ABSTRACT
This study proposes a method to prepare a crack-free poly(vinylidene fluoride) (PVDF) microfiltration (MF) membrane with enhanced antifouling property. In the study, blending 4% poly(vinylidene fluoride)-graft-poly(sulfopropyl methacrylate) (PVDF-g-PSPMA) and 1.5% potassium perchlorate (KClO4) led to crack prevention during membrane preparation via nonsolvent induced phase separation (NIPS) when compared with blending with 4% PVDF-g-PSPMA only (without KClO4). The resulting crack-free membrane (A3) had both smooth surface structure and hydrophilicity in comparison with pristine PVDF membrane (A1). In addition, blending with PVDF-g-PSPMA and KClO4 also allowed the A3 membrane to exhibit uniform pore size distribution (PSD) and smooth surface structure, compared with PVDF membrane commercially available from company "M" in Germany. The aforementioned properties led to antifouling characteristics in the crack-free membrane (A3). According to flux performances, flux recovery and cumulative permeate volume (between 120 and 240 min) of crack-free membrane (A3) were 11.41 and 17.41% superior to those of commercial membrane, respectively.
ABSTRACT
Remarkable separation performance of olefin/paraffin mixtures was previously reported by facilitated olefin transport through silver-based polymer electrolyte membranes. The mechanism of facilitated olefin transport in solid membranes of AgCF3SO3 dissolved in poly(N-vinyl pyrrolidone) (PVP) is investigated. In silver polymer electrolyte membranes, only free anions are present up to the 2:1 mole ratio of [C=O]:[Ag], and ion pairs start to form at a ratio of 1:1, followed by higher-order ionic aggregates above a ratio of 1:2. At silver concentrations above 3:1, the propylene permeance increases almost linearly with the total silver concentration, unexpectedly, regardless of the silver ionic constituents. It was also found that all the silver constituents, including ion pairs and higher order ionic aggregates, were completely redissolved into free anions under the propylene environment; this suggests that propylene can be a good ligand for the silver cation. From these experimental findings, a new mechanism for the complexation reaction between propylenes and silver salts in silver-polymer electrolytes was proposed. The new mechanism is consistent with the linearity between the propylene permeance and the total silver concentration regardless of the kind of the silver constituents. Therefore, the facilitated propylene transport through silver-polymer electrolytes may be associated mainly with the silver cation weakly coordinated with both carbonyl oxygen atoms and propylene.
ABSTRACT
The most effective ligand among -OH, -O- and -CHO for facilitated olefin transport by silver ions in room temperature crosslinked poly(vinyl alcohol) membrane has been evaluated.