Catalytic activation of PS/PMS over Fe-Co bimetallic oxides for phenol oxidation under alkaline conditions

In this study, we compared the differences between bimetallic oxides FeCo2O4 catalyzing the oxidation of phenol by peroxydisulfate (PS) and peroxymonosulfate (PMS) under near neutral and alkaline conditions. Phenol could be completely oxidized and removed in both PMS and PS systems. X-ray photoelectron spectroscopy (XPS) analysis and density functional theory (DFT) calculations showed that there was a synergistic mechanism between Co and Fe on the catalyst surface. Although the PMS-FeCo2O4 system reached the fastest reaction rate of 1.5 × 10−1 min−1, it showed a higher oxidants consumption and more residual total organic carbon (TOC) (36%) in solutions after reactions. Quenching experiments and electron paramagnetic resonance (EPR) analysis showed that sulfate radical (SO4−), hydroxyl radical (OH) and singlet oxygen (1O2) played important roles in the oxidation of phenol in PMS system. While in the PS-FeCo2O4 system, in addition to free radical reactions, the non-radical mechanisms between PS and the catalyst surface played a major role in phenol oxidation, and the soluble organic matter in the PS system could be completely removed. Thus, PS has a better application prospect in the treatment of phenol. This discovery has certain guiding significance for catalyst modification and doping to improve catalyst activity and the choice of oxidant.