Improving the water permeability and antifouling property of the nanofiltration membrane grafted with hyperbranched polyglycerol

This study evaluated the performance of the high performance nanofiltration (NF) membrane by grafting the recently developed hyperbranched polyglyceml (hPG) with a unique three-dimensional (3D) globular structure and superhydrophilicity on thin-film composite (TFC) polyamide layer. The hPG modified TFC (hPG-TFC) NF membrane possessed an outstanding hydrophilic surface and high permeance without compromising salt rejection. Compared with the pristine TFC membrane, the hPG modified membrane exhibited a permeate flux increase of 30% while maintaining Na2SO4 rejection of 97%. Irrespective of foulants, the hPG grafted TFC persistently generated an enhanced antifouling ability. Among the model foulants, the humid acid shows the most severe fouling potential for NF membranes. Notwithstanding, the hPG-TFC exhibits an improved normalized water flux of 65% and flux recovery of 75%, much higher than the pristine TFC membrane (44% and 47%, respectively). In addition, in order to better understand the antifouling behavior of our hPG modified NF membranes, the Q-sense quartz-crystal microbalance with dissipation (QCM-D) was used to determine both the adsorption rate and amount of model foulants on the membrane surface. Therefore, the successful application of 3D hPG polymers on the NF membrane should serve as a source of inspiration for the surface engineering of high performance TFC membrane with high water permeability and enhanced antifouling performance in pressure-driven NF membrane processes.