Green modification of P84 co-polyimide with 8-cyclodextrin for separation of dye/salt mixtures

Novel beta-cyclodextrin (8-CD) incorporated P84 co-polyimide nanofiltration (NF) membranes were prepared via interfacial polymerization between N, N-bis(3-aminopropyl)-1,3-propanediamine (APPD) and beta-cyclodextrin (8-CD) in a green solvent. The effects of concentration and hydroxyl groups of 8-CD on separation performance, surface hydrophilicity, and antifouling performance of the prepared membranes were analyzed. The results demonstrate that the 0.38-CD/APPD/P84 membrane has a pure water permeability of 209.07 Lm-2 h-1 bar-1 at 2 bar. The membrane also shows effective dye/salt separation with a high dye rejection of 99.1 % to Congo red and a high salt permeation of 92.13 % to NaCl. The resultant membranes can also effectively separate binary dye solutions with different molecular weights because of the unique cavity structure of 8-CD and inclusion complexation. In addition, the membranes exhibit excellent antifouling characteristics because the unreacted hydroxyl groups in the outer cavity of 8-CD initiate strong hydrogen bonding with water molecules, which blocks the interaction between pollutants and the membrane surface. Comparing with other reported membranes, the newly developed nanofiltration (NF) membrane exhibits a higher water permeability and comparable separation performance to dye/salt mixtures. Furthermore, the membrane maintains a high dye rejection (Congo red, 98.67 %) and salt permeation (NaCl, 95.93 %) even at a high NaCl concentration of 40,000 ppm in dye/salt mixtures. Therefore, the novel ll-CD incorporated NF membrane has a prominent potential for the treatment of salt -containing dye wastewater treatment with better dye/salt separation.

Automated summary

Novel beta-cyclodextrin (8-CD) incorporated P84 co-polyimide nanofiltration (NF) membranes were prepared using a green solvent. The membranes showed high separation performance, surface hydrophilicity, and antifouling characteristics. The membranes exhibited high water permeability, effective dye/salt separation, and the ability to separate binary dye solutions with different molecular weights. The membranes also maintained high dye rejection and salt permeation even at high NaCl concentrations in dye/salt mixtures. Therefore, the 8-CD incorporated NF membrane has great potential for the treatment of salt-containing dye wastewater.