Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: The copper sulphate leach solutions produced during the final pressure leach stages in base metal refinery processes contain low concentrations of other precious metals (OPMs, namely Rh, Ru and Ir ) and impurities in addition to the base metals (BMs) of interest. Se and Te impurities, in particular, must be removed from the leach solution before it is fed to copper electrowinning because these species have adverse effects on electrowinning efficiency. Currently, these elements are being precipitated from the leach solution with sulphurous acid. Se precipitation is satisfactory but Te removal still proves challenging. Previous studies have shown that tellurium can either be precipitated as cuprous telluride from copper sulphate solutions by reduction with sulphurous acid alone, or by the addition of SO2 as a precipitating agent and metallic copper as an additional precipitating agent. The objective of this study was to evaluate the effects of different process variables on Te and Se recovery in order to propose operating conditions at which increased tellurium precipitation can be achieved with minimal co-precipitation of base metals of interest (notably Cu and Ni). This would also aid in the development of a better understanding of tellurium and selenium precipitation mechanisms in CuSO4-H2SO4 medium. / AFRIKKANSE OPSOMMING: Die kopersulfaat logingsoplossing wat gedurende die finale druklogingstadia in basis metaal raffinaderye produseer word bevat, behalwe vir die basis metale van belang, ook lae konsentrasies ander edelmetale (AEM, naamlik Rh, Ru, en Ir) sowel as onsuiwerhede. Se en Te onsuiwerhede, in die besonder, moet vanuit die logingsoplossing verwyder word voordat die oplossing na die koper elektrowinning gevoer word omdat hierdie spesies negatiewe effekte op die elektrowinning effektiwiteit het. Hierdie elemente word tans met swaweligsuur vanuit die logingsoplossing gepresipiteer. Se presipitasie is voldoende, maar die Te verwydering bly steeds problematies. Vorige studies het getoon dat tellurium as kuprotelluried vanuit kopersulfaat oplossings presipiteer kan word deur middel van reduksie met swaweligsuur alleen, of met die byvoeging van SO2 as presipiteermiddel en metallieke koper as addisionele presipiteermiddel. Die doelwit van hierdie studie was om die effekte van verskillende prosesveranderlikes op Te en Se presipitasie te ondersoek ten einde bedryfstoestande voor te stel wat verbeterde tellurium presipitasie toelaat met minimale kopresipitasie van basis metale van belang (hoofsaaklik Cu en Ni). Dit sal ook bydra tot die ontwikkeling van ʼn beter begrip van die tellurium en selenium presipitasie meganisme in ʼn CuSO4-H2SO4 medium.