Adsorption of ³H-labeled 17-β estradiol on powdered activated carbon

Three source waters, two model waters (Ultrapure (natural organic matter (NOM)-free)) water and Suwannee River NOM isolate by reverse osmosis (SR-NOM)) and a natural water (Colorado River water (CRW)), were tested. Those waters were selected to represent a relatively hydrophobic NOM (SR-NOM) and a relatively hydrophilic NOM (CRW) based on their specific ultraviolet absorbance (SUVA = UVA₂₅₄/DOC) values. The adsorption of an estrogenic compound, 17β-estradiol (E2), on powdered activated carbons (PACs) was investigated. Kinetic and PAC dose-response experiments were performed with PACs at an initial concentration of 0.1 nM (27 ng L^-1). Additional experiments were also performed at various initial concentrations ranging from 0.025 nM (6.8 ng L^-1) to 5.0 nM (1360 ng L^-1) to determine the effects of initial concentration on E2 adsorption. In separate experiments, 17β-estradiol was introduced to PAC as a pure component, in binary mixtures with other salts (NaCl, Na₂SO₄, and CaCl₂), and under varying pH conditions (4.0, 7.5, and 11.0) to determine the effects of pH and background ions on E2 adsorption. Samples were measured by liquid scintillation counting using ³H radio-labeled E2. Without preconcentration, a method detection limit using the liquid scintillation counter was 0.005 nM (1.36 ng L^-1), respectively. Increasing contact time and PAC dose improved compound removal. Activated carbon is a viable technology for water treatment plants.