Effect of Ion-Pair Formation on Boron Adsorption by Kaolinite

Shas V. Mattigod, James A. Frampton and Chin H. Lim
Department of Soil and Environmental Sciences, University of California Riverside, California 92521

Abstract: Boron adsorption on 2-0.2-µm size fractions of kaolinite at 25° ± 2°C at pH values between 6.0 and 10.5 was studied. The kaolinite sample was pretreated to remove any surface oxide and hydroxide coatings. The initial concentrations of boron in solution ranged between 2 and 10 mg/liter with either KClO4 or Ca(ClO4)2 as background electrolyte at constant ionic strength of 0.09 ± 0.01 mole/liter. Boron speciation in equilibrium solutions was calculated by using the chemical equilibrium computer program GEOCHEM. The adsorption of boron on kaolinite in either medium showed similar dependence on pH and initial boron concentrations. Boron adsorption at higher pHs was noticeably higher in Ca(ClO4)2 medium as compared to KClO4 medium. These differences were attributed to the formation and adsorption of CaB(OH4)+ ion-pair species.

Key Words: Adsorption • Boron • Ion pair • Ion speciation • Kaolinite

Clays and Clay Minerals; October 1985 v. 33; no. 5; p. 433-437; DOI: 10.1346/CCMN.1985.0330509
© 1985, The Clay Minerals Society
Clay Minerals Society (www.clays.org)