Host-guest nanofiltration membranes having amino-complexed cucurbituril supramolecular channel for monovalent/divalent salts separation

Nanofiltration (NF) is widely used in separation of ions with different sizes and charges. However, thin-film composite NF membrane is hard to reach satisfied selectivity for monovalent/divalent salts separation. Herein, a novel host-guest NF membrane was designed and fabricated with cucurbituril-polyethyleneimine (CB-PEI) complex, which provided a “ring-like” supramolecular channel. The results indicated that CB-PEI/PSf membrane showed attractive separation performance for monovalent/divalent salts separation, purification and desalination of small molecule solutions. The as-prepared CB-PEI/PSf membrane exhibited superior pure water permeability up to 25.6 L·m−2·h−1·bar−1, and salt rejections of 97.4%, 90.6%, 41.9% and 12.4% to MgSO4, Na2SO4, MgCl2 and NaCl, respectively. The monovalent/divalent selectivelies for NaCl/MgSO4 and NaCl/Na2SO4 reached up to 30.0 and 8.9, respectively. Besides, the CB-PEI/PSf membrane exhibited very high separation factors for medicine/NaCl and dye/NaCl mixtures. Moreover, NF membrane processes were designed and operated for monovalent/divalent mixed salt separation by using CB-PEI/PSf membrane. The NaCl with mass fraction above 98% was successfully recovered after the single-stage membrane separation of NaCl/MgSO4 mixture and the two-stage membrane separation of NaCl/Na2SO4 mixture. Therefore, this novel host-guest NF membranes and process design provide a valuable basis for the industrial application of monovalent/divalent salts separation.