Toward Sustainable Zinc Electrowinning: Manganese-Induced Degradation of the IrO2−Ta2O5 Mixed Metal Oxide Anode and Its Mitigation Method

Abstract The zinc industry faces an urgent need to replace lead-based electrodes with cleaner and more sustainable alternatives. Mixed metal oxide (MMO) anodes offer a promising solution, but their industrial adoption is limited by manganese-induced degradation. This study presents a systematic evaluation of commercial Ti/IrO2−Ta2O5 anodes under realistic industrial conditions over multiweek electrowinning and cleaning cycles. Fresh MMO anodes exhibited significantly improved energy efficiency in zinc electrowinning, operating at cell voltages of 650 mV lower than conventional lead anodes while maintaining current efficiencies above 93%, enabling energy savings of up to 19.5%. Electrochemical tests confirmed a critical Mn2+ tolerance threshold around 100 mg·L−1: below this level, voltage increased gradually over time, whereas higher concentrations promoted diffusion-limited MnO2 deposition and accelerated coating degradation. Based on the time-dependent cell voltage behavior, predictive equations were developed to estimate cleaning intervals, offering a quantitative tool to optimize maintenance scheduling. Surface analysis showed that flat regions with thinner Ta2O5 top layers were more prone to damage, while mud-cracked regions with thicker coatings demonstrated greater durability. A nondestructive FeSO4/H2SO4 cleaning method effectively removed MnO2 with minimum damage on the oxide layer. Notably, anodes subjected to three full electrowinning−cleaning cycles at 200 mg·L−1 Mn2+ retained low cell voltages with only ~20 mV performance loss, highlighting excellent regenerability of the electrode surface. These findings demonstrate that MMO anodes, when paired with effective maintenance protocols, can achieve meaningful energy savings and markedly reduce toxic waste generation, paving the way for sustainable, large-scale implementation in zinc electrowinning.