Kinetic and Thermodynamic Studies on the Reactivity of Hydroxyl Radicals in Wastewater Treatment by Advanced Oxidation Processes

The removal of dyes from wastewater, is one of the major environmental concerns due to their high color density, and they are toxic at even low concentrations. Adsorption process by advanced oxidation processes (AOPs) has been found to be a more effective method than classical methods for treating dye-containing wastewater. This research, is to investigate the decolorization abilities of azo dye in order to treat organic polluted wastewaters efficiently by AOPs. Various operational parameters such as pH, initial dye concentration and catalyst loading were investigated on the use of ZnO/W in the adsorption of Reactive Red 31 (RR 31) dye. The study also focused on the kinetic and thermodynamic investigation such as activation energy (Ea), standard Gibbs free energy (ΔG0), standard enthalpy (ΔH0), and standard entropy (ΔS0). The kinetics of adsorption of dye followed a pseudo-first order kinetic model. Further, thermodynamic study showed that the photocatalytic decolorization of this dye is an endothermic and spontaneous reaction. This study represents a success of thermodynamic for the application in environmental area. Additionally, cost analysis of the process was discussed. The treatment effectiveness was reported as the electrical energy consumed per unit volume (EEO) of waste-water treated required for 100% decolorization of the investigated compound.