Effect of organic matter and allophane on adsorption of polyethylene glycols onto some soils

Abstract

Polyethylene glycols were adsorbed onto some soils that had been previously leached with hot water to remove water-soluble organic substances and then either oven-dried or kept moist. The amount of glycol adsorbed onto the dried soils decreased as organic matter content increased. The amount adsorbed onto the moist soils showed a different trend. The parameters for an adsorption equilibrium model based on statistical thermodynamic considerations, namely the equilibrium constant, Ka, and the total volume of the adsorbed phase, w1(0), were estimated in order to interpret this adsorption behaviour. The change in Ka (indicating the change in nature of the soil surface due to drying) significantly depended on allophane content, while the value of w1(0) (representing the amount of surface exposed) was more affected by organic matter content. In addition, the relationship of w1(0) to the liquid limit confirms the validity of w1(0) in modelling soil-water systems.