Final Report: Destruction of PCBs, CAHs, CFCs and Organic Nitro/Nitrate Wastes in Soils and Bulk with Ca/NH3 at Ambient TemperatureEPA Grant Number: R826180
Title: Destruction of PCBs, CAHs, CFCs and Organic Nitro/Nitrate Wastes in Soils and Bulk with Ca/NH3 at Ambient Temperature
Investigators: Pittman, Charles U.
Institution: Mississippi State University - Main Campus
EPA Project Officer: Lasat, Mitch
Project Period: February 1, 1998 through January 31, 2001 (Extended to January 31, 2002)
Project Amount: $317,027
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Air , Engineering and Environmental Chemistry
The overall objective of this research project was to develop basic knowledge on the use of solvated electron chemistry (for example: Na/NH3 or Ca/NH3) for possible use as a single, multifunctional, portable technology applicable to both onsite in situ and onsite ex situ destruction of polychlorinated biphenyls (PCBs), chlorinated aromatic hydrocarbons (CAHs), chlorofluorocarbons (CFCs), munition/explosive residues, discarded propellants, and chemical warfare agents. The specific objectives included: (1) complete dechlorination of CAHs, PCBs, chlorinated pesticides, chlorinated olefins such as tetrachloroethylene, in Na/NH3, or in Ca/NH3, in the presence of increasing quantities of water and learning if the reaction of solvated electron with water competes with dechlorination; and (2) destruction (complete dechlorination) of PCBs, CAHs, tetrachloroethylene, and chlorinated pesticides in a variety of wet soils. The key goal was to remediate PCB-contaminated and CAH-contaminated soils in the presence of water without excessive consumption of Na or Ca via onsite slurrying of contaminated soil in Na/NH3 or Ca/NH3. Similar reductions of CFCs, nitro compounds both neat and in soils, were studied. Further objectives included determining if explosive/propellant wastes (nitro and nitrates) and chemical warfare agents could readily be destroyed.
PCBs, and other chlorinated aromatic compounds, are distributed in soils and sludges at more than 400 sites in the United States. CAHs occur as serious contaminants at 358 major hazardous waste sites in the United States, and they migrate vertically through soils to form dense non-aqueous phase liquids (DNAPLs) on aquifer bottoms. Nitro compound wastes abound around amunition plants and nitration operations. Every state is represented in this problem. Thus, a national need exists for both in situ and ex situ methods to destroy these pollutants in soils and sludges rapidly at ambient temperature before they migrate into groundwater.
We have demonstrated that both Na/NH3 and Ca/NH3 solutions (solvated electrons) will dechlorinate PCBs and CAHs in seconds at ambient temperature, even in the presence of excess water. The PCB- and CAH-contaminated soils (as received clay, loam, and sandy soils containing up to 25 percent water) were successfully decontaminated within 30 seconds at 25°C. The PCB and CAH destruction efficiencies were greater than 99.9 percent. Na/NH3 was more efficient than Ca/NH3. This advantage of Na versus Ca increases as the H2O/RCl increased. Rates of dechlorination of carbon tetrachloride (CCl4), CH3CCl3, and some chloroaromatics were found to occur at diffusion controlled rates, as demonstrated by reductions in Na-deficient environments. Intermediate dechlorinated products, such as CHCl3 or CH2Cl2, were not observed in CCl4 reductions. Only CH4 and CCl4 were detected. Chlorinated phenols (pentachlorophenol; 2,4,6-trichlorophenol; and 2-chloro-4-fluorophenol) are all completely dechloronated at room temperature.
CB- and Dioxin-Contaminated Sludges and Oils. A sample of river sediment from the PCB-contaminated New Bedford Harbor Sawyer St. superfund site in Massachusetts was washed with diisopropylamine by the RCC B. E. S. T. process to give an oil concentrate with a PCB level of 32,800 ppm. Dioxins/furans (TEFs) also were present at 47,000 ppt. The concentrate was treated with Na/NH3. After treatment, the PCB level was only 1.3 ppm, well below regulatory requirements for disposal in nonhazardous waste landfills. Dioxins present also were readily remediated. This study also illustrates that the Na/NH3 process can remove lead, selenium, and arsenic to below detection limits. The metals were removed from the solid matrix during transport of liquid ammonia from the reactor vessel. Metals were recovered from the ammonia recycle unit for fixing and disposal.
Decontamination of Oils. Contaminated transformer oils and cutting fluids have been readily remediated using Na/NH3. Oils containing more than 20,000 ppm of PCBs have been detoxified to levels below 0.5 ppm. Typically, 2 to 4 percent weight Na in liquid NH3 was used. The NaNH3 also was used to remediate dioxins in waste oil from the McCormick and Baxter site in California. Dioxins were reduced to ppt levels.
Decontamination of Explosives Wastes in Soil. The explosives octahydro-1,3,5,7-telenitro-1,3,5,7-tetrazocine (HMX), 1,3,5-trinitro-hevahydro-s-triazine (RDX), and 1,2-dinitrobenzene, present in 9.6 to 3,580 mg/kg of soil (from Los Alamos) were decontaminated to the detection limit (0.03 mg/kg) using a single Na/NH3 treatment at 39°C (destruction efficiency > 99.999 percent).
Treatment of Polycyclic Aromatic Hydrocarbons With Na/NH3. Pure samples of polycyclic aromatic hydrocarbons (PAHs) are readily destroyed by solvated electrons in NH3. Oligomeric Birch reduction type products are obtained. These reactions are slower than dehalogenation, as was demonstrated by the rapid formation of benzene, toluene, and napthalene in Na/NH3 from their corresponding monochloro derivatives. Chlorine loss takes place before further reduction of PAHs occurs. Soils contaminated with PAHs were remediated to below detection levels. Mononuclear aromatics (benzene, toluene, anisole, nitrobenzene) undergo ring reduction according to the well-known Birch reduction.
Several soils, purposely contaminated with 1,1,1-trichloroethane, 1-chlorooctane, and tetrachloroethylene, were remediated by slurrying the soils in NH3 followed by addition of sodium. The consumption of sodium per mole of chlorine removed was examined as a function of both the hazardous substrate's concentration in the soil and the amount of water present. The Na consumption per Cl removed increases as the amount of water increases and the substrate concentration in soil decreases. However, remediation was still readily accomplished from 5,000 or 3,000 ppm to sub-ppm levels of RCl in the presence of substantial amounts of water. The PCB- and dioxin-contaminated oils were remediated with Na/NH3, as were PCB-contaminated soils and sludges from contaminated sites. The Ca/NH3 treatments also successfully remediated PCB-contaminated clay and sandy and organic soils, but laboratory studies demonstrated that Ca was less efficient than Na when substantial amounts of water were present. The advantages of solvated electron reductions using Na/NH3 include: (1) very rapid dehalogenation rates at ambient temperature; (2) soils (even clay soils) break down into particles and slurry nicely in NH3; (3) liquid ammonia handling technology is well known; and (4) removal from soils, recovery, and recycle of ammonia is easy due to its low boiling point. Finally, dechlorination is extremely fast even for the "corner" chlorines in the substrate Mirex.
Defluorination of Aliphatic and Aromatic Fluorinated Compounds. The defluorination of aliphatic (1-fluorononane, 1-fluorooctane, fluorocyclohexane) and aromatic compounds (fluorobenzene, fluorinated phenols) by Na/NH3, has been accomplished. Furthermore, addition of MgCl2, CaCl2, SrCl2, BaCl2, and AlCl3 has been found to speed up the C-F bond cleavage in fluorinated phenols. The 1-fluorononane defluorinated slowly in Na/NH3. The rate is far too slow to be useful in wet soils. Alkaline earths Ca/NH3 and Sr/NH3 did not speed up defluorination. However, rapid cleavage of fluorine occurred when Na/NH3 was added to TiCl4/C9H19F. Further studies employing neat TiCl4/1-fluorononane reactions revealed that an explosively fast, exothermic reaction occurs between alkyl fluorides and TiCl4. The TiCl4 exchanges chlorine into the alkane and rips out F- to form TiCl3F. A similar reaction occurs with the model secondary alkyl fluoride, fluorocyclohexane, and with ,,-trifluorotoluene. Then rapid dechlorination can occur in Na/NH3.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
|Other project views:||All 22 publications||8 publications in selected types||All 5 journal articles|
||Kinney PL, Northridge M, Gronning E, Joseph E, Frantz S, Prakash S. On the front lines of environmental interventions to reduce asthma. American Journal of Public Health 2002;92:1-3.||
||Pittman Jr CU, Yang C. Dechlorination of polychlorobiphenyls using NaBH4 and NaBH4/LiCl at 120-310C in glyme solvents. Journal of Hazardous Materials 2001;82(3):299-311.||
||Pittman Jr CU, He JB. Dechlorination of PCBs, CAHs, herbicides and pesticides neat and in soils at 25°C using Na/NH3. Journal of Hazardous Materials 2002;92(1):51-62.||
||Sun GR, He JB, Pittman CU Jr. Destruction of halogenated hydrocarbons with solvated electrons in the presence of water. Chemosphere 2000;41(6):907-916.||