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Layered graphene oxide (GO) membranes have been widely employed for water desalination in forward osmosis (FO) systems, however, the balance between performance and long-term stability of membranes is still a trade-off in the practical application. A newly developed laminar GO-based FO membrane was prepared by a two-step protocol, including acid treatment of GO before crosslinking and reduction of GO by hyperbranched polyethylenimine (HPEI), and followed by coating HPEI-reduced graphene oxide (HPEI:rGO) laminates by polyethylene glycol (PEG). It is suggested that the long-chain and amino-enrichment HPEI polymer can be covalently bonded with the acid-treated GO at elevated temperatures. This chemical process partially removed oxygen-containing functional groups of GO and formed a nanocomposite structure with tuned interlaminar spacing for better selectivity of NaCl ions. Subsequently, the infiltration of PEG molecules through the HPEI-rGO structure improved the hydrophilicity, and hence the water permeability across the PEI60k:rGO/PEG membrane. In this study, the resultant membrane exhibited water flux of 7.7 LMH, salt rejection efficiency of 97.9 %, and low reverse solute flux of 0.56 gMH in an FO filtration process. Also, synergistic effects of the double-polymer modification reinforced enhancement of dimensional integrity and durability of the membrane structure in both ionic and harsh conditions. • Robust PEI60k:rGO modified PEG membrane was chemically fabricated for FO desalination. • Acid treatment effectively activated and formed strong GO functional frameworks. • Addition of PEG molecules noticeably enhanced hydrophilicity of PEI60k:rGO membrane. • PEI60k:rGO/PEG membrane remarkably showed high flux, selectivity, and stability.
Edokali et al. (Sat,) studied this question.