HR: 16:25h
AN: H54C-02    [Abstracts]
TI: Development and Assessment of Oil-in-Water Emulsions for Encapsulation of Reactive Iron Particles for Subsurface Delivery
AU: * Berge, N D
EM: Nicole.Berge@tufts.edu
AF: Tufts University, 200 College Ave., Medford, MA 02155, United States
AU: Taghavy, A
EM: Amir.Taghavy@tufts.edu
AF: Tufts University, 200 College Ave., Medford, MA 02155, United States
AU: Ramsburg, A
EM: Andrew.Ramsburg@tufts.edu
AF: Tufts University, 200 College Ave., Medford, MA 02155, United States
AB: Reactive iron particles hold promise for use in the destruction of contaminants in the subsurface environment. Application of these nano- to submicron-scale particles, however, may be limited by poor subsurface transport and non-uniform distribution of the reactive material. Delivery issues are particularly important when evaluating the efficacy of iron-based technologies for treatment of dense non-aqueous phase liquid (DNAPL) source zones. Current approaches for the delivery of reactive iron particles within DNAPL source zones are hindered by particle agglomeration, flow bypassing, and presence of non-target reactions. Encapsulation of the reactive particles within an oil-in-water emulsion is a novel approach that may overcome these limitations. Development of kinetically-stable, iron-laden, oil-in-water emulsions commenced by identifying surfactant-based coatings to increase the stability of commercially-available iron particles within non-polar organic phases (e.g., soy oil). A phase inversion technique was employed to disperse approximately 10% wt of the iron-laden, organic phase within a continuous aqueous phase containing nonionic emulsifiers. Emulsions were designed to ensure emulsifier proportions yielded hydrophilic-lipophilic balances affiliated with oil-in-water emulsions. Micrographs of the oil-in-water emulsions suggest that the average diameter of the oil droplets is approximately one micrometer. The presence of iron within oil droplets was confirmed in the micrographs and supported by an absence of iron agglomeration within the continuous phase. Bulk characteristics of each emulsion (density and viscosity) were used in conjunction with interfacial tension measurements in total trapping number analyses to assess the propensity of these emulsions to mobilize an entrapped trichloroethene (TCE)-DNAPL. Results suggest that the emulsions described herein should not cause significant mobilization of entrapped TCE-DNAPL in fine-to-medium grain sandy media. Column experiments are being conducted to evaluate the transport of these emulsions through sandy media. Preliminary results from experiments with iron-free emulsions suggest conductivity reductions occurring during emulsion flushing are not the result of extensive pore-clogging but rather are due to viscosity changes (emulsion viscosities range from 2 to 10 cP). Current efforts are focused on assessing and comparing both transport and reaction of commercially available iron particles and iron-laden emulsions within sandy porous media.
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting