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LOW-TEMPERATURE, LIQUID-PHASE PROCESSES 124 search for cleanup techniques for water contaminated with chlorinated hydrocarbons are both relevant to destruction of bulk agents and their detoxified by-products. Little work has actually been done on these applications, however. Lawrence Livemore Laboratory has proposed the use of electrochemically generated peroxydisulfate salts for detoxification and for completion of the oxidation process (Cooper, 1992). These salts can be purchased commercially. At 100°C, 98 to 99 percent oxidation of surrogates for products of agent detoxification were oxidized (to CO2) in 3 minutes. This reaction is routinely used for elemental analysis; however, for some refractory materials, such as esters and carboxylates, a catalyst is used to ensure conversion. Catalysts include Co (III), Ag(II), and UV light. Use of peroxydisulfate salts as an oxygen source produces a very large waste stream of sulfate and sulfuric acid (about 30 times the weight of the original agent). Recycling the sulfate and sulfuric acid for electrolytic regeneration is proposed by the investigators of the process. Peroxydisulfate is manufactured by electrochemical oxidation; however, systems development for removal of undesired by-products containing phosphorus and halogens will be needed. Because of its low cost, availability, and lack of troublesome residue, H2O2 is an attractive candidate. However, it requires activation for this use. Fenton's reagents (H2O2 catalyzed by iron or cobalt) are standard laboratory reagents for oxidation and are of considerable current interest for possible use in contaminated water and soil cleanup (Sun and Pignatello, 1993). For this application these compounds' strengths and limitations need to be established. Interference by halogen and phosphorous compounds and the ability to oxidize refractory organics are important considerations. Cooper (1992) suggested that use of Fenton's reagents followed by peroxydisulfate oxidation could be an optimal combination. Electrochemical Oxidation Electrochemical oxidation of organic waste compounds is being studied for application to wastes from isotope separation and to sites where groundwater contamination has occurred (see Appendix J for a more detailed discussion). Although chemical intermediates are synthesized commercially through direct oxidation, the mediated electrochemical oxidation (MEO) process appears to be that most applicable to oxidation of chemical warfare agents and their organic by-products. The potential for completion of oxidation is of interest; however, a combination of detoxification and complete oxidation is probably also feasible. The MEO process generates reactive ions such as Ag2+, Co3+, or Fe3+, which can react with an organic compound and water to produce CO2.
