Removal of Natural Hormones by Nanofiltration Membranes:  Measurement, Modeling, and Mechanisms

• Published in: Environmental science & technology Vol. 38; no. 6; pp. 1888 - 1896
• Main Authors: Nghiem, Long D, Schäfer, Andrea I, Elimelech, Menachem
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.03.2004
• Subjects: Applied sciences; Diffusion; Exact sciences and technology; Filtration; Gonadal Hormones - isolation & purification; Hormones; Hydrogen Bonding; Measurement; Membranes; Membranes, Artificial; Models, Theoretical; Nanoparticles; Other wastewaters; Pollution; Retention; Wastewaters; Water Pollutants - isolation & purification; Water treatment and pollution; Polymeric membrane; Porous membrane; Hydrophobic compound; Retention; Estradiol; Modeling; Membrane separation; Domestic waste water; Nanofiltration; Testosterone; Pore size; Adsorption; Size effect; Estrone; Physicochemical purification; Progesterone; Waste water purification; Sex steroid hormone; Comparative study
• ISSN: 0013-936X; 1520-5851
• 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.