Enhancement of ultrasound-assisted degradation of Eosin B in the presence of nanoparticles of ZnO as sonocatalyst

Abstract

In this research, ZnO nanoparticles, as a sonocatalyst for degradation of Eosin B dye under ultrasonic irradiation, were synthesized. Various experimental conditions (ultrasound irradiation power: 50–250 W, ultrasound irradiation time: 10–70 min, catalyst dosage: 1–3 g/L and initial dye concentration: 5–25 mg/L), using ZnO nanoparticles were investigated in order to find the optimal condition for the degradation of Eosin B. The crystalline and grain size of samples were obtained using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), 15 and 30 nm, respectively. The nanoparticles structure was observed in the form of hexagonal. The band-gap of the prepared nanoparticles was measured as 2.9 eV which is appropriate for sonodegradation process under ultrasonic irradiation. Results demonstrated that Eosin B degradation efficiency was enhanced considerably in sonicated samples compared to non-sonicated ones. The experiments were analyzed via response surface methodology (RSM) based on central composite design (CCD). Analysis of variance (ANOVA) confirmed a good reliability of quadratic response surface model for predicting the sonocatalytic efficiency at various operational parameters (R2 = 0.9918 and Adjusted R2 = 0.9841). Results indicated that increasing the ultrasound power and time led to enhancement of Eosin B removal efficiency, while increasing the dye concentration caused to its decreasing. The degradation of dye, increased by enhancement of the catalyst dosage, where in the specified value (2.17 g/L) it began to decrease. The optimization of the process showed the maximum sonocatalyst degradation of 93.46% at irradiation power, irradiation time, catalyst dosage and dye concentration of 250 W, 70 min, 2.17 g/L and 5.08 mg/L, respectively. Kinetic studies showed that the sonodegradation of Eosin B corresponds well to first-order reaction.