Mechanochemical Reduction of Perchlorate under Ambient Conditions

Perchlorate (ClO4–) is a widespread contaminant that poses a significant threat to human health. Its reductive removal is typically challenging, requiring carefully engineered catalysts or harsh reaction conditions. In this study, we report a catalyst-free process for ClO4– reduction that operates without the need for heating or pressurization. By leveraging the hot-spot theory in mechanochemical ball milling, transient high temperatures, estimated as 400–500 °C, are generated at localized impact sites, enabling the reduction of ClO4– by iron from stainless steel (SS) milling balls. The ball milling approach proves highly effective for ClO4– reduction in both solid and aqueous phases. Notably, the ClO4– reduction kinetics in water are 3 orders of magnitude faster than those reported in previous studies using zerovalent iron as the reductant. The process also demonstrated strong durability in the presence of common competitive anions. Additionally, by combining theoretical modeling and scale-up treatment, we confirmed that the proof-of-concept developed on a bench-scale planetary ball mill is effectively transferable to pilot-scale tumbler ball mills, featuring the scalability and practical applicability of this new reaction principle.