Selected factors affecting the elimination of hormones from water using nanofiltration

The study shows comparative results of the nanofiltration of a mixture of nine sex hormones (estrogens and progestogens) using two membranes which differed in the polymer they were made of cut-off and desalting degree determined by the removal of sodium chloride (NaCl) and magnesium sulphate (MgSO₄). A higher retention coefficient of 74.1-100% was obtained for an integrally asymmetric membrane prepared from cellulose acetate (NF-SF10) of a relatively high desalting degree (NaCl and MgSO₄) and a volume permeate flux of NaCl solution (J_Cl) lower than the one determined for MgSO₄ (J_Mg). Nanofiltration of waters displaying changeable concentrations of organic matter revealed only a slight impact of the parameter on the retention coefficient of sex hormones; however, the results were higher than the ones found for the filtration of deionised water which contained the compounds tested. Filtration of deionised water with the mixture of sex hormones was described by a correlation between the retention coefficient and their adsorption on and in the structure of the membrane. Lower adsorption of the hormones on the membrane by approx. 21% (NF-SF10) and 30% (NF-DS5DK) on average under filtration conditions tested in the study was observed when calcium ions Ca²⁺ were added to water, reducing their transport properties. However, the retention coefficient for the tested compounds did not change.