Graphene oxide modified graphitic carbon nitride as a modifier for thin film composite forward osmosis membrane

• CN/rGO was used as additive for fabricating PES substrate for FO membrane.
• The amount of CN/rGO has significant effect on the properties of PES substrate.
• A small amount of CN/rGO in the substrate decreases the S value.

Reduced graphene oxide (rGO) modified graphitic carbon nitride (g-C3N4), CN/rGO, was synthesized as a modifier for porous polyethersulfone (PES) substrate for the preparation of thin film composite (TFC) polyamide forward osmosis (FO) membrane. The effect of CN/rGO addition on the PES substrate formation was investigated using viscosity and light transmittance measurements, and the PES–CN/rGO substrates and the FO membranes were characterized by SEM, TEM, AFM, XPS and contact angle measurements. The results indicated that the addition of CN/rGO had a significant effect on the membrane properties. The FO membrane with an appropriate amount of CN/rGO in the PES substrate exhibited excellent FO performance. The osmotic water flux with 0.5 wt% CN/rGO in the substrate of TFC membrane reached 41.4 LMH using 2 M NaCl as draw solution and deionized water as feed, which was around 20% greater than with the control membrane without CN/rGO. The FO performance improvement should be attributed to the modified structure of the PES substrate, and thus lower structure parameter and the reduction of ICP. This study suggests that CN/rGO is an effective additive for modifying the porous substrate for the development of FO membranes.

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