Mössbauer studies of illites and heat-treated illite as related to coal-conversion processes

• Published in: Fuel (Guildford) 1980-01, Vol.59 (11), p.767-771
• Main Authors: Saporoschenko, Mykola, Twardowska, Helena, Smith, Gerald V., Hinckley, Conrad C., Shiley, Richard H., White, W.Arthur
• Format: Article
• Language: English
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(80)90252-5

Mossbauer spectra of iron species in the following illites were studied: Grundite, Fithian, Minerva, and New Albany. Spectra of samples of Fithian illite heated at temperatures of 225, 700, and 1000 °C were also obtained. Analyses of these spectra provide Mössbauer parameter values of iron species in the illites and heat-transformed illite for comparison with similar species found in coals containing illites and in coal process residues derived from them. The illites contain both ferric and ferrous species. Mössbauer parameters for one of the ferric species, designated M(2), are virtually the same as those of pyrite. The two species are therefore difficult to distinguish from one another. Values of the concentration of pyrite in coals and shales may be inflated if the pyrite concentration is measured by Mössbauer spectroscopy. Mössbauer spectra of the heat-treated illite samples reveal changes in iron distribution, principally at the 700 and 1000 °C levels, where there are found three and six different iron species respectively. These changes are accompanied by reduction of ferric to ferrous iron. This process should be integrated into any assessment of the iron chemistry which accompanies coal-conversion processes.