PCB destruction: A novel dehalogenation reagent

Abstract

Alkali metal polyethylene glycolate complexes (APEGs) are being investigated as reagents for the in-situ decontamination of soils containing PCBs and other haloorganics in the U.S. Environmental Protection Agency's Industrial Environmental Research Laboratory, Cincinnati, Ohio. APEG reagents can be formulated with either an alkali metal or hydroxide and the corresponding polyglycol or polyglycol monoalkyl ethers. These alkali PEGs were found to be very reactive toward halogenated organics, particularly at elevated temperatures (ca. 60–100°C) and have been applied for decontamination of PCBs in transformer oils. The primary products were an alkali metal halide, i.e., sodium chloride in the case of PCBs and polyglycol ether aromatics. The reaction mechanism is nucleophilic substitution at the halogen-carbon bond. The reactive APEG species is theorized to be a crown ether metal coordinated structure. Previous formulation of these APEGs required reaction of the alkali metals with a desired polyethylene glycol under anhydrous conditions. These formulations were very susceptible to decomposition by water, and dehalogenation rates were likewise vastly reduced. Recent studies have shown that this is not an insurmountable problem when APEGs are formulated with the alkali metal hydroxide. This work examines the effect of APEG concentration and dilution in water and organic solvent on the dehalogenation of Aroclors 1242 and 1260 with potential application for the in-situ destruction of PCBs in soils.