New pathway for utilization of jarosite, an industrial waste of zinc hydrometallurgy

Generated by zinc hydrometallurgical production and containing several toxic species, jarosite has been little used or beneficiated to date. Utilization of jarosite can save mining resources by producing valuable products, and reduce potential hazards from jarosite disposal. To avoid high energy consumption as in the roasting steps of the current jarosite process, hydrometallurgy has been used in the various steps of an original process aimed at producing valuable zinc-iron alloys from industrial jarosite waste. The process designed consists of three main steps: (i) jarosite leaching by sulfuric acid solutions yielding Fe(III) and Zn(II) species; (ii) reduction of Fe(III) to Fe(II) upon addition of industrial blende; and (iii) electrodeposition of the alloy from the recovered acidic Fe-Zn solution. Care was also taken to limit the amount of alkali to be added by maintaining the pH in a narrow range; moreover, no specific additives were employed. The various steps of the process have been investigated and the most suitable conditions for high yields have been identified. Among the various impurities in the minerals used and recovered from the acidic solution, copper ions had to be removed by preferential electrodeposition prior to deposition of Zn-Fe alloys. Nevertheless, these results indicated the need for a divided cell to avoid galvanic interference in this last operation from the Fe(II)/Fe(III) couple, which was found to reduce the faradaic yield for alloy deposition from 69% in the first minutes to 30% after 30 min.