Performance And Mechanism Of CuO/CuMgFe-LDHs Catalyzed Persulfate Degradation Of Ciprofloxacin

Persulfate（PDS）advanced oxidation process can catalyze the generation of strong oxidizing species（sulfate radical·SO₄^-,hydroxyl radical·OH,and non-radicals）from PDS by catalytic materials to remove hard-to-degrade organic pollutants,which has a wide prospect in environmental pollution treatment.Currently,layered double hydroxides（LDHs）are often used as catalytic materials in PDS technology due to their anion exchange properties.However,factors such as p H and coexisting anions can greatly affect the performance of LDHs catalyzed PDS.In this paper,a novel nanocomposite CuO/CuMgFe-LDHs material was prepared by loading Cu O on Cu Mg Fe-LDHs to achieve efficient degradation of ciprofloxacin（CIP）by catalytic PDS,and reveal the mechanism of CIP degradation by PDS catalyzed by CuO/CuMgFe-LDHs under different initial p H conditions,based on which the catalytic material applied to the degradation of CIP in hypersaline water to elucidate the effect of salt ingredient on the PDS-catalyzed CIP degradation by CuO/CuMgFe-LDHs.（1）CuO/CuMgFe-LDHs composite was synthesized by co-precipitation method,and their performance in catalytic PDS degradation of CIP was investigated.The CuO/CuMgFe-LDHs were characterized by X-ray diffraction（XRD）,Fourier transform infrared absorption spectrometry（FT-IR）,thermogravimetric analysis（TG）,scanning electron microscopy（SEM）,and zeta potential to confirm that CuO/CuMgFe-LDHs is a composite material combining Cu O and Cu Mg Fe-LDHs with more active sites and larger specific surface area.more favorable for adsorption and catalytic degradation of CIP.The degradation efficiency reached 86.2%after 120 min under the conditions of catalyst dosage of 0.5 g/L,PDS concentration of 0.25 m M,CIP concentration of 30 mg/L and no p H adjustment.In addition,the utilization rate of PDS reached 50.4%,the catalytic performance of CuO/CuMgFe-LDHs material could still reach 71.7%after five cycles,and the dissolution amounts of Cu²⁺and Mg²⁺were 0.17mg/g,0.04 mg/g,and no Fe³⁺dissolution,respectively.Therefore,CuO/CuMgFe-LDHs is considered as an environmentally friendly material for efficient degradation of CIP.（2）The effect of initial p H on the degradation of CIP by CuO/CuMgFe-LDHs catalyzed by PDS was investigated.The degradation effect of CIP was above 85%when the initial p H was in the range of 4～10.However,the catalytic mechanism of PDS varied at different p H.Through the radical quench experiments,electron spin resonance（ESR）analysis and catalyst characterization before and after the reaction,the results demonstrated that no active species such as·OH,·SO₄^-,¹O₂,·O₂^–were found at p H=5.2,and the degradation of CIP was mainly achieved by the electron transfer of PDS adsorbed on the surface of CuO/CuMgFe-LDHs process（ETP）was achieved.Compared to the free radical pathway,ETP is less disturbed by solution p H,inorganic ions and dissolved organic matter,while ensuring high CIP degradation rate.A large amount of·SO₄^-was produced to degrade CIP at p H=9.In addition,an electron transfer process dominated by CuO/CuMgFe-LDHs-PDS complex attacking cyclopropyl at p H=5.2 was found by liquid chromatography mass spectrometry（LC-MS）.In contrast,the radical degradation pathway was found to attack the quinolone ring with·SO₄^-,under alkaline conditions at p H=9.（3）CuO/CuMgFe-LDHs has good ability to catalyze the degradation of CIP by PDS in high-salt wastewater.The optimal reaction conditions were:catalyst injection of 0.5 g/L,PDS concentration of 0.75 m M and Na Cl concentration of 10-30 g/L.Under these conditions,the degradation efficiency of CIP was 85.2%.the degradation efficiency of CuO/CuMgFe-LDHs could still reach 75.9%after five cycles,and the dissolution amounts of Cu²⁺and Mg²⁺were 0.32 mg/g,0.10 mg/g,and no dissolution of Fe³⁺.The effect of different water matrices on the degradation of CIP by CuO/CuMgFe-LDHs catalyzed by PDS in a high saline environment was further investigated.The degradation rate of CIP in tap water was 78.6%,and the degradation rate of CIP in actual reservoir water was 69.3%.In conclusion,CuO/CuMgFe-LDHs has great potential for application in environmental treatment and protection.