| Light irradiation assisted Fenton reaction, namely photo-Fenton reaction, can enhance the removal efficiency of organic contaminants and enlarge the pH range of application. As one kind of potential photo-electric material, the utilization of graphene modifying the textural properties of the catalyst support can exhibit the co-catalysis effect on the photo-electric conversion mechanism and the electric transmission capability at the maximum extent, as well as disperse the active metal components more uniformly, which leads to accelerating the photo-Fenton reaction and thus promoting the catalytic degradation efficiency. In this work, a novel catalyst, i.e., graphene-α-FeOOH modified mesoporous support (Al-MCM-41, MCM-41 and γ-Al2O3) catalyst using ferrous ion induced self-assembly process was developed and used to catalytically degrade the phenol model wastewater in the photo-Fenton reaction with a 500 W xenon lamp supplying the simulated solar light. The main results demonstrated that:During the ferrous ion induced self-assembly procedure, ferrous ions were oxidized into α-FeOOH anchoring onto the reduced graphene fragments, while the initial graphene oxide was reduced into graphene sheets by ferrous ions in the hydrolysis and redox reaction under the heating flux. The generated composite gh/α-FeOOH was distributed well and modifying onto the surface textural structure of the mesoporous supports.According to the comparison of the structural characteristics and catalytic properties among the gh/α-FeOOH oriented catalysts, gh/α-FeOOH-Al-MCM (based on Al-MCM-41) possessed the higher catalytic capacity than gh/a-FeO OH-MCM (based on MCM-41) and gh/α-FeOOH-Al2O3 (based on γ-Al2O3). The optimizing parameters for composite components of gh/α-FeOOH-Al-MCM followed respectively as:2g Al-MCM-41,30 ml GO (7.75 mg·mL-1) dosage,5% wt Fe2+ adding and 2.33 mass ratio of GO/Fe2+. The assistance of simulated solar light supplied by the xenon lamp strengthened the catalytic degradation efficiency of phenol using gh/α-FeOOH-Al-MCM in the Fenton reaction, shortened the reaction time and enlarged the pH range of application, which exerted completely the enhanced synergistic effect of composite components among α-FeOOH, graphene and Al-MCM-41. The catalytic capability of gh/α-FeOOH-Al-MCM was retained to a considerable extent after the 5th reuse experiment. The Mn2+/Fe2+(or Ce2+/Fe2+) binary induced catalyst material possessed less catalytic properties than gh/α-FeOOH-Al-MCM.The suitable pH range of application in the photo-Fenton reaction using gh/a-FeOOH-Al-MCM is from 4 to 9, in which the optimizing parameters of the catalyst and H2O2 dosages were 0.5mg·L-1and 10mM respectively. As for the light source irradiation, the phenol degradation efficiency using gh/a-FeOOH-Al-MCM mainly followed the sequence:mercury lamp> xenon lamp> filter ahead of xenon lamp (producing visible light)> real solar light> dark room. The heterogeneous photo-Fenton reaction made the main contribution in the catalytic phenol degradation using gh/a-FeOOH-Al-MCM under the simulated solar light irradiation, though the dissolving iron from the catalyst also took part in the photo-Fenton reaction. Different types of anions (Cl-、SO42-、NO3-、HCO3-、HPO43-), low-molecular organic acids (citric acid, oxalic acid, tartaric acid) or natural organic matters (HA and FA) inhibited the catalytic capability of gh/a-FeOOH-Al-MCM in the photo-Fenton reaction to a certain extent. Assistance of simulated solar light accelerated the generating rate of oxydic free radicals (included·OH and ·O2) in the photo-Fenton reaction using gh/a-FeOOH-Al-MCM. |
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