Sonocatalytic removal of naphthalene from an aqueous solution using ZnO nanoparticles

Abstract

This research presents the sonocatalytic degradation of naphthalene from an aqueous medium using a zinc oxide (ZnO) catalyst synthesised by the thermal decomposition method. The present paper also aims to apply the response surface methodology for the evaluation of the effect of different parameters on the degradation rate. The optimum parameters were found to be 50 min of reaction time, 2.2 g/l of the ZnO catalyst mass, 30 °C, 280 V, and 80 mg/l of initial concentration under a constant ultrasonic treatment at 20 kHz and 260 W of power intensity. The elemental composition of the catalyst was as follows: Zn 25.18%, O 37.03%, Mg 3.20%, K 0.83%, Ca 4.05%, N 5.07%, Na 4.13%, Cl 3.43%, and Fe 0.32%. Fourier Transform Infra-Red (FTIR) confirmed the Zn–O bond stretching at 510 cm−1. The degradation efficiency of naphthalene was almost double when the ZnO catalyst was used. The naphthalene degradation rate was a first-order reaction. Analysis of variance (ANOVA) results show that the quadratic model is suitable for the obtained data (P-value = 0.0001) and in an optimal process, performance conditions were set equal to 100%. Regression analysis with a high correlation coefficient (R2 = 0.989) and the model F-value of 6.94 indicated the adequacy of the model. The reusability study revealed that ZnO as a catalyst sustained the catalytic activity over five cycles.