Intercalation of Hydroxy‐Aluminosilicate and Hydroxy‐Aluminum in Montmorillonite and Resultant Physicochemical Properties

<jats:title>Abstract</jats:title> <jats:p>Both hydroxy‐aluminosilicate (HAS) and hydroxy‐Al (HyA) ions can be adsorbed into the interlayer spaces of montmorillonite (Mt), resulting in an expanded structure; however, the differences in the adsorption and the surface properties of the intercalated clay complexes still remain to be established. The objective of this study was to investigate the influences of the coexistence of silicic acid with HyA ions on the formation and surface properties of the HAS‐Mt complexes, in comparison with the HyA‐Mt complex and Mt. Most of the intercalation reactions of HAS and HyA ions by Mt came to apparent completion within 10 min. Compared with the original Mt, the HyA‐Mt complex had more external specific surface, pore area, and pore volume, and less internal specific surface; the HAS‐Mt complex had less external and internal specific surface, pore area and pore volume. The transmission electron micrographs and the analysis of the particle‐size distribution by small‐angle x‐ray scattering indicated that both HyA‐Mt and HAS‐Mt complexes formed domains of clay particles associated into larger particles. The HAS‐Mt complex exhibited a higher point of zero salt effect (PZSE) value than the HyA‐Mt complex. The pH‐dependent cation‐exchange (CEC) value was greater in the HAS‐Mt complex than in the HyA‐Mt complex; therefore, the variable charge in the former was more dominant than in the latter. The surface chemistry of HAS‐ and HyA‐intercalated clay complexes pertaining to dynamics of nutrients and pollutants in various pedogenic environments merits close attention.</jats:p>