor can be considered as an alternative to common mercury electrodes, carbon paste and bismuth film electrodes for electrochemical detection of PGMs in environmental samples. Thirdly, this study dealt with the development of a bismuth-silver bimetallic nanosensor for differential pulse adsorptive stripping voltammetry (DPAdSV) of PGMs in environmental samples. The nanosensor was fabricated by drop coating a thin bismuth-silver bimetallic film onto the active area of the SPCEs. Optimisation parameters such as pH, DMG concentration, deposition potential and deposition time, stability test and interferences were also studied. In 0.2 M acetate buffer (pH = 4.7) solution and DMG as the chelating agent, the reduction signal for PGMs ranged from 0.2 to 1.0 ng/L. The detection limit for Pd(II), Pt(II) and Rh(III) was found to be 0.07 ng/L, 0.06 ng/L and 0.2 ng/L, respectively. Good precision for the sensor application was also obtained with a reproducibility of 7.58% for Pd(II), 6.31% for Pt(II) and 5.37% for Rh(III), for three measurements. In the study of possible interferences, the results have shown that Ni(II), Co(II), Fe(III), Na+, SO42- and PO43- does not interfere with Pd(II) in the presence of DMG with sodium acetate buffer as the supporting electrolyte solution. These possible interference ions only interfere with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) as the supporting electrolyte solution.
Necib, Ammour Ouarda. "Effect of platinum group metal (PGM) additions on the stress corrosion cracking resistance of type 304 stainless steel in pressurised water reactors." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/effect-of-platinum-group-metal-pgm-additions-on-the-stress-corrosion-cracking-resistance-of-type-304-stainless-steel-in-pressurised-water-reactors(d7578933-6268-4fe8-819e-7b9b066f5c2e).html.
Sýkora, Jiří. "Využití iontoměničů pro prekoncentraci platinových kovů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-295670.
Gxoyiya, Babalwa Siliziwe Blossom. "Synthesis and evaluation of PGM-selective ligands." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1007849.
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Caddy, Irene. "A platinum life cycle assessment : potential benefits to Anglo Platinum / I. Caddy." Thesis, North-West University, 2011. http://hdl.handle.net/10394/6279.
Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2011.
Tooze, R. P. "Organometallic compounds of platinum group metals." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37880.
Isbilir, Amina. "Tridentate ligands with platinum group metals." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42777.
Roberts, Yvonne V. "Macrocyclic complexes of platinum group metals." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/11897.
Fotheringham, John David. "Heterobimetallic complexes of the platinum group metals." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/10906.
Shams, Leyla. "Accumulation of platinum group elements by the marine microalga, Chlorella stigmatophora." Thesis, University of Plymouth, 2010. http://hdl.handle.net/10026.1/309.
Harding, Nigel Anthony. "β-thia-alkyl complexes of platinum group metals." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283721.
Auer, Derek. "Flow-injection analysis of the platinum-group metals." Doctoral thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/17511.
To date the principle methods for the determination of the platinum-group metals (PGMs) use an "off-line" assay with flame-atomic absorption spectrometry and visible spectrometry. Both suffer numerous interferences and involve time-consuming and arduous laboratory separation methods prior to analysis. An "on-line" method for the rapid assay of the PGMs is indeed a lacking component in the analysts' repertoire of methods. This study describes the development of spectrophotometric methods for the determination of the PGMs using flow-injection analysis (FIA). The principle of exploiting the remarkably specific and selective reaction of stannous halides with the PGMs to yield a series of intensely coloured complexes in acidic solutions forms the basis of these methods. The reaction is subject to relatively few interferences from other transition metals. A high speed scanning spectrophotometer is employed to obtain second order data. The successful manipulation of the data enables the determination of PGMs as single components and also simultaneously in mixtures. Attention is focused on the establishment of principles for successful multi-component analysis of PGMs. The development of a software program for multi-wavelength data manipulation was mandatory and is described. Criteria for successful selection of analytical wavelengths are discussed. The usefulness of multi-dimensional graphical data representation is demonstrated in a stop-flow study of the palladium reaction with tin (II) chloride. Qualitative information is provided regarding the nature of complexes and their interactions. Correlation of spectrophotometric data with complex solution colour changes is made. The requirements for future progress in multi-component FIA determinations as well as the direction for future research conclude the study.
Bradley, Ena. "Electrochemistry of platinum group metals in ionic liquids." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705896.
Harlow, Karsten James. "Imidazolidene and alkylidene complexes of the platinum group metals." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313729.
Rioche, Cyrille Christophe. "An investigation of platinum group metals for environmental catalysis." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492038.
Heaton, Stephen Nicholas. "Vinylsilane and silyl hydride complexes of platinum group metals." Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295650.
Totland, Marina. "Determination of the platinum group metals in geological materials." Thesis, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390298.
Savage, Paul David. "Organometallic compounds of rhenium and the platinum group metals." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46494.
Arnold, Philip M. "Coordination chemistry of platinum group metals with sulphur-containing ligands." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249298.
Jeffery, Edward. "Hydrogenation of ketones over platinum group metals : a DFT study." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54642/.
Freestone, Timothy. "Some aspects of the biocompatibility of the platinum group metals." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316572.
McKenzie, S. G. "The effect of platinum group metals on duplex stainless steel." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37782.
Morton-Fernández, Brian. "Synthesis and characterisation of dithiolato complexes with platinum group metals." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3556.
Wilson, Andrew Matthew. "Ditopic reagents for the solvent extraction of platinum group metals." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/16864.
Flynn, Allison. "Transition metals as anti-tumoral agents : some structure-function relationships of the platinum group metals /." Master's thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-03022010-020016/.
Kaukonen, R. (Risto). "Sulfide-poor platinum-group element deposits:a mineralogical approach with case studies and examples from the literature." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514289545.
Shi, Peipei. "Geochemical assessment of the bioavailability of platinum group metals for phytomining." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57880.
Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
Wright, Edward Anthony. "A study of the hydrogen evolution reaction on platinum group metals." Thesis, University of Exeter, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414258.
Morales-Morales, David. "New sulphur complexes of platinum group metals as potential homogeneous catalysts." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242265.
Javu, Bulelwa Patricia. "Multi-component Platinum Group Metals for the methanol electro-oxidation process." University of the Western Cape, 2018. http://hdl.handle.net/11394/6571.
The purpose of this study was to develop a high performance-lower cost catalyst to be applied in Direct Methanol Fuel Cells (DMFC). The study also aimed to prepare plurimetallic supported platinum (Pt), platinum-ruthenium (PtRu), platinum-ruthenium-vanadium (PtRuV) and platinum ruthenium-vanadium-iron (PtRuVFe) upon multi-walled carbon nanotube (MWCNT) as well as upon multiwalled carbon nanotube-titanium oxide (MWCNT/TiO2) supports. Platinum is very active but prone to poisoning by carbon monoxide (CO), which may be present in the fuel used in fuel cells. The focus on the use of methanol was because of its better reaction kinetics, and better performance in direct methanol fuel cells (DMFC) better than proton exchange membrane fuel cell (PEMFC). When Pt is alloyed with another platinum group metals (PGM) the alloying decreases the over-potential for reactions critical in the fuel cells. Proton exchange membrane fuel cell (PEMFC) performance may be improved at low metal loading, when supported pluri-metallic catalysts are applied since the trimetallic catalysts may promote high catalyst utilisation. In practice, DMFC require electrodes with a Pt loading to achieve acceptance fuel cell (FC) power performance. The aim of this study was therefore the reduction of the catalyst loading through further improvement of mass activity of Pt based catalysts by partial substitution of the noble metal/metals, and the use of a carbon support that will provide high surface area, good electrical conductivity and high stability. MWCNT supported pluri-metallic (PtRuVFe,) and bimetallic (PtRu) nanoparticles possessed characteristic of increased surface area, improved electron transfer rate, enhance electro-catalytic activity and promoted stability.
McInnes, Eric J. L. "Physico-chemical studies of coordination complexes of the platinum group metals." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/12617.
Zhou, Yi. "Platinum group metals catalyzed steam methane reforming via micro-channel reactor." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/8703.
Steam methane reforming is a well-established industrial process used for generating hydrogen and synthesis gas. By performing this reaction in micro-channel reactors it is possible to take advantage of increased heat and mass transfer rates, allowing equipment size and residence times to be decreased by an order of magnitude which, in turn, leads to the possible utilisation of small scale steam reformers for portable fuel cell power systems. In this study, two commercial steam reforming catalysts, namely catalysts YR and XR, and a single in-house synthesised Rh/Al2O3 catalyst were studied in both packed bed and microchannel reactor configurations. All these catalysts exhibited stable activity in the packed bed reactor experiments.
Surakitbanharn, Yosyong. "The efficient separation of platinum group metals using centrifugal partition chromatography." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186074.
Wang, Sherrie Fang. "The coordination chemistry of tripodal phosphine chalcogenide ligands with platinum group metals." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ34289.pdf.
Mwase, James Malumbo. "Hydrometallurgical extraction of platinum group metals from a low-grade ore concentrate." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/8966.
The aim of this study is to investigate the economic and technical feasibility of processing platinum group metals (PGMs) and base metals (BMs) from a low-grade ore concentrate produced in the concentrator plant at Lonmin Pic. The PGMs of particular interest are platinum, palladium, ruthenium and rhodium, while the BMs of interest are copper and nickel. The ore concentrate, as a by-product, represents only 5 % of the total PGM value but as much as 70 % of the total tonnage of material processed in the concentrator plant. Further upgrading this material is not considered a viable route. However, even this low PGM content in the concentrate material accumulates to appreciable value on an annual basis motivating the need to develop alternative methods of extracting value from it. Initial estimates indicate that extraction levels of at least 50 % of the PGMs and 50 % of the BMs would need to be achieved, using low cost hydrometallurgical processes, to make the venture economically viable. These methods would exclude treatment via the smelter and pressure leaching: which are costly. energy intensive and result in leaching of large quantities of non-valuable elements. Previous studies revealed that organic acids had the potential to economically extract the PGMs under alkaline conditions, and BMs under acidic conditions, from various ores and concentrate materials. A literature survey confirmed that certain organic acids can be used to leach metals from ores and concentrates via chemical complexation. It further revealed that other chemical agents. namely cyanide, thiosulphate and bisulphide, were similarly capable of strongly complexing PGMs under various conditions of pH and temperature. The survey also revealed industrially established methods for extracting BMs from low-grade ores and concentrates. Based on this material, this study experimentally evaluated these options with the intent to propose a flowsheet to treat the concentrate material. This was conducted in two phases of experimental work.
Chatterjee, Sayandev. "Cooperative Two-Electron Reagents of Lower Transition Metals of Group 10." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250266435.
Nassar, Roger Abdo. "Coordination of some monodentate and hybrid multidentate phosphine ligands to platinum group metals." Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30050.
Bernardis, Francesco Luigi. "Development of novel chromatographic media for the separation of the platinum-group metals." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410220.
Murray, Angela Janet. "Recovery of platinum group metals from spent furnace linings and used automotive catalysts." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/7210/.
Tsoureas, Nikolaos. "Synthesis of phosphine - and pyridine - functionalised N-heterocyclic carbene complexes of platinum group metals." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494717.
Brothwood, Susan. "Vehicle related emissions of platinum group elements and other heavy metals in the urban environment." Thesis, Aberystwyth University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289175.
Mulwanda, James. "Recovery of dissolved platinum group metals from a pregnant copper sulphate leach solution by precipitation." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86538.
ENGLISH ABSTRACT: In Base Metal Refineries (BMRs), the copper sulphate leach solution produced during the final pressure leaching stage contains impurities such as selenium and tellurium, as well as other precious metals (OPMs, namely Rh, Ru, and Ir). Se and Te are removed by precipitation with sulphur dioxide prior to electrowinning of Cu. While a small percentage of the dissolved OPMs precipitate with the Se and Te, the largest portion remains in solution and is recycled to the first stage leach. If a larger portion of the OPMs in solution can be recovered in the Se/Te precipitation stage, OPM losses and the OPM inventory of the plant can be reduced. The aim of this project was to determine operating conditions that would allow maximum OPM recovery with minimal Cu and Ni co-precipitation in the Se/Te removal section of a BMR. The effects that the operating temperature, pressure, stirring rate, reagent type, and reagent quantity have on the metal precipitation behavior and precipitate characteristics were determined experimentally. Thio-urea and sulphurous acid were evaluated as precipitation reagents for temperatures of 80°C and 160°C, stirring rates of 250 rpm and 500 rpm, and pressures equal to ambient pressure and 7 bar. 200 % and 320 % excess thio-urea and 720 % and 960 % excess sulphur dioxide were used. The precipitation of OPMs with sulphur dioxide was generally poor; the maximum percentage Rh, Ru, and Ir precipitated were 35 %, 18 %, and 20 %, respectively. It was, however, found that the OPM precipitation increased as the reagent amount was increased. Increasing the temperature further increased Rh and Ir precipitation but affected the Ru precipitation negatively. Thio-urea precipitated virtually all of the Rh contained in the solution irrespective of the values of the process variables studied. As was the case with sulphur dioxide, increasing the amount of thio-urea added resulted in increased Ru and Ir precipitation, while higher temperatures favored Ir precipitation but not Ru precipitation. The maximum percentage Ru and Ir precipitation achieved with thio-urea were 87 % and 60 %, respectively. Complete Se precipitation was observed at all process conditions, while Te precipitation increased as the operating temperature and the reagent quantity were increased. Maximum Te precipitation of 98 % and 90 % were achieved when using 320 % excess thio-urea and 960 % sulphurous acid quantities, respectively, at 160°C and a stirring rate of 250 rpm. Increasing the reagent quantity and temperature did, however, also result in increased copper and nickel precipitation. The statistical analysis of the results allowed regression models to be fitted to predict the percentage metal precipitation as a function of the investigated process variables. These models were used to define an objective function to determine the optimal operating conditions. A temperature of 80oC, a pressure of 7 bar, and 200 % excess thio-urea were proposed as the optimum operating conditions that would yield 98 % Rh, 75 % Ru, and 48 % Ir precipitation with less than 5 % Cu and Ni co-precipitation. Experimental validation tests confirmed the model predicted values and proved repeatability of the experimental data.
AFRIKAANSE OPSOMMING: Die kopersulfaat logingsoplossing wat tydens die finale drukloging stadium in Basis Metaal Raffinaderye (BMRe) produseer word, bevat onsuiwerhede soos selenium en tellurium sowel as ander edelmetale (AEMe, naamlik Rh, Ru, en Ir). Se en Te word voor Cu elektrowinning verwyder deur middel van presipitasie met swaweldioksied. Alhoewel ʼn klein persentasie van die opgeloste AEMe saam met die Se en Te presipiteer, bly die grootste gedeelte in oplossing en word gevolglik na die eerste loging stadium hersirkuleer. AEM verliese en die AEM inventaris van die aanleg kan verminder word indien ʼn groter gedeelte van die AEMe in die Se/Te presipitasie stadium herwin kan word. Die doel van hierdie projek was om bedryfstoestande te bepaal om maksimum AEM herwinning met minimale Cu en Ni kopresipitasie in die Se/Te verwyderingseksie van ʼn BMR te behaal. Die effekte wat bedryfstoestande soos temperatuur, druk, roerder tempo, tipe reagens, en hoeveelheid reagens op die metaal presipitasiegedrag en presipitaat eienskappe het, is eksperimenteel bepaal. Tio-ureum en swaweligsuur is evalueer as presipitasie reagense vir temperature van 80°C en 160°C, roerder tempo’s van 250 rpm en 500 rpm, en drukke gelyk aan omgewingsdruk en 7 bar. 200 % en 320 % oormaat tio-ureum en 720 % en 960 % oormaat swaweldioksied is gebruik. Die presipitasie van AEMe met swaweldioksied was swak in die algemeen; die maksimum persentasie Rh, Ru, en Ir presipitasie wat behaal is, is 35 %, 18 %, en 20 %, onderskeidelik. Daar is egter gevind dat die AEM presipitasie toeneem indien die hoeveelheid reagens toeneem. ʼn Toename in die temperatuur het verder tot ʼn toename in Rh en Ir presipitasie gelei, maar dit het Ru presipitasie negatief affekteer. Tio-ureum het basies al die Rh in oplossing laat presipiteer, ongeag die waardes van die ander prosesveranderlikes wat ondersoek is. Soos wat die geval vir swaweldioksied was, het ʼn toename in die hoeveelheid tio-ureum ʼn toename in die Ru en Ir presipitasie tot gevolg gehad, terwyl hoër temperature Ir presipitasie bevoordeel en Ru presipitasie benadeel het. Die maksimum persentasie Ru en Ir presipitasie wat met tio-ureum behaal is, is 87 % en 60 %, onderskeidelik. Volledige Se presipitasie is by alle proses toestande waargeneem, terwyl Te presipitasie toegeneem het soos wat die temperatuur en die hoeveelheid reagens toegeneem het. Maksimum Te presipitasie van 98 % en 90 % is behaal toe 320 % oormaat tio-ureum en 960 % oormaat swaweligsuur, onderskeidelik, by 160°C en ʼn roerder tempo van 250 rpm gebruik is. ʼn Toename in die hoeveelheid reagens en die temperatuur het egter ook meer koper en nikkel presipitasie tot gevolg gehad. Die statistiese analise van die resultate het dit moontlik gemaak om regressie modelle te pas om die persentasie metaal presipitasie as ʼn funksie van die ondersoekte veranderlikes te voorspel. Hierdie modelle is gebruik om ʼn doelfunksie te definieer ten einde die optimale bedryfstoestande te bepaal. ʼn Temperatuur van 80°C, ʼn druk van 7 bar, en 200 % oormaat tioureum is voorgestel as die optimale bedryfstoestande wat 98 % Rh, 75 % Ru, en 48 % Ir presipitasie met minder as 5 % Cu en Ni kopresipitasie tot gevolg sal hê. Eksperimentele geldigheidsbepalingtoetse het die waardes wat deur die modelle voorspel is bevestig en die herhaalbaarheid van die eksperimentele data bewys.
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