Retention of selected steroids on a silt-loam soil

Abstract

This study used batch-equilibrium techniques to evaluate the soil sorption and desorption of target steroids, representative of the estrogen, androgen, progestogen and corticosteroid families. The sorption kinetics exhibited an immediate rapid sorption followed by a slow process with a duration dependent on soil particle size. Adsorption and desorption isotherms could be described by the Freundlich equation, in a non-linear form (1/n < 1). High organic carbon-water partitioning coefficient (K_OC) values indicate that a large mass fraction of the hormones will be associated with the sorbed phase. As a result of the poor linear correlation between log K_OC and log K_OW (octanol-water partition coefficient), it could be assumed that both hydrophobic and hydrogen bonding interactions contribute to the sorption mechanisms of the selected steroids. A hysteresis phenomenon was observed, varying with particle size, indicating strong irreversible interactions between some steroids and soil.

Keywords:

• Steroids
• adsorption
• desorption
• soil