Abstract:
Partial stabilization of Fe(II) in chemically reduced smectite, which normally readily under- goes reoxidation in air, was achieved. The purpose of this study was to determine if Fe(II) can be stabilized in reduced smectites by Li fixation upon heating. More than 80% of total Fe in ferruginous smectite SWa- 1 was reduced to Fe(II) using the citrate-bicarbonate-dithionite (CBD) method while purging the clay dispersion with N2. The reduced smectite was Li-saturated, washed free of excess ions, freeze-dried, and heated in N 2 atmosphere at 260~ for 24 h to produce Li-fixation. This treatment caused partial stabili- zation of Fe(II) in the clay structure. Chemical analysis, M6ssbauer spectroscopy, and Fourier transform infrared (FTIR) spectroscopy proved that >20% of total Fe was Fe(II) after reoxidation with oxygen in a water dispersion, a treatment which causes complete reoxidation of Fe(II) in reduced Na-smectites. Decomposition of the OH-stretching band evident in the IR spectra indicated migration of Li into the vacant octahedra. Some of the OH groups in the reoxidized smectite were found in local trioctahedral configurations, associated with the A1Fe(II)Li or Fe(III)Fe(II)Li groupings of central atoms in the octa- hedral sheet.
