Adsorption of hydrophilic and hydrophobic pharmaceuticals on RO/NF membranes: Identification of interactions using FTIR

This article examines the adsorption of pharmaceuticals on reverse osmosis (RO) and nanofiltration (NF) membranes. The membranes were characterized in terms of Fourier transformation infrared (FTIR) spectra, surface charge, hydrophobicity, pore size distribution, and roughness. Five pharmaceuticals were used to determine their rejection and possible interactions with the membranes. Albendazole, a hydrophobic pharmaceutical, adsorbed on the NF (NF270) and RO (XLE) membranes. FTIR spectra showed significant changes (new peaks/bonds) on the membranes, confirming that adsorption plays an important role in the overall mechanism of rejection in the case of hydrophobic compounds. Hydrophilic pharmaceuticals (sulfaguanidine, trimethoprim, hydrocortisone, and procaine) did not adsorb on the XLE membrane, showing that size exclusion and electrostatic repulsion were both dominant removal mechanisms. This article gives new insights into NF membranes in the treatment of hydrophilic compounds. The results clearly show the adsorption of hydrophilic compounds on the NF membranes since H-bonds and p-p interactions were observed on their FTIR spectra. Therefore, both the hydrophobic and the hydrophilic adsorption have to be taken into account when considering the removal mechanism, especially in the case of NF membranes. (C) 2016 Wiley Periodicals, Inc.