In Situ Remediation Practice Leader
Woodard & Currran, Inc.
Greg has over 20 years of experience focused on in-situ chemical and bioremediation remedies, groundwater and surface water biogeochemistry and site characterization. He specializes in combining innovative in situ technologies and implementing them with advanced, proven delivery methods to provide successful remediation approaches.
Abiotic Destruction of 1,2,3-Trichloropropane (TCP) using Catalyzed ZVI
Abiotic Destruction of 1,2,3-Trichloropropane (TCP) using Catalyzed ZVI Greg Booth (Woodard & Curran, Inc.) Nicole Lapeyrouse and Cherie Yestrebsky (University of Central Florida) Background/Objectives: The chlorinated alkane 1,2,3-trichloropropane (TCP) has been widely used as a cleaning and degreasing solvent and has been found as an impurity in soil fumigants, creating both point and non-point source contamination. The EPA has classified TCP as a likely carcinogen and does not currently have an MCL (maximum contaminant level) established in drinking water, but does provide a chronic oral reference dose (RfD) of 0.004 mg/kg/d and a drinking water equivalent level (DWEL) of 0.1 mg/L. Chlorinated alkanes are recalcitrant to degradation in the environment due to their chemical and physical properties, which includes high volatility, low water solubility and high density (>1). It has been previously established that the reactivity of TCP with granular ZVI is minimal. The use of bi-metallic nano particles (e.g., palladized ZVI) has been shown to dechlorinate TCP. The objective of this presentation is to introduce laboratory treatability data for the destruction of TCP in water, using small micron ZVI catalyzed with vitamin B12 and discuss the potential application for in-situ destruction of TCP. Approach/Activities: To evaluate whether vitamin B12 could catalyze the electron transfer processes between ZVI and chlorinated alkanes, batch reactions were performed in order to assess the associated degradation mechanisms. Dechlorination byproducts were con?rmed through gas chromatography-mass spectrometry (GC-MS) coupled to a purge and trap. Free chloride was quanti?ed by ion chromatography (IC) utilizing suppressed conductivity detection. Results/Lessons Learned: Reductive dechlorination of TCP did not occur when exposed to reactive ZVI particles (< 5 micron) alone. However, in the presence of ZVI combined with vitamin B12, complete reductive dechlorination was observed and followed a pseudo-?rst-order reaction, with a rate constant of 0.287 days-1 ± 0.012. Propene was the only degradation byproduct observed during neat TCP experiments. Additionally, dissolved chloride levels increased throughout the duration of the experiment and mole balance calculations indicate a 72% recovery of chloride. The formation of propene and increase of chloride in solution provide direct evidence for the dechlorination of TCP in the presence of small micron ZVI and vitamin B12. The application of small micron ZVI catalyzed with vitamin B12 for in situ remediation of chlorinated alkanes can be considered in conjunction with the emulsified zero valent iron (EZVI) technology. Due to the emulsion structure, the vitamin B12 can be incorporated into the EZVI such that the B12 and ZVI are together in the aqueous interior of the emulsion. Vitamin B12 in combination with iron shows promise as a catalyst in the reductive dechlorination of chlorinated alkanes and potentially other halogenated compounds, thereby expanding the scope of ZVI treatable contaminants.