The Nature of Free and Bound Water in Water and Solute Permeation of Cellulose Acetate Membranes in Reverse Osmosis

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  • OGAWA Yoshihiro
    Department of Chemistry, Faculty of Science, Science University of Tokyo
  • SUZUKI Sho
    Department of Chemistry, Faculty of Science, Science University of Tokyo

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Other Title
  • 逆浸透法酢酸セルロース膜における溶質および水の膜透過におよぼす自由水と結合水の性質
  • ギャクシントウホウ サクサン セルロース マク ニ オケル ヨウシツ オヨビ

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Abstract

Cellulose acetate membranes were prepared from several Manjikian type casting solutions by changing the ratio of weight percent of formamide (F) to cellulose acetate (CA), that is, F/CA-value from 0.74 to 2.94. For these membranes, their transport coefficients (Lp, σ, and P) in Spiegler-Kedem equation and coupling coefficient Lpπ were obtained by reverse osmosis experiment. The free and bound water content in these membranes were investigated by means of differential scanning calorimetry.<BR>An attempt was made to obtain the correlation between both the free and bound water content and the phenomenological coefficients (Lp and Lpπ). The Lp and (-Lpπ) can be represented in terms of the external velocity of water (υw/ΔP) and the velocity of solute relative to that of water (υw-υs)/ΔP, per unit pressure, respectively, as reported by Katchalsky and Curran.<BR>It was stated that the coupling coefficient (-Lpπ)=(υw-υs)/ΔP was concerned with the bound water content, and the hydraulic permeability Lp=(υw/ΔP), also with the bound water content so far as 2 of F/CA-value, but above 2, the Lp, with the free water content.<BR>In the range (F/CA-value<2) that the role of bound water take spart in water permeation, the increase of the bound water content gave little effect on the solute permeation, but in the range (F/CA-value>2) that the role of free water does part in water permeation, the amount of solute permeation through the membranes increased steeply.

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