High-performances membranes for pervaporation I. Poly(vinyl alcohol)–poly(N-vinyl pyrrolidone) blends |
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Authors: | Quang-Trong Nguyen Zhenghua Ping Jean Nel |
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Institution: | Quang-Trong Nguyen,Zhenghua Ping,Jean Néel |
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Abstract: | Dense membranes were prepared from poly(vinyl alcohol)–poly(N-vinyl pyrrolidone) (PVA–PVP) blends of different compositions and studied in swelling and dehydration by pervaporation of three organic solvents contaminated by 5 wt% water. The swelling generally increases with the PVP content. No extraction occurs in water–tetrahydrofuran (THF) and water–methyl ethyl ketone (MEK) mixtures. In ethanol containing 10 wt% of water, there is no extraction for blends containing less than 40 wt% PVP and an increasing extraction beyond this PVP content. The pervaporation flux of the water–ethanol mixture increases drastically at the same threshold whereas the water permselectivity falls to a low level. The values of the diffusion and permeability coefficients determined from transient permeation of the test water–ethanol mixture exhibit a similar sudden increase at the same PVP content threshold. This singular behavior of the blend membranes is interpreted by a strong affinity of the PVP component to ethanol, combined with a disappearance of crystallites in the blend at this threshold. Consequently the amorphous membrane can swell freely according to the affinity of the PVP component, leading to the observed behavior. |
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Keywords: | Poly(vinyl alcohol) Poly(N-vinyl pyrrolidone) Blend Pervaporation Diffusion coefficient Organic solvent dehydration |
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