Enhanced sonocatalysis of textile wastewater using bentonite-supported ZnO nanoparticles: Response surface methodological approach

• Sonocatalytic treatment of an azo dye and real textile wastewater were studied.
• Bentonite carrier enhanced sonocatalytic activity of ZnO nanoparticles.
• Low particle size of bentonite-supported ZnO nanoparticles played significant role.
• Operational parameters were optimized for maximum decolorization efficiency.

The scope of this study was the use of bentonite as the carrier of ZnO nanoparticles for enhancing the sonocatalytic decolorization of Basic Red 46 (BR46) in the aqueous phase. The results demonstrated the higher sonocatalytic activity of bentonite-supported ZnO nanoparticles (BSZNs) in comparison with the suspended ZnO nanoparticles (SZNs). The particle size of BSZNs (5–40 nm) was lower than that of SZNs (20–120 nm). Due to the immobilization of ZnO nanoparticles, a specific surface area of 80.6 m2/g was obtained for the BSZNs, which was higher than the specific surface area of the raw bentonite (42.2 m2/g). Optimization of the process via response surface methodology (RSM) based on central composite design (CCD) showed the maximum sonocatalytic decolorization efficiency (%) of 89.92% in which the initial dye concentration, the ZnO/bentonite ratio, the sonocatalyst dosage, and the initial pH were 6 mg/L, 0.3, 2.5 g/L and 9, respectively. The byproducts generated during the sonocatalysis of BR46 over BSZNs were identified using gas chromatography–mass spectrometry (GC-MS) analysis. From an application viewpoint, the sonocatalysis of real textile wastewater resulted in a COD removal efficiency (%) of about 44% within a reaction time of 150 min.