Decreased cross-linking in interfacial polymerization and heteromorphic support between nanoparticles: Towards high-water and low-solute flux of hybrid forward osmosis membrane.

Realizing that one main factor affecting development of forward osmosis (FO) membrane was internal concentration polarization (ICP), graphene oxide (GO) with two-dimensional structure and oxidized carbon nanotubes (OCNTs) with one-dimensional structure were linked by oxygen-containing groups to form water channels in the polyamide layer. OCNTs and GO were used for producing reactions among oxygen-containing groups of nanoparticles and polymer chains, and oxygen-containing groups were fully exposed because GO and OCNTs restrained aggregation. Decrease of cross-linking degree for interfacial polymerization layer was confirmed due to reaction from GO/OCNTs/m-phenylene diamine/1,3,5-benzenetricarbonyl trichloride. Moreover, OCNTs formed an appropriate supporting effect for GO to improve hydrophilic properties, which was confirmed by transmission electron microscopy, scanning electron microscope and contact angle. Resulting membrane PA-GO-OCNTs showed high water flux (114 LMH and 84.6 LMH in the PRO (active layer facing draw solution) and FO (active layer facing feed solution) mode, respectively) and low solute flux (5.17 gMH and 3.4 gMH in the PRO and FO mode, respectively) under this condition that 0.5 M NaCl and deionized water were used as draw solution and feed solution respectively. It was worth mentioning that water flux of FO membrane was far higher than that in reported literatures while its structural parameter S was only 203 μm, which led to decrease of ICP.