Ultrafast loose nanofiltration membrane intercalated by in-situ grown nanoparticles for dye purification and reuse

Loose nanofiltration membrane is regarded as an effective separation technology for dye purification and reuse, but is still restrained by the trade-off between the permeance and the dye/salts selectivity. Herein, we report the fabrication of an ultrafast loose polyamide nanofiltration (NF) membrane on the nanofibrous support layer with uniform in-situ grown ZnO nanoparticles. It was found that embedding ZnO nanoparticles provides more water channels and increased effective filtration area, thus enhancing the water permeation without trading off the dye/salt selectivity. The fabricated NF membrane with an in-situ formed ZnO-nanoparticle interlayer exhibits an ultrahigh water permeance up to 375 L m−2 h−1 bar−1, which increased by approximate seven-fold than that of virgin NF membrane (54 L m−2 h−1 bar−1) without nanoparticles intercalated, and attains high rejection of organic dyes (>91 % for Congo red, >92 % for Methyl blue, and >98 % for Victoria blue B) but low rejection of inorganic salts (<5 %). The synergy of steric exclusion and charge effect dominate the high selectivity of dye and salts. This study unlocks a new avenue to synthesize ultrahighly permeable-selective loose NF membranes.