Effects of aluminogermanate imogolite nanotube orientation on mass transport across polyamide nanocomposite membranes

Nanocomposite membranes were synthesized by incorporating aluminogermanate imogolite nanotubes (GeINTs) into polyamide thin-films. Thin-films were prepared by interfacial polymerization using m-phenylenediamine (MPD) and 1,3,5-trimesoylchloride (TMC). The GeINTs were surface modified with hydrophobic vinyl terminated polydimethylsiloxane (PDMS) and their orientation manipulated using an alternating current (AC) electric field. The prepared GeINTs were characterized by their physical morphology, surface chemistry, orientation, and aggregation status in the relative media. Specific water flux and salt rejection were evaluated using dead-ended filtration and cross-flow systems. By incorporating vertically aligned (theta = 90 degrees) PDMS modified GeINTs, the specific flux increased 205% when the GeINT concentration was 5 mg/g compared to the membrane without GeINTs. This was due to the higher water permeability within the incorporated GeINTs compared to that of the pure polyamide. In contrast, when the orientation of the GeINTs was parallel (theta = 0 degrees) to the membrane surface, the increase in specific water flux (105%) was less substantial. This was attributed to the varied and elongated water flow paths in the nanocomposite membrane by the randomly oriented nanotubes.