Sorption of 17β-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 degreesC. The clay minerals sorbed more E-2 than the oxide, with sorption capacity increasing in the order goethite less than or equal to illite < kaolinite much less than montmorillonite. Uptake by goethite was rapid, with the maximum sorption (ca. 10% E-2 sorbed from a I 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. (C) 2003 Published by Elsevier Inc.