Ca-K-Na exchange equilibria on a smectitic soil

Modeling the variation of selectivity coefficient

Shin-Ichiro Wada, Hiroshi Seki

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

We conducted binary and ternary cation exchange experiments on a smectitic soil and calculated the Vanselow selectivity coefficients. The values of the natural logarithm of the Vanselow selectivity coefficient for Ca→Mg exchange, In cKMg/Ca, slightly scattered around an average of −0.553. The values of In cKK/Caand In cKNa/Cain respective binary systems, on the other hand, significantly varied as the mole fraction of K in the exchanger phase increased. In the Ca-K-Na ternary system, cKK/Cavaried in quite a similar manner as in the binary system whereas In cKK/Cabehaved differently. Based on these observations, we modeled the variation of the selectivity coefficients using the data from ternary exchange experiments. The obtained equations are: In cKK/Ca=−4.271.NK,+4.220, In cKNa/K=2.417.NK,−2.742, and In cKK/Ca−In cKNa/Ca+ 2ln cKNa/K= 0, where NKis the mole fraction of K in the exchanger phase.

Original languageEnglish
Pages (from-to)629-636
Number of pages8
JournalSoil Science and Plant Nutrition
Volume40
Issue number4
DOIs
Publication statusPublished - Jan 1 1994

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smectitic soils
cation exchange
modeling
ion exchange
soil
experiment

All Science Journal Classification (ASJC) codes

  • Soil Science
  • Plant Science

Cite this

Ca-K-Na exchange equilibria on a smectitic soil : Modeling the variation of selectivity coefficient. / Wada, Shin-Ichiro; Seki, Hiroshi.

In: Soil Science and Plant Nutrition, Vol. 40, No. 4, 01.01.1994, p. 629-636.

Research output: Contribution to journalArticle

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abstract = "We conducted binary and ternary cation exchange experiments on a smectitic soil and calculated the Vanselow selectivity coefficients. The values of the natural logarithm of the Vanselow selectivity coefficient for Ca→Mg exchange, In cKMg/Ca, slightly scattered around an average of −0.553. The values of In cKK/Caand In cKNa/Cain respective binary systems, on the other hand, significantly varied as the mole fraction of K in the exchanger phase increased. In the Ca-K-Na ternary system, cKK/Cavaried in quite a similar manner as in the binary system whereas In cKK/Cabehaved differently. Based on these observations, we modeled the variation of the selectivity coefficients using the data from ternary exchange experiments. The obtained equations are: In cKK/Ca=−4.271.NK,+4.220, In cKNa/K=2.417.NK,−2.742, and In cKK/Ca−In cKNa/Ca+ 2ln cKNa/K= 0, where NKis the mole fraction of K in the exchanger phase.",
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N2 - We conducted binary and ternary cation exchange experiments on a smectitic soil and calculated the Vanselow selectivity coefficients. The values of the natural logarithm of the Vanselow selectivity coefficient for Ca→Mg exchange, In cKMg/Ca, slightly scattered around an average of −0.553. The values of In cKK/Caand In cKNa/Cain respective binary systems, on the other hand, significantly varied as the mole fraction of K in the exchanger phase increased. In the Ca-K-Na ternary system, cKK/Cavaried in quite a similar manner as in the binary system whereas In cKK/Cabehaved differently. Based on these observations, we modeled the variation of the selectivity coefficients using the data from ternary exchange experiments. The obtained equations are: In cKK/Ca=−4.271.NK,+4.220, In cKNa/K=2.417.NK,−2.742, and In cKK/Ca−In cKNa/Ca+ 2ln cKNa/K= 0, where NKis the mole fraction of K in the exchanger phase.

AB - We conducted binary and ternary cation exchange experiments on a smectitic soil and calculated the Vanselow selectivity coefficients. The values of the natural logarithm of the Vanselow selectivity coefficient for Ca→Mg exchange, In cKMg/Ca, slightly scattered around an average of −0.553. The values of In cKK/Caand In cKNa/Cain respective binary systems, on the other hand, significantly varied as the mole fraction of K in the exchanger phase increased. In the Ca-K-Na ternary system, cKK/Cavaried in quite a similar manner as in the binary system whereas In cKK/Cabehaved differently. Based on these observations, we modeled the variation of the selectivity coefficients using the data from ternary exchange experiments. The obtained equations are: In cKK/Ca=−4.271.NK,+4.220, In cKNa/K=2.417.NK,−2.742, and In cKK/Ca−In cKNa/Ca+ 2ln cKNa/K= 0, where NKis the mole fraction of K in the exchanger phase.

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