Tight UF membranes with ultrahigh water flux prepared by in-situ growing ZIF particles in NIPS process for greatly enhanced dye removal efficiency

Tight ultra-filtration (TUF) membranes with in-situ grown zeolitic imidazole framework (ZIF) particles embedded in and packed under porous polysulfone (PSF) separating layers were prepared using non-solvent induced phase separation (NIPS) processes. Imidazole ligands contained in casting solutions were released and reacted with divalent Zn2+ cations pre-loaded on non-woven fabric supporting layers. The capillary filling pore size and molecular-weight-cut-off (MWCO) Stokes solute rejection pore size of the formed ZIF/PSF TUF were tuned by varying the loading levels of Zn (II), polyvinylpyrrolidone (PVP) and imidazole, as well as the NIPS reaction time. With thinned PSF separating layer (200–500 nm) and embedding water permeating short-cuts from the ZIF particles, ZIF/PSF TUF membranes showed 7 times higher water permeance (up to 250 L/(m2 h bar)) and greatly enhanced dye/salt retention selectivity, bearing high potential for applications in dye and textile waste water treatment processes.