Pd@WO3-Graphene as an Effective Visible-Light Photocatalyst for Degradation of Acid-Blue-92 Textile Dye

The fast growth of technology along with the expansion of industries has exacerbated environmental pollution. The diversity and broad application of various chemicals in the textile and agriculture industries, and eventually, the release of wastewater of such activities into the environment is a severe threat for aquatic ecosystems. Advanced oxidation methods based on the production of active species, such as hydroxyl radicals, nonselectively destroy a wide range of contaminants. Among the advanced oxidation methods, heterogeneous photocatalysts using semiconductors attracted a great deal of interest. In this project, Pd doped WO3 nanoribbons on a graphene substrate were prepared via the hydrothermal method and were used as photocatalysts to degrade a textile dye (Acid Blue 92). The effect of Pd and graphene incorporation on the surface properties, morphology, and photocatalytic activity of WO3 nanoribbons was investigated using XRD, BET, SEM, FTIR, DRS, and XPS techniques. The BET results demonstrated that the synthesis of WO3 nanoribbons on graphene oxide substrate and the reduction of obtained photocatalyst in the H2 atmosphere increased the surface area of the photocatalyst up to twice its normal size. In the next step, the ability of the photocatalyst to degrade blue-acid 92 textile dye in the presence of visible light was investigated and the degradation rate was calculated. The results confirmed that the reduced nanocomposite in the presence of H2 atmosphere in comparison with other samples has the highest dye degradation rate of 9×10-3min-1 with an efficiency of 60%. This nanocomposite, with its high surface area, facilitates the adsorption of dye-molecules on the active sites of the surface, thus greatly increasing the rate of degradation of the contaminant adsorbed on the photocatalyst surface. Eventually, different kinetic models were applied to investigate the reaction kinetics, and in each case, the correlation coefficient was calculated. The results of correlating the experimental data with the kinetics equations depicted that the dye degradation kinetics according to the Langmuir-Hinschlod model has a quasi-first-order mechanism.