Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
  • A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
  • A62D3/38—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by oxidation; by combustion
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
  • A62D2101/20—Organic substances
  • A62D2101/22—Organic substances containing halogen
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
  • A62D2101/20—Organic substances
  • A62D2101/28—Organic substances containing oxygen, sulfur, selenium or tellurium, i.e. chalcogen

Definitions

• the invention is directed to a process for the decontamination of solids contaminated with polychlorinated dibenzodioxins (PCDD) and / or polychlorinated dibenzofurans (PCDF).
• PCDD polychlorinated dibenzodioxins
• PCDF polychlorinated dibenzofurans
• PCDD / PCDF-containing gases are cleaned by passing them over a fixed bed or fluidized bed made of incombustible materials such as silicas, zeolites, silicates, TiO2 or Al2O3 and with Caro's acid or a their salts are brought into contact, whereby the PCDD and PCDF pollutants are oxidatively destroyed.
• incombustible materials such as silicas, zeolites, silicates, TiO2 or Al2O3
• Caro's acid or a their salts are brought into contact, whereby the PCDD and PCDF pollutants are oxidatively destroyed.
• this document gives no suggestion to decontaminate solids contaminated with PCDD / PCDF with oxidizing agents other than Caro's acid.
• U.S. Patent 4,632,742 teaches a process for decontaminating mineral oils and soils contaminated with polychlorodiphenyls, polychlorodibenzodioxins, and polychlorodibenzofurans. Decontamination is carried out by treating the contaminated material with a reagent composed of (a) a polyalcohol or polyethylene glycol, (b) a base, such as alkali or alkaline earth carbonate, and (c) an oxidizing agent or a free radical source, such as alkali or alkaline earth peroxide. wherein organically bound halogen is converted into inorganic halide.
• a reagent composed of (a) a polyalcohol or polyethylene glycol, (b) a base, such as alkali or alkaline earth carbonate, and (c) an oxidizing agent or a free radical source, such as alkali or alkaline earth peroxide. wherein organically bound halogen is converted into inorganic
• the treatment can be carried out at room temperature or elevated temperature and good decontamination can be achieved, it should be regarded as a disadvantage that, in addition to a peroxide, a base and additionally an alcoholic compound must also be present during the decontamination. This makes the decontamination of particulate materials more difficult because the actual decontamination treatment requires an expensive separation of the alcohols and salts.
• the aforementioned reagent can also be used in such a way that it is applied as a film to a particulate solid support and the liquid to be decontaminated is coated over the coated support is directed.
• the document does not teach the decontamination of a particulate solid.
• the object of the present invention is accordingly to provide a process for the direct decontamination of PCDD / PCDF-contaminated solids which can be carried out in a simple manner, the pollutants being oxidatively destroyed under mild conditions.
• the process should avoid the disadvantages of the previously known processes, such as the use of a number of auxiliaries and their elaborate removal and disposal after the actual decontamination.
• PCDD polychlorinated dibenzodioxins
• PCDF polychlorinated dibenzofurans
• PCDD polychlorinated dibenzodioxins
• PCDF polychlorinated dibenzofurans
• the decontamination according to the invention it is possible to largely reduce the content of the polychlorinated dibenzodioxins / dibenzofurans adsorbed on the solid by oxidative degradation thereof; Degradation rates of at least 70%, mostly more than 80% and often more than 90% are generally achieved.
• PCDD / PCDF residual contents of less than 5 ng / g solids can usually be achieved in accordance with the Hazardous Substances Ordinance (GefStoffV) applicable in the FRG.
• the initial contents of the contaminated solids can range between a few ng / g solid and a few micrograms / g solid, depending on their origin.
• PCDD / PCDF contents of the contaminated solids are calculated from the sum of the contents of the following PCDD or PCDF isomers: 2,3,7,8-tetrachlorodibenzodioxin (TCDD); 1,2,3,7,8-penta-CDD; 1,2,3,6,7,8-hexa-CDD; 1,2,3,7,8,9-hexa-CDD; 1,2,3,4,7,8-hexa-CDD; 2,3,7,8-tetrachlorodibenzofuran (TCDF); 2,3,4,7,8-penta-CDF and 1,2,3,6,7,8-hexa-CDF.
• TCDD 2,3,7,8-tetrachlorodibenzodioxin
• TCDF 2,3,7,8-penta-CDD
• 1,2,3,6,7,8-hexa-CDF 1,2,3,6,7,8-hexa-CDF.
• the decontamination can be carried out either using an aqueous solution containing hydrogen peroxide or using gaseous hydrogen peroxide.
• the concentration of the aqueous hydrogen peroxide solution can be in a wide range. A 10 to 50% by weight hydrogen peroxide solution is usually preferred.
• the contacting is usually carried out at a temperature in the range between 10 and 95 ° C., preferably at room temperature to 60 ° C.
• the treatment can be carried out by pumping the aqueous hydrogen peroxide solution through a bed containing the contaminated solid until the desired degree of decontamination is reached. In many cases it is also sufficient to leave a mixture of the contaminated solid and the aqueous hydrogen peroxide solution in a container and to stir it only if necessary. After draining off the aqueous hydrogen peroxide solution, the solid is washed with water.
• the solution containing hydrogen peroxide used in the process according to the invention can, in addition to an essentially pure hydrogen peroxide solution, also be an aqueous solution of sodium percarbonate, since sodium percarbonate releases hydrogen peroxide as an H2O2 addition compound immediately after being dissolved in water.
• an aqueous sodium percarbonate solution if the resulting alkalinity within the scope of Decontamination process does not interfere or even serves for neutralization or in the decontamination of acidic components.
• this gas mixture is passed through a bed containing the contaminated solid.
• air containing 0.01 to 1% by volume of hydrogen peroxide is passed through the solid bed.
• This treatment is usually carried out over a period of several hours. The treatment can be carried out at room temperature or at an elevated temperature.
• the process according to the invention can be used to decontaminate different solids which contain adsorbed PCDD's and PCDF's without the pollutants being converted from the solid phase into a gaseous phase, but rather being directly oxidatively destroyed almost quantitatively.
• the process is characterized by extraordinary simplicity, which was not to be expected in view of the usually very difficult to destroy polychlorinated dibenzodioxins and dibenzofurans.
• apart from hydrogen peroxide or sodium percarbonate no further auxiliaries for decontamination are required.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Processing Of Solid Wastes (AREA)
• Fire-Extinguishing Compositions (AREA)
• Treatment Of Sludge (AREA)

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Citations (5)

• 1995
  • 1995-03-01 EP EP95102847A patent/EP0679411A1/fr not_active Withdrawn
  • 1995-04-26 JP JP7102518A patent/JPH081131A/ja active Pending
  • 1995-04-28 HU HU9501244A patent/HUT70699A/hu unknown

Patent Citations (5)

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