Adsorption and Movement of Endosulfan in Soils: A Verification of the Co-Solvent Theory and a Comparison of Batch Equilibrium and Soil Thin Layer Chromatography Results

Abstract

Batch equilibrium and soil thin-layer chromatography (soil TLC) techniques were used to investigate the influence of different volume fractions (fs = 0.25, 0.50, 0.75 and 1.0) of organic co-solvents (acetone and methanol) on the adsorption and movement of endosulfan in three different types of Indian soils (silt loam, loam and sandy loam).The measured equilibrium adsorption isotherms for all three soils studied were L-shaped for both co-solvent/water mixtures at all fs values. All isotherms were in close agreement with the Freundlich equation. Higher adsorption of endosulfan was observed on silt loam soil followed by loam and sandy loam soils at all fs values for both co-solvent systems, as was anticipated from the values of the Freundlich constants, K, and the partition coefficients, KD. The order of the K and KD values also confirmed that endosulfan adsorption was higher in methanol/water mixtures than in acetone/water mixtures and decreased with increasing fs values.The Rf values obtained from soil TLC...