Efficient nitrate reduction over Fe-Cu bimetals under UV irradiation: Performance and mechanisms

Nitrate (NO 3 - ), a prevalent pollutant in aquatic ecosystems, poses significant ecological and human health risks due to its excessive accumulation, which accelerates eutrophication. In this study, a novel bimetallic material (B-Fe/Cu) was synthesized via high-energy ball milling using micron-sized zero-valent iron (ZVI) and copper salts. When integrated with ultraviolet (UV) light, the UV/B-Fe/Cu system achieved complete conversion (100%) of 10 ppm NO 3 - -N within 120 minutes. Intriguingly, abundant Cu species were found to mediate the efficient redox cycling between Fe 3+ and Fe 2+ , and superoxide radicals (O 2 ·- ) facilitated the redox cycling between Fe 3+ /Fe 2+ and Cu 2+ /Cu + , while the localized micro-acidic microenvironment of B-Fe/Cu enabled the dynamic pH regulation during nitrate reduction. These triple functionalities ensured the full nitrate conversion in UV/B-Fe/Cu system without toxic NO 2 - byproduct formation across a wide pH range of 3.0-11.0. Furthermore, the UV/B-Fe/Cu system demonstrated exceptional operational stability and environmental robustness, retaining >90% reduction efficiency after four consecutive reuse cycles. These insights advance the rational design of iron-based materials for scalable and sustainable water purification technologies.