Utilização de montmorilonita organofilizada para aplicações de liberação controlada de herbicida

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 toxic and have great carcinogenic potential. Thus, the aim of this work was to evaluate the 2,4-D sorption behavior by an organically modified montmorillonite nanoclay using kinetic and thermodynamic approaches. Adsorption isotherm and kinetic studies, that were conducted varying the temperature and pH conditions indicated a high 2,4-D adsorption capacity of the nanoclay from aqueous medium. The best fitted models were the Freundlich and the pseudo-first-order for the isotherm and kinetic studies, respectively. The determination of the thermodynamic and kinetic parameters of adsorption indicated that the adsorption mechanism probably involved physisorption. The characterization revealed that the 2,4-D adsorption caused a partial exfoliation of the montmorillonite structure, probably due to the high concentration utilized. Through the release studies, it was observed that the 2,4-D release from the nanoclay occurs in two steps, a high initial burst release followed by a slow one. The results demonstrated by this study indicates the feasibility of the proposed system, enabling the 2,4-D use in controlled release systems or even water treatment applications.