Comparison of transport of alkali halides and nitrates across asymmetric cellulose acetate and polyamide, composite poly(etherurea), and cation exchange membranes
✍ Scribed by Wolfgang Pusch
- Book ID
- 103059378
- Publisher
- Elsevier Science
- Year
- 1991
- Tongue
- English
- Weight
- 503 KB
- Volume
- 83
- Category
- Article
- ISSN
- 0011-9164
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✦ Synopsis
Using typical s ite poly(ether-urea 3" thetic membranes (asymmetric CA and polyamide, compos-, strong cation exchange membrane), hydrodynamic permeabilities, &,, normalized salt permeabilities, P$d, and asymptotic rejections, rm, for alkali chlorides and nitrates as well as for sodium halides were obtained from hyperfiltration experiments with 0.01 m and partially with 0.2 m brine solutions. Usin the measured transport parameters, partition coefficients, Ks, and diffusion co-2 cients, D,,, within the membranes were estimated. In general, the partition coefficients of the asymmetric CA membranes for the alkali chlorides increase in the following order CsCl < RbCl < KC1 N LiCl c NaCl whereas no such clear sequence exists with the alkali nitrates. On the other hand, the sequence is nearly reversed with the cation exchange membrane. The normalized salt permeabilities, Ps/d (d = effective membrane thickness), of sodium salts increase in the order Cl-< Nor-< Br-< I-for all membranes except the CK-1 membrane which exhibits a reversed sequence. Moreover, varying the cation or anion, respectively, the normalized salt permeabilities of the CK-1 membrane vary according to Walden's rule A. n = const. .T (A = equivalent conductivity, 7 = viscosity, T = absolute temperature). It is tried to correlate the variations of the cation and anion partition coefilcients, Ks = Kc0 =_l -ropr as well as of the normalized permeabilities, PJd, with the Gibbs free energy of hydration of the alkali ions, AGkr