Selective leaching of nickel and cobalt from sintered nickel alloy by oxygen pressure acid leaching process

In this work, oxygen pressure acid leaching is implemented to augment the leaching efficiency of valuable metals from sintered nickel alloy. Techniques investigation shows that NiO in the sample and NiO coated by Ni 2 O 3 impede the ongoing dissolution of nickel during atmospheric acid leaching. The nickel oxides undergo conversion into soluble nickel sulfate via oxygen pressure acid leaching. Thermodynamic analysis indicates that in the system of pH<6.26, temperature >146 °C and potential >0.20 V, a substantial portion of both nickel and cobalt dissolved into the solution as metal ions, while most of the iron is hydrolyzed to Fe 2 O 3 in residue. The optimized leaching conditions are: H 2 SO 4 concentration of 150 g/L, leaching temperature of 180 °C, oxygen partial pressure of 2 MPa, liquid-to-solid ratio of 10 mL/g, stirring rate of 400 r/min, and time of 150 min. Given these circumstances, the leaching efficiencies of Ni, Co and Fe were 97.42%, 96.30% and 10.05%, correspondingly. Reaction kinetics studies indicate that the leaching process of nickel was dictated by a controlled model of surface chemistry, featuring an apparent activation energy of 43.73 kJ/mol. This study offers a viable and environmentally-friendly methodology for the leaching of nickel from sintered nickel alloy.