Preparation And Photocatalytic Performance Of Magnetic Iron-based Composite Photocatalytic Materials

Photocatalysis has become a new advanced oxidation technology due to its advantages of utilizing light energy,high efficiency and greenness.However,traditional photocatalysts have problems such as difficulty in recycling and high recombination rate of photogenerated electrons-holes,which limit the practical application of photocatalytic technology.The development of new photocatalysts that are easy to recycle and efficient has become a research trend.In addition,it is difficult for a single photocatalytic technology to meet the increasingly difficult pollutants with the development of economy.In order to further improve the photocatalytic performance,the development of photocatalytic synergy with multiple advanced oxidation technologies has become a research hotspot.Based on this,two types of magnetic iron-based composite photocatalytic materials were prepared in this paper,and a photocatalytic synergy with multiple advanced oxidation technologies under visible light was constructed to remove refractory antibiotics and heavy metal ions in water.The photocatalytic synergy with multiple advanced oxidation processes were investigated to provide new ideas for the efficient removal of pollutants from water.The research content and results are as follows:1.Magnetic iron-based composite photocatalyst N-Ti O₂/Fe₃O₄/r GO（NTFG）was prepared by hydrothermal combining magnetic iron tetroxide（Fe₃O₄）,nitrogen-doped titanium dioxide（N-Ti O₂）and reduced graphene oxide（r GO）.The photocatalytic synergistic activation of sodium persulfate（PDS）and hydrogen peroxide（H₂O₂）by NTFG in visible light（Vis）was constructed,namely NTFG/PDS/Vis and NTFG/H₂O₂/Vis systems,respectively.Tetracycline hydrochloride（TCH）was selected as the target pollutant to investigate the photocatalytic and synergistic activation properties of these two systems.The results showed as follows:N-Ti O₂and Fe₃O₄nanoparticles were orderly distributed on the surface of r GO sheets.Compared with N-Ti O₂and Fe₃O₄,NTFG has the strongest absorption capacity in visible light and the lowest photogenerated electron-hole complexation rate,indicating that the photocatalytic performance is enhanced by the compounding of NTFG.The rate constant（k）of NTFG photocatalytic degradation of TCH was 0.0418 min^-1,and that of NTFG/PDS/Vis and NTFG/H₂O₂/Vis systems were 0.1531 and 0.1133 min^-1,respectively,indicating that the photocatalytic performance of NTFG was significantly improved by the synergistic activation of PDS and H₂O₂.After 5th cycle degradation of TCH,the efficiency in both systems still reached more than 90%,indicating that NTFG has stable photocatalytic performance in both systems.The NTFG/PDS/Vis system produced hydroxyl radicals（·OH）,superoxide radical(O₂^·-),sulfate radical(SO₄^·-)and hole（h⁺）,and the NTFG/H₂O₂/Vis system generated·OH,O₂^·-and h⁺.The introduction of H₂O₂and PDS can capture the photogenerated electrons generated by NTFG,inhibit the recombination of photogenerated electrons and holes,and enhanced the photocatalytic performance of NTFG.Based on this,the mechanism for the photocatalytic synergistic activation of PDS and H₂O₂by NTFG were elucidated,respectively.The possible degradation pathways of the two systems were proposed,with the NTFG/PDS/Vis system mainly undergoing reactions such as demethylation and N dealkylation reactions and ring opening,and the NTFG/H₂O₂/Vis system mainly undergoing reactions such as hydroxylation,demethylation and ring opening.Degradation intermediates of these two systems were predicted by quantitative structure-activity relationship（QSAR）,and the result indicate that some intermediates are more toxic than TCH itself,and the time should be appropriately extended to reduce the toxicity of intermediates.2.Based on magnetic Fe₃O₄,it was compounded with titanium dioxide（Ti O₂）and molybdenum disulfide（Mo S₂）by hydrothermal method to produce magnetic iron-based composite photocatalyst Ti O₂/Fe₃O₄/Mo S₂（TFM）.The TFM photocatalytic synergistic activation of potassium peroxymonosulfate（PMS）system（TFM/PMS/Vis）was constructed with TCH and hexavalent chromium（Cr（VI））as the target pollutants to evaluate the photocatalytic performance and synergistic activation performance of TFM.The results showed as follows:the Ti O₂and Fe₃O₄nanoparticles were ordered and attached to the curly-shaped Mo S₂sheet-like layer structure.In addition,TFM has the strongest visible light absorption ability and the lowest recombination rate of photogenerated electrons and holes,which improves the photocatalytic performance of TFM.The value of k were 0.048 and 0.052min^-1for TFM-photocatalytic treated TCH and Cr（VI）,respectively,and the value of k were0.355 and 0.436 min^-1for TFM/PMS/Vis-treated TCH and Cr（VI）,respectively,indicating that the synergistic activation of TFM photocatalysis with PMS activation significantly enhanced the TFM photocatalytic performance.TFM is highly reusable in the TFM/PMS/Vis system with stable photocatalytic performance.·OH,O₂^·-,h⁺and SO₄^·-are the main reactive oxygen species in the TFM/PMS/Vis system,and the introduction of PMS can promote Fe（III）/Fe（II）cycling and radical generation,enhancing TFM photocatalytic performance.Based on the above analysis,TFM photocatalytic synergistic activation of PMS was innovatively used to simultaneously remove TCH and Cr（VI）composite wastewater,and explores the feasibility of PMS activation to enhance the photocatalytic performance from the mechanism in this paper.