Autoclave Leaching of Arsenic from Copper Concentrate and Matte

Abstract

Results are given for autoclave leaching of concentrates and mattes from polymetal semiproduct melts containing arsenic alongside copper. The possibility is demonstrated of selective copper and arsenic leaching into solution. It is confirmed that with autoclave leaching arsenides are broken down better than for natural arsenic-containing minerals. 83% of fraction 44 μm. In the first stage, concentrate was treated with acidified copper sulfate solution (180°C; original concentration 10 g/dm 3 H 2 SO 4 ; 16% solid fraction of concentrate in pulp; duration 1.5 h). With an increase in copper sulfate consumption from 20 to 43 g/dm 3 (molar ratio Cu:As = 1.2-2.7), the transfer of iron into the solution increased from 22 to 40%, arsenic from 4.4 to 26.3%; and with Cu:As > 2.0, the role of copper sulfate consumption appeared to be insignificant. With an increase in temperature from 140 to 160°C (Cu:As = 1.2; 10 g/dm 3 H 2 SO 4 ; duration 1,5 h), the transfer of arsenic into the solution increased from 20.6 to 31.5% and iron from 27 to 26%; at 180-200°C, the transfer of iron into solution, and espe- cially arsenic, decreased to 22.0 and 5-7%, respectively; the copper content in the final solution was markedly reduced. Phase analysis data for cakes showed that there was a marked increase in the content of chalcosine and iron arsenate. Apparently with an increase in temperature chalcopyrite becomes an active precipitating agent for copper and strengthens hydrolysis of arsenic-containing anions and iron (III) sulfate with the formation of insoluble iron arsenate. Favorable results were not given by an increase in original solution acidity from 5.0.to 53 g/dm 3 H 2 SO 4 (180°C, Cu:As = 2.5, duration 1.5 h), the transfer of iron and arsenic into the solution increased by 7-10%, and the degree of copper deposition decreased by 30%. In balanced tests (160-180°C, Cu:As = 2.7), not more than 40-42% As and 52-56% Fe passed into the solution, and up to 62-70% Cu was precipitated; cake composition, %: 37-40 Cu, 16-18 Fe, 27-29 S, 0.6-0.7 Sn. Thus, during hydrothermal treatment of original concentrate with acidified copper sulfate solution it was impossible to achieve good arsenic extraction