Rejection of pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) by low pressure reverse osmosis membranes

Abstract

This paper aims to elucidate retention characteristics of some pharmaceuticals and personal care products (PPCPs), and endocrine disrupting chemicals (EDCs), by two polyamide low pressure reverse osmosis (LPRO) membranes. Feed solution pH did not have an influence on rejections of undissociated solutes, which was most likely governed by adsorption, size exclusion and diffusion simultaneously. Size exclusion was presumably dominant, especially with tight membranes (UTC-70U). Rejections of the solutes with low dipole moment (<1.0 debye) decreased with increasing octanol-water partition coefficient (K(ow)). The solutes with large K(ow) values were most likely adsorbed on membrane and subsequently passed through it resulting in larger diffusion coefficient (D(p)). The rejections decreased with increasing D(p) values irrespective of their dipole moments. Rejections of solutes with comparatively larger dipole moments might be dominated by diffusion and/or convection rather than their hydrophobicity. However, rejections of solutes with hydroxyl and carboxyl functional groups by UTC-60 increased with solution pH. More than 80% rejections were obtained for degree of dissociation (alpha)>0.5. Electrostatic repulsion played a key role for rejection of dissociated solutes, especially by loose LPRO membranes. Therefore, assessing the dissociation degree at desired pH values can be a key step to obtain an insight of rejection mechanisms by polyamide membranes.

Performance of nanofiltration membrane in rejecting trace organic compounds: Experiment and model prediction

“…The performance of NF in removing TOrCs has been extensively investigated in laboratory and onsite studies using both simulated and natural water [7][8][9][10][11][12][13][14][15][16]. Many brands of NF membranes have been tested for a large number of TOrCs.…”

“…An apparent time-dependency of the rejection ratio by NF was also observed for some uncharged TOrCs [17,18], which strongly suggests membrane adsorption affecting the rejection performance. Less polar (indicated by low dipole moment) and more hydrophobic (indicated by high octanol-water partition coefficient) compounds can usually be preferentially adsorbed [12]. Adsorption usually impairs the rejection performance after the NF membrane adsorption capacity is exhausted.…”

Distribution and Diffusion Behaviors of Perfluorinated Compounds with Low Pressure Reverse Osmosis Membranes

“…It is to be noted that the apparent diffusion coefficient (D p ) values for the PFCs in this investigation are about three orders of magnitude larger than those for pharmaceuticals and endocrine disruptors with UTC-70 membrane (Ozaki et al, 2008). Correlations among these parameters for the compounds in this investigation are illustrated in Fig.…”

“…Although RO membrane filtration is the most efficient method in separating all kinds of solutes in water, it has been a costly method until now owing to a very high pressure involved with it. Low pressure reverse osmosis (LPRO) membranes have emerged as the promising alternative to RO membranes during the past decade (Koyuncu et al, 2001;Ozaki et al, 2002Ozaki et al, , 2005Ozaki et al, and 2008. The LPRO membranes can be used under very low pressures (< 1.0 MPa) while their pollutant removal efficiencies are comparable to those of RO membranes.…”

“…Molecular sieving, electrostatic repulsion, adsorption and diffusion have been pointed out as important solute retention mechanisms for RO membranes (Nghiem et al, 2002;Kimura et al, 2003b), NF membranes (Bruggen et al, 2002;Kimura et al, 2003a;Braeken et al, 2006) and LPRO membranes (Ozaki et al, 2002(Ozaki et al, , 2005(Ozaki et al, and 2008. Furthermore, only inorganic anions, pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) have been tested as solutes in almost all the investigations carried out to date.…”