Enhanced surface activation process of persulfate by modified bagasse biochar for degradation of phenol in water and soil: Active sites and electron transfer mechanism

Carbon-based catalysis for green and sustainable degradation of phenol in water and soil has attracted extensive concern. In this study, mesoporous biochar produced by bagasse calcination with KOH and CaCl2 modified activation (Ca/BS-800-KOH) was used to stimulate persulfate (PS) for the surface oxidation degradation of phenol, which exhibited excellent removal rate of 90% in 60 min (k = 0.0404 min(-1)) with a relatively low dosage (0.066 g/L). Compared with untreated materials (BS-800, 27% removal rate in 180 min), after KOH and CaCl2 treatment, the functional groups (C-OH), increased porosity, defective structure and the more efficient electron transfer of Ca/BS-800-KOH were probably responsible for its good adsorptive and catalytic performance, which also closely related to the inactivation of Ca/BS-800-KOH. In the (Ca/BS-800-KOH)/PS/phenol system, PS was successfully activated in the presence of catalyst, and radical and non-radical reaction pathways were firstly found, in which the non-radical pathway like O-1(2) accelerated quickly the oxidative degradation of phenol. While in radical pathway involving SO4 center dot(-) and center dot OH, center dot OH was the main oxidative species and also played an irreplaceable role in the degradation of phenol. The Ca/BS-800-KOH as a medium promotes the electron transfer between phenol (electron donor) and PS (electron acceptor), in which Ca accelerates the electron transfer rate on the surface of Ca/BS-800-KOH, thereby causing oxidative degradation of phenol. The superior removal efficiencies of common environmental pollutants (all more than 93%) and phenol in water (100%) and soil samples were found. This research proposed an insightful mechanism of the low cost and feasible carbon-material-based PS-AOPs in degrading organic pollutants.