Photo-assisted advanced oxidation processes for efficient removal of anionic and cationic dyes using Bentonite/TiO2 nano-photocatalyst immobilized with silver nanoparticles

Abstract Azo dyes with high mobility are widely distributed in industrial wastewater and due to the harmful effects of these chemicals, their removals from wastewater draw increasing attention and various technologies have been developed, amongst which photo-assisted advanced oxidation processes are more effective and promising. In this study, surface modification of bentonite as an important geotechnical material in the fields of environmental engineering was performed by sol-gel synthesized titanium dioxide nanoparticles and then different content of silver nanoparticle precipitation. The prepared Bentonite/TiO2/Ag nanocomposites were analysed using different techniques and used to remove poly azo anionic direct red 80 and azo cationic methylene blue dyes under UV photocatalytic degradation, hydrogen peroxide-assisted photocatalytic degradation, catalytic hydrogen peroxide oxidation, and adsorption processes. Moreover, the effect of different parameters affecting the dye removal such as initial pH, dye concentration, and H2O2 concentration was examined. Dye degradation efficiencies of various processes were compared that they were higher in the order: hydrogen peroxide-assisted photocatalytic degradation >UV photocatalytic degradation > adsorption > catalytic hydrogen peroxide oxidation. The highest dye removal efficiencies were obtained 77 and 100% for direct red 80 and methylene blue, respectively, related to 0.03 g of the nanocomposite with 0.25% silver content in the advanced oxidation process.