Rejection of pharmaceutically active compounds by forward osmosis: Role of solution pH and membrane orientation

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. a b s t r a c tThe effects of feed solution pH and membrane orientation on water flux and the rejection of carbamazepine and sulfamethoxazole were investigated using a bench scale forward osmosis (FO) system. Water flux was pH-dependent in both membrane orientations. In addition, water flux increased while the specific reverse salt flux and hydrogen ion flux decreased with increasing feed solution pH. Water flux was lower in the normal FO mode compared to that in the pressure retarded osmosis (PRO) mode because osmotic pressure differential was reduced due to the internal concentration polarisation (ICP) phenomenon. The rejection of neutral carbamazepine was generally pH independent in both membrane orientations. The rejection of carbamazepine in the PRO mode was lower than that in the FO mode due to the higher concentration gradient caused by concentrative ICP in porous supporting layer. Steric hindrance was probably the main separation mechanism for the neutral carbamazepine in the FO process. On the other hand, the rejection of sulfamethoxazole was significantly affected by the feed solution pH in both membrane orientations. Variation in the rejection sulfamethoxazole could be attributed to the electrostatic repulsion between the negatively charged FO membrane surface and varying effective charge of the sulfamethoxazole molecule. Crown

Removal of dissolved organics from produced water by forward osmosis

“…6. The RSF obtained under the FO mode was consistently less than those obtained under the PRO mode which is consistent with the results previously obtained by Xie et al [34]. Fig.…”

Minimizing structural parameter of thin film composite forward osmosis membranes using polysulfone/halloysite nanotubes as membrane substrates

“…For example, the TFN 0.5 membrane tested with 2 M NaCl draw solution exhibited around 43.25 L/m 2 h water flux and 27.52 g/m 2 h solute flux during evaluation at PRO configuration, which was much higher compared to 27.71 L/m 2 h and 14.62 g/m 2 h obtained in FO orientation. Decrease in osmotic pressure differential due to ICP phenomenon can be considered as the main reason for the lower water flux in FO orientation [55]. Fig.…”

Biodegradation of cellulose triacetate and polyamide forward osmosis membranes in an activated sludge bioreactor: Observations and implications

“…By contrast, no clear correlation between the rejection and molecular weight was observed for non-ionic hydrophilic TrOCs ( Figure 6). This observation was possibly due to the different molecular shapes and dipole moments of these hydrophilic compounds [53].…”