Synthesis And Catalytic Properties Of Cu Doped Al₂O₃/g-C₃N₄ Heterogeneous Fenton-like Catalysts

In recent years,for the purpose of overcoming the shortcomings found in the application of traditional Fenton and homogeneous Fenton-like oxidation,researchers have devoted themselves to the development of heterogeneous Fenton-like catalysts,which can degrade pollutants with high efficiency,make full use of oxidants and reduce the leaching of metal components.Comparing with Fe,Cu can react more rapidly with H₂O₂ and be less affected by reaction pH.Cu-based catalysts can be more stable in solution and generate less mineral sludge.These make Cu-based catalysts very popular.Herein,three kinds of Cu-based catalysts were synthesized,Cu/Al₂O₃,CuO/m-C₃N₄and Cu/Al₂O₃/g-C₃N₄,which were used to remove phenol in water.Studies were conducted to explore the mechanism of the catalytic reaction.The characterization of catalysts by XRD,SEM,FTIR and XPS proved that three Cu-based catalysts has been successfully synthesized.Carrier materials could not degrade phenol before loading copper/copper oxides on them.Under the optimum preparation conditions,the degradation rate constants of phenol in 25?by Cu/Al₂O₃,CuO/m-C₃N₄ and Cu/Al₂O₃/g-C₃N₄ could reach 0.0102 min^-1?within 2 h?,0.0240 min^-1?within 30 min?,0.0216 min^-1?within 2 h?,while the leaching of Cu were 43.6?mol/L,11.1?mol/L,18.5?mol/L,respectively.The doping amount of copper,the concentration of H₂O₂,the dosage of catalysts and the reaction temperature had significant effects on the reaction process.The optimal experimental conditions were different duing to the different properties of catalysts.Radical scavenging experiments and EPR tests were conducted to explore the mechanism of catalytic degradation of three materials.For all of these three catalysts,HO·and O₂·^-were produced by H₂O₂ oxidating?Cu⁺on the surface of catalysts,while the reduction processes of?Cu²⁺could be different since carrier materials had different properties.Phenol could complex with?Cu²⁺on the surface of the three materials,during which process electrons given by phenol could reduce both?Cu²⁺and H₂O₂ and produce extra HO·.As for Cu/Al₂O₃,phenol could occupy most of active sites on the surface of catalyst,while H₂O₂ had little chance of contacting?Cu²⁺owing to the fact that the active sites on the surface of Cu/Al₂O₃ were limited.Only a minority of?Cu²⁺was reduced by H₂O₂.As for CuO/m-C₃N₄,the surface of m-C₃N₄ provided a large number of active sites so that there was no need for H₂O₂ to compete with phenol.The reduction of?Cu²⁺could be achieved quickly by H₂O₂ and the consumption of H₂O₂was also fast.As for Cu/Al₂O₃/g-C₃N₄,the reduction processes of?Cu²⁺were similar to the processes of Cu/Al₂O₃.Besides,modification brought by g-C₃N₄ enhanced the ability of transferring electrons so that?Cu²⁺could also be reduced by gaining electrons from g-C₃N₄.