Theoretical simulation and experimental study on nickel, cobalt, manganese separation in complexation–precipitation system

The theoretical simulations and experiments on metal separation in complexation–precipitation system of Me(Ni, Co, Mn)–OH−–NH3–CO32- were carried out. The Gibbs free energy change ΔG for metal precipitation reactions was calculated. The ΔG–pH curves showed that the precipitation difficulty order was Mn > Co > Ni at pH range of 8–11. Separation experiments indicated that Mn and Co were able to precipitate successively in solution of different compositions mainly in the forms of carbonates. pH, initial carbonate concentration [C] and initial ammonia concentration [N] had different influence on Ni, Co and Mn precipitation behaviors: the separation effect was best at about pH 10; [C] had little effect on the metal separation in the [C] range of 0.05–0.4 mol/L; changing [N] could regulate precipitation step by step, as Ni in solution and Mn/Co in precipitate at [N] 1 mol/L, and Ni/Co in solution and Mn in precipitate at [N] 2.5 mol/L. The experimental results basically consisted with the theoretical predictions. The Ni solution after Mn/Co precipitation could be electrodeposited to obtain Ni metal. Finally a separation process in complexation–precipitation system of Me(Ni, Co, Mn)–OH−–NH3–CO32- characterized by the theoretical simulation was proposed, of which the Ni, Co and Mn precipitation could be predicted or controlled by flexibly importing parameters of [C], [N], pH, etc. The process can provide a reference to metal comprehensive recovery from similar nickel–cobalt secondary resources.

► Ni, Co and Mn separation was studied in complexation–precipitation system of OH−–NH3–CO32-. ► Theoretical simulation combined experimental method were employed. ► Mn and Co were precipitated mainly as carbonates step by step. ► Ni was electrodeposited from the solution after Mn and Co precipitation.