Co-Authors:
Yariv, S., Department of Inorganic and Analytical Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
Ovadyahu, D., Department of Inorganic and Analytical Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
Nasser, A., Department of Inorganic and Analytical Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
Shuali, U., Israel Institute for Biological Research, Ness-Ziona, 70450, Israel
Lahav, N., The Seagram Centre for Soils and Water Research, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, 76100, Israel
Abstract:
The dehydration of laponite and montmorillonite treated with tributylammonium chloride was studied by DSC, TG and X-ray diffraction. Dehydration of the organo-laponite took place in one stage at 320-475 K, whereas that of the organo-montmorillonite occurred in two stages, at 320-435 and 435-485 K. The first stage was attributed to loss of water of the hydrophobic hydration zone. The second stage was specific for montmorillonite and was attributed to water molecules forming hydrogen bonds with the oxygen planes of the silicate layers. Hydrogen bond formation was attributed to the tetrahedral substitution of Al for Si. The organo-laponite has a lower molar heat of dehydration than laponite, indicating that the interlayer water clusters of the organo-clay are smaller than those of the untreated clay. The molar heat of dehydration of untreated montmorillonite is less than that of untreated laponite, indicating that water clusters in the interlayer of the former are smaller. The molar heat of dehydration of organo-montmorillonite is higher at the second dehydration stage than at the first, because at this stage water molecules which form hydrogen bonds with atoms from the oxygen plane are evolved. In organo-montmorillonite, water molecules from the non-structured zone form water bridges between adjacent oxygen planes, thus preventing crystalline swelling. In organo-laponite, non-structured water molecules do not form strong hydrogen bonds with atoms from the oxygen plane, water bridges between adjacent oxygen planes are weak, and crystalline swelling is thus prevented to a limited extent only. © 1992.
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