Sorption of 17beta-estradiol onto selected soil minerals.

Sorption of the endocrine-disrupting chemical 17beta-estradiol (E(2)) from aqueous solutions to goethite, an iron oxide, and the clay minerals kaolinite, illite, and montmorillonite (K and Ca forms) was measured at 25 degrees C. The clay minerals sorbed more E(2) than the oxide, with sorption capacity increasing in the order goethite <or= illite < kaolinite << montmorillonite. Uptake by goethite was rapid, with the maximum sorption (ca. 10% E(2) sorbed from a 1 ppm solution) reached within seconds. Initial sorption to the clay minerals was similar, but then it continued more slowly until about 10-15% of the total estradiol had been taken up after a period of 3 days by kaolinite and illite, and about 65% by montmorillonite. There was little pH dependence on the sorption, except for the goethite case where a sorption maximum occurred at pH 7-7.5. Most of the sorbed E(2) was desorbed from goethite, kaolinite, and illite into water or methanol easily and quickly (within seconds), but none was desorbed into either solvent from montmorillonite. These results suggest that E(2) is adsorbed at the surfaces of goethite, kaolinite and illite, but taken up into the interlayer spaces of montmorillonite. The c-axis spacing of montmorillonite decreased after sorbing E(2), indicating expulsion of water upon uptake of E(2) into the interlayer regions.