Now, Huijuan Liu and colleagues report a flow-through redox-neutral electrochemical reactor (FRER) designed to address the challenge of removing organic pollutants from high-salt wastewater (Nat. Nanotechnol. https://doi.org/10.1038/s41565-024-01669-3; 2024). This technology utilizes a chlorination–dehalogenation–hydroxylation (CDH) pathway involving free radical–free radical cross-coupling to eliminate contaminants. A distinctive feature of this system is the ultraviolet irradiation component, which is isolated from the electrochemical cell and instead is connected via water circulation. This set-up photolyzes chlorine into reactive chlorine species and hydroxyl radicals. The electrochemical reactor employs RuO2-coated and palladium cluster-coated porous titanium as the anode and cathode, respectively, in close proximity (4 mm apart compared with the 2 cm spacing in conventional reactors). The chlorine evolution reaction occurs at the anode, producing chlorine to oxidize organic compounds. The cathode is designed for organic carbon removal. This system effectively targets the typical pollutants found in hypersaline landfill leachates and wastewater from pharmaceutical and coal-to-chemical facilities, including benzoic acid, bisphenol A, chlorophenol, phenol and cefixime.
Experiments showed that the FRER achieved a total organic carbon removal rate of more than 75% for a variety of the abovementioned compounds. This process maintained continuous decontamination for more than 360 hours and sustained a stable decontamination rate for real high-salt wastewater for 2 consecutive months. When integrated with an ED system, the FRER-ED set-up demonstrated a NaCl removal ratio of 98%, with up to 95% of the clean water being desalinated and recovered. Further integration with BMED facilitated conversion into alkali (1.5 M) and acid (1.3 M). Mechanistic studies revealed that, compared with traditional advanced oxidation processes, the FRER utilizes a thermodynamically and electrochemically favorable CDH mineralization pathway, making it effective for removing organic impurities from various high-salt wastewaters.
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