Perchlorate Reduction with Integrated Photochemical and Catalytic Processes

Perchlorate (ClO 4 – ) contamination in water poses significant public health risks due to its endocrine-disrupting properties and resistance to degradation by conventional chemical treatment methods. The concerns about oxychlorine anions (ClO x – ) also impact destruction technologies for perfluoroalkyl and polyfluoroalkyl substances (PFAS). The stepwise reduction of ClO 4 – often shows intriguing chemical challenges due to the unique reactivity of ClO x – intermediates, which motivates innovation in process design. This study presents a two-stage treatment train combining photochemical treatment with catalytic reduction to achieve complete ClO 4 – removal in complex water matrices. The optimized UV/sulfite + iodide (UV/S+I) system achieved efficient ClO 4 – reduction. Surprisingly, the chlorate (ClO 3 – ) intermediate is more sluggish than ClO 4 – under UV/S+I treatment. To overcome this challenge, we integrated the H 2 +Mo–Pd/C catalytic process as a post-treatment and achieved rapid ClO 3 – reduction to Cl – . The high performance of the treatment train is validated in practical matrices of tap water and synthetic ion exchange resin regenerant brine. The photochemical stage also degraded nitrate (NO 3 – ) and PFAS, which inhibited ClO 4 – reduction at various levels. The treatment train overcomes individual technology limitations while maintaining robustness against the challenging water matrices, offering a practical solution to perchlorate-related scenarios that require comprehensive treatment of various pollutants.