2000 Progress 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 Period Covered by this Report: February 1, 2000 through January 31, 2001
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
Objective:The major objective is to develop basic knowledge on the use of solvated electron chemistry for possible use as a single, multifunctional, portable technology applicable to both onsite in situ and onsite ex situ destruction of PCBs, CAHs, CFCs, munition/explosive residues, discarded propellants, and chemical warfare agents. The immediate objectives include the complete dechlorination of CAHs in Na/NH3 and Ca/NH3 in the presence of increasing quantities of water, and learning if the reaction of solvated electron with water competes with dechlorination. Another objective is the destruction (complete dechlorination) of PCBs and CAHs in a variety of wet soils. The key goal is 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, are being studied.
Progress Summary:PCB- 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.TM 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 over 20,000 ppm of PCBs have been detoxified to levels below 0.5 ppm. Typically, from 2 to 4 percent wt. 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.
Treatment of Polyaromatic Hydrocarbons with Na/NH3. Pure samples of polyaromatic 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.
Decontamination of B4 Clay Soil Containing Lindane. A wet clay soil, type B4, was contaminated with 5,000 ppm of the persistent pesticide lindane (C6H6Cl6) and then treated with Na/NH3 at room temperature. Two grams of soil per 10 mL of NH3 was the soil/NH3 ratio used. The stoichiometry of Na was varied between Na/Cl ratios of 4.16 to 12.5. When a Na/Cl ratio of 12.5 was used, 87 percent of the Lindane was converted to benzene and 1,3-dichlorobenzene was the major isomer (11 percent) that remained. The use of larger amounts of Na allowed complete dechlorination to be achieved.
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 in our laboratory. Furthermore, addition of MgCl2, CaCl2, SrCl2, BaCl2 and AlCl3, has been found to speed up the C-F bond cleavage in fluorinated phenols. 1-Fluorononane defluorinated slowly in Na/NH3. After 15 minutes at room temperature, only 39 percent fluorine cleavage occured in a 12-mole excess of Na. The activation energy was 11.4 kcal/mole. 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. Some unknown products and 89 percent C9H20 were obtained. Further studies employing neat TiCl4/1-fluorononane reactions revealed that an explosively fast, exothermic reaction occurs between alkyl fluorides and TiCl4. TiCl4 exchanges chlorine into the alkane and rips out F- to form TiCl3F. The reaction proceeds with more fluoroalkane to eventually produce TiClF3 and 3 RCl. This rapid F/Cl exchange proceeds through a cationic mechanism, but it does not isomerize the hydrocarbon chain in the reaction of either 1-fluorooctane or 1-fluorononane with TiCl4. A similar reaction occurs with the model secondary alkyl fluoride, fluorocyclohexane, and with a, a, a-trifluorotoluene. Then rapid dechlorination can occur in Na/NH3.
The cleavage of aromatic fluorines is not as fast as chlorine cleavage. Fluorobenzenes were defluorinated by solvated electron reactions in liquid NH3 where either alkali or alkaline metals are the electron source. Calcium and sodium were the best metals for aromatic defluorinations. When sufficient sodium was not available during reductions of p-chlorofluorobenzene to remove all the halogens, more fluorine was found in the resulting products. However, this did not lead to a selective reduction procedure because the reactions are so fast they occur in close to diffusion controlled rates.
Remediation of Soils Contaminated with Fluorobenzene or p-Chlorofluorobenzene. The B4 clay soil (contaminated with 5,000 ppm of fluorobenzene or 5,000 ppm of p-chlorofluorobenzene) was treated with Na/NH3. Substantial reductions in these pollutants occurred. This work is preliminary.
Future Activities:More work on PAHs (neat with H2O present and in wet soils) and aliphatic and aromatic nitro compounds will be performed to see the Na consumptions required for various structures. This should include model compound and soil work. Studies of defluorination (model compounds), and selective defluorination in the presence of other halogens such as chlorine (model compounds) will be conducted. Because C-F bonds are hard to break, developing rapid defluorination methods is important.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 22 publications||8 publications in selected types||All 5 journal articles|
||Sun GR, He JB, Zhu HJ, Pittman CU. Cleavage of arylalkylsilanes by sodium amide in liquid ammonia. Synlett. 2000;(5):619-622.||
||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.||