Sonocatalytic Degradation of Tetracycline by Sm-Doped ZnS Nanoparticles: Optimization and Kinetics of Process

Tetracycline (TC) is one of the most prevalent antibiotics which is used to treat the infectious diseases. Entrance of this pharmaceutical compound to the environment can lead to numerous problems. Therefore, this study was conducted with the aim of evaluation of the removal efficacy of TC by sonocatalytic process using samarium-doped zinc sulfide (Sm-ZnS). In this study, Sm-ZnS nanoparticles were synthesized through an ultrasound-assisted co-precipitation method and were used for sonocatalytic degradation of TC. The sonocatalytic experiments were conducted in a flask equipped with a water bath under the ultrasonic (US) waves resulting from a probe at different operational conditions. The results showed that the degradation efficiency increases with the increase of catalyst amount (0.2-1 g/L), US power (30-50 W) and time (10-30 min), and reduces with the increment of the TC initial concentration (10-30 mg/L). Modeling and optimization of the process by response surface methodology revealed that under the optimum conditions ([TC]0= 15 mg/L, [Sm-ZnS]0= 0.4 g/L, US power= 45 W and t= 15 min), degradation efficiency reached 97%. Kinetics studies showed that the sonocatalytic process follows the pseudo-first-order model with the rate constant of 0.223 min-1. Based on the results it can be concluded that the sonocatalytic process using Sm-ZnS catalyst can be used as an effective and available method to remove TC from sewage and pharmaceutical wastewater.