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S. Krehula, M. Ristic, M. Reissner, C. Frandsen, S. Music:
"57Fe Mössbauer Spectroscopy Analysis of Fe-Bearing Phases in the Manufacture of TiO2 Pigment";
Poster: Mediterranean Conference on the Applications of the Mössbauer Effect MECAME2016, Cavtat, Croatia; 31.05.2016 - 03.06.2016.

TiO2 white pigment [1] has found important applications in catalysis, printing inks, plastics, papers, solar cells and pharmaceuticals. In the manufacture of TiO2 pigments two technologies are used. Ilmenite ore is used in the production of TiO2pigment by sulphate process, whereas rutile ore is used in the production of TiO2 pigment by chloride process. In the present work the possibilities of Mössbauer spectroscopy in analysis of Fe-bearing phases which appear in the manufacture of TiO2 pigment by sulphate process will be shown and discussed. XRD, FE-SEM/EDS and magnetometry were also used as supporting techniques. Ilmenite ore from Australia used in the manufacture of TiO2 pigment (Cinkarna, Celje, Slovenia) is analyzed. In this technology it is very important to know the Fe2+/Fe3+ ratio in ilmenite ore [2,3]. Generally, ilmenite can be associated with other minerals, such as hematite, magnetite, rutile, fayalite, zircon, quartz and various aluminosilicates [1]. Mössbauer spectra of ilmenite ore were recorded from RT to liquid He temperature. The changes in the Mössbauer spectra, as well as corresponding magnetometric measurements were discussed. In the manufacture of TiO2 by sulphate process a significant amount of copperas (FeSO4·7H2O) crystallizes as a by-product. In the technology mentioned copperas is calcined with the aim to produce H2SO4 acid which is returning to the process of ilmenite ore digestion. The RT Mössbauer spectrum of calcined copperas showed the superposition of one sextet corresponding to hematite and one central quadrupole doublet of small relative intensity. However, the Mössbauer spectrum of the magnetic fraction separated from calcined copperas with permanent magnet also showed the presence of substoichiometric magnetite (Fe3-xO4). Sulphur detected by EDS analysis of calcined copperas was a result of incomplete oxidation of copperas. Copperas produced as a by-product undergoes oxidation at ambient conditions and this can be lso monitored by Mössbauer spectroscopy. Copperas can be utilized in the manufacture of yellow pigment (α-FeOOH) with the aim to optimize the cost of TiO2 pigment production.