MEASUREMENT OF PHYSICAL PROPERTIES OF COLLOIDAL SYSTEMS USING AN AUTOMATED TENSION CELL
Abstract
A tension cell device was described which was able to automatically maintain constant pressure loads (2 cm to 19 cm H(,2)O) and collect outflow data for flow systems involving water saturated, deformable porous media. Using this data, various flow parameters were obtained: Dm, material diffusivity; K, hydraulic conductivity; S, effective surface area; k, permeability; and (alpha), the coefficient of bulk compressibility. The flow parameters were a function of a variety of factors related to particle arrangements, which were controlled to a large extent by the nature of the forces operating between particles. Physical phenomena which influenced particle arrangements, such as surface charge, particle size, morphology, and surface modification by the adsorption of surface-active agents were examined with the use of the tension cell. Three different clay materials were examined: montmorillonite, sepiolite and kaolinite. Each material had a different morphology, particle size and surface charge properties. Their different particle network resulted in different consolidation behavior. The smooth deformation of the cake observed in montmorillonite was suggestive of the formation of a strong network. The absence of electrostatic repulsive forces between the particles of sepiolite resulted in an irregular structural deformation of the network. Flocculation of kaolinite particles in suspension led to a chaotic and erratic consolidation of the gel network. Deflocculation resulted in a smoother consolidation due to the presence of interparticle repulsion which minimized particle interactions. Adsorption of a non-ionic surface-active agent smoothed the consolidation process of kaolinite suspensions by imparting some degree of steric stabilization. Addition of an anionic surface-active agent prevented abrupt collapse of the structure due to ionic stabilization. Structural orderliness was greater when a cationic surface-active agent was adsorbed to kaolinite discharged particles. It was believed that a more ordered array of particles within the network occurred during consolidation due to a more face-to-face interaction between the particles upon addition of the cationic surfactant. Particle interactions were confirmed by rheological data including rheogram curves and Power Law parameters. The gelation properties of the clay systems were examined. The information gained by analyzing the flow properties was applied to the problem of understanding and controlling particle arrangements in colloidal systems.
Degree
Ph.D.
Subject Area
Pharmacology
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