Continuous Mechanochemical Depassivation of Zero-Valent Iron for Enhanced Persulfate Activation and Rhodamine B Degradation

This study aims to develop a mechanochemical reactor (MCR) integrated with persulfate-based advanced oxidation processes (SR-AOPs) to overcome zerovalent iron (ZVI) passivation for efficient degradation of high-concentration Rhodamine B (RhB) in textile wastewater. By employing high shear and mechanical collisions, the MCR continuously refreshes ZVI surfaces, enhancing Fe 2+ release and persulfate activation. The MCR achieves 96.3% RhB degradation (500 mg·L –1 ), 68.3% COD reduction, and 74% TOC removal in 60 min, significantly outperforming the traditional stirred reactor (TSR: 22.7%, 17.8%, 9%). SO 4 · – and ·OH radicals drive Csp 3 –N/Csp 2 –N bond cleavage and aromatic ring hydroxylation, ensuring rapid decolorization and mineralization. The MCR maintains high performance across pH 3–11, RhB concentrations of 50–1000 mg·L –1, and anionic interferences, with degradation rates of 66.5%–99.0%. Simulated wastewater tests and economic-environmental assessments confirm its scalability and sustainability, establishing the MCR as a transformative solution for high-load dye wastewater treatment.