A promising new methodology for treating sub-surface contaminant plumes involves the coacervation of polyelectrolyte-micelles. Polyelectrolytic surfactants can form micelles, bipolar organic molecules, which can adsorb onto solid surfaces through coacervation. In this state, they act as filters, with the ability to bind organic molecules. Furthermore, their charge characteristics can be altered after organic trapping, allowing for a re-solubilization of the organic molecules. In this way, this chemical technology could be used to emplace a reversible geochemical fence downstream of polluting organic plumes.
We performed the first test of this technology with geologic materials to assess the potential of the theoretical possibilities mentioned above. Using sand and a model organic solvent with well-known chemical characteristics (Orange OT dye in an ethanol matrix), we attempted to first coat sand with polyelectrolyte-micelle coacervate, then to adsorb the model organic onto the sand. Our tests were successful. Little of the model organic adsorbed on to the plain sand, and little adsorbed when the coarcervate had previously been formed. Maximum adsorption occurred when the polyelectrolyte micelles were titrated to the point of coacervation in the presence of sand, followed by treatment with the model organic solution. This indicates that a polyectrolyte-micelle solution could be introduced into a subsurface system, then driven to coacervation via ionic strength changes. Questions to address through experiments and field work include testing this technique on a range of organic pollutants, examining permeability loss with increased organic trapping, and assessing the feasibility of adjusting ionic strengths and pH in the subsurface.
AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana