Tandem Dual-Anode Electrochemical Reactor for Valorizing Chlorinated Aromatic Pollutants into Tailorable Polymeric Adsorbent

Electrochemical degradation of halogenated aromatic compounds typically presents a fundamental trade-off between energy-intensive mineralization and partial dehalogenation, which can yield persistent toxic intermediates. Herein, we introduced a dual-anode electrochemical reactor employing sequential hydroxylation and direct electron transfer (DET) mechanisms for the efficient destruction of chlorinated aromatics coupled with carbon resource recovery. The reactor integrated a Ce-doped tin antimony oxide (Ce-ATO) anode and a defective ATO anode. As a proof of concept, 2,4-dichlorophenoxyacetic acid (2,4-D), a widely produced pesticide, was first converted into 2,4-dichlorophenol via hydroxylation reaction at the Ce-ATO anode. This intermediate subsequently underwent DET at the downstream defective ATO anode, generating organic radicals that underwent radical–radical coupling to form oligomers. The inclusion of a proton exchange membrane into the reactor maintained an acidic microenvironment, which enhanced •OH-mediated oxidation and promoted adsorption. The system achieved over 95% removal of 0.45 mM 2,4-D at a current of 1 mA and a membrane flux of 150 LMH, and a corresponding hydraulic retention time of 0.8 min, with an oligomer recovery rate of 62% obtained at 5 mM 2,4-D under otherwise identical conditions. The recovered oligomers were readily pyrolyzed into microporous carbon with a high surface area (454.47 m2·g–1) and demonstrated excellent adsorption capacity for 4-chlorophenol (217.31 mg·g–1). Furthermore, the system demonstrated robust performance when applied to complex pharmaceutical wastewater. This work offered a sustainable strategy for simultaneous decontamination and resource upcycling in high-salinity wastewater streams.