Efficiency Evaluation of Chitosan-graphene Oxide Composite in Diethyl Phthalate and Diallyl Phthalate Removal from Synthetic Wastewater: A Kinetic, Isotherm, and Thermodynamic Analysis

Background and Over the last few years, phthalic acid esters (PAEs) have attracted great attention due to their extensive production and use. These compounds are not only associated with endocrine disruption and cancer, but also considered as emerging and hazardous pollutants. Large amounts of PAEs are detected in industrial wastewaters. Due to the widespread use of adsorption method in industrial wastewater treatment, this study aimed to synthesize chitosane-graphene oxide composite and use it in diethyl phthalate (DEP) and diallyle phthalate (DAP) removal from industrial wastewater.
For the purpose of the study, Hummer’s method was used with some modifications to prepare graphene oxide synthesis. Adsorbent characteristics were analyzed using SEM and XRD techniques. The effect of pH, contact time, adsorbent dose, and concentrations of DEP and DAP was determined. Subsequently, the isotherm, kinetic, and thermodynamic equations of adsorption were investigated based on optimum conditions.
According to the results, the highest removal efficiency rates for DEP and DAP were 96% and 99%, respectively, which were observed in pH=4, contact time of 180 min, 0.3 g/L of adsorbent dose, and 15 mg/L initial concentration of PAEs. Isotherm and kinetic studies also showed that adsorption process of PAEs followed the Langmuir and Freundlich models (R2>0.96) and pseudo-second order model kinetics (R2>0.99), respectively. In evaluating the thermodynamic reaction, the positive values of ΔH˚ and negative values of ΔS˚ illustrated that the reactions were endothermic and spontaneous, respectively.
Chitosan-graphene oxide composite is capable of removing DEP and DAP effectively and can be used as an efficient adsorbent for the related industrial wastewater treatment.