Enhanced elimination of V5+ in wastewater using zero-valent iron activated by ball milling: The overlooked crucial roles of energy input and sodium chloride

The ball-milling technology , a highly efficient and cost-effective method, had excellent application prospects for overcoming passivation issues of normal zero-valent iron (ZVI) to enhance the decontamination efficiency. In this work, we investigated the effects and mechanisms of pH, process control agents (PCA), and main process parameters on the removal of V 5+ using ball-milled zero-valent iron (ZVI bm ). The results showed that ZVI was successfully activated due to mechanochemical action. The enhanced proton conductivity of ZVI bm leaded to the rapid production of more Fe 2+ , thereby resulting in an order of magnitude higher elimination of V 5+ by ZVI bm than by ZVI under near-neutral conditions. In addition, the introduction of NaCl in the ball milling process could not only effectively alleviate the agglomeration phenomenon of ZVI bm , but also effectively enhance its activity. Unexpectedly, due to over-compaction and small size effects, excessive energy input weakened the reactivity of ZVI bm on V 5+ elimination. Various characterization results confirmed that the removal of V 5+ by ZVI bm was dominated by reduction and supplemented by adsorption. This work updated the basic understanding of the critical effects of process parameters and NaCl on ZVI bm in the remediation of vanadium-containing wastewater.