Recovery of iron from zinc leaching residue by selective reduction roasting with carbon

Abstract

The recovery of iron from zinc leaching residue by selective reduction roasting with carbon was studied. The effects of roasting temperature, duration time and mass ratio of carbon to residue on decomposition of ZnFe2O4, iron recovery and iron grade were investigated based on thermodynamic calculation and phase composition analysis of zinc leaching residue. 58.6% of iron grade in magnetic concentrate and 68.4% of iron recovery were achieved after the residue roasted at 750°C for 1h under carbon to residue mass ratio of 4%. The phase composition of roasted residue indicated that the ZnFe2O4 decomposed in four stages: reduction of ZnFe2O4 to ZnO and Fe3O4, reduction of Fe3O4 to FeO, formation of Fe0.85−xZnxO and reduction of FeO to Fe. A technological process for simultaneously recovering iron and zinc from zinc leaching residue is proposed.