SYNTHESIS OF LARGE-SWELLING Na-TYPE BENTONITE BY HYDROTHERMAL ION EXCHANGE

Abstract

Herein we synthesized Na-type bentonite by hydrothermal ion exchange from Ca-type bentonite. Ca²⁺ ions in the montmorillonite layer in bentonite were exchanged for H⁺ or Na⁺ ions by hydrothermal treatment using ion-exchanged water or NaCl aqueous solution, respectively. The swelling index of the resulting Na-type bentonite, treated with the NaCl aqueous solution, was in the range from 11.2 to 15.0 mL/2 g, close to that of Na-activated bentonite. Likewise, using aqueous Na₂CO₃ solution, Ca²⁺ ions in the montmorillonite layer in bentonite were exchanged for Na⁺ ions by hydrothermal treatment. The swelling index of the sample treated with aqueous Na₂CO₃ solution was in the range from 18.2 to 25.3 mL/2 g, as large as that in natural Na-type bentonite.