Highly efficient activation of peroxymonosulfate by natural negatively-charged kaolinite with abundant hydroxyl groups for the degradation of atrazine

In this study, natural kaolinite, an abundant, low cost, thermally and chemically stable, and easily recyclable material was evaluated for the performance to activate peroxymonosulfate (PMS) by the degradation of atrazine. Based on radical quenching experiments and electron spinning resonance (ESR) spectra, hydroxyl radical (OH) and sulfate radical (SO4−) were identified to be the primary reactive species. The effects of catalyst loading, initial reaction pH, PMS dosage, initial atrazine concentration, and the presence of inorganic ions (Cl−, NO3−, HCO3− and H2PO4−) were also investigated in this work. Interestingly, the presence of H2PO4− enhanced the degradation efficiency of atrazine via promoting the decomposition of PMS. The transformation products were detected on a quadrupole time-of-flight liquid chromatography/mass spectrometer (Q-TOF-LC-MS) and the possible degradation pathway of atrazine was proposed. Based on comprehensive characterizations of crystal phase and crystallinity, porosity and pore structure, surface morphology, functional groups, and valence state of specific elements, the catalytic ability of natural kaolinite towards PMS is attributed to the abundant surface-bonded and structural hydroxyl groups. This study provides new insights of PMS activation by natural minerals for the degradation of refractory and deleterious contaminants in wastewater treatment.