Cobalt recovery from cobalt-bearing waste in sulphuric and citric acid systems

Abstract

Sulphuric and citric acid systems were used to recover Co from cobalt-bearing waste in this paper. The cobalt-bearing waste was leached sufficiently with the Co leaching efficiency over 99% in both systems, but the leaching efficiency of other metals Fe, Mn and Cu was lower in citric acid (H3Cit) system. The thermodynamic simulation showed that the complexing effect of citric acid changes the precipitation property of different metal ions, which makes them more difficult to be separated by precipitation in H3Cit system than in H2SO4 system. Thus, the impurities in H2SO4 system were removed by pre-precipitation of Fe at pH3.5 followed by solvent extraction; while the impurities in H3Cit system were removed by direct extraction. In H2SO4 system, 96.2% Mn, 95.4% Fe and 93.2% Cu were removed by D2EHPA extraction at pH3 with the cobalt loss over 30%; while in H3Cit system, 92.0% Mn, 73.7% Fe and 25.4% Cu were extracted at lower pH of 1.5 with the cobalt loss of 18.8%. Finally Co(OH)2 and crude CoFe2O4 were obtained from H2SO4 system and H3Cit system, respectively.