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Soil Science Society of America Journal Abstract -

Rheology of Sodium and Potassium Illite Suspensions in Relation to Colloidal Stability


This article in SSSAJ

  1. Vol. 57 No. 3, p. 697-704
    Received: Jan 27, 1992

    * Corresponding author(s):
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  1. Dean Hesterberg  and
  2. A. L. Page
  1. Dep. of Soil Science, North Carolina State Univ., Box 7619, Raleigh, NC 27695-7619
    Dep. of Soil and Environmental Science, Univ. of California, Riverside, CA 92521



To further understand the colloidal behavior of clay minerals in soils, rheological properties of illite suspensions were investigated and related to colloidal stability. Using a concentric cylinder viscometer to measure shear stress as a function of shear rate, Bingham yield stresses (τB) and plastic viscosities (ηpl) were determined for homoionic Na- and K-saturated illite suspensions varying in pH, NaCIO4 or KCIO4 concentration, and suspended solids concentration. For a given Na or K concentration, τB typically decreased with increasing pH. At a given pH >5.5, both τB and ηpl increased with increasing electrolyte concentration; but for Na-illite, constant values of τB and ηpl were observed at higher electrolyte concentrations. The Na or K concentration yielding the greatest increase in τB or ηpl per unit increase in concentration was usually less than, but correlated with, published critical coagulation concentrations (CCCs) of Na- or K- illite. With increasing solids concentration at pH 7, τB increased curvilinearly for unstable suspensions and linearly for stable suspensions. In light of published models of non-Newtonian flow, data for unstable suspensions at pH 7 suggested that interparticle bonding energy or the number times energy of bonds within flocs was greater for K-illite in 25 mol K m−3 than for Na-illite in 60 mol Na m−3.

Contribution from the Dep. of Soil and Environmental Sciences, Univ. of California, Riverside and the Institute for Soil Fertility Research, Haren, the Netherlands.

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