Bioleaching of chalcopyrite and pyritic chalcocite using indigenous mesophilic microorganisms

Abstract: This scientific endeavour is a comparative study of the copper (bio)leaching process from chalcopyrite and pyritic chalcocite and its application as an alternative route for the conventional treatment of copper from sulphide ores around the Lufilian Arc in the Katanga copper belt (case study of Kamoa deposit) in the Democratic Republic of the Congo (DRC). The first findings were linked to the characterisation of the two campaigns in the form of bulk core samples collected from the Kamoa ore body: ‘campaigns 1 and campaign 2’ (chalcopyrite and pyritic chalcocite). The chemical and mineralogical characterisations confirmed that assumption, which means that copper, is mainly bearing under the form of chalcopyrite for the first campaign and chalcocite enclosed in pyritic ore. The second result was related to the bacterial isolation, physicochemical control of bacterial activities and the bacterial identification and numeration by means of 16SrRNA sequencing analysis. The Biomolecular analysis confirmed the presence of five DNA classes identified which are Gammaproteobacteria, beta proteobacteria, Alphaproteobacteria, Bacilli, Acidobacteria that were highly identified and numbered from the designed synthetic sample, among them, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans species which are most known for their biotechnological interest. The third findings from correlating the comparative study of copper leaching in ferric sulphate and copper bioleaching from chalcopyrite and pyritic chalcocite. The tests were in atmospheric conditions and in autoclave for predicting the chemical solubilisation and mechanisms to be considered in this research during bioleaching. Regarding the conventional method (leaching in ferric sulphate) several variables were studied, and optimal conditions were retained with pH 1.5, a pulp density of 2% (w/v) with 4g/L at 70° C, a stirring speed of 150 rpm, and hydrogen peroxide of 1.5 M was also retained as a supplementary additive for both campaigns (78. 52% for chalcopyrite and 82. 5% for pyritic chalcocite). During the chemical leaching process, it was noted that stirring speed does not have a significant effect during the leaching process this why, the optimal condition was fixed at 150 (rpm), which can be predicted due to the high presence of silica, carbonated compound and iron by-product formed during the dissolution time. Concentration below 1.5 M has a significant influence on increasing the dissolution yield – but with a limitation due to the slight destruction of the jarosite formation. Thus, above this limit, the copper dissolution action emerges as too faulty and enriches the inhibited character over the grain surface. Furthermore, the positive effect related to the added catalyst on the pH was reported as conversely proportional to the concentration increase – thereby highlighting an optimal output with 86.60 % at pH level 1. 5, taking into consideration the acid consumption for chalcopyrite and 89.70% for pyritic chalcocite. The copper dissolution rates and iron were correlated in these leaching conditions. Refractory copper sulphide ores can be leached with mesophilic bacteria and took an average of 7 days...M.Tech. (Extraction Metallurgy