Investigation of Kinetic and Thermodynamic Parameters in the Removal of 2-Chlorophenol from Aqueous Medium by Ultraviolet and Ultrasonic Waves in the Presence of Zinc Oxide Nanocatalyst Synthesized by Green Method

 The present study investigates the kinetic and thermodynamic parameters in removing one of the essential phenolic derivatives (2-chlorophenol) by zinc oxide nanocatalysts synthesized by the green method, during photocatalytic and sonocatalytic progress.

 The present study is an experimental study conducted in the research laboratory of the Department of Chemistry of Ardabil Islamic Azad University. In order to evaluate the efficiency of the photocatalytic and ultrasonic process in the removal of 2-chlorophenol, the first nanocatalyst was prepared by the green method using a paper flower species called Bougainvillea spectabilis. After ensuring the synthesis accuracy with the help of various technologies, essential parameters affecting the removal efficiency of 2-chlorophenol, such as concentration, amount of nanocatalyst, solution pH, and temperature, were investigated, and the most suitable conditions for removal during photocatalytic and ultrasonic processes were identified.

 The XRD spectrum confirms the synthesis of zinc oxide nanocrystals. The uniform hexagonal nature of ZnO nanoparticles with a size between 12 and 31 nm was confirmed using SEM and TEM images. Elemental analysis (EDX) showed that the synthesized pure nanoparticles contained 74.94 wt. % of zinc and 25.06 wt. % of oxygen. Examination of 2-chlorophenol removal from aqueous solution in dark conditions showed that the Langmuir and Freundlich isotherm models best follow the removal process. Investigation of the removal kinetics of the studied phenolic derivative with high line regression coefficient introduced pseudo-second-order kinetics for the removal process of 2-chlorophenol.

 According to the thermodynamic parameters obtained in this study, the negative values of Gibbs free energy changes (ΔG°) at all temperatures studied during the photocatalytic and sonocatalytic removal process showed that the removal reaction is spontaneous. Also, the positive enthalpy changes (ΔH°) during the removal process by the nanoparticles synthesized from the paper flower indicated that the removal process is endothermic. Our research showed that the synthesized nanoparticles could be used for photocatalytic and sonocatalytic removal of 2-chlorophenol from the aqueous medium with an efficiency of 90.21 and 82.54%, respectively.