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Comparative rheological behavior of suspended clays with varying ionic composition

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Title:Comparative rheological behavior of suspended clays with varying ionic composition
Authors:Dangler, E. W (Edgar W.), 1920
Soil physics
Date Issued:1973
Abstract:A rheological study was conducted on six clays with the objectives of studying the dependence of viscosity on clay concentration (water content) for important soil mineralogical groups, evaluating the effects on viscosity of chemical treatment induced by changing pH, electrolyte concentration, and composition of the exchange complex, and using interpretation, based on interparticle interactions and predictive model equations to explain observed viscosity differences. The clays were selected to represent 2:1 (montmorillonite and vermiculite), 1:1 (kaolinite and halloysite), and amorphous metal hydroxides and alumino silicate (Akaka and Choyo) structural types. Viscosities of various suspensions were measured by use of a rotational, the MacMichael, viscometer. Supporting experiments were conducted to investigate interparticle configurations by direct electron-microscopic examinations. development of gel structures was monitored by tension measurements in suspension. Results showed that: 1. The order of increasing viscosities for similar concentrations of clay in water was generally as follows: Choyo clay, vermiculite, halloysite, Akaka clay, kaolinite, and montmorillonite. 2. The presence of magnesium on the exchange complex of clays decreased the viscosities of three clay-water systems, namely montmorillonite, kaolinite, and Choyo clay in water. This was attributed to reduction of the extent of the electrical double layer around the clay particles which favored a decrease in number of particles through face-face attraction. The other three, vermiculite, ha11oysite, and Akaka, became more viscous when the exchange surface was saturated with Mg2+. 3. Addition of NaC1 first caused a reduction in viscosity of sodium saturated montmorillonite, vermiculite, and Choyo clay suspensions. This was attributed to hydrolysis and subsequent formation of more flocculated H, A1-c1ays in the absence of electrolyte. Further increases in NaC1 concentration resulted in increased viscosities. In contrast to these three clays, an inverse relationship existed between viscosity and NaC1 concentration for Na-kao1inite and Na-Akaka clay systems. No definite effect of electrolyte concentration was noted on Na-ha11oysite. 4. Addition of MgC12 to Mg-Choyo clays resulted in a viscosity increase that varied directly as the concentration of MgC12• Conversely, viscosities of the five other Mg-c1ays were inversely related to MgC12 concentration. 5. Sodium saturated crystalline clays suspended in dilute NaC1 generally showed viscosity highs at pH 4 and viscosity lows at pH 10. On the other hand, sodium saturated amorphous clays, had viscosity lows at pH 4. Na-Akaka clay had maximum viscosity at pH 7. The viscosity of Na-Choyo showed a continued rise to pH 10. 6. All the Mg-c1ays suspended in dilute MgC12 solutions had their highest viscosity values at pH 10. However, the Mg-kao1inite system had essentially equal viscosities at pH 4, 7, and 10. 7. Measurable tensions of 1-2 cm were detected in very dilute Na-montmori11onite and Na-vermicu1ite systems indicating that interparticle configurations may occur at clay concentrations far below those necessary to form observable rigidity or gel structure. Sodium clay systems that yielded the highest viscosities required the most clay for tension response. 8. Electron micrographs of freeze-dried clay suspensions failed to reveal edge-face or edge-edge interparticle configurations. Evidence was found for face-face positioning of sheets in Na-montmorillonite that had been freeze-dried in NaCl as well as in Na-kaolinite freeze-dried in HCI.
Thesis (Ph. D.)--University of Hawaii at Manoa, 1973.
Bibliography: leaves [214]-219.
xiii, 240 l illus., tables
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Appears in Collections: CTAHR Ph.D Dissertations
Ph.D. - Agronomy and Soil Science

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