Hungarian journal of industrial chemistry, 1985
Vassányi, I. et al.: Examination of Changes in Phase and Chemical Composition of Pyrophyllite-lTc on Chlorination
HUNGARIAN JOURNAL OP INDUSTRIAL CHEMISTRY VESZPRÉM Vol. 13. pp. 1-10 (1985) EXAMINATION OF CHANGES IN PHASE AND CHEMICAL COMPOSITION OF P Y ROPH YLLITE - ITc ON CHLORINATION I. Vassányi, S. Szabó, Mrs. Zs. Csikós, and R. Jelinkó* (Department of Mineralogy, Veszprém University of Chemical Engineering, Veszprém, Hungary, and *Research Institute of Technical Chemistry of the Hungarian Academy of Sciecnce, Veszprém, Hungary) Received: April 20, 1984. Phase and chemical changes of pyrophyllite-lTc resulting from heat treatments at 873, 973, 1123 and 1273 К in a CO/CI2 atmosphere were determined. Three models were established for the structures of the solid chlorination residues. According to the most likely models, the chlorination residues of pyrophyllite-lTc are mixtures of dehydroxylated pyrophyllite having vacancies and amorphous SÍO2. Introduction Since our knowledge about the kaolinite-chlorine reaction has in effect increased [1,2] the examination of other minerals with layer silicate structure has become necessary. This paper deals with the chlorination of pyrophyllite [Si4Al2O10(OH)2] of the layer silicates. Description of sample Pyrophyllite used in the experiments was from a Hungarian deposit at Pázmánd. The material originally contained a major amount of contamination from haematite (a-Fe203), geothite (<x-FeOOH), alunite [KA13(0H)6(S04)2] quartz (a-quartz, Si02) and rutile (Ti02), and a minor amount of anatase (Ti02). After decomposition much of the quartz, haematite, goethite and almost all the titanium dioxide had been removed. Residue of quartz had been dissolved with HF, the alunite with NaOH and the ferrous phases with HC1. The pyrophyllite so cleaned contained only a very small amount of alunite. Triclinic and monoclinic pyrophyllite is known [3, 4, 5, 6]. On the basis of X-ray diffraction examinations (Figure 1 ) the pyrophyllite from Pázmánd has proved to be tricUnic-lTc. Its chemical composition (Table 2) and the stoichiometric formula calculated from it [7] allow the assumption to be made of an almost ideal pyrophyllite structure.