Groundwater cleanup research conducted at the University of Central Florida and at NASA’s Launch Complex 34 on Cape Canaveral Air Force Station is demonstrating the feasibility of using emulsions containing iron particles to expedite dehalogenation of dense nonaqueous-phase liquids (DNAPL’s). The emulsion consists of a surfactant-stabilized, biodegradable oil-in-water emulsion with nanoscale or microscale iron particles contained within the emulsion droplets. It has been demonstrated that trichloroethylene (TCE) diffuses through the oil membrane of the emulsion particle, whereupon it reaches the surface of an iron particle and dehalogenation takes place. The reaction by-products of the dehalogenation reaction, primarily ethene (low level of chlorinated products detected only after using ultrasound to burst the droplets), diffuse out of the emulsion droplet. Laboratory studies have demonstrated this type of emulsion system could be injected into the ground where DNAPL contamination exists. Using this system, liquid TCE is degraded at a rate comparable to the degradation of dissolved-phase TCE by iron particles, while pure iron has a very low degradation rate for free-phase TCE. In laboratory studies, the iron-emulsion systems were injected into a soil matrix, where they became immobilized and were not moved by flowing water. This study showed that surfactant micelles possess the ability to pull pooled TCE into emulsion droplets where degradation of TCE takes place.

Key accomplishments:

• Testing of various emulsion possibilities.
• Optimization of emulsion mixture for TCE treatment.
• Testing of nanoscale and microscale iron emulsions.
• Column studies of nanoscale iron emulsions.

Key milestones:

• 2001: Laboratory development of emulsified zero-valent iron completed.
• 2002: Laboratory column tests completed. EZVI injected into the subsurface at Launch Complex 34, Cape Canaveral Air Force Station in July.

Contact: Dr. J.W. Quinn (Jacqueline.Quinn-1@ksc.nasa.gov), YA-C3-C, (321) 867-8410
Participating Organization: University of Central Florida (C. Clausen, C. Geiger, and D. Reinhart)