Papers by Keyword: Covellite

Abstract: Currently the vast majority of the world’s copper is obtained through sulfide mineral processing. Among the copper sulfides, chalcopyrite is the most economically relevant due to its abundance. Therefore, several technologies have been developed in order to achieve an efficient copper extraction from copper sulfides. Among these developments, the hydrometallurgical options of bioleaching as well as chemical chloride leaching are prevailing for secondary copper sulfides due to their good results at lab, pilot and industrial scale. Examples such as the Bacterial Thin-Layer technology developed by Minera Pudahuel in the ́80s (CL Patent 32025), as well as the Cuprochlor® process developed by Minera Michilla (CL Patent 45163), coming to the more recent “Heap leaching method” (US Patent WO2014030048A1) and the mixed version of the “Chloride method for bioleaching” patented by BHP Billiton (US Patent WO2012001501A1), are some examples that are currently being extended to the efficient copper extraction from chalcopyrite. In this work, we have compared at lab-scale BioSigma’s bioleaching technology and the industrial state-of-art chloride leaching for a mainly chalcopyritic copper sulfide ore. The metallurgical and microbial results, and the economical evaluation and comparative analysis clearly show that bioleaching presents several advantages compared to chloride leaching, being the biotechnological option more cost-effective and therefore industrially applicable.

Abstract: Electrochemical behaviors of chalcopyrite, covellite, chalcocite and bornite in 9K medium at 65 °C were compared in this paper to verify they whether or not the intermediate products of chalcopyrite. The results confirmed that bornite, chalcocite and covellite are the intermediate products of chalcopyrite. Chalcocite and bornite can both oxidize to covellite.

Abstract: Bioleaching is the biological conversion of an insoluble metal compound into a water soluble form. In this process metal sulfides are oxidized to metal ions and sulfate by acidophilic microorganisms capable of oxidizing Fe2+ and/or sulfur-compounds. The metal solubilization from sulfide minerals is a chemical process which requires Fe3+ reduction. It is an environmentally friendly technique and an economical method for recovering metals that requires low investment and operation costs. In this work we studied the bioleaching of two kinds of acid-soluble copper sulfides, one easily leached by mesophilic bacteria (covellite), and the other one refractory to their activity (chalcopyrite), in acidic media with or without Fe2+ ions. We studied attached and planktonic populations of autotrophic bacteria, such as Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans in pure or mixed cultures. The influence of a heterotrophic microorganism, Acidiphilium cryptum, was also studied. Attachment was evaluated with fluorescence staining and FISH using four specific probes. L. ferrooxidans showed highest initial attachment in all cases. The presence of Ap. cryptum increased the cell attachment compared with the autotrophic pure cultures. It was possible to correlate experimental data with a mechanism of bacterial-metal sulfide oxidation, the polysulfide pathway for acid- soluble metal sulfides.

Abstract: Based on the bioleaching mechanism and electrochemical studies of covellite, the dissolution rate of covellite mineral is accelerated through increasing the redox potential (Eh) of the leach. In the present work, some methods were adopted to enhance the bioleaching of covellite concentrate (collected from Zijinshan copper mine, Fujian province, China) by adding different oxidants such as pure pyrite, ferric ions and H2O2. The goal of this study was to provide appropriate operating parameters for the industry application and increase the efficiency of the bioleaching of copper mine. The results showed that the optimal way to increase the redox potential (Eh) level was the addition of pure pyrite. This method could effectively raise the Eh of bioleaching process while the effect of environmental change was negligible. It could quicken the leaching process and enhance the final copper recovery through the addition of pyrite by 1:1 or 1:2 ratio of covellite concentrate to pyrite.

Abstract: My perceptions of the biohydrometallurgical field span four decades and stem from being a professional microbiologist conducting academic research and research for process development and applications. My experiences have given me an appreciation for knowledge gained through fundamental research and the transfer of this knowledge to development of commercial scale applications of microbial processes. The symposia series for international activities in biohydrometallurgy has been a major factor in advancing knowledge and applications for microbial bioleach systems. The first international biohydrometallurgy meeting was held in Braunschweig, Germany in 1977. This was the predecessor for the International Biohydrometallurgy Symposia. As evident from the Symposia, advances in development and applications of biohydrometallurgy technologies follow an evolutionary, rather than revolutionary progression from demonstration of knowledge at the laboratory scale to engineering commercial plants.