| Recently, g-C3N4, as new type of photocatalytic materials, has attracted a great deal of attention owing to its suitable band-gap width and visible light absorption performance. However, photoelectron-hole pairs of the single g-C3N4 material has been proved to have high recombination rate, which limits its photocatalytic activity. This kind of weakness becomes a technical "bottleneck" and impedes its further development. In order to expand the g-C3N4 catalyst’s absorption range of radiation, reduce the high recombination rate between the photoelectrons-hole pairs, simplify the catalyst recycling process and improve the utilization efficiency of repetition, we respectively synthesize Ag2O/g-C3N4/Fe3O4 and ZnO/g-C3N4/Fe3O4 magnetic composite materials by coprecipitation and hydrothermal-coprecipitation method in this work. During the experiment, g-C3N4 material is prepared by calcination adopting melamine as precursor. The structures are characterized by X-ray diffraction(XRD), thermogravimetric analysis(TG), Fourier infrared spectroscopy(FT-IR), Transmission electron micro scopy(TEM), Energy dispersive X-ray spectrometer(EDS) and solid UV-vis diffuse reflection spectroscopy(UV-Vis) method. With rhodamine B(RhB) and 3,4-dichforophenol(3,4-DCP) as the targeted pollutants, the photocatalytic performance of the composite sample Ag2O/g-C3N4/Fe3O4 and ZnO/g-C3N4/Fe3O4 are evaluated. The mechanism of catalytic oxidation process is taken onto preliminary discussions in the meantime.1 The results from characterization of composite materials show that Ag2O, ZnO and Fe3O4 nanoparticles are uniformly deposited on the surface of g-C3N4 sheet, which is conducive to the proliferation of simulated sunlight by a variety of ways and enhance its photocatalytic activity. It is convenient to repeatedly use because the catalyst can be easily separated from the system by external magnetic field because of the presence of magnetic Fe3O4 nanoparticles in the material.2 The Ag2O/g-C3N4/Fe3O4 magnetic composite materials are applied in the RhB photocatalytic degradation, several important affecting factors of photocatalytic oxidation were discussed including the mass ratio of Ag2O and g-C3N4, the content of Fe3O4, pH, catalyst quantity, initial concentration of RhB and salinity. At the same time, the reaction mechanism of this, degradation process has been preliminary explained. The experimental results show that:(1) The catalyst has the highest catalytic activity when the mass ratio of Ag2O, g-C3N4 and Fe3O4 was 1:1:1. The targeted pollutant, the initial concentration of 20 mg-L-1 RhB solution, could completely degrade within 60min using 5mg composite marerials;(2) Different substances added in the system act as the active ingredient removers in the photocatalytic degradation process. The results indicate that h+plays a leading role in the degraded process of RhB by the composite material.3 In this paper,3,4-DCP was selected as the target contaminant to explore the effect of photocatalytic degradation of ZnO/g-C3N4/Fe3O4 magnetic material. The effective factors of degradation effect, such as the mass fraction of each component in the catalyst, pH, salinity, initial concentration of the pollutants and the amount of catalyst were discussed. Meantime, the cycle-use times of the materials and the mechanism of degradation were also investigated. The results show as follows:(1)When the mass fraction of ZnO, g-C3N4, Fe3O4 was 1:4:2.5, degradation effect of the pollutan is the best and removal ratio of 3,4-DCP could reach 90%;(2)The increase of solution pH is in favour of light catalytic degradation, while the salinity has no obvious effects on the degradation of pollutants in the system;(3)The active ingredient·O2- was considered as the main substance contributing to influence the degradation efficiency,(4)As for catalytic ability, there is no obvious change is found when the regenerated catalyst was repeatedly used several times.
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