Laboratory studies on cleaning of slags from copper smelters

Abstract

The use of sulfide washing combined with carbothermic reduction as a technique for recovering As, Bi, Sb, and Cu from reverberatory furnace slag was examined. Samples of slag were melted under an argon inert atmosphere at temperatures in the range of 1373 to 1573 K and treated with iron sulfide and carbon. A low grade matte was produced. The effects of reaction time, agitation, addition of fluxes and process temperature on the recovery of the minor elements and copper in the matte were investigated. 1473 K is the maximum temperature required for the effective matte-slag separation. Recovery of all the four elements increased with increasing reaction time. At 1473 K the optimum reaction time is four hours. The equilibrium distribution ratio for Cu is calculated to be 41. Fluxing additions have no significant effect on the recovery of copper. Addition of Cao, SiO2 and CaF2 increased the recovery of As, Bi and Sb. CaO is the most effective flux for increasing the recovery of the minor elements. The maximum recoveries of As, Bi and Sb were 79%, 37% and 68% respectively and were obtained with 3 to 4% CaO addition. Agitation of the melt by bubbling argon gas decreased the recovery of As, Bi and Sb. However, with agitation, high recovery of Cu was achieved in a shorter reaction time. The knowledge obtained in this investigation will be helpful in choosing optimum operating parameters for industrial slag cleaning processes.