A Metal-organic composite ultrafiltration membrane synthesized via Quadratic phase inversion

Abstract

• Stainless steel wire mesh as substrate was used to fabricate composite UF membrane. • A novel strategy denoted as“Quadratic Phase Inversion (QPI)” was proposed. • Composite UF membrane showed high pure water flux and desirable BSA rejection. • Composite UF membrane prepared with “QPI” showed superior running stability. According to the Pore-flow model describing the mass transfer process of Ultrafiltration (UF) membranes, the thickness of the separation layer directly determines the separation performance of an UF membrane: pure water flux (PWF) and foulant rejection. However, the flexibility and limited supporting capacity of the conventional supporting layer (non-woven fabric) limits the further reduction of the separation layer thickness. In this study, stainless steel wire mesh (SSWM) was employed as the supporting layer to fabricate a metal/polymer composite UF membrane via a novel strategy denoted as “Quadratic Phase Inversion (QPI)”, in which the SSWM was firstly modified with a casting solution with low PVDF concentration, and then another PVDF selective layer was constructed on the modified substrate with the conventional phase inversion method. Orthogonal experiment was conducted to optimize the fabrication parameters. A series of characterization was adopted to analyze the performance and structural evolution. The results demonstrate that a composite UF membrane with ultrathin PVDF selective layer could be fabricated on the PVDF modified SSWM. The optimized sample was obtained with the SSWM modification reagent of 3 wt% PVDF, the casting solution of 20 wt% PVDF, the casting thickness of 75 μm, and NMP as solvent, which had a MWCO of 149 kDa and mean pore diameter of 7.2 nm. Meanwhile, it presented a high PWF around 448.8 L m −2 h −1 bar −1 , desirable BSA rejection about 96.3% and good operation stability. The outcome of this research is expected to provide a valuable route for promoting the separation performance of UF membranes.