In this paper, the influence of zinc and iron reaction in sulfuric acid leaching system, the influence of the parameters on the leaching of zinc sulfate and the reaction conditions for the subsequent leachate purification were systematically studied. It is suggested that the primary zinc and iron phases in metallurgical zinc-bearing dust sludge are ZnO, ZnS, ZnFe2O4, Fe, Fe2O3 and Fe3O4. In Zn-Fe-H2O system, as the concentrations of zinc and iron ions in solution increase, each component therein remains unchanged. The dominant area is subjected to change with solution pH. When the potential and pH are respectively controlled within a different scope, Zn, Fe separation proceeds at the different levels. Fe2O3 is difficult to be leached when sulfuric acid is used as an agent. ZnO is leached while the iron ion is inhibited by pH control. It is found by comparison of lg[C]-pH maps of Fe2O3 and Fe(OH)2, Fe(OH)3 that in the treatment of subsequent leachate, Fe2+ can be oxidized into Fe3+ by adding an proper amount of the oxidant to solution, and Fe3+ forms Fe(OH)3 sediment by additive NaOH in solution. This hits the mark of iron removal. The research results have important theoretical significance for the leaching and purification process of alkali leaching-electrolysis process.
zinc-bearing dust sludge, leaching, thermodynamics, potential (φ)-pH dominant area diagram
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