Chlorine Resistance of Thin Film Composite Polyamide Membrane Functionalized by Poly(amidoamine) Dendrimer

Surface modification is one of the most techniques to improve the performance of thin film composite polyamide membrane (TFC). In this study, 0.5, 1, and 1.5 w/v% concentrations of the second generation of poly(amidoamine) dendrimer polymer (PAMAM, G2) were utilized to investigate the improvement of membrane performances. Physicochemical properties of the pristine and modified membranes were characterized using water contact angle measurement, ATR-FTIR, and SEM. Membranes separation performance was examined in a forward osmosis system using synthetic brackish water. 1% concentration of PAMAM (TFC-1% PAMAM) was considered as the optimized modified membrane with the best water flux and salt rejection results. According to the results, the water flux of TFC-1% PAMAM compared to that of pristine TFC decreased, while the salt rejection increased, respectively. In addition, passive chlorination tests were performed for pristine TFC and TFC-1% PAMAM. It was observed that the water flux for the unmodified TFC increased from 5.0±1.1 to 5.8±0.8 (16% increased). In contrast, the water flux for TFC-1% PAMAM increased from 4.7±0.6 to 4.9±0.6 (4% increased). Salt rejection for unmodified TFC decreased from 97.6±0.9 to 93.7±1.5 (4% decreased) and for TFC-1% PAMAM decreased from 98.5±0.3 to 95.5±1.2 (3% reduction). The results confirmed the membrane performance improvement after surface modification by PAMAM. The enhanced chlorination resistance of TFC-1% PAMAM was attributed to the scavenger role of the extra amine and amide groups in PAMAM