Coupling Ozone Preoxidation with Sludge-Based Biochar Adsorption for Enhanced Removal of Norfloxacin and Oxytetracycline: Performance and Mechanism

This study addresses antibiotic pollution in water bodies and sludge disposal difficulties by developing a sludge-based biochar composite material (SBC-MMT) from sludge and montmorillonite (mass ratio 1:2) as raw materials. The mixture was calcined at 400 °C for 90 min to extract norfloxacin (NOR) and oxytetracycline (OTC). The substance has a flaky, rough texture. At a dose of 1.2 g/L and a pH of 7, it achieved removal rates of 82.85% and 69.65% for NOR and OTC mixed wastewater, respectively, with an initial concentration of 100 mg/L. The adsorption capacities were 65.72 and 56.42 mg/g, respectively. The adsorption behavior is consistent with pseudo-second-order kinetics and the Freundlich model, indicating a heterogeneous monolayer adsorption process driven by chemical adsorption and governed by surface diffusion and intraparticle diffusion. In the ozone coupling process, with ozone aeration controlled at 0.1 m3/h and SBC-MMT dosage at 1.2 g/L, after 60 min of reaction in the ozone-mechanical inclined plate sedimentation tank, the removal rates for NOR and OTC were 76.7% and 63.5%, respectively. The ozone-folded plate sedimentation tank required 90 min of reaction time, achieving removal rates of 60.3% and 42.1%. It shows that hydroxyl radicals produced by ozone can break down antibiotics, and SBC-MMT adsorbs leftover contaminants via hydrogen bonding and electrostatic interactions. This study, based on the ″treating waste with waste″ idea, effectively integrates sludge resource utilization with antibiotic pollution management, serving as a model for enhancing wastewater treatment procedures.