Competitive and complementary adsorption of bisphenol A and 17alpha-ethinyl estradiol on carbon nanomaterials

Competitive adsorption between organic chemicals is an important process affecting their environmental behavior and risk. Overlapping of adsorption sites between solutes was often emphasized in the literature. However, chemicals with different properties may complementarily occupy different sorption sites. The objective of this study was to test this hypothesis by collecting detailed information on competitive and accumulative adsorption of different chemicals on carbon nanomaterials (CNMs). Bisphenol A (BPA) and 17alpha-ethinyl estradiol (EE2) are different with regard to their hydrophobicity and molecular structures, and they were selected as model chemicals. The cumulative adsorption of both BPA and EE2 in bisolute adsorption experiments resulted in much higher total adsorption than in single-solute adsorption experiments. A new competitive-complementary adsorption concept was proposed. This information indicates that the modeling concept of competitive adsorption should be improved to better understand the fate and risk of both CNMs and organic chemicals.