Effect of Exchangeable Ions and Ionic Strength on Boron Adsorption by Montmorillonite and Illite1

R. Keren and G. A. O'Connor
Institute of Soils and Water, Agricultural Research Organization The Volcani Center, Bet Dagan, Israel
Department of Agronomy, New Mexico State University Las Cruces, New Mexico 88003
1 Journal article 856, Agricultural Experiment Station, New Mexico State University, Las Cruces, New Mexico 88003.

Abstract: The effects of exchangeable Na and Ca and the ionic strength of NaCl and CaCl2 solutions on the boron adsorption by the Na and Ca forms of montmorillonite and illite at pH 9 were studied. The boron adsorption by montmorillonite was greater for the Ca form than for the Na form at any boron activity in solution and at any ionic strength. For example, the amount of boron adsorbed by Na- and Ca-montmorillonite was 2.9 and 4.3 µmole/g, respectively, at an ionic strength of 0.36 and a boron activity of 0.875 mmole/liter in equilibrium solution. The boron adsorption by illite was much greater than by montmorillonite. For example, the amount of boron adsorbed by Na-montmorillonite and Na-illite was 1.5 and 8.7 µmole/g, respectively, at an ionic strength of 0.02 and a boron activity of 0.5 mmole/liter. However, the nature of the exchangeable cation had little effect on the boron adsorption by illite. The effect of the ionic strength on the boron adsorption by Na-montmorillonite was greater than that observed for either Ca-montmorillonite or illite. The data suggest that the negative electric field around the clay particles is one of the main factors controlling boron adsorption at alkaline pHs.

Key Words: Adsorption • Boron • Cation exchange • Illite • Ionic strength • Montmorillonite

Clays and Clay Minerals; October 1982 v. 30; no. 5; p. 341-346; DOI: 10.1346/CCMN.1982.0300504
© 1982, The Clay Minerals Society
Clay Minerals Society (www.clays.org)