Degradation of ciprofloxacin using heterogeneous Fenton catalysts derived from natural pyrite and rice straw biochar

The increased use of antibiotics and the discharge of antibiotic wastewater have caused severe pollution, and there is an urgent need for innovative treatment technologies. In this study, a novel catalyst derived from two low-cost materials natural pyrite (FeS2) and rice straw biochar (BC) for the heterogeneous Fenton degradation of ciprofloxacin (CIP) was prepared, namely natural pyrite modified rice straw biochar (FeS2/BC). The catalyst was synthesized by grinding and calcination without adding any chemical reagents. The effects of catalyst dosage, pH value, hydrogen peroxide concentration, different anions and reusability on CIP degradation were investigated. Under the optimal conditions, the FeS2/BC system can degrade 96.8% of CIP (30 mg/L) within 20 min, thereby realizing the rapid degradation of CIP. Except HCO3−, common anions in water including Cl−, NO3− and SO42− displayed no impact on the CIP degradation. Excellent degradation performance was owed to the synergy of attack by free radicals and adsorption. Hydroxyl radical(•OH), superoxide radical (O2•−) and sulfate radical (SO4•−) existed in the system at the same time and •OH was the dominant active species for degrading CIP. Both biochar and S(−Ⅱ) promoted the conversion of Fe species. This work provides a novel heterogeneous Fenton catalyst from the resource utilization of solid waste, and realizes waste elimination and pollution reduction simultaneously, which has good scientific and practical value.