[CCoE Notice] Thesis Defense: Characterizing Salinity-Dependent Double layer effects on Clay Properties

[Grayson, Audrey A]

Master’s Thesis Defense

Characterizing Salinity-Dependent Double layer effects on Clay Properties

Panuswee Dwivedi
Date: Thursday, December 7, 2017

Location: Energy Research Park, Building 9, Room 124
Time 3:00 to 5:00 PM

Committee Chair: Dr. Michael T. Myers

Committee Members:
Dr. Lori Hathon
Dr. Konstantinos Kostarelos


The terminal velocity of a settling spherical particle in a laminar flow environment is described by Stoke’s Law as a product of particle sizes squared and the difference of densities of the solids and the fluid. We decoupled the effects of density and particle sizes performing a series of experiments to characterize influence of clay mineral double layer effects on the porosity, and textural properties as a function of salinity. We performed settling experiments in distilled water, and 75,000 ppm NaCl solution for three different mud-rock samples having different CEC values. NMR spectroscopy, Thermogravimetric Analyses (TGA), and grain density calculations using Boyle’s Law experiments were performed to compare the properties of the samples after settling.

In the settling column, the settling rate is a function of particle-size, with larger floccules settling with a higher velocity. An increase in salinity in the column increases the flocculation of clay particles. The volume of bound water associated with clay minerals, increases with decreasing particle size. Once the settling experiments were complete (constant hydrometer readings), sample material was divided into three different particle sizes. The volume of associated bound water was calculated for each size fraction (diameters ranging from ~0.1 to 0.04 mm, 0.04mm to 0.01mm and finer) of the samples for both salinity experiments using NMR spectroscopy. TGA was also performed on each sample to validate with the bound water volume measured using NMR. Boyle’s Law experiments were performed on each grain-size fraction to calculate the grain density as a function of salinity dependent particle-size. Both, NMR porosity and grain density are functions of the bound and free water volumes. The SEM images of the final samples will be used to visually characterize grain size and clay morphology.

Increasing salinity causes clay particles to bind together rapidly, and more strongly than in distilled water. As salinity increases, and particle size decreases, dewatering of the slurries take longer. This influences the measured grain density. At a given particle size, clay minerals saturated with brine are less dense than those saturated with distilled water. These data were interpreted using the model of Hill, Shirley and Klein model.

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