Heterogenizing MnO2 nanostructure with industrial impurity ions for lead leakage-preventable anodes in zinc electrowinning

Abstract

γ-MnO2 precoated lead (Pb)-based anodes have shown high initial activity in heavy-metal pollution reduction and production improvement for zinc electrowinning in laboratory. However, the accumulated impurity ions (M) in industrial MnO2-precursors restrict its industrial application. Herein, the heterostructure-induced rich oxygen-vacancies for M-MnO2 and its higher activity (Pb/Co-MnO2>Pb/Ni-MnO2>Pb/Fe-MnO2≈Pb/Cu-MnO2>Pb/MnO2) was reported. However, it reached a concentration threshold and afterwards provided the inhibited activity. Moreover, the Pb2+ diffusion-induced lead leakage is the dominant factor in the inactivation of anodes before extrinsic mechanical effects manifest, which follows: Pb/Fe-MnO2>Pb/Cu-MnO2>Pb/MnO2≈Pb/Ni-MnO2≈Pb/Co-MnO2. Instead, due to the enhanced activity and suppressed lead leakage, Pb/Co-MnO2 avoided about 12.4% and 72.3% lead-containing anode slime in comparison with Pb/MnO2 and Pb/Fe-MnO2 and minimized the contamination of zinc products by lead. Such complex effects also provide a cost-effective and environmental-friendly strategy for lead-leakage preventable Pb-based anodes in zinc electrowinning as it can reduce the exogenous dopants usage while still delivering competitive electrooxidation activity-stability.