Improved stability in SBA-15 mesoporous materials as catalysts for photo-degradation processes

Abstract

SBA-15 materials were modified with Cr, Ni and Fe and characterized by ICP, SAXS, XRD, N2 adsorption, TPR and UV–Vis DRS. Their photo-catalytic activity was evaluated for the degradation of Acid Orange 7 (AO7) in aqueous suspensions irradiated by artificial UV–Vis light. The results showed that the Cr-modified catalyst exhibited the highest activity. The presence of Cr6+ highly dispersed on the internal surface of the SBA-15 structure would be responsible for this observed behavior. Then, when TiO2 was loaded on this solid, the photo-activity was increased due to a heterojunction effect between the two metals. Moreover, the TiO2 cover resulted in the Cr species protection leading to a notable decrease of the Cr leaching into the reaction medium. In addition, comparing with the already reported results for modified MCM-41 catalysts, the solid synthesized here allowed achieving the solution biodegradability in shorter irradiation periods and could be re-used even after four cycles without loss of activity. Thus, the high performance of this material leads to make it a very promising photo-catalyst for pre-treatment of recalcitrant contaminants present in aqueous effluents.