Fe-doped ilmenite CoTiO3 for antibiotic removal: Electronic modulation and enhanced activation of peroxymonosulfate

Heterogeneous Fenton-like catalytic oxidation is a promising method for organic pollutants removal. However, the catalytic activity is restricted by the redox cycles of active sites. In this study, Fe was doped into ilmenite cobalt titanate to prepare Fe-doped CoTiO3 catalysts for antibiotic tetracycline (TC) degradation. Experiments and theoretical calculations illustrated that doping Fe in CoTiO3 increased the electron density of Co atoms of active sites, enhancing the redox cycles during peroxymonosulfate (PMS) activation, and facilitating the generation of radicals for degrading pollutants. After doping Fe, over 99% of TC (20 mg/L) can be degraded in 40 min, and the reaction rate increased 5 folds compared with the pristine CoTiO3. The inherent crystal stability of ilmenite guarantees the reusability of catalysts and limited cobalt ions leaching (≤0.22 mg/L). Besides, the impacts of PMS concentration, catalyst dosage, initial pH, coexisting ions, and reaction temperature on TC removal were systematically investigated, and the possible degradation pathway was proposed. Quenching experiments and electron paramagnetic resonance (EPR) spectra indicated that sulfate radicals and singlet oxygen participated in TC degradation. This work provides new clues and strategies to construct highly efficient catalysts for heterogeneous catalytic oxidation.