Characterisation of the hydroxy-interlayered vermiculite from the weathering of illite in Jiujiang red earth sediments

Abstract

The clay mineralogy and formation of hydroxy-interlayered vermiculite (HIV) in the Jiujiang red earth sediments were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and inductively coupled plasma-atomic emission spectrometer (ICP-AES) analyses. The 1.4-nm peak of HIV did not change after Mg2+ saturation and glycol solvation, but it exhibited partial collapse to 1.0 nm after K+ saturation followed by heat treatment at successively higher temperatures. HIV was also characterised by FTIR adsorption bands at ~3485 cm–1 and ~3415 cm–1, which did not change with increasing temperature. DSC analysis revealed that the dehydroxylation of hydroxides in the interlayer of HIV began at ~400°C, and a further dehydroxylation was confirmed by the XRD of the sample heated to ~600°C. The ICP-AES analysis of sodium citrate extracts showed that the Al concentration was higher than that of Fe, indicating that the Al was probably present as hydroxy-Al in the interlayer of HIV. The presence of hydroxy-Al polymers in the interlayer influenced both expandability and thermal properties of HIV clays from Jiujiang red earth sediments.