Degradation of sulfamethoxazole by peroxymonosulfate catalytically activated with MnSiOx/Fe@C catalyst: synergistic mechanism and toxicity analysis.

To address the challenges of rapid Fe(II) consumption, high metal leaching, and limited activity in single-metal catalyst systems during peroxymonosulfate (PMS) activation, this study engineers a hierarchically structured MnSiOx/Fe@C bimetallic catalyst. The catalyst integrates Fe0 nanospheres into vermiculite-derived layered manganese silicate, stabilized by a carbon network derived from pyrolyzed Fe-based metal-organic frameworks (Fe-MOFs). Theoretical calculations reveal that Fe0 serves as a sustained electron donor, enhancing Mn sites' electron density to drive Mn(II/III/IV) and Fe(II/III) valence cycling, accelerating the cleavage of O-O bonds in PMS (1.326 Å to 1.469 Å, DFT). Under optimized conditions (0.2 g/L catalyst, 0.2 g/L PMS, pH = 6.5), complete sulfamethoxazole (SMX, 20 mg/L) degradation is achieved within 60 min (k = 0.0583 min-1), with negligible Fe/Mn leaching (< 0.035 mg/L). Quenching experiments confirm singlet oxygen (1O2) as the dominant reactive species (72 % contribution), synergized by •OH and •SO4- via Fe0 oxidation and Mn valence transitions. The catalyst demonstrates robust adaptability in complex water matrices (HCO3-, H2PO4-, SO42-, NO3-, Cl-, C2O42-, and humic acid) and real water samples (lake, well, and rainwater), achieving 100 % SMX removal and retaining 91.7 % activity after 4 cycles. Toxicity assessments reveal that the acute toxicity of degradation intermediates is reduced by 80 % compared to SMX, confirming environmental safety. This work provides mechanistic insights and technical references for the rational design of bimetallic catalysts and the effective treatment of antibiotic-contaminated water.