Water Permselective Membrane Research Articles

Relationship between permselectivity and permeability in pervaporation of water/alcohol mixture

The evaporation mechanism of a water/alcohol mixture with a polymeric membrane was investigated. Flory-Huggins thermodynamics was adopted to introduce the selective dissolution factor, R. It was shown that the value of R of a water permselective membrane increases as permeability decreases, and that it has no upper limit. For an ethanol permselective membrane, R has a maximum value at a certain value of the swelling ratio. Making some assumptions for R, a semi-quantitative relationship between permselectivity and permeability, J, was derived for a water permselective membrane and examined experimentally. When the swelling ratio is changed, it can be said that selectivity is proportional to J 1−( 1 s ) depending on s, the molecular volume ratio of water to alcohol.

Attachment of Membrane Separator for Removal of Radon to Ionization Chamber Installed for Tritium Stack Monitor

The effect of background counts induced by α-particles mainly from Rn in air was removed by the attachment of a water-permselective membrane separator to a tritium stack monitor equipped previously. Water vapor, after permeating the membrane selectively, was carried by N2 gas into an ionization chamber where the activity of tritium was measured. The consumption of N2 gas for carrier was reduced by recycling the gas through dehumidification processes; (1) condensation by pressure, (2) condensation by refrigeration and (3) adsorption (by adsorbents), so that there is no added daily work arising from the attachment for maintenance of the tritium monitor.

Attachment of membrane separator for removal of radon to ionization chamber installed for tritium stack monitor.

The effect of background counts induced by α-particles mainly from Rn in air was removed by the attachment of a water-permselective membrane separator to a tritium stack monitor equipped previously. Water vapor, after permeating the membrane selectively, was carried by N2 gas into an ionization chamber where the activity of tritium was measured. The consumption of N2 gas for carrier was reduced by recycling the gas through dehumidification processes; (1) condensation by pressure, (2) condensation by refrigeration and (3) adsorption (by adsorbents), so that there is no added daily work arising from the attachment for maintenance of the tritium monitor.

Selective separation of water from water–ethanol solution through quarternized poly(4‐vinylpyridine‐co‐acrylonitrile) membranes by pervaporation technique

AbstractPolymer membranes having cationic charge site, poly(1‐alkyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (alkyl: methyl, butyl, or octyl) were prepared in terms of coulombic interaction for separation of water–ethanol mixtures. The incorporation of cationic charge site into the membrane led to improve not only separation factors (selectivity toward water) but also flux number in the separation of aqueous ethanol solution by pervaporation technique. Target values, which were requested to have from the viewpoint of industrial utilization for separation of aqueous ethanol solution were attained as follows: separation factor toward water over 50 and flux value over 500 g m−2 h−1, through poly(1‐methyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (membrane 3) (quarternized fraction of pyridinium moiety, 89.5%; mol fraction of pyridinium moiety, 0.034) and poly(1‐butyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (membrane 5) (quarternized fraction, 100%; mol fraction of pyridinium moiety, 0.038). It was found that the introduction of cationic charge site into the membrane was one of feasible methods to obtain suitable membranes for water permselective membranes in the separation of water–ethanol mixtures.