In different nonferrous metal-producing industry sectors, the impurity element iron has to be removed from the process solution. Examples for the arising residues are jarosite or goethite precipitates from nickel or zinc production but also red mud from aluminum production. Regardless of environmental concerns, the material is landfilled in almost any case, although valuables such as indium, silver, nickel or zinc are present in considerable amounts. Within the presented research, a low-carbon-dioxide-emitting, multimetal recovery from such iron-containing residues by means of a selective chlorination extraction has been fundamentally evaluated by experiments but also by comprehensive thermodynamic calculations. This paper summarizes the thermodynamic fundamental concept exploited to separate the dominating iron matrix from the valuable elements and shows verification experiments in a laboratory size of several grams. Through thermodynamic calculations and small-scale experiments with pure metal oxides and sulfates, it has been proven that the metal chlorides AlCl3· 6H2O, FeCl3· 6H2O and MgCl2· 6H2O are viable and effective reactants for chlorination. In trials with actual industrial iron precipitation residues from the zinc industry, especially, the use of MgCl2· 6H2O and FeCl3· 6H2O leads to high extraction rates for the investigated valuable metals Ag, Au, Bi, Cu, In, Pb, Sn and Zn.
Full-text paper:
Mining, Metallurgy & Exploration (2023) 40:2023–2036, https://doi.org/10.1007/s42461-023-00872-5
