Ultrasound-assisted high-efficiency separation and purification of Ni2+ and Co2+ impurities from zinc sulfate electrolyte

In the zinc hydrometallurgical process, the deep removal of deleterious Ni 2+ and Co 2+ ions from zinc sulfate electrolytes remains a major challenge. This study introduces an ultrasonic-enhanced zinc powder replacement method as a green and efficient strategy to address this issue. The results demonstrated a remarkable enhancement in purification efficiency, with the removal rates of Ni 2+ and Co 2+ ions increasing by 14.01% and 13.92%, respectively, compared to the conventional method. Electrochemical analysis showed that ultrasonic treatment enhanced the potential difference of Ni 2+ and Co 2+ ions removal by zinc powder replacement, promoted the in-situ renewal of zinc anode surface, and thus improved the purification rate. This enhancement directly promoted the adsorption and desorption dynamics of the impurity ions on the zinc surface. Morphological characterization of the purified slag provided further evidence, showing that ultrasound effectively refined the zinc powder particles, increased their specific surface area, and intensified the solid-liquid interaction. Finally, electron paramagnetic resonance detection confirmed that ultrasound significantly enhanced the formation of strong reducing free hydrogen atoms, which actively contributed to the reduction and removal of Ni 2+ and Co 2+ ions. This work not only develops a viable purification strategy but also provides a comprehensive theoretical understanding of the ultrasonic enhancement mechanism, offering valuable guidance for achieving efficient separation in zinc sulfate electrolytes.