Adsorption-desorption characteristics of atrazine on activated charcoal and kaolin composite matrices and the In vitro performance of their CRFs

ABSTRACT The study reported in this paper examined the adsorption-desorption behaviour of atrazine on activated charcoal (Ac)/kaolin (K) composite matrices as a means of determining their suitability in preparing controlled release formulations (CRFs) of the herbicide atrazine. This is to devise a technique for protecting the environment from pesticide contamination. Adsorption experiments were carried out in buffered solutions, followed by desorption in soil to determine rates of atrazine release over time in the different media. The adsorption process was found to be independent of pH within the pH range of 5-8 studied. The adsorption data at pH 5, 6, and 8 (KH2PO4) and 24 °C for the different surfaces were fitted to the Langmuir and the Freundlich Isotherms. The regression coefficient, R2 was used to determine the isotherm model that better fitted atrazine sorption on the composite matrices. The obtained R² values in the composite surfaces showed that the Langmuir isotherms were a marginally better fit than the Freundlich isotherms. The calculated favourable adsorption constant, RL, all being less than unity in the surfaces, indicates that the composite matrices have a high affinity for atrazine.