Bentonite is widely used in various branches of industry due to its special properties like low hydraulic conductivity, high sorption capacity, low permeability. High temperature stability of bentonite determines its usefulness for industrial applications. The thermal stability of the bentonite from Lower Silesia region (Wilków, Pogórze Kaczawskie, SW Poland) has been tested at various temperatures between 100oC and 800oC. Raw bentonite sample contained montmorillonite (47%), magnesioferrite (30%), orthoclaste (11%) and goethite (8%). Decomposition of bentonite at high temperatures was followed by Mössbauer spectroscopy investigations. The changes in the Mössbauer spectra well reflected various phases of decomposition and transformation, because Fe-bearing minerals make up the majority (89%) in all present phases of the investigated bentonite. At a temperature of 400oC the process of dehydroxylation of montmorillonite started, and continued up to 700oC. The recrystallization of montmorillonite to illite was observed in a temperature above 700oC. In a temperature range from 400oC to 500oC conversion of goethite to hematite took place. Mössbauer spectrum obtained after heating at 800oC showed hematite as the main iron oxide phase with approximately the same relative ratio of iron oxides and hydroxides as in the starting material.Keywords: Bentonite, high temperature affects, Mössbauer spectroscopy, Febearing minerals
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