Adsorption and photocatalytic oxidation of dimethyl sulfide and ethyl mercaptan over layered K1-2xMnxTiNbO5 and K1-2xNixTiNbO5

Layered K1-2xMxTiNbO5 (M = Mn, Ni) was prepared by ion-exchange of KTiNbO5 obtained by the solid-state method with Mn2+ and Ni2+. The crystal structure and optical property of the as-prepared K1-2xMxTiNbO5 were studied using powder X-ray diffraction and ultraviolet (UV)-visible light diffuse reflection spectroscopy. The adsorption feature and photocatalytic oxidation activity of dimethyl sulfide (DMS) and ethyl mercaptan (EM) over the as-prepared K1-2xMxTiNbO5 were evaluated using infrared spectroscopy. K1-2xMxTiNbO5 showed a higher interval between sheets and a stronger absorbance to visible light than KTiNbO5. After ion-exchange with Mn2+ and Ni2+, the band-gap energy of KTiNbO5 was shifted from 3.35 to 2.97 eV and 2.45 eV, respectively whereas the weak interaction between K1-2xMxTiNbO5 and DMS/EM was little affected by the exchanged cation. The photocatalytic oxidation activity of K1-2xMxTiNbO5 for DMS or EM depended on the special cation. K1-2xMnxTiNbO5 emerged a photocatalytic activity only under ultra-light irradiation, which converted DMS to sulfoxide and sulfone, and EM to sulfonic acid. However, K1-2xNixTiNbO5 emerged the photocatalytic activity under visible light besides under ultra-light irradiation; EM was converted to sulfonic acid by visible irradiation, but to sulfate and carbonate by UV radiation.