Patent Number: 056132417
Section: summary

FIELD OF THE INVENTION The present invention relates to the treatment of halogen-containing wastes and other waste materials. More particularly, the invention relates to a process for treating halogenated waste materials by introducing the waste materials into a bath of molten glass containing a sacrificial metal oxide. BACKGROUND OF THE INVENTION Many industrial waste materials, such as radioactive wastes, chemically hazardous wastes, or toxic elemental wastes, present difficult disposal problems due to the hazard of the material and the intensely regulated nature of these materials. When halogens are contained within such waste material, the halogens create unique problems, which are not adequately addressed by conventional treatment methods. Sources of halogen-containing waste include, not only processes that create halide salts or halogens-containing compounds, but also wastes contaminated by radioactive or other hazardous materials. A chloride salt purification process used to process plutonium in a weapons complex is one example of a process generating halogen-containing waste. That process generates large quantities of chloride-containing radioactive wastes. Halogen-containing plastics, used as components of radioactive or chemically hazardous wastes streams or equipment are another example of halogen-containing wastes. These also require treatment for such disposal. Halogen-containing compounds are also used to create chemically resistant or fireproof manufactured goods which also present unique disposal problems. Examples include many plastics, such as Hypalon.RTM. plastic, a product of Dupont, Wilmington, Del., which are used to insulate electrical wire. Hypalon.RTM. plastic also contains valuable lead oxide that should be recovered both for recycling and to avoid long-term problems with the toxicity of the lead. In other cases, plastic within a waste material must be destroyed to recover copper and other valuable materials. Thus, a problem with many halogen-containing waste materials is that they were originally designed with great care not to burn or be damaged by chemicals. Though very desirable in a manufactured product, these properties cause difficulties in the treatment and disposal of such materials. With their water solubility, another significant problem with many halogen-containing wastes and waste forms (e.g. salts) is leaching and groundwater contamination. If a high quality waste form is to be made, the halogens should be removed from the waste before or during conversion to a waste form used for disposal. SUMMARY OF THE INVENTION The present invention addresses problems existing with the treatment of halogen-containing waste materials as well as other waste materials. Importantly, the present invention separates halogens from a waste material being treated, such as radioactive and hazardous wastes, and, thus, allows production of a non-halogen, high durability waste form. High concentrations of halogens in wastes imply low performance by the final waste disposal form. A second important feature of the invention is its ability to recycle reagents from the waste material treatment process. This is important to both minimize costs and avoid creating other hazardous wastes. Third, the present invention may be used to treat and/or destroy wastes made from materials designed to be difficult to destroy. Accordingly, in one embodiment, the present invention provides a process for treating a halogen-containing waste material. This process comprises the steps of: providing a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material, where the sacrificial metal oxide is present in at least a stoichiometric amount with respect to the halogen in the waste material; introducing the waste material into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide which is a gas at the temperature of the molten glass; separating the gaseous metal halide from the molten glass; contacting the gaseous metal halide with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal-containing precipitate and a soluble alkali metal halide; separating the precipitate from the aqueous scrubber solution; and removing the molten glass containing the treated waste material as a waste glass. In another embodiment, the present invention provides a process for the conversion of waste material containing halogen-containing compounds, elemental metal or carbon-containing compounds. This process comprises the steps of: providing a bath of molten glass containing at least one sacrificial metal oxide, where at least one sacrificial metal oxide is capable of reacting with a halogen in the waste material, or of oxidizing elemental metal or carbon-containing compounds within the waste material, and the sacrificial metal oxide is present in at least a stoichiometric amount for the reaction or the oxidation; introducing the waste material into the bath of molten glass to cause a reaction between the waste material and the sacrificial metal oxide, wherein at least one sacrificial metal oxide reacts with a halogen in the waste material to yield a metal halide which is a gas at the temperature of the molten glass and at least one sacrificial metal oxide oxidizes elemental metal to form an oxide of the elemental metal which is soluble in the molten glass or oxidizes the carbon-containing compound thereby reducing the sacrificial metal oxide to its elemental metal; separating the gaseous metal halide from the molten glass; contacting the gaseous metal halide with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal-containing precipitate and a soluble alkali metal halide; separating the precipitate from the aqueous scrubber solution; removing the molten glass containing the treated waste material as a waste glass; and recovering the elemental metal derived from the sacrificial metal oxide from the bath.