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Investigation of the effects of polyelectrolyte coatings on colloid transport in porous media

Description: Goal is to study the repulsive interaction forces between humic- coated colloids and negatively charged porous media surfaces. Filtration experiments were carried out on hematite coated with humic acid or NOM, in porous media or packed bed (silica bed). Effects of Ca[sup 2+] are being studied. Results so far indicate that many humic coating properties (molecular size, acidity, polarity, surface conformation) have an important effect on colloid attachment rates but very little effect on colloid electrophoretic mobility; steric repulsive forces are proposed to account for these observations. Some humic coatings are more effective in enhancing colloid transport in quartz beds than in enhancing colloid stability. Other effects are discussed.
Date: January 1, 1993
Creator: Olson, T.M.
Partner: UNT Libraries Government Documents Department

Surface chemistry investigation of colloid transport in packed beds. Final report, August 1, 1989--July 31, 1996

Description: The importance of colloids as co-transport agents for pollutants in subsurface systems hinges on the extent to which electrostatic or other sources of repulsive colloid-collector interactions inhibit their filtration. When electrostatic interactions are favorable, for example when the colloid and groundwater media have opposite charge, colloids may be expected to travel only a few centimeters in saturated porous media. Repulsive electrostatic interactions between colloids and aquifer media with the same charge sign are postulated to significantly mobilize particles. As it happens, however, theories describing particle filtration from first principles, i.e., DLVO (Derjagin and Landau, Verwey and Overbeek) theory, dramatically underestimate filtration rates when colloid-collector interactions are electrostatically repulsive. One of the primary objectives of the project was to experimentally investigate potential reasons for the historical lack of agreement between particle filtration models based on DLVO theory and observed particle deposition rates. An important hypothesis of the study was to test the validity of the assumption of surface homogeneity, as required by these models. The approach was to focus on collector surfaces that were commonly used as model systems, e.g., glass beads and quartz sand. Laboratory-scale column filtration experiments were conducted with colloidal polystyrene latex spheres. Collector surface preparation and cleaning approaches were examined, as well as the effects of solution chemistry.
Date: December 31, 1996
Creator: Olson, T.M.
Partner: UNT Libraries Government Documents Department