Adsorption and visible light-driven photocatalytic degradation of Rhodamine B in aqueous solutions by Ag@AgBr/SBA-15

Abstract

A novel composite, Ag@AgBr/SBA-15, was successfully synthesized by dispersion of AgBr on mesoporous silica SBA-15, characterized by several techniques, such as XRD, N2 adsorption−desorption, SEM & EDS, UV−vis spectrum and XPS, and utilized for visible light photocatalytic degradation of dye Rhodamine B (RhB) in aqueous solutions. The results showed that for the various AgBr loadings in the composites, RhB photocatalytic degradation efficiency arrived at the maximum of 77% at 50% loading, or with 50Ag@AgBr/SBA-15. Under the combined mode, the RhB removal reached 88% at 0.3g/L of 50Ag@AgBr/SBA-15 dosage, 20mgL−1 of initial RhB concentration, 4.28 of unadjusted initial pH and 20°C. The RhB photocatalytic degradation followed well with the second-order kinetics, and the increase of the 50Ag@AgBr/SBA-15 dosage, the decrease of the initial RhB concentration and the optimal initial solution pH would be favorable to RhB photocatalytic degradation. The quenching tests demonstrated that the RhB photocatalytic degradation was mainly attributed to the generation of active species such as O2−,OH and h+. Moreover, the adsorption characteristics of 50Ag@AgBr/SBA-15 were investigated, with its pHpzc of 6.21 acquired and the conclusion that the RhB adsorption isotherm well followed Langmuir model drawn. Additionally, photocatalyst 50Ag@AgBr/SBA-15 can be effectively regenerated with the H2O2 solutions under visible light irradiation, and reused for up to five runs for the degradation of RhB in the presence of visible light, with RhB removal more than 75% and Ag+ leaching undetected for each run.