Effect of ionic strength on swelling and the exchange of alkaline earth cations in soil organic matter
Abstract
We studied the equilibrium specificity of 33% neutralized Ca- and Ba-peat (CaP-33 and BaP-33) for Ca2+ and Ba2+ at three different ionic strength levels (I = 0.0040, 0.0082, and 0.0150) by batch equilibration ion exchange experiments. Volume swelling using the pycnometer method and water adsorption of H- and Ba-form peat samples at the three ionic strength levels were also determined. Preference for Ba2+ over Ca2+ in both CaP-33 and BaP-33 decreased with ionic strength until a reversal in preference (Ca2+ over Ba2+) was observed at the highest ionic strength level. The Vanselow selectivity coefficients remained constant with surface composition, and they were similar in both CaP-33 and BaP-33, indicating that the exchange reaction is reversible. The least swollen form was H-peat, and Ca-peat showed slightly less swelling than Ba-peat. A decrease in volume swelling and water adsorption was observed as ionic strength increased, the decrease being greater for CaP-33 than for BaP-33. These phenomena were explained in terms of increasing association of Ca2+ with the carboxylate sites in peat. Increasing association results from a decrease in the average dimension of the exchanger as well as a decreasing dielectric constant as the internal solution becomes more concentrated with increasing ionic strength. © 1988 The Williams and Wilkins.
Source or Periodical Title
Soil Science
ISSN
0038075X
Page
67-72
Document Type
Article
Recommended Citation
Baes, A. U. and Bloom, P. R., "Effect of ionic strength on swelling and the exchange of alkaline earth cations in soil organic matter" (2021). Journal Article. 3722.
https://www.ukdr.uplb.edu.ph/journal-articles/3722