Preliminary Study on the Removal of Steroidal Estrogens Using TiO2-Doped PVDF Ultrafiltration Membranes
Steroidal estrogens are a representative type of endocrine-disrupting chemical contaminant that has been detected in surface water. In this paper, modified polyvinylidene fluoride (PVDF) membranes were prepared by adding different amounts of polyvinyl pyrrolidone (PVP) and nano-TiO 2 particles. PVDF-PVP membrane adsorption, UV photolysis and PVDF-PVP-TiO 2 membrane photocatalysis performance were investigated by considering the rejection of estrone (E1) and 17β-estradiol (E2) in the cross-flow
... iltration experiments. The mechanism of photocatalytic degradation on TiO 2 -doped PVDF membranes was also evaluated. The results from the study indicated that adding PVP and nano-TiO 2 appropriately in PVDF membranes could be an effective method for better E1and E2 rejection due to adsorption and photocatalytic degradation. surface water of the Pearl River and Gongjiang River in southern China ranged from limit of detection (LOD) 8.2 ng/L and LOD 1.5 ng/L, respectively  . Lu monitored the Yellow River basin in Xi'an and found average E1 and E2 concentrations of 1980 and 1330 ng/L, respectively, in the dry season; 540 and 230 ng/L, respectively, in the normal season; and 140 and 90 ng/L, respectively, in the wet season  . Thus, there are steroid hormone pollution problems in different river basins and water systems throughout the world. The presence of steroidal estrogen compounds in water environments leads to the necessity of developing effective treatment techniques, either as a supplement for drinking water treatment systems to prevent the potential risk to human health or for treatment processes for municipal wastewater sludge and animal manure. Steroidal estrogen removal methods include the membrane process, advanced oxidation, adsorption, biological methods, etc. . Snyder used different membranes to remove 36 types of pharmaceutical and personal care products (PPCPs) and EDCs in water; the results showed that microfiltration and ultrafiltration had a certain effect on the removal rate of steroidal estrogens, but the removal rate was not high enough  . Ohko investigated E2 degradation via photocatalysis using TiO 2 as a slurry system, but it had disadvantages compared to the immobilized systems as the TiO 2 must be removed afterwards  . Not surprisingly, each removal option has advantages and limitations, and it is essential to adapt these options to the removal application. The technological development of ultrafiltration membrane modification provides a new approach to fixed TiO 2 photocatalysts [12, 13] . We can manufacture a nano-TiO 2 immobilized in an ultrafiltration membrane and use this type of membrane to remove steroidal estrogens under UV photocatalysis. This approach may couple with membrane filtration and photocatalytic degradation during the reaction and probably enhance the contaminant removal efficiency. In the meantime, the problem of recycling and reusing nanomaterials can also be solved to reduce the risk of nano-material environmental pollution. This study developed a type of polyvinylidene fluoride (PVDF)-polyvinylpyrrolidone (PVP)-TiO 2 nano-inorganic modified ultrafiltration membrane via a blending method to fix nanomaterials in the modifid membrane. This new modified ultrafiltration membrane with adsorption and catalytic performance can not only improve the effect of the ultrafiltration membrane for the removal of steroidal estrogen but it can also provide a new technology to solve the problems of recycling nanomaterials. We studied the effect of the PVDF-PVP membrane, UV photolysis and the PVDF-PVP-TiO 2 membrane on the removal of E1 and E2 from water and described the PVDF-PVP-TiO 2 membrane reaction mechanism via a reaction kinetics model.