Influence of the Fe³⁺–for – Al³⁺Octahedral Substitutions on the IR Spectra of Montmorillonite Minerals

Abstract

Abstract The influence of octahedral replacement of Al3+ by Fe3+ on the infrared spectra of montmorillonites in the domain of OH vibrations is presented. The obtained results suggest that in the domain of OH-bending vibration, the absorption band from 870 cm−1 (Al3+ -OH-Fe3+) can not be detected in the spectra of montmorillonites when the octahedral Fe3+ content is below 0.10-0.15 (per half unit cell) In the domain of OH-stretchtng, the increasing Fe3+ -for-Al3+ substitution in the dioctahedral series of smectites causes a continous shift of the absorption band ascribed to M3+ - OH - M3+ vibrations to lower frequencies.