The use of microorganisms notably bacteria in mineral processing industry is presently one of the leading emerging pre-treatment techniques being employed for the processing of double refractory gold ores and concentrates. Currently numerous studies are in progress to further improve upon the efficiency of the bacterial process and to investigate the potential of other microorganisms. In this study, microbial pre-treatment of double refractory gold ore (sample A) and concentrate (sample B) was investigated using a white-rot fungus, Tramestes versicolor (ATTC 20869). Pulp density, temperature, pH and retention times were the process variables considered. Preliminary studies investigated the amenability of selected pure sulfide sulfur minerals, various types of coal and ore sample A to fungal degradation. Various pre-treatment scenarios were also studied to optimize gold extraction. These were single stage, a two-step and two stage processes involving the well known chemolithotrophic bacteria Acidithiobacillus thiooxidans (ATTC 15494), Acidithiobacillus ferrooxidans (ATTC 19859) and Leptospirillum ferrooxidans (ATTC 53992), the bacterium, Streptomyces setonii (ATTC 39116) and the white-rot fungus, Tramestes versicolor. Preliminary results for sample A indicated that T. versicolor did not degrade sulfides significantly at its optimum growth conditions (pH range of 4.5 – 5.0) and carbonaceous matter was not degraded but rather passivated as preg-robbing decreased significantly. Lignite was inert to passivation by T. versicolor unlike bituminous coal and to lower extent anthracite. Stimulated alkaline conditions (pH range of 9.5 – 10.5) recorded the overall best sulfur oxidation. Results of both the single stage and two-step processes confirmed that carbonaceous matter was passivated by T. versicolor; as preg-robbing decreased significantly from 18.1% to ≤ 1.0%. Gold extraction by cyanidation of the pre-treated sample A was 82.5% for the two-step as against 80.5 % for the single stage and 15.0% for the untreated sample. Application of the two-step and single stage process conditions to sample B resulted in 93.3% and 89.9% gold extraction respectively as against untreated concentrate of 30.5%. For the various two stage pre-treatment processes investigated, the abiotic - S. setonii process recorded the best gold extraction of 81.5% for sample A. S. Setonii degraded carbonaceous matter unlike T. versicolor which passivated it. However, it takes only 3 - 7 days for T. versicolor to effect passivation and eliminate preg-robbing while 14 - 56 days is required for S. setonii to degrade carbonaceous matter significantly. The result of the novel microbial pre-treatment process indicated that sulfide sulfur was degraded under alkaline conditions and carbonaceous matter passivated by T. versicolor at its optimum growth conditions. This led to a significant improvement in gold extraction from the double refractory gold ore and concentrate investigated. / Thesis (Master, Mining Engineering) -- Queen's University, 2008-09-22 16:42:01.272

O ouro, assim como outros bens minerais, é uma commodity, ou seja, um produto não diferenciado, com preço determinado pelo mercado internacional, sem a interferência de seus produtores. Diante desse cenário, associado à exaustão dos depósitos minerais de maiores teores, as mineradoras vêm buscando melhores formas de aproveitamento de matérias-primas minerais mais complexas quanto à extração e ao beneficiamento. Os retornos financeiros são obtidos no estrito controle da produção com redução de custos e mitigação de perdas nas operações unitárias. A caracterização tecnológica está inserida como uma abordagem multidisciplinar e fundamental para o melhor aproveitamento dos bens minerais. Possibilita um maior conhecimento do minério e das associações minerais presentes, que auxiliará no desenvolvimento das alternativas de explotação e na otimização do processo em funcionamento. Dentre os procedimentos de caracterização das associações minerais mais acurados citam-se os sistemas automatizados de análise de imagens adquiridas por microscopia eletrônica de varredura. Permitem a avaliação qualitativa ou quantitativa de grande número de partículas quanto à composição química e mineral, partição de elementos nos minerais presentes, formas de associações e liberação entre os minerais. Este estudo se concentra na caracterização de quatro amostras mineralizadas a ouro, de diferentes regiões do Brasil, pela análise automatizada de imagens e por métodos laboratoriais de separações minerais e extração hidrometalúrgica do ouro. A combinação de procedimentos laboratoriais com a análise de imagens permitiu confrontar os resultados das recuperações potenciais, fornecendo subsídios para abordagens de processo, para obtenção da máxima recuperação do ouro e para diagnosticar as características interferentes nesses processos. / Gold and other mineral goods are considered commodities, i.e., a non-differentiated product, at a price determined by the international market, without control of its producers. Given this, coupled with the exhaustion of mineral deposits of higher content, mining companies have been trying to find best procedure alternatives of more complex raw mineral matter. The financial returns are achieved by means of strict production controls, cost reduction and mitigation of losses in unit operations. In this context, process mineralogy is a multidisciplinary and fundamental approach to the better use of mineral goods. Enables a greater knowledge of the ore and its associations, to assist in the development of process alternatives to optimize mineral beneficiation plants. SEM-based automated images analysis is one of the most precise procedures to characterize mineral associations. These systems allow the qualitative or quantitative evaluation of a large number of particles, both as to its chemical and mineralogical content, partition of elements of interest among different minerals, phase\'s associations and liberation. This study focus on the characterization of four gold-mineralized samples from different regions of Brazil, through SEM-based automated image analysis and mineral separations at laboratory scale. The combination of experimental procedures with images analysis allowed the comparison of the results of possible recoveries, providing subsidies for process approaches, to obtain the maximum recovery of gold, and to diagnose the interfering features in these processes.

O ouro, assim como outros bens minerais, é uma commodity, ou seja, um produto não diferenciado, com preço determinado pelo mercado internacional, sem a interferência de seus produtores. Diante desse cenário, associado à exaustão dos depósitos minerais de maiores teores, as mineradoras vêm buscando melhores formas de aproveitamento de matérias-primas minerais mais complexas quanto à extração e ao beneficiamento. Os retornos financeiros são obtidos no estrito controle da produção com redução de custos e mitigação de perdas nas operações unitárias. A caracterização tecnológica está inserida como uma abordagem multidisciplinar e fundamental para o melhor aproveitamento dos bens minerais. Possibilita um maior conhecimento do minério e das associações minerais presentes, que auxiliará no desenvolvimento das alternativas de explotação e na otimização do processo em funcionamento. Dentre os procedimentos de caracterização das associações minerais mais acurados citam-se os sistemas automatizados de análise de imagens adquiridas por microscopia eletrônica de varredura. Permitem a avaliação qualitativa ou quantitativa de grande número de partículas quanto à composição química e mineral, partição de elementos nos minerais presentes, formas de associações e liberação entre os minerais. Este estudo se concentra na caracterização de quatro amostras mineralizadas a ouro, de diferentes regiões do Brasil, pela análise automatizada de imagens e por métodos laboratoriais de separações minerais e extração hidrometalúrgica do ouro. A combinação de procedimentos laboratoriais com a análise de imagens permitiu confrontar os resultados das recuperações potenciais, fornecendo subsídios para abordagens de processo, para obtenção da máxima recuperação do ouro e para diagnosticar as características interferentes nesses processos. / Gold and other mineral goods are considered commodities, i.e., a non-differentiated product, at a price determined by the international market, without control of its producers. Given this, coupled with the exhaustion of mineral deposits of higher content, mining companies have been trying to find best procedure alternatives of more complex raw mineral matter. The financial returns are achieved by means of strict production controls, cost reduction and mitigation of losses in unit operations. In this context, process mineralogy is a multidisciplinary and fundamental approach to the better use of mineral goods. Enables a greater knowledge of the ore and its associations, to assist in the development of process alternatives to optimize mineral beneficiation plants. SEM-based automated images analysis is one of the most precise procedures to characterize mineral associations. These systems allow the qualitative or quantitative evaluation of a large number of particles, both as to its chemical and mineralogical content, partition of elements of interest among different minerals, phase\'s associations and liberation. This study focus on the characterization of four gold-mineralized samples from different regions of Brazil, through SEM-based automated image analysis and mineral separations at laboratory scale. The combination of experimental procedures with images analysis allowed the comparison of the results of possible recoveries, providing subsidies for process approaches, to obtain the maximum recovery of gold, and to diagnose the interfering features in these processes.