Polyamide/nitrogen-doped graphene oxide quantum dots (N-GOQD) thin film nanocomposite reverse osmosis membranes for high flux desalination

Thin film nanocomposite (TFN) has been shown as a promising platform to further increase water permeability of commercial polyamide membrane in reverse osmosis (RO) desalination. Identification of novel and effective nano-additives, which are significantly smaller than the typical thickness of polyamide membranes (~ 200 nm) and can be facilely incorporated into the interfacial polymerization (IP) process, is crucial to pursue this route. In this study, we prepared nitrogen-doped graphene oxide quantum dots (N-GOQD) and for the first time, fabricated polyamide/N-GOQD TFN membranes by IP for RO desalination application. We found adding only 0.02 wt/v% N-GOQD into polyamide membrane drastically increased water permeability by approximately 3 times, while maintaining similar salt rejection as the pristine polyamide membrane. Enhanced water permeability resulted from the improved hydrophilicity of the membrane surface, increased effective membrane surface area, and introduction of larger cavity at the interface between N-GOQD and PA matrix. In addition, favourable chemical bonding between polyamide and N-GOQD also greatly improved thermal stability of polyamide membrane, as indicated by thermal gravimetric analysis (TGA) measurements.