Interactions of polymers, surfactants, bacteria and particle surfaces

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Any surface in a solution or suspension will be modified by the adsorption of species from that solution surrounding it. The adsorption of these species dramatically changes the surface properties, and is the preliminary step in a variety of important processes. We are particularly interested in the adsorption of positively charged surfactants and polymers, especially where the latter can act as flocculants. Flocculation - the aggregation of particles such as kaolin (clay)- is important in such processes as papermaking, and the clarification of drinking water. Surfactants can absorb onto surfaces and can change the properties of a system, often by solubilizing substances with little affinity for water. Thus, the presence of a surfactant can interfere with the process of flocculation. Although the actions of single flocculants and surfactants are well defined, and some work has been done on dual systems, much less is known about systems containing multiple components. We have chosen to further study these systems by examining their absorption of infrared (IR) light. The wavelength at which IR light is absorbed is distinctive for different compounds. We are able to prepare stable films of clay and other particles from their suspension in methanol, and then use IR methods to measure absorbances which are characteristic of the species of interest. The shifts in the wavelengths and intensities of these absorbances can tell us about the way each species absorbs onto the particle as a function of time, and how it interacts with other species on the surface. We will use the same approach to monitor oil-kaolin aggregates and study the formation of bacterial biofilms on them, in order to determine whether biofilm formation on their surface is important in bioremediation of the oil. The formation of complexes between cationic polymers and other dissolved species affects their behavior as flocculants. These complexes will be characterized by their motion in an applied field (capillary electrophoresis), and their ability to adsorb onto kaolin films, as followed by IR absorbance measurements.