Nghiem Long D, Schäfer Andrea I, Elimelech Menachem
Department of Chemical Engineering, Environmental Engineering Program, Yale University, New Haven, Connecticut 06520-8286, USA.
Environ Sci Technol. 2004 Mar 15;38(6):1888-96. doi: 10.1021/es034952r.
The removal mechanisms of four natural steroid hormones-estradiol, estrone, testosterone, and progesterone-by nanofiltration (NF) membranes were investigated. Two nanofiltration membranes with quite different permeabilities and salt retention characteristics were utilized. To better understand hormone removal mechanisms, the membrane average pore size was determined from retention data of inert organic solutes of various molecular weights and a pore transport model that incorporates steric (size) exclusion and hindered convection and diffusion. Results indicate that, at the early stages of filtration, adsorption (or partitioning) of hormones to the membrane polymer is the dominant removal mechanism. Because the adsorptive capacity of the membrane is limited, the final retention stabilizes when the adsorption of hormones into the membrane polymer has reached equilibrium. At this later filtration stage, the overall hormone retention is lower than that expected based solely on the size exclusion mechanism. This behavior is attributed to partitioning and subsequent diffusion of hormone molecules in the membrane polymeric phase, which ultimately results in a lower retention. Hormone diffusion in the membrane polymeric matrix most likely depends on the size of the hormone molecule, hydrogen bonding of hormones to membrane functional groups, and hydrophobic interactions of the hormone with the membrane polymeric matrix.
研究了纳滤（NF）膜对四种天然甾体激素——雌二醇、雌酮、睾酮和孕酮的去除机制。使用了两种具有截然不同的渗透率和盐分截留特性的纳滤膜。为了更好地理解激素去除机制，根据各种分子量的惰性有机溶质的截留数据以及结合了空间（尺寸）排斥、受阻对流和扩散的孔传输模型，确定了膜的平均孔径。结果表明，在过滤初期，激素在膜聚合物上的吸附（或分配）是主要的去除机制。由于膜的吸附容量有限，当激素在膜聚合物中的吸附达到平衡时，最终截留率会稳定下来。在这个过滤后期阶段，总体激素截留率低于仅基于尺寸排斥机制所预期的截留率。这种行为归因于激素分子在膜聚合物相中的分配及随后的扩散，这最终导致截留率降低。激素在膜聚合物基质中的扩散很可能取决于激素分子的大小、激素与膜官能团的氢键作用以及激素与膜聚合物基质的疏水相互作用。
