Effects of polyethylene glycol and glutaraldehyde cross-linker on TFC-FO membrane performance

Polymers containing polyethylene glycols (PEGs) and Glutaraldehyde (GLA) cross-linker in the casting solution can improve the membrane performance such as porosity and swelling properties in the fabrication process. The highly hydrophilic polyethylene glycols (PEGs) including PEG 20000, PEG 6000, and PEG 1000 were utilized as the additives to modify the membrane structure. GLA was also added into the PEGs combined with a polysulfone (PSf) substrate to create a cross-linked polymer in the PSf membrane structure. This cross-linker significantly improved the water flux by increasing the porosity and decreasing the swelling within the PSf membrane structure. The hydroxyl hydrophilic functional group in GLA enhanced the water permeability by grafting the polymer chains. The newly developed cross-linker not only reduced the swelling in the membrane structure but also created tightly linked between the monomers to reduce the solute diffusion through the membrane. The presence of the PEG can enhance the TFC-FO membrane hydrophilicity by changing the PSf polymer nature, and PEG 6000 showed a better performance with macrovoid-free sponge-like structure and lower surface roughness. The combination of PEG 6000 (wt.% = 17%) and cross-linker exhibited an excellent performance with water flux of 6.22 L/m²h and reverse salt flux of 1.79 g/m²h when using 2 M NaCl as the draw solution and deionized water as the feed solution.