Reductive Dehalogenation of DNAPLS using Emulsified Nano-Scale Zero-Valent Iron

C.L. Geiger, C.A. Clausen, D. Reinhart, K. Brooks, C. Clausen, L. Filipek, T. Krug, S. O'Hara, D. Major, and J. Quinn, 2002, "Reductive Dehalogenation of DNAPLS using Emulsified Nano-Scale Zero-Valent Iron" Paper 2C-32, in: A.R. Gavaskar and A.S.C. Chen (Eds.), Remediation of Chlorinated and Recalcitrant Compounds 2002, Proceedings of the Third International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2002)

Research conducted at the University of Central Florida demonstrated the feasibility of using emulsions containing iron particles to expediate dehalogenation of DNAPL. The emulsion consisted of a surfactant-stabilized, biodegradable oil-in-water emulsion with nanoscale or microscale iron particles contained within the emulsion droplets. It was demonstrated that TCE diffuses through the oil membrane of the emulsion particle whereupon it reaches the surface of an iron particle in the interior aqueous phase and dehalogenation takes place. The reaction by-products of the dehalogenation reaction, primarily ethene (low level of chlorinated by-products detected only after using ultrasound to burst the droplets), diffuse out of the emulsion droplet. Laboratory studies also demonstrated that this type of emulsion system could be injected in-situ to the DNAPL pool in a soil matrix by using a simulated push well technique. Using this system, liquid TCE was degraded at a rate comparable to the degradation of dissolved-phase TCE by iron particles, while pure iron had 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 has shown that surfactant micelles possess the ability to pull pooled TCE into emulsion droplets where degradation of TCE takes place.

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