Efficient removal of iron during partial neutralization of nickel laterite acid leach solution: DFT calculation and experimental verification of mechanism

Partial neutralization is typically used to remove Fe3+ ions from the acid leach solution of laterite. However, during this process, significant amounts of Mg2+, Ni2+, Co2+, and SO2-4 are lost. With increasing initial Fe3+ concentration and solution pH, the severity of loss increases, with the precipitation of Fe3+. In this study, the mechanisms of ion co-precipitation during partial neutralization were investigated. Based on density functional theory calculations, a precipitation pathway through the formation of [Fe4(OH- )2(SO2-4)4]& BULL;[2SO2-4 & BULL;yH2O]& BULL; [M2+] was proposed. The differential charge density diagram indicated that the O atoms acted as the charge acceptors and maintained the precipitate structure. The coordination between M2+ and SO2-4 could be destroyed via intense agitation, releasing approximately 100% of Mg2+, Ni2+, and Co2+ ions from the precipitates to the solution. Furthermore, the addition of cationic or anionic surfactants limited the formation of these coordination bonds. The highest retention percentages of Mg2+, Ni2+, and Co2+ in solution were 99.4, 99.6, and 99.9%, respectively, after adding 2 x 10-5 mol/L of sodium dodecylbenzenesulfonate (CTAB). In addition, a high temperature could break these coordination bonds. The retention percentages of Mg2+, Ni2+, and Co2+ increased from 82.6, 85.2, and 86.5% to 99.9, 99.6, and 99.8%, respectively, as the temperature increased from 25 to 65 degrees C. These results confirmed the rationality of the proposed structure of the precipitate.

Automated summary

The mechanisms of ion co-precipitation during partial neutralization were investigated, and it was found that intense agitation and high temperature could break the coordination bonds between ions. The addition of cationic or anionic surfactants limited the formation of these bonds.