Optimization, kinetics and thermodynamics of photocatalytic degradation of Acid Red 1 by Sm-doped CdS under visible light

摘要： Sm-doped CdS nanoparticles were synthesized through an ultrasound-assisted co-precipitation method and their photocatalytic efficiency was investigated by applying them to photodegradation of Acid Red 1 (AR1) under visible light. The effect of the operational factors on the photocatalytic process was systematically evaluated using response surface methodology. Under the optimal conditions ([AR1]0= 15 mg L-1, [2% Sm-CdS]0= 1 g L-1, pH= 4 and t= 94 min), more than 83% of the AR1 molecules were degraded. The kinetics of the process was well described by the Langmuir-Hinshelwood’s pseudo-first-order model (kapp= 0.0163 min-1). Furthermore, thermodynamics of the process was demonstrated by the activated complex theory of Eyring, which declared that the photocatalytic process is endothermic and nonspontaneous in the temperature range of 25–45°C. In addition, the main products and intermediates of AR1 degradation were determined by the GC-MS technique.