Mineralogical characterisation and surface properties of sepiolite from Polatli (Turkey)

Sepiolite is one of the most important industrial minerals, due primarily to its surface properties related to its structure. Sepiolite contains alternating 2:1 polysomes that produce tunnels at the inner part of the fibre and channels at the edge of the fibre. Sepiolite is a mineral with notably wide variations in the crystal-chemistry, crystallinity and texture, depending on the formation conditions, which results in highly different characteristics and properties. In this work, six sepiolite samples from the Polatli area (Turkey) are studied, comparing their mineralogical and textural features. The mineralogical composition of the samples is similar: carbonates constitute the main impurities, dolomite appears in all samples studied in different proportions, and small amounts of calcite, quartz and palygorskite have been identified. There is a variation in almost all the reflections of sepiolite, the 110 d-spacing ranges between 12.31 angstrom and 12.05 angstrom, this variation is related to the crystal-chemistry of the mineral. The impurities are clearly identified in the IR spectra, in which in addition to the carbonates the presence of the palygorskite polysomes is also detected by the band located at similar to 3620 cm(-1). The differences in the surface properties found in this study (specific surface area between 122 m(2) g(-1) and 376 m(2) g(-1) and microporous area between 55 m(2) g(-1) and 168 m(2) g(-1)) cannot be related only with the content in impurities, but with the texture and the possible presence of intergrowths. (C) 2016 Elsevier B.V. All rights reserved.