Kinetics and equilibrium of the adsorption process of dimethoate with corn stalk

Abstract

The corn stalk (CS) is a waste material generated from the corn crop, with important cellulose and hemicellulose content within its structure. This study has been focused on evaluating the possibility of using CS as an adsorbent for the removal of organophosphate dimethoate pesticides in aqueous solutions. The adsorption study was conducted to determine the effect of adsorbent dose, initial pH, and contact time to dimethoate solution at the initial concentration of 50 mg.L−1. The process conditions were established at initial pH of 11, adsorbent dose of 1.5 g/100 ml, and equilibrium time of 140 minutes. It was verified that dimethoate removal is favored in an alkaline medium. The process kinetic was adjusted to the pseudo-n order model and pseudo-second order model to a lower extent, with several limiting stages, as it was demonstrated through the Weber-Morris model. The equilibrium isotherms were analyzed by employing, the Langmuir, Freundlich, Toth, Sips, and Redlich-Peterson models, where the Sips, Redlich-Peterson, and Toth models proved to be the best adjustment for experimental data, representing better the dimethoate adsorption process in CS.