Plasma regulates active sites on biochar to boost peroxomonosulfate activation for phenol degradation

Metal-free biochar (BC), as a green catalyst, has exhibited superior engineering applications potential in wastewater purification. However, the performance of the pristine BC for peroxymonosulfate (PMS) activation is unsatisfactory. To this end, this work innovatively employed the plasma modification of BC and thus improving its catalytic activity. The plasma-modified BC (0.2 g/L) was used to thoroughly degrade phenol (10 mg/L) at 100 min, and its oxidation rate constant (0.0483 min −1 ) and TOC removal rate (46%) are 18-fold and 2.1-fold that of pristine BC, respectively. Significantly, a quantitative structure-activity relationship (QSAR) was established in the PMS/BC system. It was confirmed that the ketone carbonyl content and the degree of carbon structural defects were the critical factors in the biochar for phenol degradation. Theoretical calculations further verified that the single-vacancy defect and ketone carbonyl (C O) in biochar is the essential reaction sites. These sites give rise to the unequal distribution of electrons in the carbon structure. Meanwhile, the potential difference between the HOMO of BC and the HUMO of PMS drives the electron transfer to activate PMS. Herein, we provide an effective method to regulate the active sites, thereby further promoting the environmental application of biomass-derived carbon materials. • The plasma was used to effectively regulate the reactive sites of biochar. • The mechanism of electron transfer PMS activation was revealed by DFT calculations. • The role of oxygen groups and structural defects in biochar catalysis were studied.