Dye sieving and dye/salt separation PEI-based loose nanofiltration membrane modified by NH2-MIL-101(Fe) and polyphenol coating

Effective dye sieving and dye/salt separation could recycle valuable resources during textile wastewater treatment. In this work, a loose nanofiltration (NF) membrane with outstanding performance was constructed with facile materials including the surface polyphenol coating and the polyetherimide (PEI) support. Firstly, the mixed matrix support membrane was prepared by incorporating Fe-based MOF NH2-MIL-101(Fe) into PEI membrane via non-solvent induced phase separation (NIPS) method, then the polyphenol coating based on vanillyl alcohol, which was the characteristic component derived from Gastrodia elata Blume, was co-deposited on the support PEI membrane, followed by the treatment of 1,3-propane sultone. In this way, the optimal loose NF membrane could have a high good pure water permeability (87.9 L·m−2·h−1·bar−1) while high dye/salt selectivity was reached (Selectivity: 58.9 for Congo Red/NaCl; 46.8 for Conge Red/Na2SO4). Moreover, a mixture of large molecule dye and small molecule dye could be sieved and the optimal loose NF membrane showed outstanding antifouling capacity with the flux recovery ratio of 85.7%, 98.1%, and 97.9% respectively for bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA), which was further analyzed and calculated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The long-term stability during EBT/Na2SO4 mixture filtration endowed the membrane with great potential in treating textile wastewater.