High efficient dye removal with hydrolyzed ethanolamine-Polyacrylonitrile UF membrane: Rejection of anionic dye and selective adsorption of cationic dye.

The dye-water treatment using UF membrane is still a challenge. In the present study, the optimized PAN-ETA ultrafiltration membrane was hydrolyzed and subsequently characterized by SEM, IR, CA, XPS, NMR, mechanic measurement, etc. The obtained membrane (H-PAN-ETA) was used for dye removal and it showed both an excellent anti-dye fouling and a good rejection property for anionic dyes. I.e. 96% rejection for methyl blue (MB), 99% for congo red (CR), 94% for acid fuchsin (AF) with no sign of contamination by dye. The flux of H-PAN-ETA membrane maintained at 50-53 L m-2⋅ h-1 during a 10-h filtration, which is higher than that of tight UF membranes reported. Meanwhile, H-PAN-ETA membrane was able to selectively remove cationic dyes, such as methylene blue (MEB), rhodamine B (RB) and, crystal violet (CV), or the mixture of anionic dye/cationic dye by adsorption process. Its adsorption capacity remained unchanged after 20 cycles. Finally, the immobile electrical double layer (EDL) theory combined with electrostatic force was introduced to explain the separation mechanism of charged UF membrane, which is helpful to instruct the preparation of UF membrane for dye removal.