High permeance nanofiltration thin film composites with a polyelectrolyte complex top layer containing graphene oxide nanosheets

A graphene oxide (GO) nano-additive was incorporated into a polyelectrolyte complex (PEC) to prepare water selective membranes for a water desalination process. The synthesized thin film composites consisted of a PEC-GO separation layer, a microporous poly(vinylidene fluoride) layer, and a non-woven substrate. The crosslinking agent glutaraldehyde (GA) was used to enhance the stability of the PEC composite membranes. The resulting membranes were investigated in nanofiltration systems to examine their permeance and salt rejection efficiency. The results demonstrated that 100 ppm GO in the PEC exhibited a high desalination efficiency on a 1000 ppm NaCl solution. This composite exhibited permeance values in the range of 69–89 kg m−2 h−1 MPa−1 for various salt solutions. The Na2SO4 solution resulted in the highest rejection ratio of 62.1%, followed by the NaCl rejection (38.6%). The MgCl2 and MgSO4 solutions had lower rejections of 12.2% and 22.0%. It seems that the GA_PEC-GO composite was more efficient in removing divalent ions than monovalent ions, while maintaining high filtration flux.