Preparation and characterization of PVDF-PFS A blend hollow fiber UF membrane

摘要

Polyvinylidene fluoride (PVDF)-perfluorosulfonic acid (PFSA) blend hollow fiber ultrafiltration (UF) membranes were prepared by wet-spinning method using pure water as an external coagulation solution. Coagulation kinetics of PVDF-PFSA-DMAc system was measured by light transmittance experiment. Using PEG10000 (M_w = 10,000), lysozyme (M_w = 14,400), PEG20000 (M_w = 20,000) and BSA (M_w = 67,000), the separation performances of PVDF-PFS A blend hollow fiber UF membranes were obtained. Based on the experimental results, the delayed demixing process was observed for the dope solution M-1 without PFSA-H while the instantaneous demixing process was observed for the others with PFSA-H in the dope solutions M-2 to M-6. The precipitation rate increased with the increment of the PFSA-H concentration in PVDF-PFSA dope solution. The bore fluid solution with 95:5 DMAc:H_2O resulted in single finger-like voids for PVDF-PFSA-H UF membrane. The pure water permeation flux of PVDF-PFSA-H UF membranes firstly increased from <0.1 x 10~(-5) to 119.1 x 10~(-5) L m~(-2) h~(-1) Pa~(-1) (<0.1 to 119.1 Lm~(-2)h~(-1) bar~(-1))for M-1 to M-4(1) and 137 x 10~(-5) L m~(-2) h~(-1) Pa~(-1) (137 L m~(-2) h~(-1) bar~(-1)) for M-4(2), and decreased from 119.1 x 10~(-5) to 79 x 10~(-5) L m~(-2) h~(-1) Pa~(-1) (119.1 to 79Lm~(-2) h~(-1) bar~(-1)) for M-4(1), M-5 and M-6 as the PFSA-H concentration changed from 0% to 5% and total PVDF-PFSA-H concentration was 20wt.%. The molecular weight cut-off (MWCO) of PVDF-PFSA blend hollow fiber UF membranes spun from 20 wt.% PVDF-PFSA-H concentration with 3-5 wt.% PFSA-H was about 20,000 while that spun from 22 wt.% PVDF-PFSA-H or PVDF-PFSA-Na concentration with 5 wt.% PFSA-H or PFSA-Na was about 10,000. As the W_(PFSA-H)/W_(PVDF) increases from 2/18 to 5/15 for M-3-M-6, J_(BSA)/J_w, increases from 0.53 to 0.79. The anti-fouling property of PVDF-PFSA-H blend UF membrane is superior to PVDF-PFSA-Na blend membrane. Based on FTIR spectra, PFSA-H existed in PVDF-PFSA blend hollow fiber UF membranes. There is no obvious variation of the intensity of the characteristic peak at 983 cm~(-1) assigned to C-O-C group of PFSA-H molecules. This also illustrated that PVDF-PFSA-H blend hollow fiber UF membranes were stable.