Symmetric dual-cathode sandwich system for enhanced peroxymonosulfate electrochemical activation and stable water decontamination: performance and mechanism

Abstract

The current peroxymonosulfate-electrochemical advanced oxidation process (PMS-EAOP) systems face the challenges of poor stability and efficiency, limiting the application in industry and practical scenarios. Herein, a dual-cathode sandwich (DCS) PMS-EAOP system was established for efficient degradation of aqueous emerging contaminants with long-term stability. A titanium-based antimony/iridium-doped tin oxide (Ti/AITO) anode was enclosed symmetrically by dual stainless-steel cathodes, achieving reliable water purification through a synergistic mechanism of reactive oxygen species generation and direct electron transfer (DET)-based non-radical pathways. Comprehensive investigations were conducted on the degradation performance of diverse pharmaceutical and personal care products and endocrine-disrupting chemical. Operational parameters were systematically optimized to maximize pollutant removal efficiency. Mechanistic insights were gained through degradation pathway analysis, toxicity assessment, and radical species identification. The removal of the model ranitidine contaminant with a pseudo-first-order rate constant of 0.198 min⁻¹ was attributed to the synergistic action of •OH, SO₄•⁻ and ¹O₂, and the DET-based non-radical pathway. The DCS-PMS system demonstrated robust operational stability in complex water matrices, including natural and urban water bodies, and maintained exhilarating performance under long-term continuous operation for over 60 h. Notably, the system achieved a ∼67 % total organic carbon removal within 120 min when applied to high-concentration real antibiotic wastewater. This work offers insights for advancing the development of EAOPs with scalable design, simple assembly, and high durability in wastewater treatment.