Montmorillonite and modified montmorillonite supported ZnO catalysts

Abstract

The purpose of this study is to prepare ZnO supported montmorillonite based catalysts by using co-precipitation technique. The photocatalytic activities of the as-prepared catalysts are studied for degradation/decolorization of methyl orange (MO) under UV irradiation. The morphological aspects of the catalysts are examined by X-ray diffractometer (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) and elemental mapping analysis, surface area analyzer (BET) and UV-Vis diffuse reflectance spectrometry (UV-Vis DRS). XRD results supply information about the ZnO crystalline sizes of the catalysts. SEM (EDX) analysis shows the differences in the surface morphologies of the bare clays and supported catalysts. For all supported catalysts, the characteristic ZnO band edge is detected within UV region and also increments in the surface areas and pore volumes are noticed by the BET measurements. Freundlich adsorption model explains the dark adsorption behavior of the supported catalysts. ZnO loading amounts, affect the photoactivities. Degradation/decolorization processes follow pseudo first order kinetics. Langmuir-Hinshelwood model is found to be applicable for the supported catalysts. The re-use abilities of the catalysts are controlled. A decomposition mechanism of the MO is postulated.