Activation Of Peroxymonosulfate By Modified Copper Ferrite Under Visible Light For Degradation Of Pharmaceutically Active Compounds

In recent years,pharmaceutically active compounds（PhACs）have received much attention due to their adverse effects on animals and humans when they are discharged into water environment in large quantities.Traditional water treatment technologies are not effective in removing PhACs from the aquatic environment,thus the development of new technologies for PhACs wastewater has become a hot topic in this research fields.This paper reviews the harmful effects of PhACs on the water environment and the current status of water treatment technologies for the removal of PhACs.The copper ferrate（CuFe₂O₄）nanoparticles have received wide attention in photocatalytic activation of PMS because of their stable spinel structure,low ion leaching,and narrow band gap for visible light（VL）absorption.However,CuFe₂O₄ nanoparticles suffer from the high photogenerated electron-hole recombination rate,and agglomeration.In this study,it was found that nitrogen-carbon doping of CuFe₂O₄nanoparticles（CuFe₂O₄@NC）could enhance the absorption of visible light and reduce the electron-hole recombination of CuFe₂O₄ nanoparticles,thus improving their activation performance for peroxymonosulfate（PMS）under visible light.Subsequently,Al₂O₃ceramic membranes（ACM）were used as carriers to support CuFe₂O₄ nanoparticles to solve the problem of agglomeration.In addition,the electron transfer rate of CuFe₂O₄nanoparticles was accelerated by the in situ sulfidation.The main research work of this thesis is as follows:（1）Activation of PMS by CuFe₂O₄@NC under visible light for degradation of MNZThe nitrogen-carbon doping of CuFe₂O₄ nanoparticles（CuFe₂O₄@NC-2）was synthesized by chitosan as a precursor of nitrogen and carbon by annealing under an N₂atmosphere.The morphology and structure of CuFe₂O₄@NC-2 were characterized by scanning electron microscope（SEM）,Raman spectra and Fourier transform infrared spectrometer（FT-IR）.The UV-Vis diffuse reflection spectroscopy（UV-Vis-DRS）and a series of electrochemical characterizations demonstrated that the nitrogen-carbon doping enhanced the absorption of visible light and reduced the electron-hole recombination of CuFe₂O₄.CuFe₂O₄@NC-2 showed excellent activation of PMS under visible light,and the degradation rate of metronidazole（MNZ）reached 99.4%within15 min.In this study,it was found that highly alkaline conditions（p H=11）promoted the degradation of MNZ by the CuFe₂O₄@NC-2/PMS/VL system.In addition,the presence of anions（Cl^-、NO₃^-and H₂PO₄^-）and HA was found to inhibit the degradation of MNZ to varying degrees.The quenching experiments,EPR results,and fluorescence detection showed that the CuFe₂O₄@NC-2/PMS/VL system produced OH^·,SO₄^·-,O₂^·-,h⁺and ¹O₂ as active species.Based on the degradation products detected by LC-MS,3possible degradation pathways of MNZ were proposed.The results of T.E.S.T.calculations and flow cytometry showed that the CuFe₂O₄@NC-2/PMS/VL system was effective in reducing the toxicity of MNZ transformation intermediates as well as the overall solution.In addition,the CuFe₂O₄@NC-2 still exhibited more than 80%removal efficiency for MNZ after 4 cycles of use,indicating it exhibits good stability.（2）Activation of PMS by ACM@S-CuFe₂O₄ under visible light for degradation of CQACM@CuFe₂O₄ was firstly prepared by in situ growth of CuFe₂O₄ on the surface of Al₂O₃ ceramic membrane（ACM）by annealing under an N₂ atmosphere,and then ACM@S-CuFe₂O₄-2 was synthesized by in situ sulfidation of ACM@CuFe₂O₄ by Na HS.The morphology and structure of the prepared ACM@S-CuFe₂O₄-2 composites were characterized using SEM and FT-IR.In addition,the photocatalytic performance of ACM@S-CuFe₂O₄-2 was investigated by electrochemical characterization,demonstrating that in situ sulfidation accelerated electron transfer.ACM@S-CuFe₂O₄-2 showed excellent activation performance for PMS under visible light,and the degradation rate of chloroquine phosphate（CQ）reached 98.7%within 30 min.In this study,high alkaline conditions（p H=11）were found to promote the degradation of CQ by the ACM@S-CuFe₂O₄-2/PMS/VL system.The quenching experiments and EPR experiments showed that the ACM@S-CuFe₂O₄-2/PMS/VL system produced ¹O₂,SO₄^·-,OH^·,O₂^·-as well as h⁺as active species.Based on the degradation products detected by LC-MS,the possible degradation pathway for CQ was proposed in this study,and the toxicity of the intermediates was evaluated using T.E.S.T.calculation software.In addition,flow cytometry was used to quantify the toxicity presented by the overall solution at different reaction times.Moreover,ACM@S-CuFe₂O₄-2 exhibited a removal efficiency of 82.2%for CQ after 5 cycles of use,indicating it exhibits good stability.