Evaluation of removal and adsorption of different herbicides on commercial organophilic clay

Abstract

In this work, commercial organophilic clay was used in adsorption studies for the liquid phase of Atrazine, Ametryn, Diuron, and 2-(2,4-dichlorophenoxy)acetic acid (2,4-D) in a batch type system. The affinity study showed that clay is a promising material to remove contamination from agricultural activities. The adsorbent material showed a great removal capacity, especially for Diuron because that reached a higher value than 98%. The adsorption rate was evaluated by pseudo-first-order, pseudo-second order, Elovich, intraparticle diffusion, and external film mass transfer (EFMT) models. In these models, the pseudo-second order and EFMT models represented properly experimental data for Atrazine, Ametryn, and Diuron, whereas the Elovich model was the most predictive for 2,4-D. The maximum adsorption capacities in the monolayer for each contaminant were obtained by the equilibrium isotherms, and the values were 2.275, 25.253, 47.149, and 6.450 mg g−1 for Atrazine, Ametryn, Diuron, and 2,4-D, respectively. In addition, the Langmuir model was the best adjustment to equilibrium data for Atrazine, Ametryn, and Diuron adsorption. For 2,4-D, the model that best represented the experimental data was Freundlich. Finally, characterization techniques indicated that herbicide adsorption contributed to textural, chemical, morphological, and thermal modifications in the clay mineral.