Specifying the structural formula of kaolinite from the Orenburg Region by means of spectroscopic methods

Kaolinite certification is necessary when using it as a raw material in the ceramic industry. The kaolin clay deposit discovered in the Orenburg Region in 2018 is presumably the largest in the country. Within the Koskolskaya area, 5 mineral deposits have been described. Three of them are particularly promising deposits of high-quality kaolin clay. Previously, studies of the technological and physical characteristics of clay from this deposit were carried out. The purpose of our study was to derive and specify the structural formula of kaolinite contained in the clays. After elutriation and grinding in a ball mill, natural clay was sifted through a sieve with meshes of 40 μm. The conducted IR, Raman, and EPR spectroscopy, as well as DTA allowed us to monitor the process of metakaolinisation, which occurs as a result of dehydration of kaolinite (i.e. the process of transformation of kaolinite into metakaolinite). Spectroscopic methods made it possible to analyse the parameters of the fine structure, in particular, the degree of crystallinity of kaolinite particles and the occurrence of iron and magnesium ions in hydroxyl sheets. Conducting a series of experiments, we managed to specify the structural formula of the kaolinite of the Koskolsky deposit of the Orenburg region: K,Na,Ca,Ba Al Fe ,Fe Mg Mn,Cr 0.16 3.62 3+ 2+ 0.11 0.27 0.01 Si Ti O OH 3.86 0.14 10 8. The square brackets indicate the cationic compositions of the hydroxyl and siloxane sheets that formed the surface charge of the mineral particles. Compensator ions remain outside the square brackets. Thus, in our study we assessed the substance used as a raw material in the ceramic industry and determined the role of elutriation and mechanical treatment of kaolin clay