Enhancing the desalination performance of forward osmosis membrane through the incorporation of green nanocrystalline cellulose and halloysite dual nanofillers

Abstract

BACKGROUND: Membrane fouling remains an unmet challenge for all membrane processes, including osmotically driven forward osmosis (FO). Membrane modification is a straightforward and feasible approach to enhancing fouling resistance. In this study, thin film nanocomposite (TFN) membranes incorporated with dual nanofiller were prepared. Halloysite nanotube (HNT) was incorporated into the polysulfone substrate while functionalized nanocrystalline cellulose (NCC) was embedded within the polyamide (PA) thin layer of the TFN. RESULTS: The formation of crystalline needle-like NCC was observed through X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images. TFNs embedded with functionalized NCC at different loadings were characterized in terms of morphology, surface roughness and hydrophilicity, separation performance and antifouling propensity. The incorporation of hydrophilic NCC has significantly reduced the water contact angle from 69° for the TFN0.0 to 45° for TFN incorporated with 0.1 wt/v% of NCC. The water flux of TFN0.05, as the best performing membrane, was recorded as 21.34 L/m2 h. This was about 140% greater than that of TFN0.0 at the same operating conditions. The embedment of NCC also reduced the extent of concentration polarization (CP) in TFN0.05, which resulted in better protein fouling resistance and lower water flux decline in comparison to neat membranes. CONCLUSIONS: Overall, the enhancement of both the water flux and antifouling properties of the membrane, without compromising the salt rejection when a low amount of NCC (<0.1 wt/v%) was incorporated into the thin PA layer, demonstrated the potential of dual nanofillers TFN for effective forward osmosis desalination application.