Enhanced Performance of Thin Film Composite Forward Osmosis Membranes with Green Synthesized Graphene Quantum Dots

The main drawbacks in forward osmosis (FO) process include high specific reverse solute flux (SRSF), reduced water flux, as well as fouling of membranes. In the current study, these challenges were addressed by the addition of graphene quantum dots (GQDs) obtained from a green sustainable source, in the selective layer of the thin film composite membranes, which were supported with an innovative polyethersulfone nanofiber support layer. Eucalyptus tree leaves were used to prepare GQDs by following a simple hydrothermal technique which required just distilled water, and there was no requirement for reducing agents or any organic solvents. The advanced solution blow spinning technology was employed for the preparation of the nanofiber support. The GQDs were incorporated in the selective later during the interfacial polymerization process to make thin film nanocomposite membrane and different characterizations were performed to confirm the formation of GQDs as well as its successful incorporation within the polyamide selective layer. These novel membranes have been tested for their performance in the FO process. To the best of our knowledge, this is the initial research work that reported the ultra high water flux as well as antifouling ability of the solution blown spun nanofiber-supported thin-film composite membranes. The effect of different GQDs concentrations on the performance of forward osmosis membrane, its long-term FO testing, effectiveness in cleaning, as well as its organic fouling resistance were examined. The performance of the thin film composite membrane in FO process was enhanced with the incorporation of 0.05 wt.% concentration of GQDs. Overall, the current work established that these advanced membranes showed a super high water flux of 3526 L/m²h, low SRSF of 7.46 g/m²h, better salt rejection as well as better antifouling performance in the forward osmosis process. These membranes have high potential for the scale-up of FO process.