Combination of co-pyrolyzed biomass–sludge biochar and ultrasound for persulfate activation in antibiotic degradation: efficiency, synergistic effect, and reaction mechanism

A carbon material Cu-corn straw-sludge biochar (Cu-CSBC) was prepared by hydrothermally modifying sewage sludge and corn stover. The composite coupled to ultrasound can effectively catalyze the activation of PS for organic pollutants degradation, and the removal rate of 20 mg/L TC reached 89.15% in 5 min in the presence of 0.5 g/L Cu-CSBC and 3 mM PS. The synergistic effect between the factors in the system, the reaction mechanism, and the efficient removal of TC in the aqueous environment were explored in a Cu-CSBC/US/PS system established for that purpose. Quenching experiments and electron paramagnetic resonance analysis both demonstrated the Cu-CSBC/US/PS system generated •OH, SO4–•, 1O2, and O2- •, which involved in the reaction. The Cu, carboxyl, and hydroxyl groups on the Cu-CSBC surface promoted the generation of radicals and non-radicals for the degradation process, which was dominated by both radical and non-radical pathways. The degradation pathway is proposed by measuring the intermediate products with LC-MS. Finally, the stability of the Cu-CSBC/US/PS system was tested under various reaction conditions. This study not only prepared a novel biochar composite material for the active degradation of organic pollutants by PS but also provided an effective method for the resource utilization of solid waste and sludge treatment. HIGHLIGHTS Cu-CSBC prepared from co-pyrolyzed biomass–sludge to activate PS.; US and Cu-CSBC have a positive synergistic effect on the system.; The TC removal efficiency of the Cu-CSBC/US/PS system exceeded 99%.; The US can promote the production of free radicals in the system.; The main intermediates and pathways of TC degradation were identified.;