Evaluation of adsorption, photocatalysis, and combinational methods for the treatment of a cationic dye-bearing wastewater

The primary purpose of this investigation is to prepare, and assess the performance of ZnO-modified bentonite as a very cheap, available and efficient hybrid compound with easy and fast synthesis method as well as possessing adsorption and photocatalytic properties together for successful application in wastewater treatment industries. In this regards, adsorption, photocatalytic degradation, and combined adsorption/photocatalytic degradation of Basic Blue 41 (BB41) from aqueous solutions were evaluated using bentonite, ZnO nanoparticles, and ZnO-modified bentonite, respectively. The adsorption experiments were examined at various operational condition using bentonite, and the adsorption data were surveyed by adsorption isotherms and kinetics. The results were shown that the Langmuir isotherm and pseudo-second-order kinetics were the best fitting models and the adsorption capacity of bentonite for the adsorption of BB41 were calculated 833.33 mg g⁻¹. The ZnO nanoparticles and ZnO-modified bentonite were synthesized applying solution combustion method by microwave and the samples were characterized by SEM, TEM, FTIR and X-ray diffraction methods. The activity of ZnO nanoparticles as a photocatalyst were studied using UV illumination for the degradation of BB41 in a batch reactor. The operational variables and kinetics of photocatalytic decolorization were investigated. At the end, ZnO-modified bentonite was applied to investigate the photocatalysis-assisted adsorption process to examine both adsorption and degradation of BB41. The extent of mineralization was determined using TOC analyzer. The final results strongly recommend using ZnO-modified bentonite as an excellent hybrid compound for environmental applications.