WO1999004914A2 - Method and apparatus for removing contaminants from soil - Google Patents

Abstract

The present invention comprises contacting contaminated soil with water, then heating the soil/water mixture until the water vaporizes. The water vapor carries with it some of the contaminants that are present in the soil. The water vapor with the contaminants carried with it is transferred to a condenser wherein the vapor condenses. The condensate is collected in a collection container. In most cases, the contaminants will be organics that are lighter and immiscible in water. The condensate will normally separate into two or more phases. The organic phase can then be easily removed and disposed of. Optionally, the remaining decontaminated soil may be further treated by adding an oxidizing agent to the soil. The oxidizing agent may be added directly to the soil, or may be generated in situ and then added to the soil.

Description

METHOD AND APPARATUS FOR REMOVING CONTAMINANTS FROM SOIL

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application Serial No. 60/053,461, filed July 23, 1997.

FIELD OF THE INVENTION

This invention relates to a method for removing contaminants, such as chlorinated and non-chlorinated solvents and the lighter fractions of petroleum hydrocarbons, from soils or other substrates, and for recovering the contaminants for recycling or environmentally sound ultimate disposal.

BACKGROUND OF THE INVENTION

The contamination of soils, sediments, still bottoms, filters, personal protective equipment and like materials with industrial solvents, petroleum hydrocarbons and other organic liquids is of increasing concern. Contamination of soil by such compounds occurs in a variety of ways including spills and discharges during processing, loading, storage and transport, percolation into the soil from waste lagoons and landfills, pipeline breaks, leakage from underground storage tanks, agricultural uses and from dumping.

One harm from such contamination is in the degradation of ground water and ground water aquifers especially those used as a source of potable water.

As a result of these potential harms, the government has established regulations which require that contaminated soils and waters be treated to remove these hazardous materials before they cause these harms. These regulations have established very low levels of contaminants, especially those from chlorinated and non- chlorinated solvents and hydrocarbons, which are permitted to remain in the soil or water. And, over the years, the government has continued to lower the permitted level for each of these contaminants.

Regulations governing the treatment of contaminated soils generally require excavation and treatment of those soils contaminated with petroleum hydrocarbons (TPH). There are numerous approaches to the treatment of soils to remove contaminants. One common approach is to pile the soil on a prepared pad arranged to allow for air or other gas to be drawn downwardly through the pile. The air as it passes through the soil strips volatile organic compounds from the soil and carries those compounds with it. Air is collected from pipes located in the soil pile and is then treated to remove the volatile organic compounds. The concentration of stripped organic compounds carried in the exiting air stream is quite low; often on the order of a few parts per million. A very large volume of air must then be treated during the course of a soil remediation project. Typical approaches to the treatment of such air streams includes passing the air through a column containing an adsorbent solid such as activated carbon or by fume incineration of the contaminant compounds.

Incineration of contaminated soils has been used. It is technically feasible to destroy most contaminant compounds by incineration but the technique is not practical for large soil volumes and is very costly requiring large quantities of fuel. All of the soil must be raised to incineration temperatures leaving a product which is hot and difficult to handle and to transport. U.S. Pat. No. 4,974,528 describes what might be called a modified incineration process. The '528 patent discloses a vehicle mounted, inclined rotary kiln for removing hydrocarbon contaminants from soils. Contaminated soil is fed into the upper end of the kiln and a burner assembly is located at the lower, or discharge, end of the kiln. Soil is heated to temperatures as high as

345° C. as it passes through the kiln resulting in the volatilization or burning of the lighter fraction hydrocarbons from the soil. Combustion gases are removed from the upper kiln end and are drawn through a bag house for the removal of fines. The cleaned gases are then reheated and passed to a catalytic incinerator to burn the remaining hydrocarbons in the gas.

A number of other approaches to soil remediation have been compiled by the Environmental Protection Agency in a publication entitled "The Superfund Innovative Technology Evaluation Program: Technology Profiles"; EPA/540/5-89/013, November 1989. Among the processes listed therein, the following are considered worthy of note. A vapor extraction system under development by American Toxic Disposal, Inc. of Waukegan, 111. employs a fluidized bed to remove volatile contaminants from soils and similar materials. Direct contact between the soil and a gas from a gas fired heater at a temperature of about 320°F volatilizes water and contaminants from the soil into the gas stream. Particulates are first removed from the gas stream by means of a cyclone separator and baghouse. The gas stream from the baghouse is cooled in a venturi scrubber, countercurrent washer and chiller and is then passed through a carbon bed to adsorb the remaining contaminants. Most of the soil fed to the fluidized bed is recovered as a clean, dry dust cleaned of volatiles. Other by-products include a small quantity of sludge resulting from clarification of the water used in the process; quantities of spent adsorbent carbon; a wastewater stream that might require further treatment; and small amounts of baghouse and cyclone dust. It is stated that the process can remove polychlorinated biphenyls, polynuclear aromatic hydrocarbons, volatile inorganics and some pesticides from soils.

Another process described in the Environmental Protection Agency publication is a soil washing system which has been demonstrated by Biotrol, Inc. of Chaska, Minn. Contaminated soil is subjected to attrition washing during which highly contaminated fine soil particles are separated from the coarser sand and gravel. The bulk of the soil is discharged as a clean washed product leaving a process water which contains the highly contaminated fine particles as well as dissolved contaminants. Thereafter, the fine solids are dewatered to obtain a thickened slurry and a clarified process water stream. Both the slurry and the clarified water require a secondary treatment before discharge which may be, for example, a biodegradation process. The technique was developed to clean soils contaminated with wood preserving chemicals.

U.S. Patent No. 5,256,208 discloses a method of removing volatile organic compounds by exposing the contaminants in soil to steam. The steam is then flashed off with the volatilized contaminants. The method disclosed in the '208 patent requires that steam be generated and then passed through the soil. The process requires a steam generator and an elaborate apparatus to carry out the process.

All of the soil remediation processes of the prior art have serious drawbacks. The use of air or some other gas to strip contaminant compounds from soils takes a long time, produces an uneven result as uniform percolation of air through the soil cannot easily be achieved, and requires the secondary treatment of very large air volumes. Incineration is very costly, produces a product that is difficult to handle and, in some instances, requires contaminant removal from the incinerator flue gas. The fluidized bed system also is energy intensive, requires extensive treatment of the exiting gas stream and leaves the soil in a hot dry, dusty state while producing several by-product streams which require further treatment. All incineration systems may also contribute to other regulated gaseous contaminants being released from fuel burning.

Soil washing using attrition washing is necessarily limited to soils which are predominately sand and gravel and results as well in a silt or clay suspension which requires further treatment and is difficult to dewater. Batch low pressure steam distillation of slurries is high in energy use, limited in treatable compounds, and requires the handling of water-soil slurries with all the attendant difficulties entailed therewith.

There is clearly a need for additional simple, effective ways to clean up soils contaminated with solvents, hydrocarbons, and the like to reduce residual contaminants to the low levels required by the governmental regulations with efficient fuel usage without producing as well large volume byproduct liquid and/or gas streams requiring purification. Further, it is of considerable advantage to obtain as a product a soil suitable for replacement in the ground without further conditioning or treatment, which none of the above mentioned alternatives accomplish.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for separating and recovering volatilizable contaminants from soils, sediments, still bottoms, filters, personal protective equipment and other materials. The present invention is an effective treatment alternative to landfilling and other conventional methods which is applicable to a broad range of contaminants and soil types, and which possesses none of the drawbacks of the prior art methods. The present invention is especially useful for treating organically contaminated materials.

The present invention comprises contacting contaminated soil with water in a reactor, then heating the soil/water mixture until the water vaporizes. The water vapor carries with it some of the contaminants that are present in the soil. The water vapor with the contaminants carried with it is transferred to a condenser wherein the vapor condenses. The condensate is collected in a collection container. In most cases, the contaminants will be organics that are lighter and immiscible in water. The condensate will normally separate into two or more phases. The organic phase can then be easily removed and disposed of.

The present invention optionally includes the further treatment of the soil by conventional means to remove any remaining contaminants. The desired second treatment is with oxidants such as persulfate. (See for example, J. Cooper, et al., Lawrence

Livermore National lab. Report, SF2-3-MW, October-December 1995. Published January 27, 1996.) The persulfate can be added to the reactor during or after the vapor phase transfer. However, it is contemplated as part of the present invention that any prior art method of treating soil can be used as a second treatment. The present invention optionally provides that the oxidant may either be added directly to the reactor, or may be generated in situ and then added to the reactor. Additionally, if the oxidant is generated in situ, the spent oxidant may be removed from the reactor and regenerated before being returned to the reactor.

The present invention thus provides an inexpensive and easy method of treating contaminated soil. The present invention does not require elaborate and expensive equipment nor does it require expensive treating agents. Accordingly, it is an object of the present invention to provide a method for recovering, as well as separating, a wide range of contaminants from a variety of soil types.

It is another object of the present invention to provide a method for separating and recovering contaminants from soil which precludes any pollution and escape of contaminants to the air, surface waters or groundwater.

It is a further object of the invention to provide a method for separating and recovering volatilizable contaminants from soil in which no combustion of the vaporized contaminants produced in the drying of the soil occurs.

It is a still further object of the invention to remove volatilizable contaminants from soil to enable the soil to be returned to the site of its origination.

It is yet another object of the present invention to provide a method and apparatus that can remove a large amount of contaminant from soil.

It is another object of the present invention to provide a method and apparatus that uses water to remove organic contaminants from soil. It is yet another object of the present invention to provide a process which will produce a finished soil that complies with the current hazardous waste regulatory treatment standards.

It is a still further object of the invention to use an oxidant that may be generated in situ to further treat the soil. These and other objects of the invention will be apparent to those skilled in the art from the following description of the preferred embodiment thereof in association with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a flow diagram of the apparatus of the present invention.

FIG. 2 is a diagram of an apparatus wherein oxidant is generated outside the reactor and recycled.

FIG. 3 is a diagram of an apparatus wherein oxidant is generated inside the reactor.

DETAILED DESCRIPTION As used herein, the term "soil" is defined as unconsolidated earth material composing the superficial geologic strata (material overlying bedrock), comprising clay, silt, sand, or gravel sized particles as classified by the U.S. Soil Conversation Service, or a mixture of such materials with liquids, sludges or solids which is inseparable by simple mechanical removal processes and is made up primarily of soil by volume based on visual inspection. Soil contaminants amenable to removal by the process of this invention include that group of materials commonly referred to as organic compounds and include as well all of those soil contaminants displaying a significant partial pressure in the presence of steam at super atmospheric pressures. For the purposes of this disclosure, the term "organic compounds" or "organic contaminants" includes, but is not limited to, such materials as pesticides, herbicides, and industrial and agricultural products and by-products and wastes which ordinarily might not be considered to be volatile organic compounds.

The present invention is a method and apparatus for removing contaminants from soils, sediments, still bottoms, filters, personal protective equipment and other materials. In practicing the present invention, the contaminated soil is introduced into a reactor and water is added to the contaminated solid forming a slurry. It is important to thoroughly mix the soil with the water. The reactor is then heated until the water begins to boil. The method of the present invention physically removes volatile and semi-volatile organics by boiling the material to be treated in water, condensing the vapor and collecting the water which then contains the organics. It has been found that by using heated water in contact with the contaminated soil, the removal can be accomplished more readily and at lower temperatures than by heating the sample without water. The soil sample with the water therein can operate at reduced temperatures by reducing the pressure in the system or at temperatures above the 100° C by increasing the pressure on the system. The separation process can be improved by adding a non-volatile mineral oil to the collection vessel.

In an optional second step and, optionally in the same reactor, an oxidant, including, but not limited to, persulfuric acid, sodium persulfate, ammonium persulfate, peroxide, CI2, permanganate, and persulfate salt may be added. Preferably, the oxidant is a persulfate, such as persulfuric acid, sodium persulfate or ammonium persulfate. The oxidant is added to oxidize any remaining volatile or nonvolatile organic materials to carbon dioxide and water. If a chlorinated oxidant is used, the process will also emit HC1. In this step, the temperature may either be reduced or the boiling may be continued. However, it has been discovered that the temperature is preferably between about 40° to about 100° C. More preferably, the temperature is about 85° C. Additionally, the commercially available or pre-made oxidant may either be added directly to the reactor, or may be generated in situ. If the oxidant is persulfate and is generated in situ, there are two separate processes that may be used. In the first process, an electrolyzer having electrodes therein is used. Sulfuric acid and a sulfate and/or a bisulfate is added to the electrolyzer and the sulfuric acid, sulfate and/or bisulfate are then electrolyzed using the electrodes. The oxidant is then added to the main reactor. In the second process, the sulfuric acid, sulfate and/or bisulfate are added directly to the main reactor, which has been fitted to include electrodes, and the mixture is electrified using the electrodes to produce the oxidant within the main reactor. When generating the oxidant in situ, the raw ingredients used to produce the oxidant may include, but are not limited to, sulfuric acid, sodium sulfate, ammonium sulfate, potassium sulfate, bisulfates, or mixtures thereof. Generally, the process will operate as a batch process but can operate in a continuous mode. The combined process can treat solids contaminated with hazardous and non-hazardous organics including, but not limited to, materials such as benzene, toluene, ethylbenzene, xylene, chlorinated hydrocarbons, PCBs, CFCs, TPHs, pesticides, dioxins, acetone, ethers, amines, or organic phosphates. The present invention produces solids that meet EPA treatment standards for disposal. The process will also work on pure liquids or sludges or to decontaminate equipment.

Referring now to Fig. 1, there is schematically depicted one embodiment of the present invention. Reactor 15 is a closed reactor that is capable of being sealed from the outside atmosphere. Heating elements 17 are in contact with reactor 15. Heating can be by any conventional means including, but not limited to, electric immersion heater, steam jacket, oil bath and the like. Reactor 15 is connected to condenser 25 by transport means 20. Transport means 20 is desirably a pipe. Condenser 25 has a heat exchange means 27. Condenser 25 is connected to collection container 35 by transfer means 30.

In operation, again referring to Fig. 1, contaminated soil is introduced into reactor 15. Water is added to reactor 15. The amount of water can be from about 1/2 to 30 times the weight of soil. The reactor 15 is then heated using a conventional heating means until the water in reactor 15 begins to boil. The water vaporizes and is forced through the transport means 20 to condenser 25. The water vapor with the contaminants therein contacts the heat exchanger 27 and condenses and is collected through transport means 30 into collection tank 35.

In many instances, the soil contaminants are liquids which are essentially immiscible in water. Such contaminants are usually of different specific gravity, often lighter than water, and so the condensate will separate into two liquid phases. The top phase will ordinarily comprise the soil contaminants which are removed from tank 35 by way of line 40 for recovery or incineration or other suitable disposal or reuse. The lower liquid phase will ordinarily comprise water and is removed from tank 35 by way of line 45 and may be further treated to remove residual contaminants before discharge or recycle to the process. Condensate flowing into decanting tank 35 may also contain solids which will accumulate at the bottom of tank 35. Discharge means 50 are provided at the bottom of tank 35 to remove those accumulated solids. An additional vessel (not shown) may be used, depending upon the type of contaminant to be removed, to further treat the soil.

Additionally, an oxidant may be added to the reactor 15 to further react with any remaining contaminants to form carbon dioxide and water. The amount of oxidant that is added is dependent on the oxidant used, but generally, the amount of the oxidant added is from about 0.1 to 10 times the weight of soil.

Referring now to Fig. 2, there is schematically depicted a second embodiment of the present invention. Reactor 15 is the same as in the preceding embodiment. The second embodiment includes an electrolyzer 60 which has electrodes (not shown) therein. In this embodiment, the reactant is generated in situ inside the electrolyzer 60. To generate the oxidant, either sulfuric acid alone or sulfuric acid a sulfate, and/or a bisulfate is added to the electrolyzer and an electric current is applied to the electrodes to electrolyze the sulfuric acid, sulfate, and/or bisulfate into the oxidant. The oxidant is then added to the reactor 15 through line 65 where it reacts with any contaminants to form carbon dioxide and water. Additionally, HC1 will be generated if the oxidant contains any chlorine. The spent oxidant is then removed through line 70, which is separate from the discharge means 50, optionally filtered, and returned to electrolyzer

60. The optional filtration step (not shown) may include the use of settling tanks and/or filters to remove any solids. The spent oxidant may then be regenerated by reapplying an electric current through the electrodes. However, if desired, the spent oxidant may be removed and fresh raw materials may be added to the electrolyzer

60 for production of the oxidant. Referring now to Fig. 3, there is schematically depicted a third embodiment of the present invention. This embodiment is similar to the one depicted in Fig. 2, except that instead of electrolyzer 60, the oxidant is generated inside reactor 15. This is accomplished by including electrodes 75 within the reactor 15.

Then, the raw ingredients used to form the oxidant are added directly to reactor 15 and an electric current is applied to the electrodes to electrolyze the raw ingredients to form the oxidant, which then reacts with any remaining contaminants to form carbon dioxide and water.

The amount of oxidant that is added to the reactor, either pre- made or produced in situ, is dependent on the type of oxidant used and the manner in which it is added. If pre-made oxidant is used, then the amount of the oxidant added is from about 0.1 to 10 times the weight of soil. However, if the oxidant is generated in situ in either of the embodiments shown in Figs. 2 and 3, then the amount of oxidant added is from about 0.01 to 1 times the weight of the soil. As these numbers reflect, it is preferred that the oxidant be generated in situ as this reduces the cost of oxidant needed. This invention is further illustrated by the following example, which is not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims.

EXAMPLE 1 For Example 1, the following spike solution was prepared.

Chloroform: 8.5 ml

1,1,1 trichloroethane: 8.5 ml

Xylenes 15 ml.

Toluene 3ml.

Naphthalene 0.46 g

The solution had a density of 1.0875 g/ml. This spike solution was used to determine the effectiveness of the process.

25 g of soil was mixed with 1 ml. of spike solution and 170 ml. of deionized water (di- water). This mixture was stirred constantly and distilled until approximately 50 ml. of the initial water had been condensed. A second sample was similarly prepared and distilled until approximately 100 ml of the initial water had been condensed. A third sample was prepared and distilled until approximately 150 ml of the initial water had been condensed. Then the soil was centrifuged and decanted to separate the water. The soil was extracted with methanol ("MeOH") and analyzed by gas chromatography with mass spectrometer detector ("GC-MS").

The results are shown in Table 1. The control sample data for untreated spiked soil is reproduced for comparison and the removal efficiency has been calculated. The newly promulgated EPA soil treatment standard is provided for each contaminant. As can be seen from Table 1, the removal efficiencies were better than those proposed as new treatment standards by the EPA.

Table 1

EXAMPLE 2 For Example 2, the following spike solution was prepared.

Chloroform: 8.5 ml

1,1,1 trichloroethane: 8.5 ml

Xylenes 15 ml.

Toluene 3ml.

Naphthalene 0.46 g

The solution had a density of 1.0875 g/ml. This spike solution was used to determine the effectiveness of the process with the additional oxidant step.

25 g of soil was mixed with 1 ml. of spike solution and 100 ml. of deionized water (di-water). This mixture was stirred constantly and distilled until approximately 80 ml. of the initial water had been condensed. Three flasks (Flasks #1, #2 and #3) were placed in a water bath at 90°C. 25 g of sodium persulfate and 20 ml. of water were added to the wet soil in each flask. The mixture was allowed to react and stirring was provided manually at regular intervals. The temperature inside the flasks was maintained between 95 and 98°C. The mixture was allowed to react until no further reaction was evident. The contents of each flask were poured into plastic bottles and 20 ml. of di-water were added to rinse the remaining soil from each flask and this was poured into the corresponding plastic bottle. The water-soil mixture was thoroughly mixed and separated. The soil portion was extracted with 20 ml. of MeOH and tested using GC-MS. The tests followed the general guidelines set forth in EPA SW-846, methods 5035/8260B.

A control was prepared by mixing 25 g of soil matrix with 1 ml. of spike solution and 100 ml. di-water. This mixture was stirred well and allowed to sit tightly closed overnight. The mixture was separated. The soil portion was extracted with 25 ml. of MeOH. This MeOH was analyzed using GC-MS.

The results are shown in Table 2. The Land Disposal Restriction Universal Treatment Standard for Wastes Destined for Land Disposal ("UTS") standard is provided for each contaminant. As can be seen from Table 2, the results obtained were below the detection level and the resulting soil complied with UTS standard for each contaminant. Samples from Flasks #2 and #3 were analyzed a second time increasing the analytical sensitivity. However, the results obtained from the GC-MS were still below the detection limit. Table 1 lists the as the detection limit if the indicated results were below this level.

Table 2

EXAMPLE 3 For Example 3, the following spike solution was prepared.

Chloroform: 8.5 ml

1,1,1 trichloroethane: 8.5 ml

Xylenes 15 ml.

Toluene 3ml.

Naphthalene 0.45 g

The solution had a density of 1.0875 g/ml. This spike solution was used to determine the effectiveness of the process with the additional oxidant step and to verify the results obtained in Example 2.

25 g of soil matrix was mixed with 1 ml. of spike solution and 100 ml. di-water. This mixture was stirred constantly and distilled until approximately 80 ml. of the initial water had been condensed. Three flasks (Flasks #1, #2 and #3) were placed in a water bath at 85 to 90°C. 25 g. of sodium persulfate and 20 ml. of water were added to the wet soil in each flask. The mixture was allowed to react and stirring was provided manually at regular intervals. The temperature inside the flasks was 95 °C. The mixture was allowed to react until no further reaction was evident. The contents of each flask were poured into plastic bottles and 50 ml. of di-water were added to rinse the remaining soil from each flask and this was poured into the corresponding plastic bottle. The water-soil mixture was thoroughly mixed and separated. The purpose for this part of the procedure was to eliminate as much sodium sulfate formed as possible in the aqueous medium. The soil portion was extracted with 25 ml of MeOH and tested using GC-MS. The results are shown in Table 3. The UTS standard is provided for each contaminant. As can be seen from Table 3, the results obtained were below the detection level for the GC-MS and the resulting soil complied with the UTS standard for each contaminant. Table 3

EXAMPLE 4 For Example 4, a spike solution was prepared having the following levels of contamination:.

Component ppm Component ppm

Dichloromethane 3.96E+04 1 ,4 dichloro benzene 4.78E+04

1,1,1 -trichloroethane 4.78E+04 1, 2 diclorobenzene 4.58E+04

Tetrachloroethylene 6.33E+04 1, 3 dichlorobenzene 4.51E+04

Chloroform 4.97 E+04 2 chlorotoluene 4. 58E+04

Xylenes + ethylbenzene 9.95E+04 1,1 dichloroethane 4. 70E+04

Chlorobenzene 4.39E+04 1, 2 dichloropropane 4.55E+04

Toluene 4.43E+04 1,1, 2 trichloroethane 4.97E+04

Naphthalene 3.89E+04 1,1, 2, 2-tetrachloroethane 5.52E+04

Carbontetrachloride 5.24E+04 Trichloroethylene 4.58E+04

Benzene 4.47E+04 1, 2, 3-trichloropropane 4.82 E+04

25 g of soil matrix was mixed with 1 ml. of spike solution and 100 ml. di-water. This mixture was stirred constantly and distilled until approximately 80 ml. of the initial water had been condensed. Three flasks (Flasks #1, #2 and #3) were placed in a water bath at 85 to 90°C. 25 g. of sodium persulfate and 20 ml. of water were added to the wet soil in each flask. The mixture was allowed to react and stirring was provided manually at regular intervals. The temperature inside the flasks was 95 °C. The mixture was allowed to react until no further reaction was evident. The contents of each flask were poured into plastic bottles and 50 ml. of di-water were added to rinse the remaining soil from each flask and poured into the corresponding plastic bottle. The water-soil mixture was thoroughly mixed and separated. The purpose for this part of the procedure was to eliminate as much sodium sulfate formed as possible in the aqueous medium. The soil portion was extracted with 25 ml of MeOH and tested using GC-MS.

A control solution was prepared by mixing 25 g of soil matrix with 1 ml. of spike solution. The spiked soil was extracted with 50 ml. MeOH after it had been sitting overnight. The MeOH solution was then analyzed using GC-MS. The results are shown in Table 4. The UTS standard is provided for each contaminant. As can be seen from Table 4, the results obtained were below the detection level for the GC-MS and the resulting soil complied with the UTS standard for each contaminant.

Table 4

It should be understood, of course, that the foregoing Examples relate only to preferred embodiments of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

Claims

We claim:

1. A method of removing contaminants from soil comprising: contacting the soil with water; heating the soil/water mixture until the water vaporizes: condensing the water vapor.

2. The method of Claim 1, wherein the condensate is collected.

3. The method of Claim 2, wherein the condensate is separated into at least one phase containing the contaminants and at least one phase comprising water, further wherein the at least one phase containing the contaminants is removed.

4. The method of Claim 1, comprising the additional step of treating the soil with an oxidizing agent.

5. The method of Claim 4, wherein the oxidizing agent is selected from persulfuric acid, sodium persulfate, ammonium persulfate, peroxide, CI2, permanganate, and persulfate salt, or mixtures thereof.

6. The method of Claim 5, wherein the oxidizing agent is persulfuric acid, sodium persulfate or ammonium persulfate.

7. The method of Claim 4, wherein the oxidizing agent is added directly to the soil.

8. The method of Claim 7, wherein the oxidizing agent is added in an amount from about 0.1 to about 10 times the weight of soil.

9. The method of Claim 4, wherein the oxidizing agent is generated in situ and then added to the soil.

10. The method of Claim 9, wherein the oxidizing agent is added in an amount from about 0.01 to about 1 times the weight of soil.

11. The method of Claim 9, wherein the oxidizing agent is generated by providing raw ingredients and then supplying an electric charge to the raw materials to form the oxidizing agent.

12. The method of Claim 11, wherein the raw ingredients are selected from sulfuric acid, sodium sulfate, ammonium sulfate, potassium sulfate, bisulfates, or mixtures thereof.

13. The method of Claim 4, wherein the soil/oxidizing agent mixture is heated to a temperature of from about 40┬░ C to about

100┬░C.

14. The method of Claim 13, wherein the soil/oxidizing agent mixture is heated to a temperature of about 85┬░ C.

15. The method of Claim 1, wherein the water is added in an amount from about 0.5 to about 30 times the weight of soil.