Study On The Treatment Of Malachite Green Using Fe₃O₄/Ag₃PO₄ Composite Photocatalyst

Photocatalytic method was an effective way to remove pollutants under light illumination. With high efficiency of photocatalytic oxidation on organic compounds, it had become one of the hot sopts in water treatment field. Ag3PO4 exhibited very strong photocatalytic activity under visible light and can absorb the sunlight less than 520 nm wavelength, with the quantum yield up to 90% under visible light. Therefore, putting the visible-light-response catalyst into practical application was meaningful for the elimination of pollutants and environmental purification.At present, researches on photocatalytic materials mostly focused on improving the photocatalytic activity and enhancing recycling ability. The utilization of magnetic Fe3O4 nanoparticles provided a possible way to achieve both of the two objectives. In this study, composite photocatalyst Fe3O4/Ag3PO4 was sythesized through the combination of Fe3O4 nanoparticles and Ag3PO4 particles. The composite had high photocatalytic activity and it was easily separated from the reaction system under an applied magnetic field due to its good magnetic properties.In this study, the photocatalytic performance on triphenylmethane dyes malachite green was explored, with the composite catalyst Fe3O4/Ag3PO4 as photocatalyst and xenon light source as visible light. At the same time, the influence of reaction conditions(the initial concentration of Malachite Green, the concentration of catalyst and the co-existing anions and cations) on the degradation efficiency of malachite green was also studied. After the reaction finished, separate the magnetic composite catalyst in external magnetic field for the recycling photocatalytic experiments. Finally, photodegradation process of malachite green in photocatalytic reaction was investigated. Results showed that the composite Fe3O4/Ag3PO4 exhibited high photocatalytic activity on malachite green in simulated visible light. When the initial concentration of malachite green solution was 5 mg/L and catalyst dosage was 200 mg/L, the removal efficiency for malachite green could reach 86.83% after 60 min visible light illumination. The composite catalyst was easily separated from the reaction system in the external magnetic field and the photodegradation efficiency of malachite green could be maintained at a high level in the following two cycles. Photocatalytic degradation of malachite green was a very complex process. In the process of photodegradation, malachite green molecules developed into a series of colorless intermediates, finally, gradually mineralized to CO2 and H2 O. The degradation process of malachite green considered as the following two reactions: the step-wise N-demethylation process of malachite green and the damage of conjugated structure under the attack of ?OH hydroxyl radical. The photodegradation of malachite green using Fe3O4/Ag3PO4 composite as photocatalyst was economic and highly efficient. Most of Malachite Green in wastewater could be removed and the composite material keeps good recovery characteristics and could be used for continuous photocatalytic reaction, and the photodegradaion method of Malachite Green had some potential to practical application.