Development of novel thin film nanocomposite forward osmosis membranes containing halloysite/graphitic carbon nitride nanoparticles towards enhanced desalination performance

Abstract

In this study, thin film nanocomposite (TFN) membranes were fabricated by incorporating highly hydrophilic halloysite nanotubes (HNTs) and self-synthesized graphitic carbon nitride (g-C3N4) nanoparticles into polysulfone-based substrate and interfacially polymerized polyamide top layer, respectively. The TFN membranes were evaluated for their performance in forward osmosis (FO) applications. The XRD, ATR-FTIR, FESEM and TEM results confirmed the successful synthesis of g-C3N4 nanoparticles. The effects of nanomaterials incorporation were investigated in terms of membrane surface morphology, hydrophilicity and separation performance. When 0.05 wt/v% of g-C3N4 was added to the polyamide layer, the membrane surface contact angle was significantly reduced from 68° in the control membrane (TFN0.0) to <10° in the TFN membrane (TFN0.05), leading to high water flux of 18.88 L/m2·h (approximately 270% higher than the TFN0.0 membrane). The results have proven the predominant effect of the polyamide layer modification compared to the support modification towards FO performance enhancement. The water flux decline for the TFN0.0 and TFN0.05 membranes after a prolonged time of 1200 min was only 12% for the TFN0.05 while TFN0.0 membrane experienced 24% reduction. In addition, fouling resistance of the membranes assessed by BSA revealed that the flux of TFN0.0 has reduced by 54% after 1200 min, meanwhile TFN0.05 recorded a reduction of approximately 30%. The findings confirmed the effectiveness of g-C3N4 as a promising surface modifier for polyamide layer to simultaneously contribute to flux enhancement and increased anti-fouling properties.