2,4-Dichlorophenoxyacetic acid adsorption on montmorillonite organoclay for controlled release applications

Abstract

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most used herbicides for weed control. However, the use of large concentrations of 2,4-D is dangerous and have great carcinogenic potential. Thus, this work evaluated the 2,4-D sorption behavior by an organically modifed montmorillonite nanoclay using kinetic and thermodynamic approaches. Adsorption isotherms and kinetic studies, conducted under controlled temperature and pH conditions, indicated a high capacity of the nanoclay to remove 2,4-D from aqueous medium, being that the adsorption mechanism probably involved physisorption and chemisorption. Besides, thermodynamic parameters obtained showed that the adsorption was enthalpically driven for the physisorption step, with ΔH◦=−9.849 kJ mol−1. The analyses showed that 2,4-D adsorption caused a partial exfoliation of the montmorillonite structure, probably due to the high herbicide concentration utilized. Release studies of 2,4-D from the nanoclay showed that the desorption process occurred in two steps, a burst release of the 2,4-D molecules followed by a slow release. The results demonstrated by this study indicates the feasibility of the proposed system for controlled release or even water treatment applications.