Mn-doped copper slag with oxygen vacancies boosts peroxymonosulfate activation for ofloxacin rapid removal

This study developed a manganese-doped copper smelting slag (Mn@CSS) particle electrode to enhance peroxymonosulfate (PMS) activation for efficient ofloxacin (OFX) degradation. The Mn(II) doping strategy effectively modulated surface oxygen vacancies, with the optimal 0.08 doping ratio achieving doubled oxygen vacancy concentration compared to pristine CSS. Density functional theory (DFT) calculations revealed significantly enhanced PMS adsorption capacity, demonstrating a 57 % increase in adsorption energy (ΔE_ads = −3.31 eV for Mn@CSS vs. -2.10 eV for CSS). Notably, the OO bond length extended from 1.45 Å to 1.74 Å upon adsorption, facilitating interfacial charge transfer. Under optimized conditions (pH 7.0, 1.50 g/L catalyst dosage, 20 mg/L initial OFX concentration, and 10 mA/cm² current density), the system achieved exceptional performance with 99.90 % OFX removal and 58.79 % total organic carbon reduction within 30 min. Mechanistic investigations through electron paramagnetic resonance and LC-MS analyses identified synergistic contributions from multiple reactive species (SO₄^•-, O₂^•-, ^•OH, ¹O₂, and Fe(IV)), driving mineralization via dealkylation, decarboxylation, and ring-opening pathways. The catalyst demonstrated remarkable stability with 87 % efficiency retention after five cycles and minimal metal leaching (Fe: 1.20 %, Mn: 0.79 %). This work not only provides a sustainable strategy for solid waste valorization but also elucidates the oxygen vacancy-mediated PMS activation mechanism through integrated experimental and theoretical approaches.