Abstract
This study investigates the change in performance and properties of various forward osmosis (FO) membranes resulting from exposure to chlorine by conducting performance test and characterization using ATR-FTIR, XPS, zeta potential, NMR and, particularly, ToF-SIMS analyses. The data obtained through the ToF-SIMS measurements suggested that chlorine first reacted with the acetyl/acetate group of the cellulose triacetate (CTA)-based membrane and then with the pyranose ring. Chlorine bound to the membrane surface weakened the H-bond of the CTA-based membrane, resulting in an increase in water flux and reverse salt flux (RSF) as the chlorine exposure time or chlorine concentration increased. A high chlorine dosage cleaved the pyranose ring, leading to loss of membrane selectivity. After chlorination with a high chlorine dosage, the structure of the CTA-based membrane eventually presented fatigue upon an increase in filtration time, and the oxidation of the CTA-based membrane due to exposure to chlorine was maximal at pH 7. The polyamide (PA)-based FO membrane was more sensitive to chlorine under acidic conditions, resulting in a greater loss of selectivity than that of the CTA-based FO membrane. However, an alkaline chlorine solution insignificantly affected both the CTA-based and TFC-based FO membranes. This study shows that the TFC PA-based FO membrane yields a high water flux, but its chlorine tolerance must be improved to be practically applicable in various fields.