Investigation of chlorpyriphos removal using chitosan graphene oxide composite form aquatic solution: study of kinetics, isotherms and thermodynamics

Chlorpyriphos is one of the most important widely used pesticides in agriculture, which is discharged into the water resources and is associated with various adverse effects on human health and the environment. The purpose of this study was to evaluate chlorpyriphos removal by chitosan graphene oxide composite form aquatic solution. The characteristics of adsorptive material was determined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). First, the pHzpc was determined.Then, the effect of different parameters such as the amount of adsorbent, contact time, pH, initial concentration of chlorpyriphos and temperature were studied through batch method in order to obtain optimal conditions for the adsorption process. Then optimal pH under constant conditions was determined. Isotherm, kinetic and thermodynamic equations  of adsorption were investigated and concentration of chlorpyriphos was determined. The highest removal efficiency was 93% which was observed at pH=5, 60 minutes contact time and 0.8 g/L of adsorbent concentration and initial concentration of 1 mg/l for chlorpyriphos. The results showed that adsorption process followed pseudo-second order kinetics and equations data followed Langmuir isotherms model. Evaluation of thermodynamic parameters showed that the process of chlorpyrifos removal was endothermic and spontaneous. According to the results of this study chitosan graphene oxide composite can be a suitable adsorptive material for removal of chlorpyrifos from aquatic solutions.