Synthesis Of Ag₆Si₂O₇/mmt Photocatalysts And Their Performance In Photocatalytic Degradation Of Organic Pollutants

In recent years, silver-based catalysts have received much attention due to its high photocatlytic activities in the degradation of dyes. However, for low concentration contaminates, those catalysts show poor photocatalytic efficiency due to their small surface areas, which greatly hindered their practical applications. The silver-based catalyst has the photocatalytic properties of semiconductors, which is expected to improve the photocatalytic activity and increase the utilization ration of visible light. Besides, the particular structure properties of clays can increase the surface area of the photocatalyst significantly. In this paper, Ag6Si2O7 and Ag6Si2O7/MMT catalysts were synthesized, then their basic physical and chemical characteristics and their possible photocatalytic mechanisms during the degradation process of acid red G solution were analyzed. The research contents are as follows:A visible-light-responsive Ag6Si2O7/MMT photocatalyst was synthesized by an ion-exchange method using silver nitrate, sodium silicate and montmorillonite(MMT) as raw materials. The as-prepared samples were analyzed for the phase composition, morphology, crystal structure and the optical absorption. XRD analysis proves that Ag6Si2O7/MMT catalyst was synthesized successfully and a portion of Ag6Si2O7 was adhered to the surface of MMT, the other portion went into the interlayer of MMT. UV-Vis DRS shows that compound strength of visible light absorption enhanced with the increase of Ag6Si2O7 contents in the composite. TG-DSC curves show that the thermal stability of catalysts is well..The photocatalytic activities of the composite were evaluated for the degradation of acid red G and gaseous formaldehyde as the water and gas goal pollutant under visible light irradiation. The results show that the photocatalytic activities of Ag6Si2O7/MMT catalyst have obvious ascension compared to the pure MMT and Ag6Si2O7. The degradation rate of acid red G solution of composite reached 90% in 60 min. Besides, the formaldehyde degradation experiment was also carried out and about 60 % of the formaldehyde was degraded to CO2 by the Ag6Si2O7/MMT catalyst within 270 min.The dynamics characteristics of the degradation confirm that the degradation process of acid red G solution follows the first order kinetic. Moreover, it is confirmed that the h+ and O2�- are the major radical species in the photocatalytic degradation through terephthalic acid photoluminescence probing technique and collector of radical species. It effectively reduces the recombination of the electrons and holes in Ag6Si2O7 due to the combination, which results in higher photocatalytic activity.Compared to the pure silver-based photocatalyst, the Ag6Si2O7/MMT composite catalyst shows the advantages of low cost and high photocatalytic activity with a promising application prospect.