Removal of methomyl from aqueous solutions using reactivated carbon microspheres

Abstract

The removal of methomyl, one of the most frequent pesticides, from aqueous solutions has been studied by adsorption using the reactivated carbon microspheres separated from worn filtering protective suits. This study is significant in two aspects - the first is the in-situ adsorption of pesticides from aqueous solutions, and the second is recycling protective equipment as an effective material for water decontamination. Carbamate pesticide, methomyl is aimed to control foliage and soil-borne insect pests on various agricultural product. Also, due its toxicity, it has a great potential for usage in terroristic acts and tactical purposes during military operations. The reactivated carbon (RAC) microspheres were characterized by Scanning Electron Microscopes (SEM). The changes in relative concentration of methomyl during the adsorption onto the surface of the RAC microspheres was determinated using the UV-Visible spectrophotometer. The adsorption process is described by Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherm models. The adsorption kinetics follows the second-order kinetics model, and the thermodynamics study confirms that the adsorption is exothermic and spontaneous. At optimal conditions, the adsorption capacity was qe = 8.631 mol g-1 × 10-8 and the adsorption rate was k = 0.749 g mmol-1 min-1. The Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherm models were used to describe the adsorption process. The thermodynamic study of adsorption proves the process is spontaneous with exothermic nature.