Preparation And Mechanistic Study Of Highly Active Fenton-like Catalysts For Neutral Or Alkaline Wastewater

Advanced oxidation processes（AOPs）are a valid method for degrading intractable pollutants in water.Among them,the homogeneous Fenton reaction initiated by Fe（Ⅱ）and H₂O₂ is widely used to treat wastewaters such as printing and dyeing,oil-containing and pesticides due to the high production of highly oxidatively active·OH.However,its narrow operating pH range,the large amount of iron-containing sludge and the high costs to be consumed to adjust the pH of the solution greatly limit its use scenarios.As a result,solid catalyst-based non-homogeneous Fentons have emerged.To achieve high catalytic activity over a wide pH range,chitosan-Fe materials with graphene-like structures and cuprous-carbon nitride materials with excellent performance under alkaline conditions were selected for this study to investigate the purification mechanism in depth and to enhance the reuse performance by introducing magnetic separation techniques,providing a preliminary exploration of the materials for practical applications over a wide pH range,as follows:（1）A multi-component magnetic Fe/C Fenton catalyst with a core-shell structure was prepared using chitosan and ferrous sulphate as precursors.The FeS on the surface formed a thin layer of Fe OOH wrapped around the reductive core after acidification,and the higher graphitisation and specific surface area accelerated the electron transfer capacity and the adsorption-enrichment effect of the active sites on nearby pollutants,resulting in a catalyst that within 20 min Removal of 97.8%of the 50mg/L Acid red 73（AR 73）was achieved within 20 minutes,and at pH=8 it was still above 95%.（2）The copper-doped graphite-phase carbon nitride composites were prepared and showed superior performance under strong alkaline conditions,achieving 95%removal of 50 mg/L p-chlorophenol within 120 min at pH=11.Results of radical quenching and semi-quantitative experiments confirm the significant enhancement of ¹O₂ and·O₂^-yields under alkaline conditions and their dominance in the catalytic reaction.Density flooding theory calculations confirm the formation of electron-rich Cu（Ⅰ）-N active sites in Cu-CN materials.The nitrogen-rich lone pair electrons in g-C₃N₄ are continuously transferred through the Cu（Ⅰ）-N bridge to the adsorbed H₂O₂,resulting in rapid activation of the latter,while the resulting Cu（Ⅱ）-g-C₃N₄ can combine with·O₂^-to form Cu（Ⅱ）-O-O surface high-energy complexes,followed by the generation of Cu（Ⅰ）-N and¹O₂ by intramolecular electron transfer,ensuring stable degradation efficiency under strongly alkaline conditions;（3）Through the cross-linking effect of inexpensive oligomer polyethylene glycol（PEG）,Fe₃O₄ was successfully loaded onto the surface of Cu-CN material at room temperature to obtain magnetic cuprous-carbon nitride material,and the excellent degradation performance of the raw material under alkaline conditions was well retained,and 93.5%of the catalytic capacity of the raw material had been achieved when Cu-CN:Fe₃O₄ was=3:1.The long-chain PEG immobilised on the catalyst surface enhances the dispersion of Fe₃O₄ and inhibits the agglomeration of Cu-CN material,and the Fe-PEG anti-erosion layer formed by the two can slow down the exposure of Cu-N active site,which significantly improves the durability of the material under strong alkaline conditions.This opens a new avenue for the application of cuprite materials in practical wastewater applications.