Adsorption of Carbofuran on Soils from Water/Methanol Mixture

Adsorption of carbofuran on silt loam and sandy loam soils from water/methanol mixture at f_s values 0.08 to 0.48 has been evaluated by batch shake testing at 25° and 50°C. These data were used to evaluate the cosolvent theory for describing adsoprtion of carbofuran for methanol-water mixtures. The measured adsoprtion isotherms were non-linear, Freundlich type and yielded ‘S’ shaped curves for soils at both temperatures. The higher adsorption of carbofuran on silt loam soil than sandy loam soil was anticipated with K and K_d values. Adsorptive capacity for organic matter (K_om) and clay content (K_c) was also evaluated and found that carbofuran adsorption was better correlated with clay content than organic matter content of the soils. On the basis of adsorption isotherms, various thermodynamic parameters such as thermodynamic equilibrium constant (K_o), standard free energies (G^o), standard enthalpies (H^o) and standard entropies (S^o) changes have been calculated to predict the nature of isotherms.