Interlayer Adsorption of Polymeric Hydroxy‐Aluminosilicate Ions by Montmorillonite

Abstract

AbstractAdsorption of polymeric hydroxy‐aluminosilicate (HAS) ions by montmorillonite and the formation of siliceous Al interlayers were studied. The interaction of HAS ions with Ca‐montmorillonite exhibited a linear C‐type adsorption isotherm within the range of solution Al and Si levels commonly found in acidic soils (10−5 to 10−4 M), suggesting a high capacity of Ca‐montmorillonite to adsorb HAS ions from solution. A soluble Si concentration of >6.6 × 10−5 M was required for the formation of HAS species and their adsorption by montmorillonite. The interlayer spacing (12.2–16.8 Å at 25°C and air dried) and the intensity of the major infrared bands of the adsorbed HAS ions (940 and 3500 cm−1) in the HAS‐montmorillonite complexes were found to increase with the increasing amount of HAS ions adsorbed, which further substantiated the interlayer adsorption mechanism for HAS‐smectite interactions. The partial interlayering of HAS ions in Ca‐montmorillonite resulted in the formation of HAS‐clay complexes with basal spacings of ≈12Å (at 25°C, air dried). The data suggest that the partial hydroxy‐interlayers of natural clays in acidic environments in temperate and subtropical regions may be siliceous in nature, depending on the Si level in soil solutions and other natural waters.