Effect of synthesis method on the photocatalytic performance of zinc oxide loaded on mesostructured silica nanoparticles

Abstract

An advanced oxidation process (AOPs) using heterogeneous semiconductor photocatalysts such as TiO2, Fe2O3, ZnO, CuO, and ZrO2 have become a popular method for the removal of toxic pollutants from wastewater1,2. Among them, ZnO has been widely researched in photocatalytic applications due to its activity which is comparable to TiO2. Recently, the incorporation of ZnO into a mesoporous material support has been discussed by several research groups3,4. It is believed that the incorporation of both materials is a beneficial approach to improve the photocatalytic activity of the catalyst5,6. Therefore, in this study, two approaches have been introduced to prepare a zinc oxide loaded on mesostructured silica nanoparticles (ZnO/MSN) catalyst; in-situ (ZnO/MSNis) and impregnation (ZnO/MSNim). The effect of the preparation methods on the properties of both catalyst were studied via XRD and FTIR analysis. The introduction of zinc species onto silica framework was found to form an interaction between the host and support material. The desilication occurred in the silica framework of the MSN accompanied by isomorphous substitution of Zn2+cations to form an active species Zn–O–Si bond. The photocatalytic activity of both ZnO/MSNs were tested on photodecolorization of methyl orange (MO). The ZnO/MSNis showed the highest decolorization rate at an optimum dosage of 1 g L-1 using 3.06 × 10-2 mM MO after 8 h at pH 2 under UV irradiation. A kinetic study demonstrated that the photocatalytic reaction followed the pseudo first-order model.