Adsorption, desorption, and steady-state removal of estrogenic hormone 17beta-estradiol by nanofiltration and ultrafiltration membranes

Abstract

Nanofiltration (NF) and ultrafiltration (UF) membranes were tested in cross-flow configuration for removal of the natural estrogenic hormone 17Beta-estradiol (E2). The NF membranes, FilmTec NF270 and NF90 and Saehan NE-70 and NE-90, showed significant adsorption of E2 during the initial stage of filtration followed by relatively high steady-state rejection. The rejection ranged from 70% for the NF270 to greater than 97% for the NF90 and NE-90. UF membranes, such as Saehan UE2010 and Sterlitech GH, showed relatively low rejection (0-20 %) at steady-state, but did show significant adsorption during the initial time period. In both NF and UF, adsorbed hormone was released into the permeate stream when the feed solution was replaced with pure water. The rate of desorption was approximately the same as that of adsorption. Similar results were observed at both high concentrations (100 microgram/L), and at lower, environmentally-relevant concentrations (100 ng/L). Fouling of membranes by natural organic matter improved rejection, as did operation at higher permeate flux and higher pH. These results indicate that the high initial rejection of hormones due to adsorption on membranes may not accurately reflect true rejection of hormones by these membranes at steady state.