Synthesis and characterization of Al−Cr-pillared montmorillonite with high thermal stability and adsorption capacity

Abstract

Al−Cr-pillared montmorillonite was synthesized by using bentonite and Al−Cr pillaring solutions as starting materials. The basal spacing and specific surface areas of the materials were significantly increased relative to those of untreated clays. When the Al/Cr molar ratio (R) was 0.10, the d(001) value and specific surface area of pillared montmorillonite were 1.9194 nm and 165.7 m²g⁻¹, respectively. Thermal stability of the materials was determined using calcined tests and X-ray diffraction (XRD) analysis. The materials formed at different R(0.05;0.10;0.15;0.25) exhibit a high thermal stability at 300°C, especially at initial R=0.10, the basal interlayer spacing of materials is stabilized at 1.7313 nm after calcined at 500°C for 2 h. Adsorption behavior of the materials was studied by adsorption experiments. The results show that the Al−Cr-pillared montmorillonites exhibit much stronger adsorption capacity on Cr⁶⁺ in aqueous solution than untreated clays do.