| In recent years,the using of clean solar energy and control of environmental pollution has attracted extensive attention.Therefore,degrading organic pollutants by photocatalysis and producing hydrogen by photocatalytic degradation has become the most promising method to solve energy and environmental problems.However,limited by its wide band gap,traditional photocatalysts can only absorb UV light of the solar spectrum?ca.5%of the overall spectrum?,seriously limiting the utilization of solar light.On the other hand,separation and recovery of single micro-and nano-scale photocatalyst from the treated solution is difficult.Therefore,it is highly desirable to develop a photocatalyst with efficient visible light activity and easy solid-liquid separation for practical application in industrial processes.In this study,a Ag6Si2O7 photocatalyst with high effective photocatalytic activity in the whole visible light was selected as the base photocatalyst and supported on magnetic Fe3O4 particles to prepare Fe3O4/Ag6Si2O7,and then a Ti O2 layer was added between Fe3O4 and Ag6Si2O7 to enhance its stability.The photocatalytic activity of as-prepared materials were exmained by MB degradation under simulated visible light.Scanning electron microscope?SEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?,UV-vis diffuse reflection spectrum?UV-Vis DRS?,and vibrating sample magnetometry?VSM?were performed to characterize the composites.Influencing factors such as catalyst dosage,initial MB concentration and pH value were also investigated in batch experiments.At last,the recycling performance and photodegradation mechanism were also discussed.The results showed that:Fe3O4/Ag6Si2O7 and Fe3O4/TiO2/Ag6Si2O7 photocatalysts with narrow band gap showed strong absorption properties in both ultraviolet and visible region.MB could be rapidly degraded by these two materials under simulated visible light.When the initial concentration of MB was 5 mg/L and catalysts dosage was 0.10 g,98.6%and99.4%of MB could be removed in 10 min.These two photocatalysts in water were negatively charged at pH range from 3.0 to 10.0.Therefore,degradation of positively charged MB was not pH dependent.The saturation magnetization of Fe3O4/Ag6Si2O7and Fe3O4/TiO2/Ag6Si2O7 photocatalysts were 32.45 and 25.51 emu/g,respectively.The spent materials could be easily separated upon application of a magnetic field.The photocatalytic activity of Fe3O4/Ag6Si2O7 decreased gradually,but its high magnetic separation ability provided a possibility for its recycling.The addition of TiO2 layer enabled photoelectrons migrated to the surface of Fe3O4/TiO2,which inhibited the light corrosion of Ag6Si2O7 and enhanced the recycling performance of the composite photocatalyst.During the degradation process,MB was decomposed into some colorless intermediates and gradually mineralized into CO2 and H2O.Reactive species trapping experiments revealed that the photogenerated holes?h+?and superoxide radical?·O2-?were the mainly active species of MB degradation by Fe3O4/Ag6Si2O7 and Fe3O4/TiO2/Ag6Si2O7 photocatalysts.The high performance,excellent recyclability and good stability of as-prepared composite photocatalyst in this study make it promising employed for practical application in water treatment. |
PDF Full Text Request