Bidentate pyridine-pyrazole ligand-induced synergistic and antagonistic effects for selective separation of nickel from sulfuric acid medium

Abstract

Short-process hydrometallurgy is promising for non-traditional resource utilization due to low cost and less consumption, but it presents a great challenge to metal separation of complex leaching solutions. Herein, a bidentate pyridine-pyrazole ligand (BPP) was synthesized to realize the direct extraction of nickel from sulfuric acid leachate of laterite ore. The separation behaviors of nickel over other impurities (Co, Mn, Mg, Al, Ca, Fe, and Zn) were evaluated for the mixtures of BPP and dinonyl naphthalenesulfonic acid (DNNS). This binary system exhibits the synergistic effect on nickel and antagonistic effect on impurities, which improves the selective separation of nickel. The molar ratio of BPP/DNNS, solution pH, extractant concentration, and nickel concentration on metal extraction were investigated. The extraction efficiency of nickel reaches 95.9 % at pH = 2.5, and the separation coefficients of nickel over aluminum, manganese, and iron is 86.2, 95.4, and 69.4 at the optimal DNNS/BPP molar ratio of 1:1, respectively. Furthermore, the component interaction and coordination structure were disclosed through NMR, ATR-IR, XAS, and UV–vis spectroscopies. The mechanism analysis indicated that the exclusion of coordinated water molecules with BPP contributes to the synergistic extraction of nickel, and the intermolecular interaction between DNNS and BPP inhibits the extraction of impurities. Therefore, the pyridine-pyrazole ligand-induced synergistic and antagonistic effects will be helpful to the short process utilization of complex nickel-bearing resources.