Study On A Novel Fe-Free Photo-Electro-Fenton-Like System For Enhanced Ciprofloxacin Degradation

Ciprofloxacin（CIP）,a typical fluoroquinolone antibiotic,is used extensively not only in agriculture and aquaculture,but also in animal and human medicine.It has been reported that CIP is widely detected in aquatic ecosystems including effluents,rivers,groundwater and drinking water.Due to the stable chemical structure of CIP,it is difficult to biodegrade this compound.Furthermore,it has been proved that CIP residues lead to the formation of novel antibiotic resistant genes and bacteria,which pose tremendous threats to public health and the ecosystem.Therefore,it is urgent to find highly effective methods to remove CIP from the environment.This is beneficial to creating a green and harmonious ecological environment.In this paper,we designed a novel Fe-free photo-electro-Fenton-like（PEF-like）system by using bifunctional WO₃/g-C₃N₄ and NiO/g-C₃N₄ composite catalyst for the accelerated decomposition and enhanced mineralization of stubborn ciprofloxacin CIP.This PEF-like system accompanying visible light activation with the optimal WO₃/g-C₃N₄（1:6）and NiO/g-C₃N₄-60%composite exhibited outstanding removal efficiency of CIP compared with single photocatalysis system and electro-Fenton-like（EF-like）system,and the elimination rate reached 100%within 2 h and 1.5 h under visible light irradiation,respectively.The WO₃/g-C₃N₄（1:6）and NiO/g-C₃N₄-60%composite displayed the strongest visible light absorption,the weakest recombination of electron-hole pairs,the highest photocurrent response and the lowest electrochemical impedance compared with pristine WO₃,NiO and g-C₃N₄.Significantly,WO₃/g-C₃N₄（1:6）and NiO/g-C₃N₄-60%played double roles in the PEF-like system which not only could produce·OH,·O₂^–and h⁺during photocatalysis,but could also generate·OH through the reactions of W⁵⁺,Ni²⁺and photoexcited electrons of g-C₃N₄for decomposition of H₂O₂.It was worth noting that this bifunctional PEF-like catalyst with photoelectric synergy could replace Fe²⁺in conventional electro-Fenton reaction and the p H was broadened which still maintained efficient degradation efficiency in the acidic to neutral p H range.The PEF-like system kept high elimination rate of CIP after five consecutive runs which manifested it possessed prominent stability and feasibility.This novel Fe-free PEF-like system opens up new ways for the degradation of organic pollutants and provides new ideas for wastewater treatment.