United States Environmental Protection Agency Hazardous Waste Engineering Research Laboratory Cincinnati OH 45268 Research and Development EPA/600/S2-85/108 Dec. 1985 Project Summary Destruction of PCBs— Environmental Applications of Alkali Metal Polyethylene Glycolate Complexes Frank J. laconianni This project is a follow-up on a study which focused primarily on the feasib- ility of chemical detoxification of PCB- contaminated soil using Franklin Re- search Center's (FRC's NaPEG) Rea- gents. The research described in the full report involves primarily a laboratory study of Sodium Polyethylene Glycol, the most effective NaPEG Reagent in terms of reactivity and stability. The study was aimed at identifying treat- ment conditions necessary for the most efficient decontamination in field appli- cations. On-site and off-site field veri- fication studies were also conducted using PCB-contaminated soil from spills in Buffalo, NY and Philadelphia. PA. I n the first phase of this study, experi- ments using soils contaminated in the laboratory were presumed to demon- strate that the concentration of PCBs in soil can be reduced to below 50 ppm by direct addition of the NaPEG reagent under ambient conditions typical of an in-situ treatment of a spill. Laboratory tests conducted during the second phase of this project centered mainly on the treatment of PCB-con- taminated soil obtained from the two spill sites mentioned above. The effects of variable reaction parameters which affect the rate of decontamination were examined in detail. This Project Summary was developed by EPA's Hazardous Waste Engineering Research Laboratory, Cincinnati, OH, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Introduction The accumulation of polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxinsfPCDDs, "dioxins")insoil, sand, and living tissue is a serious problem. Although a great amount of work has been done in the area of direct chemical decomposition of these and other halogenated organics, relatively little effort has been directed toward in situ chemical detoxification. The "cleanup" of a contaminated site usually involves landfilling and is not really a permanent detoxification but rather a transfer of a toxic spill from one location to another. Landfilled toxic ma- terials are still in the environment and will persist there until they are chemically destroyed. In the chemistry laboratory at the Franklin Research Center (FRC) during the summer of 1978, a chemical reagent was synthesized for use to dechlorinate PCB oils. Since that time a series of reagents have been developed and are now called MaPEGtm* Reagents. They are essentially alkali metal polyethylene gly- colates which produce rapid dehalogena- tion of halo-organic compounds of all types—in open air systems. The aerobic nature of the NaPEG System immediately suggested its poten- "Mention of trademarks or commercial products does not constitute endorsement or recommendation for use by the U S. Environmental Protection Agency. ------- tial for use on hazardous chemical spills. In August 1 979, the U.S. Environmental Protection Agency (EPA) provided grant support to FRC to investigate the chem- istry underlying the dehalogenation pro- cess, concentrating on dechlorination of PCBs. Subsequent EPA grant assistance was provided for a limited field study of the effects of a NaPEG reagent on PCB- contammated soil. This research was described in a Project Summary entitled "Dehalogenation of PCBs Using New Reagents Prepared from Sodium Polyeth- ylene Glycolate—Application to PCB Spills and Decontaminated Soils," August 1982. Additional EPA grant assistance was awarded in 1982 for the detailed investi- gation of the effects of variable reaction parameters on the rate and extent of chemical decontamination of the sub- strate. This research focussed almost exclusively on the direct chemical treat- ment of PCB-contaminated soil. The continued laboratory investigation was aimed at identifying treatment conditions necessary for the most efficient decon- tamination in a direct field application. During the study an optimum reagent composition was selected based on chem- ical considerations. Maximum reactivity toward PCBs and other halogenated organics coupled with minimum sensi- tivity to reagent-deactivating side reac- tions was sought in selecting the best reagent formulation for further study. The full report describes the research per- formed and the results obtained. Early Experiments Using Laboratory-Contaminated Soils Laboratory experiments using simu- lated soil substrates spiked with PCBs confirmedthat PCBs aredechlorinated by the NaPEG Reagents under mild, ambient conditions. Subsequent experiments us- ing actual soils spiked with PCBs clearly show, however, that water in soil greatly reduces the rate of dechlorination and the effectiveness of the reagents on PCBs in real soils These adverse effects were greater than expected from the prelim- inary results obtained in previous studies. In addition, it was found that the most effective reagent formulation for the dechlorination of PCBs in controlled one- phase reactions and model substrates was not the most effective reagent for PCBs in soil, specifically because of its extreme sensitivity to water. The reagents described in the full report are much less sensitive to deactivation with water. The next phase of experiments show that soil freshly contaminated with 1000 ppm of Aroclor 1260 can be decontam- inated to below 50 ppm PCBs in only a few days with a direct application of Potassium Polyethylene Glycol (KPEG) 350-1. Particularly encouraging is the fact that this reagent can be used on soil containing some water and organics, and that it continues to react after several days in open air On-Site Treatment of PCB-Contaminated Soil The first completed on-site experiment in the application of reagent to contam- inated soil was carried out by FRC per- sonnel in Buffalo, NY, in August 1983. This experiment produced inconclusive results in contrast to those obtained under laboratory-controlled conditions. The only known major problem which has adversely affected the results of this initial field study involves the inhibiting effect of water on the chemical degrada- tion rate. Subsequent laboratory tests demonstrated simple techniques that may be used to minimize the adverse effects of water on the rate of decontamination. The results of more recent, systematic laboratory investigations are much more encouraging than the preliminary on-site test. The level of PCBs in contaminated soil can be reduced from approximately 1000 ppm (highly contaminated) to below 50 ppm by direct chemical treatment under relatively mild conditions. This suggests that the direct on-site chemical treatment of PCB-contaminated soil is a promising process. Results using PCB-contaminated soil from the Philadelphia, PA, site showed that significant dechlorination is achieved by simply air drying the soil at room temperature prior to the application of the reagent. Without this pretreatment, in- significant decontamination was ob- served for the relatively wet soil, even when KPEG350-1 was used. When the soil sample was obtained from the site in May 1984, it was noticed that the treated soil was still very wet. Also, water condensation was observed under the plastic sheet that covered the plot. The sheet may keep the rain out, but it also tends to keep moisture in. This was probably not a major disadvantage, how- ever, because without the cover, all but the soil particles closest to the surface would retain most of their excess mois- ture, even in extremely dry atmosphere. In light of this, thorough mixing of the soil in air, prior to reagent application, should be an essential minimum pretreatment. Excess water, if not adsorbed, can be easily removed by exposing all of the soil to the surface, even at ambient temper- atures. If such a treatment is performed on-site, especially on a warm, dry day, the promising results obtained in the labo- ratory tests may be verified. At this time, the various inhibiting effects of water are the only known major problems which have adversely affected the results of this initial field study. Air drying is a very important step which should greatly minimize these effects in field tests. The on-site treatment of soils contam- inated with PCBs and other halogenated aromatics looks very promising, based on the results obtained in the laboratory studies. Considerable work remains to be done in the area of process development, particularly with respect to reducing the inhibiting effect of water and optimizing conditions for soil decontamination. Various solvent pretreatment and soil heating methods, for example, deserve additional and scaled-up investigation. Some of these techniques are currently being studied in the laboratory. Field testing must continue, however, not only to verify laboratory results, but to provide first-hand experience in real-world situa- tions that is necessary for the develop- ment of a field process. Conclusions The results of the overall study show that FRC NaPEG Reagents can signif- icantly reduce the concentration of PCBs in contaminated soils under controlled laboratory conditions. There are, how- ever, several areas in which improvement and optimization must be achieved in order to develop a viable and economical process for chemically treating PCB-con- taminated soils in the field. The most recent results of laboratory experiments suggest that: • Application of reagent to wet soil is not as effective in reducing the concentra- tion of PCBs. The water present in a typical reaction sample greatly dilutes the reagent. Air drying of the soil is necessary prior to treatment. • Increased temperature is, as expected, more effective in reducing PCB con- centration in soils. • Increasedtemperaturealsoeases mix- ing of reagent and soil; this should aid the continued reduction of PCB in soil over a period of time. • An increase in reaction time shows continued decrease in the concentra- ------- tion of PCBs in the soil, particularly of the more active components A greater reagent to soil ratio has shown the best results. This is likely due in part to increased contact of reagent with PCBs This effect can perhaps be duplicated by a better method of mixing. In addition, in- creased reagent to soil ratio means less soil water contamination in the reagent. This should also increase the rate of dechlorination. The syringe application method, which minimizes the amount of atmospheric water coming in contact with the reagent, is sufficient; no additional advantage is realized by applying the reagent to the soil under nitrogen. Kerosene added to the soil as a solvent pretreatment is more effective in real- izing dechlorination than toluene, or no solvent at low reaction tempera- tures, but not significantly more effec- tive than no solvent pretreatment, when reactions are conducted at higher temperatures. The reagent diluted with kerosene or toluene prior to application to the soil is not as effective in dechlorinating the PCBs as the reagent alone applied to the soil. Frank J. laconianni is with Franklin Research Center, Philadelphia, PA 19103. Charles J. Rogers is the EPA Project Officer (see below). The complete report, entitled "Destruction of PCBs—Environmental Applications of Alkali Metal Polyethylene Glycolate Complexes," (Order No. PB 86-105 293/AS; Cost: $11.95, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Hazardous Waste Engineering Research Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 Official Business Penalty for Private Use $300 EPA/600/S2-85/108 ------- |