Fouling Resistance and Physicochemical Properties of Polyamide Thin-Film Composite Membranes Modified with Functionalized Cyclodextrins

Thermal and mechanical properties and fouling resistance of polyamide thin-film composite (PA-TFC) membranes modified with amino-cyclodextrins and diethylamino-cyclodextrins are investigated. It was found that the decomposition temperatures of the modified membranes were 500 degrees C and were not significantly different with those of the unmodified membranes. Differential scanning calorimetry (DSC) studies showed that the modified membranes with heating melting temperatures in the range 112.5-113.8 degrees C were more crystalline than the unmodified membranes due to the presence of cyclodextrin derivatives on the interfacial layer. The crystallization temperatures (T-c) were found to range between 128.75 and 129.03 degrees C and the glass transition temperatures (T-g) ranged between 78.67 and 79.33 degrees C. The modified PA-TFC membranes were found to have comparable ultimate tensile strengths (UTS) to the unmodified membranes, except for the membranes modified with amino--CDs, with a UTS of 20.00 +/- 0.50 MPa. The PA-TFC membranes had a lower water uptake percentage due to their enhanced crystallinity. However, these materials had a higher water permeate flux due to the hydrophilic nature of the modified membranes enhanced by the rich hydroxyl groups on the CDs. The modified PA-TFC membranes also exhibited high MgSO4 salt rejection and fouling resistance capacities compared to unmodified membranes. Different pH levels resulted in different fouling resistance patterns of the membranes. Therefore, the membranes modified with functionalized CDs were thermally and mechanically stable, had enhanced crystallinity, high divalent salt rejection and fouling resistance under different pH conditions. (C) 2016 Wiley Periodicals, Inc.