No abstract

No abstract

No abstract

physical behavior of wetted soils is of paramount importance. The rheology of aqueous suspensions of six palygorskites withWhen the electrolyte concentration in the percolating different particle morphologies has been investigated as a function solution in soil is below the flocculation value of the of clay concentration, adsorbed ion, pH, and electrolyte concentration, clay, clay dispersion occurs. Under such conditions wausing a rotary viscometer. Rheological parameters (plastic viscosity, ter flow in the soil changes from flow of solution to flow Bingham yield value, and apparent viscosity) increase with the length/ width ratio of individual palygorskite fibers. The plastic viscosity in-of clay suspension (Pupisky and Shainberg, 1979). The creases linearly with clay concentration within the range investigated presence of clay particles in the percolating solution (up to 5% w/v). The rheological parameters are higher for clays may increase significantly the viscosity of the flowing saturated with divalent ions than those for clays saturated with monosuspension and therefore may affect the hydraulic convalent ions. For ions of the same valency the rheological parameters ductivity of the soils, which is important for the managetend to increase with decreasing radius of the hydrated ion. The flow ment of irrigation. The suspension viscosity increases of suspensions is pseudoplastic regardless of the nature of the adsorbed even further when particle-particle interactions occur. ion. Measurements of electrophoretic mobility in very dilute suspen-The rheological parameters of clay suspension can sions suggest that the point of zero charge of the palygorskite surface be used to evaluate particle-particle interactions. The is at pH 4 to 4.5. Scanning electron microscopy indicates significant model of edge-to-face particle association was first prodifferences in fiber arrangement between low and high pH values. posed by Hofmann and Hausdorf (1945). The concept Face-to-face particle association occurs at low pH values, giving rise to close-packed domains of fibers, while at high pH values the fibers of face-to-face, edge-to-face, and edge-to-edge type asadopt a random orientation. The flow of suspensions is pseudoplastic sociations in suspension of platy clay minerals (such as at pH Յ 7 and changes to Newtonian at pH Ն 9. At pH Յ 7 the montmorillonite and kaolinite) was developed further rheological parameters remain relatively constant even at high electroby van Olphen (1977). These simple models of particlelyte concentrations, but at pH Ն 9 they are influenced significantly particle interactions have been helpful for understandby electrolyte addition. Electrolyte-free palygorskite suspensions at ing the stability and rheological behavior of clay-pH 7 are antithixotropic. When the pH falls below 7 or when electrowater systems. lyte is added, the suspensions coagulate and become thixotropic. Some Several studies have been devoted to the rheological rheological properties of palygorskite are similar to those of platy prop...

No abstract