An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations

 

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dc.contributor.advisor Hansford, Geoffrey Spearing en_ZA
dc.contributor.author Bailey, Andrew Douglas en_ZA
dc.date.accessioned 2016-08-22T12:23:31Z
dc.date.available 2016-08-22T12:23:31Z
dc.date.issued 1994 en_ZA
dc.identifier.citation Bailey, A. 1994. An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/21417
dc.description Bibliography: pages 121-132. en_ZA
dc.description.abstract Bacterial oxidation is currently finding significant application for the oxidative pretreatment of refractory gold-bearing sulphides. Plants processing sulphide concentrates have commonly been operated at solids concentrations of between 18 and 20 per cent (m/v) (Le 180 and 200 kg.m-3). At higher concentrations, a decline in the bio-oxidation rate has been observed. Other metallurgical processes, such as chemical leaching and cyanidation, are performed at higher solids concentrations of between 40 and 50 per cent (400 and 500 kg.m-3), providing an incentive to increase the solids concentration at which bio-oxidation plants are operated. A review of literature indicated the following factors to be potential causes of reduced bio-oxidation rates at high solids concentrations: oxygen and carbon dioxide mass transfer; a low bacteria-to-solids ratio; mechanical damage of the bacte.ria; and the build-up of inhibitory oxidation products. Interaction of these factors in the completely-mixed reactors that are commonly used for biooxidation, has confounded the interpretation of the effects of individual factors. Analysis of literature data revealed a link between the sulphide grade of a particular material and the highest solids concentration at which the bacterial oxidation rate was maximal. The oxygen demand is directly proportional to the sulphide concentration in the reactor. Correlations were used to predict the oxygen transfer potential in the experimental reactors and it was found that as long as the oxygen transfer potential exceeded the oxygen demand, the biooxidation rate was proportional to the solids concentration for a specific material. Wh~n the oxygen demand equalled or exceeded the oxygen transfer potential, then the bacterial oxidation rate was limited by oxygen availability. The sulphide grade is characteristic of a particular ore or concentrate and from the data analysis oxygen availabiiity appeared to be the underlying reason why low grade materials could be oxidised at the maximum specific bio-oxidation rate at far higher solids concentrations than high-grade f!laterials. Abstract ii The experiments performed in this study were designed to further investigate the apparent relationship, identified by analysis of literature data, between sulphide grade and the solids concentration at which the bacterial oxidation rate was maximal. The effect of both solids concentration and sulphide grade on the biooxidation rate was investigated and related to the oxygen availability in the reactor. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Chemical Engineering en_ZA
dc.title An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Engineering and the Built Environment
dc.publisher.department Department of Chemical Engineering en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Bailey, A. D. (1994). <i>An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/21417 en_ZA
dc.identifier.chicagocitation Bailey, Andrew Douglas. <i>"An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1994. http://hdl.handle.net/11427/21417 en_ZA
dc.identifier.vancouvercitation Bailey AD. An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1994 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/21417 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Bailey, Andrew Douglas AB - Bacterial oxidation is currently finding significant application for the oxidative pretreatment of refractory gold-bearing sulphides. Plants processing sulphide concentrates have commonly been operated at solids concentrations of between 18 and 20 per cent (m/v) (Le 180 and 200 kg.m-3). At higher concentrations, a decline in the bio-oxidation rate has been observed. Other metallurgical processes, such as chemical leaching and cyanidation, are performed at higher solids concentrations of between 40 and 50 per cent (400 and 500 kg.m-3), providing an incentive to increase the solids concentration at which bio-oxidation plants are operated. A review of literature indicated the following factors to be potential causes of reduced bio-oxidation rates at high solids concentrations: oxygen and carbon dioxide mass transfer; a low bacteria-to-solids ratio; mechanical damage of the bacte.ria; and the build-up of inhibitory oxidation products. Interaction of these factors in the completely-mixed reactors that are commonly used for biooxidation, has confounded the interpretation of the effects of individual factors. Analysis of literature data revealed a link between the sulphide grade of a particular material and the highest solids concentration at which the bacterial oxidation rate was maximal. The oxygen demand is directly proportional to the sulphide concentration in the reactor. Correlations were used to predict the oxygen transfer potential in the experimental reactors and it was found that as long as the oxygen transfer potential exceeded the oxygen demand, the biooxidation rate was proportional to the solids concentration for a specific material. Wh~n the oxygen demand equalled or exceeded the oxygen transfer potential, then the bacterial oxidation rate was limited by oxygen availability. The sulphide grade is characteristic of a particular ore or concentrate and from the data analysis oxygen availabiiity appeared to be the underlying reason why low grade materials could be oxidised at the maximum specific bio-oxidation rate at far higher solids concentrations than high-grade f!laterials. Abstract ii The experiments performed in this study were designed to further investigate the apparent relationship, identified by analysis of literature data, between sulphide grade and the solids concentration at which the bacterial oxidation rate was maximal. The effect of both solids concentration and sulphide grade on the biooxidation rate was investigated and related to the oxygen availability in the reactor. DA - 1994 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1994 T1 - An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations TI - An assessment of oxygen availability, iron build-up and the relative significance of free and attached bacteria, as factors affecting bio-oxidation of refractory gold-bearing sulphides at high solids concentrations UR - http://hdl.handle.net/11427/21417 ER - en_ZA


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