Estrogenic compounds removal by fullerene-containing membranes

Abstract

Estrogenic pollutants present in surface water and treated wastewater could exert significant effects on biota exposed in the receiving environment. Amongst them, the impacts of steroid estrogens such as estrone, estradiol and ethinylestradiol are prominent as they have the highest endocrine disrupting potency than other synthetic endocrine disrupting chemicals (EDCs), despite of low concentration. Since these steroid estrogens are hydrophobic compounds of low volatility, adsorption plays an important role in their removal. Therefore, hydrophobic polymer membranes and strong adsorbent could be effective in removal of estrogens from aqueous phase. In this study, new polymer membranes based on hydrophobic polymer – poly (2, 6-dimethyl-1, 4-phenylene oxide) (PPO) modified by fullerene C 60 were studied on removal and adsorptive behaviors of estrogenic compounds. The removal, adsorption rate and capacity of estrone by membranes with different fullerene compositions (PPO; 2%wtC 60-PPO; 10%wtC 60-PPO) through dead-end filtration and static adsorption experiments were investigated. SEM images demonstrated increase of pore size and porosity in top layer of fullerene-containing membranes compared to pure PPO membrane. Moreover, cross-section of PPO membrane had sponge–like structure while membranes containing C 60 (2% and 10%) had finger-like structure. As a result, the permeate flux increased with the increased percentage of fullerene in membrane. However the removal of estrone by PPO membrane with 10% fullerene did not decrease obviously compared with the one without fullerene although the flux increased by about eight times. It was observed that all of the three kinds of membrane showed very good removal of estrone (more than 96%). Results for long-term filtration showed that the 10%wtC 60-PPO membrane was able to maintain its excellent removal performance of at least 95%. The results from the static adsorption tests showed that after 12 h, all membranes reached ultimate adsorption of estrone with a similar value of adsorption capacity, although PPO membrane with 2% C 60 had the fastest rate of adsorption, followed by PPO membrane with 10% C 60 and PPO membrane before reaching the plateau value. This can probably be explained by their pore size on membrane surface and internal structure.