X-RAY DIFFRACTION AND ADSORPTION ISOTHERM STUDIES OF THE CALCIUM MONTMORILLONITE-WATER SYSTEM

ADSORPTION ISOTHERM AND X-RAY DIFFRACTION TECHNIQUES WERE USED TO STUDY THE ADSORPTION OF WATER ON A HOMOIONIC CALCIUM MONTMORILLONITE AT 25 C. THE BASAL D SPACINGS OF THE PRIMARY AND SECONDARY REFLECTIONS, THEIR INTENSITIES AND LINE BREADTH VARIATIONS WERE DETERMINED IN A SPECIALLY CONSTRUCTED X-RAY ADSORPTION CHAMBER. THE FIRST-ORDER BASAL SPACING WAS FOUND TO CHANGE IN A CONTINUOUS BUT NONUNIFORM MANNER. THE INTENSITY OF SECONDARY REFLECTIONS WAS EXPLAINED ON THE BASIS OF LAYER ELECTRON DENSITY DISTRIBUTION. A COMPARISON OF THE LINE BREADTH, INTENSITY AND ADSORPTION DATA INDICATES AN ICE-LIKE CONFIGURATION OF INTERLAYER ABSORBED WATER IN THE P/P SUB O RANGE ABOVE 0.95. PROLONGED X-RADIATION CAUSED A DISCOLORATION OF SAMPLES ATTRIBUTED TO RADIATION-INDUCED COLOR CENTERS. TWO SUCCESSIVE ADSORPTION AND DESORPTION ISOTHERMS OF WATER VAPOR ON A MONTMORILLONITE POWDER COMPRESSED AT 25 KG/CM SQ. WERE DETERMINED USING AN ELECTROBALANCE AND AN AUTOMATIC RECORDING DEVICE. THE ISOTHERMS EXHIBITED A HYSTERESIS BUT WERE COMPLETELY REVERSIBLE IN THE RELATIVE VAPOR PRESSURE RANGE FROM ZERO TO 0.20. THE RATE OF ADSORPTION WAS GREATER THAN RATE OF DESORPTION. THE LANGMUIR MONOMOLECULAR MODEL FOR THE ADSORPTION PROCESS AND THE BET /BRUNAUER, EMMETT, TELLER/ MULTI-MOLECULAR MODEL WERE COMPARED, AND THE LATTER WAS FOUND TO FIT THE ADSORPTION DATA MORE CLOSELY. THE BET EQUATION WAS FOUND TO BE APPLICABLE IN THE RELATIVE PRESSURE RANGE FROM P/P SUB O EQUAL TO 0.11 TO P/P SUB O EQUAL TO 0.27. THE SPECIFIC SURFACE AND HEAT OF ADSORPTION OF THE FIRST MONOLAYER WERE CALCULATED FROM THE BET PARAMETERS. THE ADSORPTION ISOTHERMS WERE USED TO CALCULATE THE FREE ENERGY CHANGES ON ADSORPTION. THE FREE ENERGY CHANGES ON SUCCESSIVE ADSORPTION CYCLES COMPARED FAVORABLY WITH LOOSE POWDER DATA, INDICATING THAT COMPRESSION HAD LITTLE EFFECT ON THE MAGNITUDE OF THE FREE ENERGY CHANGE. THE FREE ENERGY CHANGES WERE DIVIDED INTO TWO COMPONTNES: ONE FOR ADSORPTION ON INTERNAL SURFACES AND ONE FOR ADSORPTION ON EXTERNAL SURFACES. USING THE DATA, EXPANSION ENERGIES AND SWELLING PRESSURES EXERTED BY CALCIUM MONTMORILLONITE WERE CALCULATED . /AUTHOR/

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  • Supplemental Notes:
    • Paper sponsored by Committee on Physico-Chemical Phenomena in Soils and presented at the 46th Annual Meeting.Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
  • Authors:
    • Senich, Donald
    • Demirel, Turgut
    • Handy, R L
  • Publication Date: 1967

Language

  • English

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 23-54
  • Monograph Title: Physicochemical properties of soils
  • Serial:

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Filing Info

  • Accession Number: 00228829
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 15 2004 2:37AM