Thin film nanocomposite forward osmosis membranes based on layered double hydroxide nanoparticles blended substrates

Abstract

One of the biggest challenges for the practical application of forward osmosis (FO) is lack of high-performance FO membranes. In this study, a novel thin film nanocomposite (TFNC) FO membrane was fabricated based on a layered double hydroxide nanoparticles (LDH-NPs) blended ultrafiltration substrate. The influence of the LDH-NPs addition on the physicochemical properties of the ultrafiltration substrate and the resultant FO membrane was systematically investigated. The addition of LDH-NPs endowed the ultrafiltration substrate with increased porosity, surface hydrophilicity, surface pore diameter, mechanical strength and thermal stability. Consequently, all the resultant TFNC FO membranes obtained increased water permeability as compared with pristine FO membrane. Specifically, the TFNC membrane with a 2wt% LDH-NPs dosage exhibited a water flux of 18.1Lm−2h−1 (~42.5% higher than that of the pristine FO membrane) with little compromise in reverse salt flux. Moreover, this membrane reached a higher water flux of 26.9Lm−2h−1 when 2M NaCl was used as draw solution. The water-flux increase could be attributed to the decrease of the structural parameter (S value) of the LDH-NPs blended ultrafiltration substrate. The loaded LDH-NPs facilitated the development of a considerable amount of finger-liked macrovoids, which decreased the support layer tortuosity thus favoring the inhibition of internal concentration polarization. As a result, a moderate water flux was obtained. To the best of our knowledge, this is the first reported TFNC membrane using LDH-NPs blended substrates for FO applications.