United States Environmental Protection Agency Municipal Environmental Research 5 Laboratory Cincinnati OH 45268 Research and Development EPA-600/S2-82-021 May 1982 Project Summary Sodium Fluxing and In-Situ Classification for Hazardous Materials Disposal J. S. Greer, G. H. Griwatz, S. S. Gross, and R. H. Hiltz Toxic waste disposal has become a prime consideration in the maintenance of the ecosystem. Numerous materials of commerce pose problems in dis- posal, being unsuitable for landfill and resistant to thermal degradation. A project was instituted by the U.S. Environmental Protection Agency to evaluate new approaches to the ultimate disposal of such materials. This program, one segment of the major project, was instituted to assess two innovative techniques, in-situ glassification and reactive degradation using liquid sodium. The glassification technique was successful in the encapsulation of toxic materials. Because of the need for very high reaction temperatures. however, small but significant quanti- ties of the toxic material were vented during reaction. This difficulty could not be corrected within the limits of this contract. The use of a molten sodium medium to thermally degrade toxic materials to products acceptable for direct disposal or recovery was successfully demon- strated. Based upon the data derived and the existing state-of-the-art, a practical system to use this technique for ultimate disposal appears feasible. This Project Summary was devel- opedby EPA's MunicipalEnvironmen- tal Research Laboratory, Cincinnati, OH, to announce key findings of the research project that is fully document- ed in a separate report of the same title (see Project Report ordering informa- tion at back). Introduction As technology for the control and cleanup of hazardous material spills has evolved, the volume and types of mate- rials that must be disposed of has increased commensurately. Difficulties have arisen in the disposal of certain hazardous material categories. The short- comings of landfill disposal have been quite evident. Incineration is more re- liable, but it is not adaptable to all hazardous chemicals. The existing situation has led the Environmental Protection Agency to investigate alternate procedures for the ultimate disposal of hazardous chem- icals. As part of this general investiga- tion, a contract was awarded to MSA Research Corporation to conduct a laboratory feasibility study of two pro- cedures—sodium metal fluxing and glassification—for ultimate disposal. Both procedures had sufficient back- ground information to justify the investi- gation. At temperatures above its melting point, the ability of sodium to degrade organic compounds into simple or ele- mental substances is well known. The process, however, has never been in- vestigated as a disposal technique. The encapsulation of materials in a glass matrix has been under investiga- tion for some time as a disposal tech- nique. The approach to date has been to ------- disperse the material to be disposed in a molten glass phase. The process could be considered reasonably successful, except for the fact that the dispersed material is not always totally encap- sulated. Since dispersion cannot be accomplished on a micro scale, networks of the contained phase can persist to the surface of the total mass. A laboratory study was initiated to evaluate molten sodium as a mechanism for degrading a range of hazardous materials to disposable products and to investigate encapsulation using in-situ glass formation. The sodium fluxing process was successfully demonstrated for several categories of materials. The glassification study, although technically successful, generated some side effects that were undesirable. Glassification Study The use of glass to encapsulate toxic or radioactive materials for safe dis- posal has seen extensive development. Although several procedures have evolved, they all essentially blend the chemical to be disposed into a molten glass matrix. The basic drawback has been the difficulty of entraining the material for disposal as a discontinuous phase. Gross segregations or semi- continuous areas in the glass allow a path to the surface to occur, thereby enabling the encapsulated material to be leached by long-term exposure to the environment. This action is exaggerated when cracking or other failures occur in, the glass. This difficulty could be minimized by dispersion of the encapsulated phase on a micro scale. One approach is to use a large volume ratio of glass to material for disposal. An alternate approach, which would also result in a smaller disposal volume, appears possible if the glass phase could be pyrochemically formed in-situ. This procedure would blend glass-forming compounds with the material for disposal. A thermal reaction would fuse the mass into glass and entrain the hazardous material as discrete particles. A test program was conducted in three steps—definition of pyrochemical compositions that would form a glass, selection of an optimum system based upon leaching resistance, and deline- ation of acceptable glass/hazardous chemical ratios. The test phase was begun by evalu- ating pyrochemical glass reactions pre- viously reported.* The basic thermal reaction is given in equation 1 : 10K02 (1) B203, Si 02, and AI2Os are added as glass-forming compounds. Glass was formed by these reactions, but the off- gasing of COz caused severe porosity and impaired fusion. Additional pyrochemical reactions were evaluatedto develop an essentially gasless reaction. The restrictions im- posed by the need to stay within the glass-forming compositions limited the reactions that could be considered to the alkali and alkaline earth metal peroxides and superoxides and the metals silicon, boron, and aluminum. A large number of compositional vari- ations were evaluated. Equation 2 gives the composition finally selected as the best glass former. 8 KOz + 3 Si + 4 Al 3SiO2+2AI2 (2) To evaluate the glass-forming reaction as a mechanism of encapsulation, five nonvolatile test compounds were selec- ted. These were copper arsenate, cad- mium selenide, leaddihydroxydicarbon- ate, antimony sulfide, and ammonium dichromate. These represent toxic in- organic compounds containing heavy metal ions. They cover materials that decompose below the temperature of the pyrochemical reaction (white lead and dichromate), an intermetallic(CdSe), and compounds that could take part in the glass reaction (arsenate and sulfide). In each case, the selected compound was added as 25-volume percent of the glass-forming components. With the exception of the cadmium selenide system, all compacts formed a glass. The cadmium selenide charge resulted in a porous clinker. All compacts were subjected to 48- hour exposures to boiling water leaching studies. The averaged results of these tests are as follows: Element Arsenic Antimony Chromium Lead Selenium Cadmium Copper Leachate mg/100 ml 5.0 1.5 0.01 0.05 1.70 0.025 0.12 'Carbon Dioxide Generating Compositions, U.S. Patent No. 3,477,955. Although the leaching results wer encouraging, all fusions had as a undesirable side effect, the release c paniculate matter during reaction. Anal yses showed that between 1 and • percent of the material being encap sulated or of a product resulting from it thermal decomposition was released. The investigation established that < glass phase can be developed througl pyrochemical reaction of base compo nents and that materials can be incor porated into the glass matrix during it! formation with good resistance to ex traction by leaching. The utility of the pyrochemical systerr is compromised by the release of panic- ulate matter containing the hazardous compound during reaction. The amount lost is small compared to the total volume of reactants, but it does not appear to be a tolerable situation. Pro- cesses to alleviate the problem were defined, but not investigated. Liquid Sodium Reactions The ability of liquid sodium to degrade a broad range of chemicals is well established. Data have been developed on the fate of the basic decomposition products. With the exception of hydro- gen and nitrogen, which are released as pure gases, all other elements that would occur in toxic materials would be retained by the sodium and would be recoverable as innocuous materials. Some occur as particulates and can be filtered out. Others have temperature sensitive solubilities and can be removed through temperature control. In a few cases, distillation or dissolution of the sodium may be necessary. Because liquid alkali metals are used as heat transfer fluids, systems to handle liquid sodium are items of com- merce, and technology is available to provide a liquid alkali metal system to degrade toxic materials. Questions re- main concerning the controllability of exotherms that may result and the ability to remove or otherwise recover the ------- resultant degradation products in a practical manner. An experimental apparatus was de- signed, based upon the current practice for alkali metal handling systems, to conduct a laboratory evaluation of liquid sodium as a disposal system. Five representative hazardous materials were selected for the test program—antimony trisulfide, mercuric chloride, sodium fluorosilicate, 2-chloro-4-phenyl phenol, and parathion. Kepone was added as a test material later in the program. The reactions of the six materials with molten sodium showthatthis technique can provide the basis for the disposal of many otherwise unmanageable waste materials. As expected, the materials reacted with excess sodium to form innocuous salts, carbon, and free metals, with the release of gaseous hydrogen. The simple salts, mercuric chloride and antimony sulfide, degrade basically to the metal and appropriate sodium salt. The more complex compounds proceed through a series of intermediate reaction products but ultimately degrade to basic elements or sodium salts. This was observed in tests with 2-chloro-4-phenyl phenol, kepone, and parathion. Nitrogen was the only element that did not behave as expected. Parathion, which has a nitro substituent, should have released nitrogen, but none was found. The products of these reactions (salts, heavy metals, and free carbon) can be separated by combinations of filtering, cold trapping, solvent extraction, and/or vacuum distillation. They could be re- moved as relatively pure materials for recycling, or as innocuous waste prod- ucts that could be handled by standard disposal procedures. The potential of the system for degrad- ing essentially pure materials has been established. It is reasonably certain that using state-of-the-art technology and equipment, a system of commercial size could be developed. The full report was submitted in ful- fillment of Contract No. 68-03-2492 by MSA Research Corporation under the sponsorship of the U.S. Environmental Protection Agency. J. S. Greer. G. H. Griwatz. S. S. Gross, and R. H. Hiltz are with MSA Research Corporation, Evans City, PA 16033. John E. Brugger is the EPA Project Officer (see below). The complete report, entitled "Sodium Fluxing and In-Situ Classification for Hazardous Materials Disposal," (Order No. PB 82-196 155; Cost: $7.50, s 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: Oil'& Hazardous Materials Spills Branch Municipal Environmental Research Laboratory—Cincinnati U.S. Environmental Protection Agency Edison, NJ 08837 if U S GOVERNMENT PRINTING OFFICE, 1982 — 559-017/0720 ------- United States Center for Environmental Research Environmental Protection Information c«/ ~ _... i Agency Cincinnati OH 45268 Protect™ Agency EPA 335 Official Business Penalty for Private Use $300 RETURN POSTAGE GUARANTEED T1_ „ Third-Class Bulk Rate MERL0063240 | LOU W TILLEY ! REGION V EPA LIBRARIAN 230 S DEARBORN ST CHICAGO IL 60604 ------- |