Research On Water Purification Mechanism Of New Photocatalyst Based On Electron-hole Composite Suppression

The massive discharge of organic pollutants and heavy metals in the water environment seriously threatens water quality safety and has become a major challenge for water pollution prevention and control.Photocatalytic technology has shown great potential in treating such pollutants and has become a research hotspot in the field of water pollution.However,the problems of photogenerated electron-hole recombination,low light energy utilization efficiency,and poor catalyst stability have limited the further development of traditional photocatalytic technology.Therefore,the development of efficient and stable new photocatalysts and revealing the degradation mechanism of pollutants at their interfaces is the key to the application of photocatalytic technology to solve water pollution problems.In this study,a novel photocatalyst,iron molybdate?Fe₂?Mo O₄?₃?,was synthesized by hydrothermal and high-temperature calcination methods and a heterogeneous photocatalytically persulfate activated?HPPA?system was constructed to degrade the target pollutant bisphenol A?BPA?based on the inhibition of photogenerated electron-hole recombination of the catalyst.Studies have shown that under the Fe₂?Mo O₄?₃-HPPA system,the removal rate of pollutants can reach?98 times that of the Fenton-like reaction,and?59 times that of the photocatalytic reaction alone,all of which benefit from the synergistic effect of reactive species in the HPPA system.After 7 cycles of Fe₂?Mo O₄?₃,the removal rate of BPA still reached about 85%.Moreover,the catalyst showed good degradation performance for dyes such as Rh B,MO,MB,AO7 and the drug PHT.In this system,persulfate?PS?can quickly capture photogenerated electrons and generate sulfate radicals(SO₄^·-),which are further converted into hydroxyl radicals?^·OH?in water.After the introduction of PS,electron-enriched pollutant BPA will trap holes and be oxidatively degraded.This synergistic reaction not only inhibits the recombination of electron-hole pairs,but also enables the pollutants to be rapidly degraded through free radical attack and hole oxidation.Aiming at the problems of multiple pollutants in the water environment and the consumption of PS resources in the HPPA system.In this study,{001}crystal plane dominated and{110}crystal plane dominated new photocatalysts bismuth bromide?Bi OBr?was synthesized by crystal plane control methods,and its catalytic activity for photoreduction of Cr?VI?was investigated.The results show that under neutral conditions?p H=7.0?,Bi OBr dominated by the{110}crystal plane can more effectively reduce Cr?VI?to Cr?III?,which with lower toxicity,while on the surface of Bi OBr dominated by the{001}crystal plane,Cr?VI?can hardly be converted.It was found that the Bi OBr photocatalyst dominated by the{110}crystal plane has a large number of interlayer open channels,and Cr O₄^2-in the solution can be embedded into the Bi OBr layer through ion exchange,resulting in the remodeling of its electronic band structure.The doping of Cr O₄^2-provides both the donor energy level?O 2p?above the original valence band?VB?of the catalyst and the acceptor energy level?Cr 3d?below the original conduction band?CB?of the catalyst,thereby inhibiting photogenerated electron-hole recombination.When the Bi OBr dominated by the{110}crystal plane simultaneously treats the complex pollutant solution in which chromate and BPA coexist,chromate can play the role of PS in the HPPA system,capturing photogenerated electrons and being reduced to low toxicity valence,BPA will trap holes and be degraded.This photocatalytic reaction can achieve the simultaneous and efficient removal of two pollutants without introducing additives such as PS.