Abstract:

The purified montmorillonite with trace amounts of quartz was subjected to different concentration chromium sulphate
solutions for one week cation exchange. The obtained chromium bearing montmorillonites were verified and tested using powder X-ray
diffractometry (XRD), X-ray Flourence (XRF), Electron Spin Resonance (ESR) spectrometry and Frourie Transforming Infrar (FTIR) to
explore the occupation site of chromium. The results suggested that the Cr3 + exchanged some of the cations in octahedral or minor
cations in tetrahedral sites, such as Mn2+, Al3+ in octahedrons and Al3+ and Fe3+ in tetrahedrons, as well as the cations in the interlayer
space of montmorillonite, such as Ca2+, K+ and Na+ etc. Furthermore, based on the XRD analyses, two types of montmorillonites with
different kinds of hydration cations were present in the 0.2 mol/L chromium sulphate solutions. The hydration cations were [Cr(H2O)6]3+
and [Cr(H2O)3O3]3+, respectively. The species of hydration cation were constrained by the concentration of the chromium solution.

Key words: chromium montmorillonite；cation occupation, spectroscopical analysis