Résumé
Artificial water channel-polyamide (AWC-PA) composite membrane addresses the need for enhanced water-salt permselectivity in desalination and water treatment. An investigation of ion transport through AWCs incorporated into the active layer of a thin film composite membrane contributes to a better understanding of the selectivity of such membranes. This study investigated the rejection of Cl−, NO3−, F−, SO42−, Na+, K+, Ca2+, and Mg2+ ions with varying hydration properties through AWC-PA membranes. The influence of hydration radius on the permselectivity of AWC-PA was investigated and results were compared with the commercial BW30LE membrane. With the exception of bivalent cations, the AWC-PA membrane provided a comparable rejection (80–96%) and permselectivity (1.0–1.7 bar-1). It is suggested that strongly hydrated bivalent cations exhibited increased transport through AWC-PA in water clusters through the membrane. The AWC-PA's active layer surface charge was determined to be −37 mV above pH 5.5. A reduction in membrane surface charge by varying the pH and ionic strength reduced the rejection of anions from 80 to 40% in AWC-PA indicating that the transport of hydrated ions through AWCs nanoaggregates of the AWC-PA may occur under conditions of reduced membrane surface charge.
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•Comparable rejection by AWC-PA and BW30LE were observed in most cases.•Strongly hydrated cations exhibited lower permselectivity in AWC-PA membrane.•Decrease in surface charge reduced rejection of weakly and strongly hydrated anions.