Factors affecting the swelling and hydraulic conductivity of montmorillonite

Fushan Zhang, Purdue University

Abstract

A study was conducted on the effects of several factors on the relation between $\lambda$, the interlayer distance in montmorillonite, and $\Pi$, the swelling pressure of the montmorillonite. Also, another study was conducted on the effects of organic solutes on the hydraulic conductivity of Na-montmorillonite. The species of exchangeable cation were Li$\sp+$, Na$\sp+$ and K$\sp+$, the electrolytes were the chloride salts of these cations and the organic solutes were urea, ethanol, phenol, tertiary butanol and 1,4-dioxane. Data obtained in the first study showed that: (1) neither the species of exchangeable cation nor the electrolyte concentration affected the $\lambda$-$\Pi$ relation at relatively low electrolyte concentrations, (2) both the species of exchangeable cation and the electrolyte concentration affected the $\lambda$-$\Pi$ relation at relatively high electrolyte concentrations, (3) ethanol, tertiary butanol and urea at a concentration of 1.0 mol/l had no effect on the relation between $\lambda$ and $\Pi$, whereas, 1,4-dioxane had a profound effect on this relation, and (4) temperature had essentially no effect on the relation between $\lambda$ and $\Pi$. These results were not consistent with electric double-layer theory. The results of the second study showed that K increased steadily with solute concentration when 1,4-dioxane was the solute but rose to a maximum and fell gradually thereafter when ethanol, phenol and urea were the solutes. It is known that K is proportional to k/$\mu$, where k is the permeability of the porous medium and $\mu$ is the kinematic viscosity of the permeant solution. Plots were made of $\mu$/$\mu\sp\circ$ versus solute concentration for bulk solutions of the different organic solutes and of K$\sp\circ$/K versus solute concentration when these solutions permeated the montmorillonite. Both kinds of plots were linear. The linear plots were interpreted to mean that k$\sp\circ$/k = 1.0 and that, consequently, K$\sp\circ$/K = $\mu$/$\mu\sp\circ$. However, the rate of change of $\mu$/$\mu\sp\circ$ with solute concentration was different for the bulk solutions than for the corresponding interparticle solutions, i.e., the solutions within the pores of the montmorillonite matrix. It was reasonable to conclude, therefore, that the viscosities of bulk and interparticle solutions are affected differently by organic solutes. (Abstract shortened by UMI.)

Degree

Ph.D.

Advisors

Low, Purdue University.

Subject Area

Geochemistry|Chemistry|Agronomy

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