Clay behaviour in suspension is related to the ionicity of clay-cation bonds

Marchuk, Alla and Rengasamy, Pichu (2011) Clay behaviour in suspension is related to the ionicity of clay-cation bonds. Applied Clay Science, 53 (4). pp. 754-759. ISSN 0169-1317


The behaviour of four clays viz. an illite, a bentonite and two soil clays in relation to their dispersivity, zeta potential and mean particle size was investigated to test the hypothesis that water interaction with clays is dictated by the degree of ionicity of clay-cation bonds. The clay particle being considered as an anion with large size and high charge compared to the cations, the polarizability of the cations determine the degree of ionicity or covalency in a clay-cation bond. The ionicity indices of the cations Li +, Na +, K +, Mg 2+, Ca 2+, Sr 2+ and Ba 2+ were derived using their ionisation potentials and charge. In all homoionic clays, high and significant relationships between ionicity indices of cations in clay-cation bonds and the clay behaviour such as dispersibility (measured as turbidity of suspensions) and zeta potential confirm that the degree of ionicity in these bonds dictate the water interaction with clay particles leading to their separation from the clay aggregates. This is further confirmed by the relationship between the mean particle sizes of homoionic clays, measured in four types of clays, and the ionicity indices. Transmission electron micrographs of homoionic illites confirm the aggregation of particles in relation to the ionicity of clay-cation bonds. The strong relationship between relative zeta potential and relative turbidity suggests that the surface charge on clays is responsible for the variations in correlations between ionicity indices and clay behaviour among the four types of clays. The derived ionicity indices in the present study predict the clay behaviour in water better than either ionic potentials or Misono softness parameters.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © 2011 Elsevier B.V. Permanent restricted access to published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Date Deposited: 02 Sep 2014 01:13
Last Modified: 31 Jan 2017 01:08
Uncontrolled Keywords: clay dispersion; clay-cation bonds; homoionic clays; ionicity index; zeta potential
Fields of Research : 03 Chemical Sciences > 0301 Analytical Chemistry > 030108 Separation Science
05 Environmental Sciences > 0503 Soil Sciences > 050305 Soil Physics
02 Physical Sciences > 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics > 020201 Atomic and Molecular Physics
Socio-Economic Objective: D Environment > 96 Environment > 9614 Soils > 961499 Soils not elsewhere classified
Identification Number or DOI: 10.1016/j.clay.2011.05.019

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