Hydrothermal treatment of sinters containing thiosalts of non-ferrous metals

Abstract

Preliminary experiments have shown that the solution to the environmental problem of recycling copper-electrolyte smelting slags is by sulfidization followed by leaching and subsequent separation of selenium, tellurium, arsenic, and antimony from the solution. The first operation of this technology, which provides high selectivity, is sintering. The results obtained indicate the formation of metal thiosalts during sintering in the presence of sodium sulfate and carbonate and a reducing agent at a temperature of 800 ⁰C. An increase in temperature leads to the melting of individual components of the charge and a slowdown in the process of sulfidization of slag components. At lower temperatures, a decrease in the activity of the charge components is observed. The optimal addition of Na₂SO₄ was 27 % of the slag weight, and Na₂CO₃ - 8.5 % of the slag weight. Reducing agent consumption is 27 % of the slag weight, sintering time is 2 hours. The optimal parameters for leaching the resulting cakes are temperature 90 ⁰C, L:S ratio = 3:1, leaching duration 2 hours, and sodium sulfide concentration 2 mol/l. The best results for cake melting from cake leaching are temperature 1200 ⁰C, heating rate 10 ⁰C/min, and holding time 30 minutes. Charge composition: cake, 30 % soda ash by weight of cake, 11 % activated carbon. During the smelting, a metallized phase was obtained, consisting mainly of lead (90-91 %), and slag was obtained with a residual content of lead and copper of no more than 0.5 %.