Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency

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dc.contributor.advisorHarrison, STLen_ZA
dc.contributor.authorGituma, Mark Kinotien_ZA
dc.date.accessioned2017-01-23T07:59:00Z
dc.date.available2017-01-23T07:59:00Z
dc.date.issued2016en_ZA
dc.description.abstractElectrical and electronic equipment has become an integral part of life in the modern world. When disposed of, it is termed Waste Electrical and Electronic Equipment (WEEE) and is one of the fastest growing waste streams in the world. Disposing the WEEE has associated risks as they contain a high amount of toxic metals (e.g. lead) which can leach into the soil, they place a high load on the land and they contain valuable metals making their recovery beneficial. Printed circuit boards (PCBs) are an essential part of WEEE. Although WEEE forms a small part of the waste stream (3 %), it contains a high concentration of metals. As such, PCBs form the focus of this study. Base metals, especially copper, hamper the recovery of gold and PGMs by cyanidation. Further the copper grades of WEEE exceed those of many low grade ores exploited. Hence copper recovery from PCBs has garnered considerable focus. Bioleaching using the ferric ion and ferrous ion regeneration cycle is applied to the recovery of metals from metal sulphides in virgin ores and there is growing interest in its application to WEEE. The two sub-processes in the ferric regeneration cycle are ferric ion production through microbial oxidation of ferrous ion for growth and metabolic activity; and ferric ion consumption through the reduction of metals leading to metal dissolution. The ferric ion consumption and production rates depend on each other and other factors. The metal dissolution through ferric iron reduction is a function of ferric iron concentration, affected by how fast ferric iron is produced through microbial oxidation. Ferric iron production is a function of both the ferrous iron and ferric iron concentrations and so depends on how fast the ferrous ion substrate is produced through the dissolution of metals which consumes ferric ion in the process. Ferric ion production is also affected by the microbial population and microbial specific rates of oxidation of ferrous ion. Ferric ion consumption is also dependent on the metal dissolution rate which is affected by mass transfer limitations and the type of metal for dissolution. These are two competing subprocesses where the dissolution efficiency of metals is limited by the slower process.en_ZA
dc.identifier.apacitationGituma, M. K. (2016). <i>Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Bioprocess Engineering Research. Retrieved from http://hdl.handle.net/11427/22920en_ZA
dc.identifier.chicagocitationGituma, Mark Kinoti. <i>"Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Bioprocess Engineering Research, 2016. http://hdl.handle.net/11427/22920en_ZA
dc.identifier.citationGituma, M. 2016. Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency. University of Cape Town.en_ZA
dc.identifier.risTY - Thesis / Dissertation AU - Gituma, Mark Kinoti AB - Electrical and electronic equipment has become an integral part of life in the modern world. When disposed of, it is termed Waste Electrical and Electronic Equipment (WEEE) and is one of the fastest growing waste streams in the world. Disposing the WEEE has associated risks as they contain a high amount of toxic metals (e.g. lead) which can leach into the soil, they place a high load on the land and they contain valuable metals making their recovery beneficial. Printed circuit boards (PCBs) are an essential part of WEEE. Although WEEE forms a small part of the waste stream (3 %), it contains a high concentration of metals. As such, PCBs form the focus of this study. Base metals, especially copper, hamper the recovery of gold and PGMs by cyanidation. Further the copper grades of WEEE exceed those of many low grade ores exploited. Hence copper recovery from PCBs has garnered considerable focus. Bioleaching using the ferric ion and ferrous ion regeneration cycle is applied to the recovery of metals from metal sulphides in virgin ores and there is growing interest in its application to WEEE. The two sub-processes in the ferric regeneration cycle are ferric ion production through microbial oxidation of ferrous ion for growth and metabolic activity; and ferric ion consumption through the reduction of metals leading to metal dissolution. The ferric ion consumption and production rates depend on each other and other factors. The metal dissolution through ferric iron reduction is a function of ferric iron concentration, affected by how fast ferric iron is produced through microbial oxidation. Ferric iron production is a function of both the ferrous iron and ferric iron concentrations and so depends on how fast the ferrous ion substrate is produced through the dissolution of metals which consumes ferric ion in the process. Ferric ion production is also affected by the microbial population and microbial specific rates of oxidation of ferrous ion. Ferric ion consumption is also dependent on the metal dissolution rate which is affected by mass transfer limitations and the type of metal for dissolution. These are two competing subprocesses where the dissolution efficiency of metals is limited by the slower process. DA - 2016 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2016 T1 - Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency TI - Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency UR - http://hdl.handle.net/11427/22920 ER -en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/22920
dc.identifier.vancouvercitationGituma MK. Investigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiency. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Bioprocess Engineering Research, 2016 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22920en_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.subjectBioprocess Engineering
dc.titleInvestigating ferric ion production and consumption trends in a simulated e-waste bioleaching environment for maximum metal dissolution efficiencyen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMSc (Eng)en_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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