Design Of A New Z-type TiO₂/Ag/Ag₃PO₄ Photocatalyst And Its Degradation Performance Of Ciprofloxacin

In recent years,antibiotics have become a new type of environmental pollutants.Photocatalytic oxidation technology,driven by solar energy,is an efficient and green means of removing antibiotics from water.In this paper,a novel Z-type heterojunction Ti O₂/Ag/Ag₃PO₄（TAAPO）photocatalyst was synthesized,and its degradation performance on ciprofloxacin（CIP）under different conditions was investigated.Combined with the characterization results,the mechanism of catalyst degradation of CIP and the possible degradation paths of CIP were analyzed.The specific research contents and results of this paper are as follows:（1）TAAPO composite photocatalytic material was prepared,and its surface morphology,energy band structure and other properties were analyzed by XRD,SEM,TEM,XPS and other techniques.The diffraction peaks corresponding to the standard card of anatase Ti O₂ appeared in the XRD pattern,the characteristic peaks of elemental Ag and PO₄^3-were observed in XPS and the results of SEM and TEM showed that Ag and Ag₃PO₄ were uniformly distributed on the surface of Ti O₂,and TAAPO is distributed in layers and uniform in size.The above results show that anatase Ti O₂ was successfully synthesized,and Ag and Ag₃PO₄ were loaded on its surface by photodeposition and liquid-phase chemical methods,and the structure of anatase Ti O₂was not changed,which proved the successful synthesis of TAAPO material.（2）CIP was selected as the target pollutant for degradation,and the optimal photocatalytic degradation conditions were obtained through single-factor control experiments:when the amount of catalyst used was 0.3 g/L,the initial concentration of CIP was 15 mg/L,and p H=3.0,the removal rate of CIP by photoreaction for 120 min was about 98%,and the effect of coexisting anions in water on the degradation of CIP in this system was investigated under these conditions.The results show that the presence of SO₄^2-has a great influence,at this time,the degradation rate of CIP will drop to 77%-81%.The material stability and mineralization were studied,and the good degradation ability was still maintained after 4 cycles,and the mineralization rate of CIP reached 45.9%after 120 min.The flame atomic absorption spectrometer was used to detect whether there was a problem of Ag⁺dissolution in the system,and it was found that there was no Ag⁺dissolution in the system.The above results show that the TAAPO material has excellent performance and good stability.（3）The reasons for the improved catalytic performance of the composite photocatalytic materials were explored by means of electrochemical impedance measurement（EIS）,transient photocurrent measurement（i-t）and fluorescence photoluminescence spectroscopy（PL）.Analysis to test and calculate the energy band structure of the composite photocatalytic material;combined with the radical trapping test and EPR to investigate the active radicals in the system;the ultra-fast liquid chromatography-mass spectrometry（LC-MS）was selected.Detected the intermediate products produced during the photocatalytic degradation of CIP in the system,and speculated the possible degradation path of CIP.The results show that the potentials of the conduction band and valence band of the composite catalyst are-0.48 and 2.68 V,respectively,and·O^2-,h⁺and·OH all participate in the degradation of CIP,and·O^2-plays a leading role.CIP is mainly degraded by the cracking,defluorination and hydroxylation of piperazine ring,among which part is completely mineralized into H₂O and CO₂,and the other part generates other intermediate products.