Mechanochemically ball-milled zerovalent iron and ferrous composite for effective removal of various metal(loid)s from water

As a clean, fast, and efficient strategy for chemical synthesis, mechanochemical ball-milling approach has been developed promisingly to prepare functional materials for water treatment. Based on our previous findings that both the accelerated corrosion and facilitated electron-transfer are crucial for contaminants removal by zerovalent iron (ZVI), ball-milled FeCl₂ and ZVI (Fe²⁺-ZVI^bm) was synthesized for metal(loid)s sequestration in this study. The results showed the complete removal of Se(VI) was obtained by Fe²⁺-ZVI^bm and there was no residual Fe²⁺ in the solution after Se(VI) removal. Compared to other enhanced-ZVI techniques, Fe²⁺-ZVI^bm showed evident superiorities for Se(VI) removal in many aspects, including removal rate, removal capacity, utilization ratio of reductants, electron efficiency of reductants, specific removal capacity, adaptability of initial pH, and operation cost. The influence of storage condition on the performance of Fe²⁺-ZVI^bm was examined and the performance of Fe²⁺-ZVI^bm for Se(VI) removal could be ensured when it was sealed-stored in air. The rates and capacities of various metal(loid)s (V(V), Cr(VI), Cu(II)-EDTA, As(III), As(V), Se(IV), Sb(III)-tartrate, Sb(V), and U(VI)) removal by Fe²⁺-ZVI^bm were increased by 2.2–32.4 times and 2.8–11.6 times, respectively, compared to those by pristine ZVI. In the semi-continuous flow reactor, Fe²⁺-ZVI^bm synthesized with industrial-grade ZVI powders displayed advantages on the removal of target contaminants (V, P, Se, As) in two practical wastewaters, further revealing its great potential for application.