Forward osmosis membrane with lightweight functionalised multiwall carbon nanotube nanofillers

Thin-film nanocomposite (TFN) membranes with a polyamide (PA) active layer modified with carbon nanotubes (CNTs) hold promise for water desalination and wastewater reuse via forward osmosis (FO). We hypothesise that modifying the PA active layer with hydroxyl-functionalised multi-wall carbon nanotubes (f-MWCNTs) will enhance the water flux of the FO membrane while maximising salt rejection. TFN membranes were modified using in situ interfacial polymerisation, with varying f-MWCNT mass content to minimise agglomeration. These modified FO membranes are designated as CTFN-x, where x represents the mass content of f-MWCNTs, ranging from 0.001%, CTFN-1 to 0.008%, CTFN-8 (w/v). The surface properties of CTFN-x were characterised using electron microscopy, atomic force microscopy, and molecular spectroscopy. IR spectroscopic data confirm the successful adherence of f-MWCNTs as a bridging agent between the 1,3-phenylenediamine (MPD) and trimesoyl chloride (TMC) polymers, preserving FO membrane integrity. The CTFN-4 FO membrane shows the highest water flux (29 LMH) and the lowest reverse salt flux (2.90 gHM), attributed to preferential water flow channels in the f-MWCNTs. The integration of f-MWCNTs into the active layer improved water flux, reduced reverse salt flux, and enhanced the antifouling properties of FO membranes.