Abstract. In this study, we evaluated the photocatalytic activities of analytical reagent (AR) grade ZnO, TiO2, and SnO2 to identify a low-cost photocatalyst for dye degradation. The obtained samples of ZnO, TiO2, and SnO2 were characterised by X-ray diffractogram (XRD), scanning electron microscope imaging, and UV-VIS diffuse reflectance spectroscopy. The decolourisation of three structurally diverse dyes, namely crystal violet, basic blue, and methyl red under solar irradiation, was used to evaluate the photocatalytic activities of three metal oxides. The photocatalytic activities of the received three metal oxides were tested with the photocatalytic degradation of dyes and compared with Degussa P-25. Dye solutions with each metal oxide at initial pH 9 were subjected to irradiation under sunlight and monitored for up to the stage of complete decolourisation. The results indicate that ZnO exhibited the highest photocatalytic activity as compared to TiO2 and SnO2 as well as that of Degussa P-25 (TiO2). The photocatalytic dye decolourisation rates with ZnO were 1.14–1.35, 1.70–3.1, and 4–8.5 times higher than those of the Degussa P-25, TiO2, and SnO2, respectively. The percentage COD removal was studied for ZnO and partial removal was observed at the decolourisation stage. To enhance photocatalytic activity of AR grade ZnO, it was loaded with Ag metal and about 20 % enhancement in the activity was observed.

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<p><strong>Abstract.</strong> In a search of low cost photocatalyst for dye degradation we have evaluated photocatalytic activity of the Analytical Reagent (AR) grade ZnO, TiO<sub>2</sub> and SnO<sub>2</sub>. The photocatalytic activity was evaluated towards the decolourization of structurally diverse dyes such as crystal violet, basic blue and methyl red under solar irradiation and compared with benchmark Degussa P-25 (TiO<sub>2</sub>) photocatalyst. The received metal oxides were characterized by the different physicochemical methods of analysis. Powder XRD analysis showed that these metal oxides are polycrystalline in nature and crystallized in different crystalline phases. The crystalline phases of these oxides were found to be hexagonal for ZnO, tetragonal for TiO<sub>2</sub> and rutile for SnO<sub>2</sub>. Particle morphology was analysed through SEM imaging and it showed that these oxides consists of different particle morphologies and have different particle sizes. Band gap was evaluated from diffuse reflectance spectra and it was found to be 3.24, 3.20 and 3.66 eV respectively for ZnO, TiO<sub>2</sub> and SnO<sub>2</sub>. Among the three AR grade oxides, ZnO exhibited highest photocatalytic activity which is even higher than Degussa P-25 (TiO<sub>2</sub>) photocatalyst. About 20 % enhancement in the photocatalytic activity of AR grade ZnO was observed when silver metal loaded of on ZnO surface.</p>