Isotherms for Atrazine Desorption from Two Surface Soils

Abstract

The Freundlich isotherm model was used to describe desorption behavior of atrazine from two surface soils. Soils were contacted with five different initial aqueous atrazine concentrations—0.25, 1.0, 2.5, 10, and 25 μM—for a period of 7 days at a solid/liquid ratio of 0.175 (w/w). Desorption data was obtained by allowing the adsorbed atrazine to desorb for 14 days at solid/liquid ratios of 0.175, 0.110, 0.075, 0.047, and 0.027. Data were fitted to the Freundlich model and interpreted in terms of the linearity and capacity parameters for adsorption (n and K_F) and desorption (n^d and K_F^d). Atrazine adsorption to both soils was described as near-linear. Desorption isotherms, however, were more nonlinear than the adsorption isotherms. Desorption linearity (n^d) and capacity (K_F^d) were related to the initial aqueous concentration (C₀) of atrazine during adsorption. Both linearity and capacity were lower at smaller values of C₀ and increased logarithmically with C₀.