Highly synergistic effect for tetracycline degradation by coupling a transient spark gas–liquid discharge with TiO2 photocatalysis

Abstract

Water pollution driven by the increasing antibiotic abuse leads to serious ecological impacts and risks to human health. Non-thermal plasma, a sustainable advanced oxidation process, is considered as a promising approach for antibiotic degradation. In this study, a transient spark gas–liquid discharge was developed for the degradation of tetracycline in water and coupled with a photocatalyst (TiO2) to further improve the degradation efficiency. Results show that the discharge was accompanied by intense UV light of up to 28 μW/cm2. The tetracycline degradation performance was strongly dependent on the pulse voltage, working gas, initial concentrations of tetracycline and the catalyst addition. The best degradation performance was achieved in the plasma-TiO2 system with a degradation rate of 90.2% after 10 min treatment. The catalyst exhibits a high efficiency at lower pulse voltages, with the synergetic intensity of plasma and TiO2 showing a decreasing trend with increasing pulse voltage. Radical quenching experiments suggest that hydroxyl radical (∙OH) plays a key role in the tetracycline degradation process. A pathway for tetracycline degradation by the plasma-TiO2 process is deduced according to the analysis of the degradation intermediates. Further, seed germination and plant growth tests for the treated water demonstrated the feasibility of discharging the treated water to irrigate agricultural crops.