Electrocoagulation Assessment to Remove Benzohydroxamic Acid in Mineral Processing Wastewater

Benzohydroxamic acid (BHA), a widely used collector for oxidized ore flotation, is recognized as a persistent refractory pollutant and a major contributor to chemical oxygen demand (COD) in mineral processing wastewater. This study investigates electrocoagulation (EC) as a viable technological alternative for COD removal from BHA-containing wastewater. The experimental results revealed markedly different performances between the aluminum (Al) and iron (Fe) anode systems: the Al anodes achieved superior COD removal efficiencies exceeding 80%, whereas the Fe anodes demonstrated significantly lower removal rates of approximately 20%. Mechanistic analysis demonstrated that the high efficiency of Al-based EC arose from the generation of insoluble Al-BHA complexes, which were subsequently removed via entrapment in the Al(OH) 3 flocs. However, excessive alkalinity was found to inhibit the interactions between the Al species and BHA, resulting in decreased COD removal efficiency. For Fe-based EC systems, the suboptimal treatment efficacy was attributed to dual factors: (i) diminished chelation capacity between the Fe species and BHA, and (ii) increased solubility of the formed Fe-BHA complexes under alkaline conditions. This comparative investigation provides fundamental insights into the distinct metal–BHA interaction mechanisms governing EC performance and offers critical guidance for optimizing electrochemical treatment strategies for mineral processing wastewater.