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Title: Effect of pH in an aqueous medium on the surface area, pore size distribution, density, and porosity of montmorillonite

Abstract

Surface area, pore volume distribution, and porosity of montmorillonite are determined after being exposed to aqueous solutions with various pH values. For measurement, after each pH treatment the clay samples were freeze-dried in order to keep the structure of the clay same as that in the aqueous solution. Surface area and pore size distribution measurements were performed on an unmodified and four pH (2.5, 4.0, 5.5, 9.0)-adjusted clay samples using N{sub 2} and CO{sub 2} as adsorbates. The surface area measurements at lower pH are lower than those measured at higher pH due to the replacement of Na{sup +} ions from interlayers at lower pH which may be followed by the reduction of repulsive forces. As the pH of the montmorillonite increases to 9.0, the surface area increases almost seven times compared to that at pH 2.5. Pore size distribution was determined by CO{sub 2} adsorption at 273 K for micropores (<20 {angstrom}), by N{sub 2} adsorption at 77 K for mesopores (between 20 and 500 {angstrom}), and by using both Hg intrusion and N{sub 2} adsorption for macropores (>500 {angstrom}). Since N{sub 2} molecules undergo a molecular sieving at 77 K, CO{sub 2} gas at 273 K was usedmore » to measure the micropore surface area and gave higher surface area measurements than those measured by N{sub 2}. Surface area values measured by CO{sub 2} adsorption ranged between 30 and 200 m{sup 2}/g for montmorillonite while those measured by N{sub 2} adsorption were 13.7--70 m{sup 2}/g in the pH range studied.« less

Authors:
; ;
Publication Date:
Research Org.:
Middle East Technical Univ., Ankara (TR)
OSTI Identifier:
20013596
Resource Type:
Journal Article
Journal Name:
Journal of Colloid and Interface Science
Additional Journal Information:
Journal Volume: 217; Journal Issue: 1; Other Information: PBD: 1 Sep 1999; Journal ID: ISSN 0021-9797
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 36 MATERIALS SCIENCE; MONTMORILLONITE; PH VALUE; SURFACE AREA; PORE STRUCTURE; DENSITY; POROSITY; ENVIRONMENTAL TRANSPORT

Citation Formats

Altin, O., Ozbelge, H.O., and Dogu, T. Effect of pH in an aqueous medium on the surface area, pore size distribution, density, and porosity of montmorillonite. United States: N. p., 1999. Web. doi:10.1006/jcis.1999.6271.
Altin, O., Ozbelge, H.O., & Dogu, T. Effect of pH in an aqueous medium on the surface area, pore size distribution, density, and porosity of montmorillonite. United States. doi:10.1006/jcis.1999.6271.
Altin, O., Ozbelge, H.O., and Dogu, T. Wed . "Effect of pH in an aqueous medium on the surface area, pore size distribution, density, and porosity of montmorillonite". United States. doi:10.1006/jcis.1999.6271.
@article{osti_20013596,
title = {Effect of pH in an aqueous medium on the surface area, pore size distribution, density, and porosity of montmorillonite},
author = {Altin, O. and Ozbelge, H.O. and Dogu, T.},
abstractNote = {Surface area, pore volume distribution, and porosity of montmorillonite are determined after being exposed to aqueous solutions with various pH values. For measurement, after each pH treatment the clay samples were freeze-dried in order to keep the structure of the clay same as that in the aqueous solution. Surface area and pore size distribution measurements were performed on an unmodified and four pH (2.5, 4.0, 5.5, 9.0)-adjusted clay samples using N{sub 2} and CO{sub 2} as adsorbates. The surface area measurements at lower pH are lower than those measured at higher pH due to the replacement of Na{sup +} ions from interlayers at lower pH which may be followed by the reduction of repulsive forces. As the pH of the montmorillonite increases to 9.0, the surface area increases almost seven times compared to that at pH 2.5. Pore size distribution was determined by CO{sub 2} adsorption at 273 K for micropores (<20 {angstrom}), by N{sub 2} adsorption at 77 K for mesopores (between 20 and 500 {angstrom}), and by using both Hg intrusion and N{sub 2} adsorption for macropores (>500 {angstrom}). Since N{sub 2} molecules undergo a molecular sieving at 77 K, CO{sub 2} gas at 273 K was used to measure the micropore surface area and gave higher surface area measurements than those measured by N{sub 2}. Surface area values measured by CO{sub 2} adsorption ranged between 30 and 200 m{sup 2}/g for montmorillonite while those measured by N{sub 2} adsorption were 13.7--70 m{sup 2}/g in the pH range studied.},
doi = {10.1006/jcis.1999.6271},
journal = {Journal of Colloid and Interface Science},
issn = {0021-9797},
number = 1,
volume = 217,
place = {United States},
year = {1999},
month = {9}
}