Mo and N co-doped iron biochar materials activating peroxymonosulfate for enhanced degradation of bisphenol A: Mechanism discussion and practical application

Mo and N co-doped iron biochar material (Fe/Mo-x-NC) was prepared through one-pot calcination method with anhydrous iron chloride, ammonium molybdate, and cherry stone powder as precursors. The composite can effectively catalyze activation of peroxymonosulfate (PMS) for organic pollutants degradation, and the removal rate of 20 mg/L bisphenol A (BPA) reaches 99.08% in 30 min in the presence of 0.1 g/L Fe/Mo-0.1-NC and 1 g/L PMS. Electrochemical analysis indicates that appropriate doped Mo and N can improve the electron transfer performance of the composite, which enhances the PMS activation property for BPA degradation. Quenching experiments and electron paramagnetic resonance analysis both demonstrated that the Fe/Mo-0.1-NC/PMS system generated SO4 center dot-, center dot OH and O-1(2), which involved in BPA degradation. Moreover, a galvanic oxidation process had shown that there existed nonradical pathway which relied on electron transfer. The degradation pathway is proposed by measuring the intermediate products with HPLC-HRMS/MS. Through the exploration of the reaction mechanism, low-valence molybdenum ions can promote the cycle of Fe2+/Fe3+, and the pyridine-N and graphitic-N contained in Fe/Mo-0.1-NC can catalyze activation of PMS together with Fe2+. The designed membrane filtration device revealed the feasibility of the composite in dynamic process, which was great significant for actual operation of water treatment. Furthermore, the Fe/Mo-0.1-NC/PMS system could effectively decompose organic pollutants in the effluent from sewage treatment plant, achieving 82.6% of total organic carbon removal rate. This study not only prepared a novel heteroatom doped Fe-biochar material for PMS activation to degrade organic pollutants, but also deepened the reaction mechanism and explored its applicability for advanced treatment of real wastewater.