Selectivity of artificial water channel-polyamide composite membranes towards inorganic contaminants

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 incorpo-rated 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-, SO4 2-, 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 sur-face 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.

Automated summary

Investigation of ion transport through artificial water channel-polyamide (AWC-PA) composite membrane revealed that the membrane provides comparable rejection and permselectivity to commercial membranes, except for bivalent cations. The study also found that strongly hydrated bivalent cations enhance the transport through AWC-PA by water clusters. Additionally, reducing the surface charge of AWC-PA membrane by adjusting pH and ionic strength decreases the rejection of anions.