The behaviour of silver, its chemical compounds and arsenic during biohydrometallurgical treatment of refractory concentrates

摘要

This paper reportd the behaviour of metallic silver, its chemical compounds and arsenic during the biohydrometallurgical treatment of refractory concentrates. It was found that metallic silver and its chemical compounds dissolving during biooxidation followed by the adsorption of silver by biomass. It was noted that the rate of monomineral fractions dissolution Ag2 Te, Ag2S, Ag3SbS3 and Ag3AsS3 which were bioleached is 2 - 10 times higher than that of the initial samples. The similar trends of silver behaviour and its compounds were also found during the biohydrometallurgical treatment of refractory gold-silver flotation concentrates. After the preliminary bioleaching, the cyanidation length of flotation concentrates decreased by 3 -5 times. The recovery of silver increased by 20% -38% . It was found that in the detoxification tails of cyanide slurries obtained from flotation concentrates biotreatment arsenic was found as a crystallic phase in the form of scorodite and amorphous compounds. The composition was determined by the molar ratio Fe: As in bacterial solutions. It was shown that the concentration of arsenic in the solution is 0. 2 - 0. 4 mg/L during biooxidation of sulphides at the molar ratio of Fe : As = 6 - 8 in the bacterial solutions followed by the detoxification of cyanide tails slurry by calcium hypochlorite. In order to decrease the concentration of arsenic in a liquid phase up to 0. 05 -0. 08 mg/L, thermal processing of biotreatment products was recommended. The results obtained were confirmed by pilot plant testing and witness to the possibility of the development of efficient environmentally-friendly technology to treat refractory gold-silver arsenicbearing concentrates.