Clays and Clay Minerals, Vol. 56, No. 5, 511–519, 2008.
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Authors
Onal, Muserref
Yilmaz, Hamza
Sarikaya, Yuksel
Issue Date
2008
Type
Article
Language
Keywords
Periodicals , Geology , Porosity , Sepiolite , Surface Area , Thermal Analysis , X-ray Diffraction
Alternative Title
Some Physicochemical Properties Of The White Sepiolite Known As Pipestone From Eskisehir, Turkey
Abstract
Various physicochemical characteristics of a sepiolite sample from the Eskisehir area, Turkey, were investigated to help in making predictions about possible uses of the material. The sample was examined by chemical analysis (CA), thermal analysis (DTA/TGA), X-ray diffraction (XRD) analysis, particle-size analysis (PSA), linear dilatometry (LD), scanning electron microscopy (SEM), mercury porosimetry (Hg-Por.), and low-temperature nitrogen adsorption/desorption (N2-AD) techniques. The CA and XRD data indicated that the sepiolite contains only 6% dolomite by mass. The XRD patterns showed that sepiolite anhydride, enstatite, diopside, and opal-CT form upon heating the sepiolite above 600, 800, 900, and 1200ºC, respectively. The maximum rate of endothermic changes in the DTA and TGA curves were observed at 82, 287, and 491ºC, corresponding to the loss of external, zeolitic, and bound water from the sepiolite, respectively. Dehydroxylation and recrystallization of the sepiolite were fastest at 845ºC and 862ºC, respectively. The LD curve indicated that the shrinkage began at 800ºC and reached 4.0% at 1000ºC. The proportion of particles with diameters of <2 mm, and the external surface area of the long-term (24 h) water-treated sepiolite were determined by PSA as 79% by volume, and 8 m2g-1, respectively. The SEM view revealed discrete bundles of sepiolite fibers of various lengths. The specific surface area found from adsorption data was 316 m2g-1. The specific micro-, meso-, macro-, and total-pore volumes obtained from the combination of Hg-Por. and N2-AD results were 0.16, 0.21, 0.45, and 0.82 cm3g-1, respectively. The average macropore and micro-mesopore radii in the sepiolite were estimated (using the Hg-Por. and N2-AD data) tobe 35 and 2.4 nm, respectively.
Description
gsccm56504-ona.pdf - 435KB
Citation
Clays and Clay Minerals, Vol. 56, No. 5, 511–519, 2008.
Publisher
The Clay Minerals Society
License
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