Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants

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dc.contributor.advisorGaylard, Peteren_ZA
dc.contributor.advisorNicol, Mikeen_ZA
dc.contributor.advisorNikoloski, Aleksen_ZA
dc.contributor.authorKriek, R Jen_ZA
dc.date.accessioned2014-07-31T11:40:34Z
dc.date.available2014-07-31T11:40:34Z
dc.date.issued2008en_ZA
dc.descriptionIncludes abstract.
dc.descriptionIncludes bibliographical references (leaves 74-79).
dc.description.abstractHistorically 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.en_ZA
dc.identifier.apacitationKriek, R. J. (2008). <i>Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Bioprocess Engineering Research. Retrieved from http://hdl.handle.net/11427/5611en_ZA
dc.identifier.chicagocitationKriek, R J. <i>"Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Bioprocess Engineering Research, 2008. http://hdl.handle.net/11427/5611en_ZA
dc.identifier.citationKriek, R. 2008. Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Kriek, R J AB - 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. DA - 2008 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2008 T1 - Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants TI - Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants UR - http://hdl.handle.net/11427/5611 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/5611
dc.identifier.vancouvercitationKriek RJ. Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Bioprocess Engineering Research, 2008 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/5611en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentCentre for Bioprocess Engineering Research
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherleachingen_ZA
dc.subject.otherplatinumen_ZA
dc.subject.otherpalladiumen_ZA
dc.subject.otherrhodiumen_ZA
dc.subject.otherPGM (Platinum Group Metal)en_ZA
dc.subject.othercatalytic converter/autocatalysten_ZA
dc.subject.otherthermodynamicsen_ZA
dc.subject.otherelectrochemistryen_ZA
dc.titleLeaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviantsen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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