Statistical Optimization of Removal of Diazinon from Aqueous System Using Magnetic Bentonite Nanocomposites by Response Surface Methodology

Diazinon is one of the most generally used pesticides in agriculture. This nonselective organophosphorus insecticide acts as cholinesterase inhibitors in insects and mammals, and bring about a non-reversible phosphorylation of esterases in the organisms’ central nervous system [1]. As a result of its widespread application, the residue of this insecticide in environment such as water may be hazardous to human and animal health. Therefore, there is a need to develop a suitable and efficient water treatment method for removal of Diazinon.Bentonite is a natural clay containing montmorillonite as a major constituent. This material is one of the promising adsorbents for removing diazinon from water samples as a result of their specific surface area, low-cost, availability, high chemical and mechanical stability [2]. Recently, the performance of bentonite has been optimized using different methods. The coating of bentonite with nano-sized material is one of the most widely used methods for its novel application because they possess high surface area and therefore excellent adsorption ability [3].In this study, Magnetic Bentonite Nanocomposite was synthesized by combining bentonite with Fe3O4 through co-precipitation. Scanning electron microscopy with energy-dispersive X-ray spectrometry and infrared spectroscopy techniques were used to characterize the composite. The adsorption behaviors of the composite in diazinon removal were evaluated by batch equilibrium experiments using response surface methodology and employing a Plackett–Burman (P-B) experimental design. The influence of different parameters such as pH, contact time, agitation rate and sorbent dosage on the removal of diazinon was examined. The significance of independent variables and their interactions were tested by analysis of variance (ANOVA). The optimum contact time, pH, agitation speed and adsorbent dose were found. Under these conditions, the maximum sorption capacity for diazinon was found to be 90.53%. Kinetic and isothermal data fitted well the pseudo-second- order and the Freundlich models, respectively. The method was successfully applied for the removal of diazinon from industrial wastewater and groundwater samples. The results showed that the designed composite is a promising absorbent for the treatment of diazinon-contaminated waters.