Polyethylene microplastics as adsorbent of diazinon in aqueous environments: optimization, and modeling, isotherm, kinetics, and thermodynamic studies

Abstract MPs have raised significant public concern due to their role as carriers of organic contaminants in aqueous solutions. DZN is a non-systemic organophosphorus pesticide that poses risks to human and environmental health. This study aimed to investigate the adsorption of DZN onto PE MPs by examining factors such as PE dose, reaction time, pesticide concentration, and pH through experimental runs based on the Box‒Behnken model. According to the Langmuir model, the maximum adsorption capacity of PE for DZN was 0.35 mg/g. The results indicated that the highest adsorption rate of DZN (92%) was observed in distilled water, while the lowest adsorption rate (57%) was observed in municipal wastewater. The ΔH° and ΔS° values were obtained as − 0.16 kJ/mol and 54.41 J/(mol K), respectively. Therefore, regarding negative ΔG° values, it can be concluded that the adsorption of DZN onto PE MPs is an exothermic, highly disordered, and spontaneous process. The findings indicate a reduction in the adsorption rate of DZN as the concentrations of interfering compounds increase. These findings offer understanding of the interaction between MPs and organic contaminants, emphasizing the need for further studies and approaches to reduce their harmful impact on human health and the environment.