Features of the behavior of precious metals in the sulfide-alkaline leaching of arsenic-antimony concentrates

For the mineral resource base of metallurgy of non-ferrous and noble metals, deposits of polymetallic ores are the main source of raw materials. Against the backdrop of a global trend towards a decrease in the share of rich ores in the total volume of mining and processing, and a deterioration in the quality characteristics of ore raw materials, ore reserves containing arsenic and antimony as impurities are being developed. The authors studied the possibility of using ASL technology at atmospheric pressure for hydrometallurgical conditioning of low-quality copper concentrate. The studies were carried out on a flotation concentrate of the following composition (%): 16.1 Cu; 5.3 Zn; 23.8 Fe; 0.84 Pb; 1.36 As;0.21 Sb; 1.94 SiO2; 0.82 Al2O3, up to 24.0 g/t Ag, up to 4.0 g/t Au. As a result of the studies carried out, the features of the behavior of noble metals in the sulfide-alkaline environment during the leaching of arsenic-antimony concentrates of the Uchalinsky GOK were revealed. The dominant role of sodium sulfide in the formation of polysulfide and thiosulfate ions, which act as oxidizers for gold and silver, has been established. An analysis of the kinetic parameters indicates that the process of leaching of precious metals is limited by the rate of a chemical reaction in the absence of intradiffusion restrictions due to the possible passivation of tennantite by the formed secondary copper sulfides. The minimum threshold concentrations of sulfide and polysulfides were determined, at which a transition to the gold and silver leaching solution is possible: for sulfide more than 20 g/l-1, for polysulfides more than 2 M. The obtained product after ASL process was copper-zinc concentrate containing 0.2 % arsenic and precious metals up to 100 g/t. There are no losses of precious metals during the process.