Selective Degradation of Organic Pollutants via Peroxymonosulfate-Based Electrochemical Advanced Oxidation Driven by Different Electrodes: Performance and Influencing Factors

Electrochemical advanced oxidation processes based on peroxymonosulfate (PMS-EAOPs) have shown great promise for eliminating organic pollutants from water. However, earlier research primarily concentrated on pollutant degradation at the cathode, with little attention given to the anode’s role in PMS-EAOPs. In this work, we developed a PMS-EAOP system using nitrogen-doped carbon nanotubes (N-CNTs) as the electrocatalyst and examined the degradation of pollutants (acetamiprid (ATP) and sulfamethoxazole (SMX)) at both the cathode and anode. Our findings indicate that SMX was rapidly degraded at both electrodes, while ATP was effectively broken down only at the cathode, demonstrating the selective nature of PMS-EAOP. At a voltage of −2 V and 2.5 mM PMS, the pseudo-first-order rate constant (kobs) for ATP at the cathode reached 0.122 min−1, with over 92% removal within 30 min. In contrast, the anode exhibited high selectivity, removing ~75% of SMX (kobs = 0.041 min−1) while less than 20% of ATP was degraded. Analysis of reactive oxygen species showed that hydroxyl and sulfate radicals were produced and contributed to pollutant degradation at the cathode. In contrast, selective oxidation occurred at the anode, likely driven by direct electrolysis-induced nonradical oxidation responsible for the selective degradation. Phosphates and bicarbonates significantly inhibited the degradation of pollutants in the PMS-EAOP process (31.7–76.4%). In contrast, chloride ions exhibited an electrode-dependent effect, with the anode being less susceptible to interference from common water anions. Overall, this study highlights that while PMS-EAOP can selectively remove contaminants, the influence of water matrix components must be taken into account when treating real wastewater.