Adsorption and photocatalytic decomposition of methylene blue on surface modified silica and silica-titania

The adsorption behavior of reactants onto a silica-titania photocatalystʹs surface can affect catalytic performance. In this work, the affects of surface functionalization on the adsorption behavior of methylene blue on silica and a silica-titania photocatalyst were investigated. The materials before and after surface modification were characterized by infrared spectrometry. Adsorption isotherms of methylene blue on silica functionalized with alkyl, amino, thiol, cyano, and thiocyano groups showed distinct differences from one another as well as from the unmodified material. Silica-titania was functionalized with thiol and thiocyano groups. The methylene blue adsorption isotherms compared to unmodified silica-titania were similarly affected, but to a lesser extent. Thiocyano groups on surface modified silica-titania were stable to UV photolysis, and the material retained photocatalytic activity.