Study On Synthesis Of Ag₂CrO₄ Photocatalysts And The Photocatalytic Decomposition Of 4BS Under Visible Light

As one of the advanced oxidation processes, photocatalysis has many superiorities. It is an ideal environment treatment technology. In order to utilize solar energy and enlarge the responsive range of photocatalyst to the light, it is meaningful to find and research novel photocatalysts which have high photocatalytic activity under visible light.Visible-light-driven Ag2Cr04 has been successfully synthesized by a simple hydrothermal process. The prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and Brunauer-Emmet-Teller (BET) surface area analysis. The effects of mixing method, hydrothermal temperature, pH value of precursor and hydrothermal holding time on photocatalytic activities were investigated by the degradation of direct fast scarlet 4BS in aqueous solution at room temperature under visible-light irradiation. It is concluded that Ag2Cr04 photocatalyst, hydrothermally synthesized at 160℃and the original value of pH for 16h after being ultrasound for 30 minutes, exhibited the highest photocatalytic activity due to the good crystallization and high specific surface area. The BET surface area was 2.63m2/g for the photocatalyst. The UV-vis DRS indicated that the catalyst of Ag2CrO4 presented the photoabsorption properties from UV light region to visible light shorter than 660 nm, and band gap was estimated to be 1.88 eV.Photocatalytic degradations of 4BS were performed to investigate the influence of different conditions. The results showed that:The optimum photocatalyst dosage was 2g/L when the initial strength of 4BS was 20 mg/L, and after 150min's reaction, the removal ratio was 94.4%; with initial concentration of 4BS aqueous solution increasing from 20 mg/L to 100 mg/L, the removal ratio decreased; The reaction fitted the fist-order kinetics in the range of the examined concentration and the reaction rate constant decreased with increasing the initial concentration. It is concluded that Ag2CrO4 photocatalyst exhibited the highest photodegradation at the original value of pH. The reuse experiments indicated that the structure of Ag2CrO4 was stable after being used for five times, but photocatalytic activity slightly declined.