CA2026910C - Destruction of halogenated organic compounds - Google Patents
Destruction of halogenated organic compounds Download PDFInfo
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- CA2026910C CA2026910C CA002026910A CA2026910A CA2026910C CA 2026910 C CA2026910 C CA 2026910C CA 002026910 A CA002026910 A CA 002026910A CA 2026910 A CA2026910 A CA 2026910A CA 2026910 C CA2026910 C CA 2026910C
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
A method for the destruction of halogenated organic compounds and reduction of non-halogenated organic compounds contained in a contaminated medium, comprising: adding an aqueous solution or emulsion of a hydrogen donating organic compound to the contaminated medium, the aqueous solution or emulsion being added in an amount to provide from about 0.1 to about 20 weight percent of the hydrogen donating organic compound, based on the weight of the contaminated medium; adding an alkali metal hydroxide to the contaminated medium in an amount of from about 2 to about 20 weight percent based on the weight of the contaminated medium; heating the contaminated medium at a temperature and for a time sufficient to totally dehydrate the medium; further heating the medium at a temperature between about 200°C and 360°C for a time sufficient to effect destruction of the halogenated organic compunds; and adding an acid to the medium in an amount sufficient to provide the medium with a pH of from about 7 to about 9.
Description
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G.,~ ~E.~..~' ~..,' CJ Jx, j DESTRUCTION pF HALOGENATED ORGANIC COMPOUNDS
FIELD OF TH
The present invention relates to a method for the destruction of halogenatPd organic compounds contained in a contaminated medium. More particularly, the invention related to a method for the destruction of halogenated organic compounds and reduction of non-halogenated compounds contained in a contaminated medium by use of an inorganic nr organic hydrogen bearing compounds in contact with an alkali metal hydroxide, >3ACKGROUND OF THE ~.IyVENTION
The hazards to public health and the environment which are posed by a variety of synthetic halogenated organic compounds is well known. Compounds such as polychlorinated biphenyls (PCB's), dichlorodiphenyl trichloroethane (DDT).
dieldrin, lindane and chlordane have been found to be persistent, environmentally toxic materials which require safe and efficient means of disposal. PCB's pose a particularly serious disposal problem. Once widely used ac diplpc-.tric fluid additives in electrical equipment such as transformers and capacitors hec:ausp of their excellent insulating properties, the use of PCB's in many applications has been banned by the U.S. Environmental Protection Agency owing to their cumulative storage in the human body and extremely high toxicity. Thus, methods for the removal and/or destruetion of halogenated orr~anic compounds such as PCB's are required.
Various methods for the removal and/or the destruction or decomposion of halogenated organic compounds are known in the art. For example, the Peterson U.S. Patents Nos. 4,447,541 and 4,574,013 disclose methods for decontaminating soil which is contaminated with halogenated Organic compounds. The Peterson 11.5.
Patent No. 4,447,541 discloses process in which a reagent mixture of an alkaline constituent and a sulfoxide catalyst (DMSO) are intimately mixed with soil contaminated with PCB's. The reagent mixture affects a desorpt.ion of the halogenated contaminants from the soil and subsequently dehaloc~endted the contaminants. However, this process is disadvantageous in that the kinetics are relatively slow and therefore reduction of the PCt?; concentration to an acceptable level requires extended time periods ranging from weeks to months, the soil must be completely dry far the destruction to take place, large quantities of the reagent are required, and the sulfoxide catalyst may potentially transport contaminants prior to their destruction. The Peterson U_S. Patent No. 4,514, discloses a process wherein a heated slurry of contaminated soil is treated with a mixture of an alkaline constituent and a sulfoxide catalyst. However, t.hi~
process is similarly disadvantageous in that the sulfoxide catalyst may transport contaminants into living systems, and the sulfoxide catalyst prociuc:es odorous compounds when heated to high temperatures and decomposes into comhtistihle byproducts under elevated temperature conditions. This process is also disadvantageous in that it requires large amounts of reagen t .
The Rogers et al U.S. Patent No. 4,675,464 discloses a method for the chemical destruction of halogenated aliphatic hydrocarbons, and more particularly a method for the chemical destruction of ethylene dibromide. An alkali metal hydroxide is dissolved in an ethylene glycol and the resulting product is reacted with the halogenated hydrocarbon. Rogers et al further disclose that the reaction temperature should be maintained at 30°C or less to maintain the reaction products in solution.
The Pytlewski et al U.S. Patent No. 4,400,552 discloses a method for the decomposition of halogenated organic compounds which employs a reagent comprising the product of the reaction of an alkali metal hydroxide with a polyglycol or a polyglycol monoalkyl ether, and oxygen. The Pytlewski et al U.S. Patents No. 4,337,368 and 4,602,994 disclose similar methods of decomposing halogenated organic compounds.
However, these methods are disadvantageous in that excess amounts of the alkali metal hydroxide and polyglycol reagents are required in order to obtain a homogeneous distribution throughout the contaminated material, for example soil, sediment, sludge or the like, which is treated. Similarly, the Brunelle U.S. Patents No. 4,351,718 and 4,353,793 disclose methods for removing polyhalogenated hydrocarbons from nonpolar organic solvent solutions by treating the contaminated solutions with a mixture of polyethylene glycol and an alkali metal hydroxide. These methods are similarly disadvantageous in that excess amounts of reagent are required. Additional methods for removing and/or destructing halogenated organic compounds contained in contaminated materials are disclosed in the Howard et al U.S. Patent No. 4,327,027, the Mendiratta et al U.S. Patent No. 4,663,027, the Meenan et al U.S. Patents No. 4,685,220 and 4,793,937, the Rossi et al U.S. Patent No. 4,761,221, the Zeff et al U.S. Patent No. 4,792,407, European Patent Application No. 118,858, Chemical Abstracts, Vol. 82, No. 13962P (1975) and Kornel et al, Journal of Hazardous Materials, 12 (1985), pages 161-176. However, these and additional processes known in the art for the removal and/or destruction of halogenated organic compounds in contaminated materials are inadequate in view of the time required for acceptable levels of removal and/or destruction, the inability to remove all halogens on halogenated pollutants, the use of excessive amounts of various reagents, the production of toxic and/or combustible byproducts, and/or the failure to obtain desired removal and/or destruction levels. Thus, a need exists for additional methods for the removal and/or destruction of halogenated organic compounds in contaminated materials, which methods overcome the disadvantages of the prior art.
G.,~ ~E.~..~' ~..,' CJ Jx, j DESTRUCTION pF HALOGENATED ORGANIC COMPOUNDS
FIELD OF TH
The present invention relates to a method for the destruction of halogenatPd organic compounds contained in a contaminated medium. More particularly, the invention related to a method for the destruction of halogenated organic compounds and reduction of non-halogenated compounds contained in a contaminated medium by use of an inorganic nr organic hydrogen bearing compounds in contact with an alkali metal hydroxide, >3ACKGROUND OF THE ~.IyVENTION
The hazards to public health and the environment which are posed by a variety of synthetic halogenated organic compounds is well known. Compounds such as polychlorinated biphenyls (PCB's), dichlorodiphenyl trichloroethane (DDT).
dieldrin, lindane and chlordane have been found to be persistent, environmentally toxic materials which require safe and efficient means of disposal. PCB's pose a particularly serious disposal problem. Once widely used ac diplpc-.tric fluid additives in electrical equipment such as transformers and capacitors hec:ausp of their excellent insulating properties, the use of PCB's in many applications has been banned by the U.S. Environmental Protection Agency owing to their cumulative storage in the human body and extremely high toxicity. Thus, methods for the removal and/or destruetion of halogenated orr~anic compounds such as PCB's are required.
Various methods for the removal and/or the destruction or decomposion of halogenated organic compounds are known in the art. For example, the Peterson U.S. Patents Nos. 4,447,541 and 4,574,013 disclose methods for decontaminating soil which is contaminated with halogenated Organic compounds. The Peterson 11.5.
Patent No. 4,447,541 discloses process in which a reagent mixture of an alkaline constituent and a sulfoxide catalyst (DMSO) are intimately mixed with soil contaminated with PCB's. The reagent mixture affects a desorpt.ion of the halogenated contaminants from the soil and subsequently dehaloc~endted the contaminants. However, this process is disadvantageous in that the kinetics are relatively slow and therefore reduction of the PCt?; concentration to an acceptable level requires extended time periods ranging from weeks to months, the soil must be completely dry far the destruction to take place, large quantities of the reagent are required, and the sulfoxide catalyst may potentially transport contaminants prior to their destruction. The Peterson U_S. Patent No. 4,514, discloses a process wherein a heated slurry of contaminated soil is treated with a mixture of an alkaline constituent and a sulfoxide catalyst. However, t.hi~
process is similarly disadvantageous in that the sulfoxide catalyst may transport contaminants into living systems, and the sulfoxide catalyst prociuc:es odorous compounds when heated to high temperatures and decomposes into comhtistihle byproducts under elevated temperature conditions. This process is also disadvantageous in that it requires large amounts of reagen t .
The Rogers et al U.S. Patent No. 4,675,464 discloses a method for the chemical destruction of halogenated aliphatic hydrocarbons, and more particularly a method for the chemical destruction of ethylene dibromide. An alkali metal hydroxide is dissolved in an ethylene glycol and the resulting product is reacted with the halogenated hydrocarbon. Rogers et al further disclose that the reaction temperature should be maintained at 30°C or less to maintain the reaction products in solution.
The Pytlewski et al U.S. Patent No. 4,400,552 discloses a method for the decomposition of halogenated organic compounds which employs a reagent comprising the product of the reaction of an alkali metal hydroxide with a polyglycol or a polyglycol monoalkyl ether, and oxygen. The Pytlewski et al U.S. Patents No. 4,337,368 and 4,602,994 disclose similar methods of decomposing halogenated organic compounds.
However, these methods are disadvantageous in that excess amounts of the alkali metal hydroxide and polyglycol reagents are required in order to obtain a homogeneous distribution throughout the contaminated material, for example soil, sediment, sludge or the like, which is treated. Similarly, the Brunelle U.S. Patents No. 4,351,718 and 4,353,793 disclose methods for removing polyhalogenated hydrocarbons from nonpolar organic solvent solutions by treating the contaminated solutions with a mixture of polyethylene glycol and an alkali metal hydroxide. These methods are similarly disadvantageous in that excess amounts of reagent are required. Additional methods for removing and/or destructing halogenated organic compounds contained in contaminated materials are disclosed in the Howard et al U.S. Patent No. 4,327,027, the Mendiratta et al U.S. Patent No. 4,663,027, the Meenan et al U.S. Patents No. 4,685,220 and 4,793,937, the Rossi et al U.S. Patent No. 4,761,221, the Zeff et al U.S. Patent No. 4,792,407, European Patent Application No. 118,858, Chemical Abstracts, Vol. 82, No. 13962P (1975) and Kornel et al, Journal of Hazardous Materials, 12 (1985), pages 161-176. However, these and additional processes known in the art for the removal and/or destruction of halogenated organic compounds in contaminated materials are inadequate in view of the time required for acceptable levels of removal and/or destruction, the inability to remove all halogens on halogenated pollutants, the use of excessive amounts of various reagents, the production of toxic and/or combustible byproducts, and/or the failure to obtain desired removal and/or destruction levels. Thus, a need exists for additional methods for the removal and/or destruction of halogenated organic compounds in contaminated materials, which methods overcome the disadvantages of the prior art.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new method for the destruction of halogenated organic compounds contained in a contaminated medium. It is a further object of the invention to provide a method for the destruction of halogenated organic compounds contained in a contaminated medium which employs significantly less amounts of reagent as compared with prior art methods. It is a further object of the invention to provide such a method wherein environmentally acceptable levels of halogenated organic compounds are achieved in the treated materials. It is a related object of the invention to provide such a method wherein the environmentally acceptable levels of contaminants in the materials are obtainable within a short period of time.
These and additional objects are achieved by the present invention which relates to methods for the destruction of halogenated organic compounds contained in a contaminated medium. The methods of the invention comprise the steps of adding an aqueous solution on a solid organic hydrogen donor to a contaminated medium containing the halogenated organic compounds. An alkali metal hydroxide is then added to the contaminated medium.
Because the hydrogen donor generally is added in an aqueous solution, water distributes the reagents throughout the medium and acts as a wetting agent. The contaminated medium is then heated at a temperature and for a time sufficient to totally dehydrate the medium.
Although the water is removed, the reagents are well distributed throughout the medium and are concentrated to a very reactive state. The medium is then further heated at a temperature between about 200 and 360°C for a time sufficient to effect destruction of the halogenated organic compounds. Destruction of the halogenated compounds in the contaminated medium is more dependent on the presence of the alkali metal compound as the temperature increases within this range. Finally, an acid is added to the medium in an amount sufficient to neutralize the medium so that it may be returned to its original environment. Because aqueous solution of hydrogen donating compounds or in solid mixtures are employed, the amounts of reagents which are required for the present methods are significantly reduced. Additionally, because the reagents are well distributed throughout the medium by the aqueous solution, a homogeneous destruction of the halogenated organic compounds and reduction of thermal stable compounds is achieved.
Moreover, because lower amounts of reagent are employed, recycling of excess reagents is not required.
When this invention is practiced on contaminated fluids such as transformer oil, capacitor oil or other nonaqueous hydrocarbon systems which contain halogenated materials, the hydrogen donor if required and the alkali metal base may be directly added to media without the addition of water.
These and additional objects and advantages will become more fully understood in view of the following detailed description.
DETAILED DESCRIPTION
The present invention comprises methods for the destruction of halogenated organic compounds contained in a contaminated medium. The contaminated medium may comprise soil, sludge, sediment or a liquid. The present methods are particularly adapted for use with soils, sludges and sediments. The methods are suitable for use with mediums which contain up to and in excess of 100,000 ppm of halogenated organic compounds, aliphatic or aromatic, for example PCB's, or even higher levels of the halogenated organic compounds.
The contaminated mediums which are suitable for use in the invention may also include an absorbent or adsorbent, for example spent activated carbon or the like.
Generally, the methods of the invention comprise adding an aqueous solution of a hydrogen donor - organic compound to the contaminated medium, adding an alkali metal hydroxide to the contaminated medium, heating the contaminated medium to obtain total dehydration, and further heating the medium to destroy the halogenated organic compounds.
The water included in the hydrogen donor solution distributes the reagents throughout the contaminated medium. The hydrogen donor _-3(a) ~'R ("~ V. v ' > ~ ~ -t~ r ~t F,., ?~ ~'.~ v ;i _z_ %f and the alkali metal hydroxide react to produce a alkali metal hydride, hydrogen radicals, and other reagents not completely defined.
The aqueous solution of the hydrogen donor compound is added to the contaminated medium in an amount to provide from about 0.1 to about 20 weight percent hydrogen donor based on the weight of the contaminated medium.
Additionally, the aqueous solution contains sufficient water to effect homogeneous distribution of the hydrogen donor and the subsequently added alkali metal hydroxide throughout the contaminated medium. While the particular amount of the aqueous solution of hydrogen donor which is added to the contaminated medium generally depends on the level of halogenated organic compounds contained in the medium, in a preferred embodiment, the aqueous solution of hydrogen donor' added in an amount sufficient to provide from about 1 to about 5 weight percent hydrogen donor based on the weight of the contaminated medium.
Various, materials are known in the art and are suitable for use as hydrogen donors in this invention. Included are carbohydrates, polyhydrogxy aliphatic, amines, terpenes, hydrocarbons, fatty acids or any organic compound that decomposes and releases hydrogen as a radical or utilizable form under treatment conditions.
The alkali metal hydroxide is added to the contaminated medium in an amount of from about 2 to about 20 weight percent, again based on the weight of the contaminated medium. As with the aqueous solution of carbohydrate, the specific amount of alkali metal hydroxide which is required is dependent on the level of halogenated organic compounds contained in the contaminated medium. In a preferred embodiment, the alkali metal hydroxide is added in an amount of from about 2 to about 12 weight percent based on the weight of the contaminated medium. The metal which forms the hydroxide reagent may be any of the alkali metals, or mixtures thereof. Preferred alkali metals include lithium, sodium and potassium with sodium and potassium being particularly preferred.
After addition of the aqueous solution of carbohydrate and the alkali metal hydroxide, the contaminated medium is heated at a temperature and for a time sufficient to totally dehydrate the medium, i.e., to remove 99 + weight percent or more of the water contained therein. As will be demonstrated in the Examples, this heating step may be performed at atmospheric pressure or at reduced or elevated pressures if so desired. As noted above, the water which is included in the aqueous solution or suspension of carbohydrates allows homogeneous distribution of both the hydrogen donor and the alkali metal hydroxide throughout the medium and acts as a wetting agent and a penetrant. The reagent which results from the reaction of the alkali metal hydroxide and the hydrogen donor namely the carbohydrate is, as a practical matter, an admixture or salable in water. Moreover, when the water is removed from the medium during the dehydration step, the reagent is then concentrated to a very reactive state yet is well distributed throughout the contaminated medium.
After dehydration, the medium is further heated at a temperature between about 200 and 360°C for a time sufficient to effect destruction of the halogenated organic compounds. More preferably, the medium is heated at a temperature between about 250'C and 350°C to effeet destruction of the halogenated organic compounds. The time required for destruction of the halogenated organic compounds similarly depends upon the level of such compounds in the contaminated material. Generally however, a time period of from about 0.5 to about 4 hours is sufficient.
Finally, the medium is treated with an acid for neutralization.
Preferably, the an d is added in amount sufficient to provide the medium with a pH value of from about 7 to about 9. Suitable acids for use in the invention comprise sulfuric acid, phosphoric acid, hydrochloric acid and nitric acid.
Generally, oxygen is not a detriment to the methods of the present invention and therefore air need not be excluded. When applied to the decontamination of hydrocarbon fluids, either aliphatic or aromatic, it may be desirable to exclude air in order to prevent ignition of the hydrocarbon.
Thus, the present m~thods may be performed either in the presence or the absence of an oxygen-containing atmosphere.
Because the present methods employ relatively small amounts of both the carbohydrate or other low cost organic hydrogen donors and alkali metal hydroxide reagents, there is no need to recover excess reagents for reuse. Moreover, because the present invention employs water to wet the Contaminated medium and to distribute the hydrogen donor and alkali metal hydroxide reagents therein, the present methods are significantly less costly than prior art methods which employ polyethylene glycol to treat the contaminated medium. The present methods may be performed in either a continuous or a batch system, and, if desired, all steps may be performed in a single reactor. As will be demonstrated in the Examples, the methods of the invention reduce organic compounds, particularly haloaromatic compounds, to nondetectable levels. Additionally, the products of the present methods are non-mutagenic, non-teratogenic and non-toxic to life forms.
The methods of the present invention are demonstrated in the following Examples:
This example demonstrates the application of the method according to the present invention to a contaminated material comprising PC8 contaminated soil from Guam U.S. A. The soil contained approximately 2,000 to 2,500 ppm of a PCB
having the commercial designation Aroclor 1260. One hundred grams of the contaminated soil was placed in a round bottom flask provided with a stirrer and a distillation head condenser and receiver. To the contaminated soils was added 25 ml of water containing 5 grams of sucrose. The resulting slurry was thoroughly mixed for about five minutes after which 12.5 grams of 98 percent sodium hydroxide was added. Mixing was resumed and heating of the reaction was commenced. Water was distilled off over a 1/2 to 1-1/2 hour period, after which the contents of the reactor were further heated to a temperature between 305 and 355'C for four hours. After heating, the reactor was cooled and the contents mere neutralized by acid addition to have a pH of between 7 arid 9. The resulting product was subjected to PCB analysis which revealed that the residual PCB's remaining in the soil were IeSS than 1 ppm.
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This example further demonstrates the methods according to the present invention. One hundred grams of the PCB-containing soil described in Example 1 were placed in the same type of reactor as described in Example 1. To the mixture was added 25 ml of water containing 5 grams of sucrose. The mixture was stirred for approximately five minutes and 12.5 grams of 98 percent sodium hydroxide was added. Mixing was resumed and heating was initiated. A vacuum of about 29 inches of Hg was drawn on the reactor and water was distilled off at a temperature of from 35 to 85°C. After the water had been removed, in about 0.5 to 1 hour, the reactor contents rose in temperature to about 325 -355°C within to 30 minutes. A temperature of 345 to 350° was maintained for 1 to 1.5 hours, after which the reactor was cooled. The treated soil was analyzed for residual PCB's as in Example 1. Again, the analysis showed a residual PCB
level of less than 1 ppm.
This example demonstrates the application of the method according to the present invention to a contaminated material comprising PCB-contaminated soil from Mechanicsburg, PA., which had been spiked with pentachlorophenol to a level of 10.25 mg per 10 grams of soil. In a 100 ml round-bottom flask, 20.5 grams of the soil was placed, after which 5 ml of water containing 1 gram of sucrose were added. The contents of the flask were thoroughly mixed. After mixing, 2.0 grams of sodium hydroxide pellets were added. The flask was equipped with a distillation head, eondenser and receiving flask, and a thermoprobe was inserted through the distillation head so that the probe tip rested in the soils slurry.
The flask temperature was raised by means of a heating mantle to approximately 333 - 350°c and was maintained within this temperature range for 2 hours. After cooling, 11 grams of residual soil were removed from the reactor and adjusted to a pH of 2, with dilute hydrochloric acid (HC1). This material was then extracted, and the concentrated extract was subjected to analysis by Gas chromatography-Mass spectrometry (GC-MS). No pentachlorophenol was detected, nor were any PCB congeners detected in this treated soil extract. Further, the glassware, including the distillation head and condenser, were rinsed with acetone into the receiving flask which contained the distilled and condensed water. This water acetone mixture was adjusted to a pH of 2 with HC1 and extracted into hexane. The hexane was concentrated 10 ml and analyzed by GC-MS
as in the case of the soil extract. Again, no PCP was detected, nor any of the PCP break down products, which would be expected if no reaction had occurred.
Only traces of PCB congeners were detected in this distilled condensed material.
This example further demonstrates the application of the present methods for destruction of halogenated organic compounds. TO an additional sample of the Mechanicsburg, PA soils as described in Example 3, was added Aroc)or 1242 at 1.5 mg per l0 grams of soil, and Dieldrin at 1.75 mg per 10 grams of soil. Twenty grams of the resulting spiked-contaminated soil were placed into the same reaction equipment as described in Example 3, together with 5 ml of water 6T. ~'( V:~~ n ~ 5.'i containing 1 gram of sucrose. After mixing, 2.4 grams of sodium hydroxide in pellet form were added and the reaction equipment was set up as in Example 3.
The temperature was raised to and maintained between 330 - 345"C for 2 hours.
After cooling, the soil, as well as any condensate, was extracted and analyzed via GC-MS. Analysis of the soil revealed that no Lindane, Dieldrin, or PCB's were remaining in the treated soil sample. Analysis of the distillate revealed no Lindane or Dieldrin and only traces of PCB congeners.
xa..~ ~
example demonstrates the application of the present methods far destruction of halogenated organic Compounds namely PCB in a hydrocarbon oil.
To 50 m1 of SUN PAR LW-107 hydrocarbon oil were added 500 mg of Aroclor 1254 (a PCB) dissolved and placed into a 100 ml round bottom flask. To 'this mixture was added 2 grams of sucrose and 5 grams of sodium hydroxide pellets. The flask was fitted with a stirrer, distillation head, condenser and receiver as in the previous examples. After heating and maintaining a temperature of 350 -360°C
for one hour the analysis as performed for example above reveal that PCB's were below 1 ppm.
The preceding examples are set forth to illustrate specific emhndiments of the invention, and are not intended to limit the scope of the methods of the present invention. Additional embodiments and advantages within the scope of the claimed invention will be apparent to one of ordinary skill in the art.
Accordingly, it is an object of the present invention to provide a new method for the destruction of halogenated organic compounds contained in a contaminated medium. It is a further object of the invention to provide a method for the destruction of halogenated organic compounds contained in a contaminated medium which employs significantly less amounts of reagent as compared with prior art methods. It is a further object of the invention to provide such a method wherein environmentally acceptable levels of halogenated organic compounds are achieved in the treated materials. It is a related object of the invention to provide such a method wherein the environmentally acceptable levels of contaminants in the materials are obtainable within a short period of time.
These and additional objects are achieved by the present invention which relates to methods for the destruction of halogenated organic compounds contained in a contaminated medium. The methods of the invention comprise the steps of adding an aqueous solution on a solid organic hydrogen donor to a contaminated medium containing the halogenated organic compounds. An alkali metal hydroxide is then added to the contaminated medium.
Because the hydrogen donor generally is added in an aqueous solution, water distributes the reagents throughout the medium and acts as a wetting agent. The contaminated medium is then heated at a temperature and for a time sufficient to totally dehydrate the medium.
Although the water is removed, the reagents are well distributed throughout the medium and are concentrated to a very reactive state. The medium is then further heated at a temperature between about 200 and 360°C for a time sufficient to effect destruction of the halogenated organic compounds. Destruction of the halogenated compounds in the contaminated medium is more dependent on the presence of the alkali metal compound as the temperature increases within this range. Finally, an acid is added to the medium in an amount sufficient to neutralize the medium so that it may be returned to its original environment. Because aqueous solution of hydrogen donating compounds or in solid mixtures are employed, the amounts of reagents which are required for the present methods are significantly reduced. Additionally, because the reagents are well distributed throughout the medium by the aqueous solution, a homogeneous destruction of the halogenated organic compounds and reduction of thermal stable compounds is achieved.
Moreover, because lower amounts of reagent are employed, recycling of excess reagents is not required.
When this invention is practiced on contaminated fluids such as transformer oil, capacitor oil or other nonaqueous hydrocarbon systems which contain halogenated materials, the hydrogen donor if required and the alkali metal base may be directly added to media without the addition of water.
These and additional objects and advantages will become more fully understood in view of the following detailed description.
DETAILED DESCRIPTION
The present invention comprises methods for the destruction of halogenated organic compounds contained in a contaminated medium. The contaminated medium may comprise soil, sludge, sediment or a liquid. The present methods are particularly adapted for use with soils, sludges and sediments. The methods are suitable for use with mediums which contain up to and in excess of 100,000 ppm of halogenated organic compounds, aliphatic or aromatic, for example PCB's, or even higher levels of the halogenated organic compounds.
The contaminated mediums which are suitable for use in the invention may also include an absorbent or adsorbent, for example spent activated carbon or the like.
Generally, the methods of the invention comprise adding an aqueous solution of a hydrogen donor - organic compound to the contaminated medium, adding an alkali metal hydroxide to the contaminated medium, heating the contaminated medium to obtain total dehydration, and further heating the medium to destroy the halogenated organic compounds.
The water included in the hydrogen donor solution distributes the reagents throughout the contaminated medium. The hydrogen donor _-3(a) ~'R ("~ V. v ' > ~ ~ -t~ r ~t F,., ?~ ~'.~ v ;i _z_ %f and the alkali metal hydroxide react to produce a alkali metal hydride, hydrogen radicals, and other reagents not completely defined.
The aqueous solution of the hydrogen donor compound is added to the contaminated medium in an amount to provide from about 0.1 to about 20 weight percent hydrogen donor based on the weight of the contaminated medium.
Additionally, the aqueous solution contains sufficient water to effect homogeneous distribution of the hydrogen donor and the subsequently added alkali metal hydroxide throughout the contaminated medium. While the particular amount of the aqueous solution of hydrogen donor which is added to the contaminated medium generally depends on the level of halogenated organic compounds contained in the medium, in a preferred embodiment, the aqueous solution of hydrogen donor' added in an amount sufficient to provide from about 1 to about 5 weight percent hydrogen donor based on the weight of the contaminated medium.
Various, materials are known in the art and are suitable for use as hydrogen donors in this invention. Included are carbohydrates, polyhydrogxy aliphatic, amines, terpenes, hydrocarbons, fatty acids or any organic compound that decomposes and releases hydrogen as a radical or utilizable form under treatment conditions.
The alkali metal hydroxide is added to the contaminated medium in an amount of from about 2 to about 20 weight percent, again based on the weight of the contaminated medium. As with the aqueous solution of carbohydrate, the specific amount of alkali metal hydroxide which is required is dependent on the level of halogenated organic compounds contained in the contaminated medium. In a preferred embodiment, the alkali metal hydroxide is added in an amount of from about 2 to about 12 weight percent based on the weight of the contaminated medium. The metal which forms the hydroxide reagent may be any of the alkali metals, or mixtures thereof. Preferred alkali metals include lithium, sodium and potassium with sodium and potassium being particularly preferred.
After addition of the aqueous solution of carbohydrate and the alkali metal hydroxide, the contaminated medium is heated at a temperature and for a time sufficient to totally dehydrate the medium, i.e., to remove 99 + weight percent or more of the water contained therein. As will be demonstrated in the Examples, this heating step may be performed at atmospheric pressure or at reduced or elevated pressures if so desired. As noted above, the water which is included in the aqueous solution or suspension of carbohydrates allows homogeneous distribution of both the hydrogen donor and the alkali metal hydroxide throughout the medium and acts as a wetting agent and a penetrant. The reagent which results from the reaction of the alkali metal hydroxide and the hydrogen donor namely the carbohydrate is, as a practical matter, an admixture or salable in water. Moreover, when the water is removed from the medium during the dehydration step, the reagent is then concentrated to a very reactive state yet is well distributed throughout the contaminated medium.
After dehydration, the medium is further heated at a temperature between about 200 and 360°C for a time sufficient to effect destruction of the halogenated organic compounds. More preferably, the medium is heated at a temperature between about 250'C and 350°C to effeet destruction of the halogenated organic compounds. The time required for destruction of the halogenated organic compounds similarly depends upon the level of such compounds in the contaminated material. Generally however, a time period of from about 0.5 to about 4 hours is sufficient.
Finally, the medium is treated with an acid for neutralization.
Preferably, the an d is added in amount sufficient to provide the medium with a pH value of from about 7 to about 9. Suitable acids for use in the invention comprise sulfuric acid, phosphoric acid, hydrochloric acid and nitric acid.
Generally, oxygen is not a detriment to the methods of the present invention and therefore air need not be excluded. When applied to the decontamination of hydrocarbon fluids, either aliphatic or aromatic, it may be desirable to exclude air in order to prevent ignition of the hydrocarbon.
Thus, the present m~thods may be performed either in the presence or the absence of an oxygen-containing atmosphere.
Because the present methods employ relatively small amounts of both the carbohydrate or other low cost organic hydrogen donors and alkali metal hydroxide reagents, there is no need to recover excess reagents for reuse. Moreover, because the present invention employs water to wet the Contaminated medium and to distribute the hydrogen donor and alkali metal hydroxide reagents therein, the present methods are significantly less costly than prior art methods which employ polyethylene glycol to treat the contaminated medium. The present methods may be performed in either a continuous or a batch system, and, if desired, all steps may be performed in a single reactor. As will be demonstrated in the Examples, the methods of the invention reduce organic compounds, particularly haloaromatic compounds, to nondetectable levels. Additionally, the products of the present methods are non-mutagenic, non-teratogenic and non-toxic to life forms.
The methods of the present invention are demonstrated in the following Examples:
This example demonstrates the application of the method according to the present invention to a contaminated material comprising PC8 contaminated soil from Guam U.S. A. The soil contained approximately 2,000 to 2,500 ppm of a PCB
having the commercial designation Aroclor 1260. One hundred grams of the contaminated soil was placed in a round bottom flask provided with a stirrer and a distillation head condenser and receiver. To the contaminated soils was added 25 ml of water containing 5 grams of sucrose. The resulting slurry was thoroughly mixed for about five minutes after which 12.5 grams of 98 percent sodium hydroxide was added. Mixing was resumed and heating of the reaction was commenced. Water was distilled off over a 1/2 to 1-1/2 hour period, after which the contents of the reactor were further heated to a temperature between 305 and 355'C for four hours. After heating, the reactor was cooled and the contents mere neutralized by acid addition to have a pH of between 7 arid 9. The resulting product was subjected to PCB analysis which revealed that the residual PCB's remaining in the soil were IeSS than 1 ppm.
G;.~ ~:; f MPLE
This example further demonstrates the methods according to the present invention. One hundred grams of the PCB-containing soil described in Example 1 were placed in the same type of reactor as described in Example 1. To the mixture was added 25 ml of water containing 5 grams of sucrose. The mixture was stirred for approximately five minutes and 12.5 grams of 98 percent sodium hydroxide was added. Mixing was resumed and heating was initiated. A vacuum of about 29 inches of Hg was drawn on the reactor and water was distilled off at a temperature of from 35 to 85°C. After the water had been removed, in about 0.5 to 1 hour, the reactor contents rose in temperature to about 325 -355°C within to 30 minutes. A temperature of 345 to 350° was maintained for 1 to 1.5 hours, after which the reactor was cooled. The treated soil was analyzed for residual PCB's as in Example 1. Again, the analysis showed a residual PCB
level of less than 1 ppm.
This example demonstrates the application of the method according to the present invention to a contaminated material comprising PCB-contaminated soil from Mechanicsburg, PA., which had been spiked with pentachlorophenol to a level of 10.25 mg per 10 grams of soil. In a 100 ml round-bottom flask, 20.5 grams of the soil was placed, after which 5 ml of water containing 1 gram of sucrose were added. The contents of the flask were thoroughly mixed. After mixing, 2.0 grams of sodium hydroxide pellets were added. The flask was equipped with a distillation head, eondenser and receiving flask, and a thermoprobe was inserted through the distillation head so that the probe tip rested in the soils slurry.
The flask temperature was raised by means of a heating mantle to approximately 333 - 350°c and was maintained within this temperature range for 2 hours. After cooling, 11 grams of residual soil were removed from the reactor and adjusted to a pH of 2, with dilute hydrochloric acid (HC1). This material was then extracted, and the concentrated extract was subjected to analysis by Gas chromatography-Mass spectrometry (GC-MS). No pentachlorophenol was detected, nor were any PCB congeners detected in this treated soil extract. Further, the glassware, including the distillation head and condenser, were rinsed with acetone into the receiving flask which contained the distilled and condensed water. This water acetone mixture was adjusted to a pH of 2 with HC1 and extracted into hexane. The hexane was concentrated 10 ml and analyzed by GC-MS
as in the case of the soil extract. Again, no PCP was detected, nor any of the PCP break down products, which would be expected if no reaction had occurred.
Only traces of PCB congeners were detected in this distilled condensed material.
This example further demonstrates the application of the present methods for destruction of halogenated organic compounds. TO an additional sample of the Mechanicsburg, PA soils as described in Example 3, was added Aroc)or 1242 at 1.5 mg per l0 grams of soil, and Dieldrin at 1.75 mg per 10 grams of soil. Twenty grams of the resulting spiked-contaminated soil were placed into the same reaction equipment as described in Example 3, together with 5 ml of water 6T. ~'( V:~~ n ~ 5.'i containing 1 gram of sucrose. After mixing, 2.4 grams of sodium hydroxide in pellet form were added and the reaction equipment was set up as in Example 3.
The temperature was raised to and maintained between 330 - 345"C for 2 hours.
After cooling, the soil, as well as any condensate, was extracted and analyzed via GC-MS. Analysis of the soil revealed that no Lindane, Dieldrin, or PCB's were remaining in the treated soil sample. Analysis of the distillate revealed no Lindane or Dieldrin and only traces of PCB congeners.
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example demonstrates the application of the present methods far destruction of halogenated organic Compounds namely PCB in a hydrocarbon oil.
To 50 m1 of SUN PAR LW-107 hydrocarbon oil were added 500 mg of Aroclor 1254 (a PCB) dissolved and placed into a 100 ml round bottom flask. To 'this mixture was added 2 grams of sucrose and 5 grams of sodium hydroxide pellets. The flask was fitted with a stirrer, distillation head, condenser and receiver as in the previous examples. After heating and maintaining a temperature of 350 -360°C
for one hour the analysis as performed for example above reveal that PCB's were below 1 ppm.
The preceding examples are set forth to illustrate specific emhndiments of the invention, and are not intended to limit the scope of the methods of the present invention. Additional embodiments and advantages within the scope of the claimed invention will be apparent to one of ordinary skill in the art.
Claims (17)
1. A method for the destruction of halogenated organic compounds and reduction of non-halogenated organic compounds contained in a contaminated medium, comprising (a) adding an aqueous solution or emulsion of a hydrogen donating organic compound to the contaminated medium, the aqueous solution or emulsion being added in an amount to provide from about 0.1 to about 20 weight percent of the hydrogen donating organic compound, based on the weight of the contaminated medium;
(b) adding an alkali metal hydroxide to the contaminated medium in an amount of from about 2 to about 20 weight percent based on the weight of the contaminated medium;
(c) heating the contaminated medium at a temperature and for a time sufficient to totally dehydrate the medium;
(d) further heating the medium at a temperature between about 200°C and 360°C for a time sufficient to effect destruction of the halogenated organic compounds; and (e) adding an acid to the medium in an amount sufficient to provide the medium with a pH of from about 7 to about 9.
(b) adding an alkali metal hydroxide to the contaminated medium in an amount of from about 2 to about 20 weight percent based on the weight of the contaminated medium;
(c) heating the contaminated medium at a temperature and for a time sufficient to totally dehydrate the medium;
(d) further heating the medium at a temperature between about 200°C and 360°C for a time sufficient to effect destruction of the halogenated organic compounds; and (e) adding an acid to the medium in an amount sufficient to provide the medium with a pH of from about 7 to about 9.
2. A method as defined by claim 1, wherein the hydrogen donating organic compounds are organic compounds that decompose and release hydrogen as a radical.
3. A method as defined by claim 1, wherein the hydrogen donating organic compound is selected from the group consisting of alcohols, carbohydrates, polyhydroxy aliphatics, amines, terpenes, hydrocarbons and fatty acids.
4. A method as defined by claim 1, wherein the hydrogen donating organic compound is a carbohydrate.
5. A method as defined by claim 1, wherein the aqueous solution or emulsion is added in an amount to provide from about 1 to about 5 weight percent of the hydrogen donating organic compound, based on the weight of the contaminated medium.
6. A method as defined by claim 1, wherein the alkali metal hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.
7. A method as defined by claim 1, wherein the alkali metal hydroxide is added in an amount of from about 2 to about 12 weight percent based on the weight of the contaminated medium.
8. A method as defined by claim 1, wherein the contaminated medium is heated under vacuum to substantially dehydrate the medium.
9. A method as defined by claim 1, wherein in step (d) the medium is further heated at a temperature between about 250°C and 350°C to effect destruction of the halogenated organic compounds.
10. A method as defined by claim, 1, wherein the acid which is added to the medium to provide a pH of from 7 to about 9 is selected from the group consisting of sulphuric acid, phosphoric acid, hydrochloric acid and nitric acid.
11. A method as defined by claim 1, wherein the contaminated medium comprises soil.
12. A method as defined by claim 1, wherein the contaminated medium comprises sludge.
13. A method as defined by claim 1, wherein the contaminated medium comprises sediment.
14. A method as defined by claim 1, wherein the contaminated medium includes an absorbent comprising spend activated carbon.
15. A method as defined by claim 1, wherein the contaminated medium comprises a liquid.
16. A method as defined by claim 1, wherein the contaminated medium contains up to 100,000 ppm of halogenated organic compounds.
17. A method as defined by claim 1, wherein the medium which results from the acid addition step is returned to its original environment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002026910A CA2026910C (en) | 1990-10-04 | 1990-10-04 | Destruction of halogenated organic compounds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002026910A CA2026910C (en) | 1990-10-04 | 1990-10-04 | Destruction of halogenated organic compounds |
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| Publication Number | Publication Date |
|---|---|
| CA2026910A1 CA2026910A1 (en) | 1992-04-05 |
| CA2026910C true CA2026910C (en) | 2000-11-21 |
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| CA002026910A Expired - Fee Related CA2026910C (en) | 1990-10-04 | 1990-10-04 | Destruction of halogenated organic compounds |
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| CA (1) | CA2026910C (en) |
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| CA2026910A1 (en) | 1992-04-05 |
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