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 Fe²⁺ 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%). SO₄·^- and ·OH radicals drive Csp³-N/Csp²-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.