Design and synthesis of a new recyclable nanohydrogel based on chitosan for Deltamethrin removal from aqueous solutions: Optimization and modeling by RSM-ANN.

Abstract

In this study, a new magnetic biocompatible hydrogel was synthesized as an adsorbent for Deltamethrin pesticide removal. The optimal conditions and adsorption process of Deltamethrin by chitosan/polyacrylic acid/Fe₃O₄ nanocomposite hydrogel was studied by Response Surface Methodology by Central Composite Design (RSM-CCD) and Artificial Neural Network (ANN). This adsorbents were synthesized, and then characterized and investigated using FT-IR, XRD, FE-SEM, EDX, Map, VSM, and TGA methods. The results of these analyses showed that the nanocomposite hydrogel was well synthesized and has the ability to adsorb the Deltamethrin pesticide. The results obtained through analysis using response surface methodology showed that the maximum amount of adsorption was 99.79 % at 26 °C, while pH, initial concentration, contact time, and adsorbent dose were 7, 22 ppm, 90 min, and 1.3 g/L respectively. Comparison between results obtained from CCD modeling and artificial neural network proved that both methods had high ability to predict the adsorption process but the CCD method had higher coefficient of determination and lower error. The equilibrium and kinetic study of the process showed that the Toth isotherm model, pseudo-second-order is all suitable for expressing the adsorption process. In addition, the adsorption mechanism followed double-exponential model that combines external and internal diffusions. Results of Thermodynamic study suggested that the Deltamethrin adsorption on CS/PAA/Fe₃O₄ was a spontaneous and exothermic process. The results of the equilibrium process study revealed that the adsorption process was physical and desirable, therefore, the adsorption-desorption process was performed which showed that the composite was reusable up to 10 cycles.