Electrochemical-enhanced Fe3O4/biochar activates peroxymonosulfate (E/nano-Fe3O4/BC/PMS) for degradation of oxytetracycline

To find cost-effective and environmentally friendly free radical activators to stimulate peroxymonosulfate (PMS) oxidative degradation of organic pollutants, nano-Fe3O4/biochar (BC) composites were prepared and characterized in this work to examine their effectiveness in stimulating PMS oxidative degradation of Oxytetracycline (OTC) in water enhanced with electrochemical degradation. When the mass ratio of nano-Fe3O4 to BC is 1:1, the catalyst nano-Fe3O4/BC exhibits the most obvious degradation effect on OTC. After 4 h of degradation, the OTC concentrations were reduced from 20 to 2.65 mg L-1, while treated with a single nano-Fe3O4 and a single BC are reduced by only 67.7% and 61.8%. Anions HCO3- and H2PO4- significantly inhibit OTC degradation, and HCO3- has a stronger inhibitory effect than H2PO4-, while Cl- and NO3- can promote OTC degradation. Quenching test and electron spin paramagnetic resonance (EPR) detection showed that singlet oxygen (1O2) was the main active species in the degradation process, followed by hydroxyl radical (·OH). When reused for the third time, the removal rate of OTC by nano-Fe3O4/BC composites with mass ratios of 1:4, 1:2 and 1:1 was still more than 70%. Therefore, the nano-Fe3O4/BC composite is a promising PMS activator, which can realize the rapid oxidative degradation of OTC.