Persulfate-enhanced degradation of ciprofloxacin with SiC/g-C3N4 photocatalyst under visible light irradiation.

SiC/g-C3N4 composite (SCN) showed the potential for photocatalytic degradation of synthetic dyes, it is deserved to study whether it is effective for the photocatalytic degradation of ciprofloxacin (CIP). In this work, persulfate-enhanced CIP degradation was investigated with SCN under visible light irradiation. The results showed that the degradation efficiency of 10 mg L-1 CIP could reach 95% for 30 min under the conditions of 0.4 g L-1 SCN, 2 mM persulfate (PS) and solution initial pH 6. The degradation process abided by pseudo first-order kinetic equation, and the observed rate constant (kobs) with SCN/PS (0.132 min-1) was 13 times of that with SCN (0.0102 min-1), and twice of that with g-C3N4/PS (0.0649 min-1). The quenching experiments and electron paramagnetic resonance analysis indicated that O2-· and 1O2 played the main role and other active species (e.g., h+, SO4-· and ·OH) also participated in CIP degradation. The possible degradation pathways were proposed through identifying the intermediate products, and the main reactions may include the ring opening of piperazine, decarbonylation, decarboxylation and defluorination. Bacterial toxicity test showed that the toxicity of the reaction solution decreased dramatically after 30 min degradation. Overall, this work could provide an efficient and environmentally friendly technology for eliminating CIP.