MX2008005155A - Oxidation of organic compounds - Google Patents

Abstract

An improved method and compositions for treating organic compounds present in soil, groundwater and other environments is disclosed. The method involves the use of a composition comprising a solid state, water soluble peroxygen compound and zero valent iron.

Description

OXIDATION OF ORGANIC COMPOUNDS This application claims the benefit of US Provisional Application No. 60 / 728,626 filed on October 20, 2005.

FIELD OF THE INVENTION This invention relates to in situ and ex situ oxidation of organic compounds in soils as well as waters such as groundwater, process water and wastewater. The invention particularly relates to in situ oxidations of volatile and semi-volatile organic compounds, pesticides and herbicides, and other recalcitrant organic compounds in soil and groundwater.

BACKGROUND OF THE INVENTION The contamination of subsurface soils and groundwater by volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), as well as herbicides and pesticides is a well-documented problem. . Many VOC and SVOC contaminants travel through the soil under the influence of gravity to contaminate groundwater as water passes through contaminated soil. Among these, the volatile organic compounds or VOCs which include any, at least one chemical compound of soluble carbon of slightly in water, with Henry's Constant Law greater than 10.sup-7 atm m-.sup 3 / mol are notable. , which is toxic or carcinogenic, is capable of moving through the soil under the influence of gravity and serves as a source of water contamination by dissolution in water passing through contaminated soil due to its solubility, including, but not limited to, , chlorinated solvents such as trichlorethylene (TCE), vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane (TCA), 1,1-dichloroethane, 1, 1- dichloroethane, carbon tetrachloride, benzene, chloroform, chlorobenzenes, and other compounds such as ethylene dibromide, and methyl tertiary butyl ether. Many VOC and SVOC contaminants are also toxic or carcinogenic. These VOC and SVOC contaminants include, but are not limited to chlorinated solvents such as trichlorethylene (TCE), vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichlorethane, 1,1,1-trichloroethane (TCA) , carbon tetrachloride, chloroform, chlorobenzenes. Other examples of VOC or SVOC include benzene, toluene, xylene, ethyl benzene, ethylene dibromide, methyl tertiary butyl ether, poly aromatic hydrocarbons, polychlorinated biphenyls, phthalates, 1,4-dioxane, nitrosodimethyl amine, and methyl tert-butyl ether. The discharge of VOC and SVOC contaminants such as those listed in the contacts in the soil to aquifer contamination and degrades groundwater sources for future use. The treatment and remediation of soils contaminated with VOC or SVOC is expensive and often unsuccessful. For example, the remediation of soils contaminated with VOC which are partially or completely insoluble with water is particularly difficult. Also the remediation of soils contaminated with highly soluble but biologically organic stable pollutants such as MTBE and 1,4-dioxane is very difficult with conventional technologies. Non-aqueous phase (NAPL) liquids present in the subsurface of soil can be toxic and can slowly release dissolved VOCs into groundwater to generate sources of long-term contamination (ie decades or longer) of subsurface soil. Indeed, the subsurface groundwater pollutant column can extend from hundreds to thousands of feet from the source to the chemical pollutant. Chemical contaminants can then be transported in drinking water sources, lakes, rivers and even basements of houses through volatilization from groundwater. The technique has attempted to direct the remediation of soil and groundwater contaminated with VOC and SVOC. U.S. Patent No. 6,474,908 (Hoag, et al.) And U.S. Patent No. 6,019,548 (Hoag et al.) Teaches the use of persulfate with divalent transition metal salt catalyst to destroy VOC in the soil. A disadvantage of this technique, however, is that the divalent transition metals under oxidation and / or hydrolysis can be with precipitation. That limits the survival and transport of transition metal catalyst, and thus the persulfate reactivity of the communication field. Iron (III) is known to catalyze hydrogen peroxide reactions. (Hydrogen Peroxide; # Schumb, W.C .; Satterfield, C.N. and Wentworth, R.L .; Reinhold Publishing Corporation, New Cork, NY, 1955, pg 469). The iron (III) complex used with hydrogen peroxide shows an ability to oxidize complex pesticides (Sun, Y e Pignatello, J.J. Agr. Food, Chem, 40: 322-37, 1992). However, iron (III) is a poor catalyst for the activation of persulfate. The US Environmental Protection Agency (USEPA, by its acronym in English) has established maximum concentration limits for polluting compounds. Very low and astringent limits in the amount of halogenated organic compounds exist in drinking water. For example, the maximum concentration of solvents such as trichlorethylene, tetrachlorethylene and carbon tetrachloride in drinking water is 5 mu.g / L, and the maximum concentration of chlorobenzene, chlorinated biphenyls (PCB), and ethylene dibromide are 100 mu.g / L, 0.5.mu/L, and 0.05 .mu.g / L respectively. Meeting these limits during remediation of contaminated soils is often visually impossible using existing technologies.

A need exists for a remediation method that overcomes the deficiencies of the prior art.

Brief Description of the Invention The present invention is a method for the remediation of soil, sediment, clay, rock, and the like (in this manner collectively it refers to "soil") and groundwater (i.e. water) # found in fissures and spaces in soil, sand and rocks), process water (i.e. water containing household waste or industrial) contaminated with volatile organic compounds, semi-volatile organic compounds, pesticides or herbicides. In addition, they can be used to treat mud, sands or tar. The present method uses a composition comprising one or more solid phase and iron peroxygen compounds zero-valent under sufficient conditions to oxidize contaminants such as VOC, SVOC, herbicides and pesticides in contaminated soil and water. The method of oxidizing an organic compound involves contacting the organic compound with a composition that comprises a peroxygen compound soluble in water and zero-valent iron. The organic compound can be present in the environment including soil, groundwater, process water or wastewater. The water-soluble peroxygen compound can be one of sodium persulfate, potassium persulfate, ammonium persulfate and monopersulfate, preferably sodium persulfate. The concentration of peroxygen compound in the solution is from 0.5 mg / L to approximately 250,000 mg / L and zero-valent iron and sodium persulfate can be present in a suspension. The concentration of zero-valent iron in suspension is from 1ppm to approximately 1000ppm in metal base. Preferably, the zero-valent iron contacts the organic compound prior to contacting the organic compound with peroxygen compound. Organic compounds which can be oxidized include trichlorethylene (PCE), vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichloroethane, 1,1-trichloroethane (TCA), carbon tetrachloride, chloroform, chlorobenzenes, benzene, toluene, xylene, ethyl benzene, ethylene dibromide, methyl butyl tertiary methyl, polyaromatic hydrocarbons, polychlorinated biphenyls, phthalates, 1,4-dioxane, nitrosodimethylamine and rnetyl tert-butyl ether.

Description of preferred embodiments Generally, the present method involves the oxidation of organic contaminants such as VOC and SVOC, pesticides and herbicides present in soil and water. The method involves contacting contaminated soils and waters with a composition comprising a water-soluble peroxygen compound and zero-valent iron to oxidize contaminants such as VOC, SVOC, aromatic hydrocarbons, polychlorinated biphenyls, pesticides and herbicides. Examples of these contaminants include, but are not limited to, chlorinated solvents such as trichlorethylene (TCE)., vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane (TCA), carbon tetrachloride, chloroform, chlorobenzenes. Other examples of VOC and SVOC include benzene, toluene, xylene, ethyl benzene, ethylene dibromide, methyl tertiary butyl ether, aromatic hydrocarbons, polychlorinated biphenyls, phthalates, 1,4-dioxane, nitrosodimethylamine and methyl tert-butyl ether. In a first aspect, the oxidation of organic contaminants as listed above can be carried out by injecting an amount of a zero-valent iron suspension into an aqueous solution of one or more solid phase water-soluble peroxygen compounds in contaminated soils or waters. As used herein, "solid phase water soluble peroxygen compound" means a compound which is solid and soluble in water at room temperature and which contains an O-O group. Examples of solid phase water soluble peroxygen compounds, which may be used include dipersulfate such as sodium sulfate, potassium persulfate and ammonia persulfate. The most preferred dipersulfate is sodium persulfate since it has greater solubility in water and the least expensive. In addition, it generates sodium and sulphate under reduction, both are relatively benign from the environmental and health point of view. Potassium persulfate and ammonium persulfate are examples of other persulfates which can be used, preferably sodium persulfate since it has greater solubility in water and is less expensive. In addition, sodium and sulfate are generated after the reduction, both are relatively benign from the environmental and health point of view. Potassium persulfate and ammonia persulfate are examples of other persulfates which can be used. Sodium persulfate, however, is in # order of magnitude less soluble in water than potassium persulfate, and ammonium persulfate is even less desirable which can be broken down into constituents such as ammonia ion which are potential health problems. The measurement of the zero-valent iron particle in the suspension may vary from the nanoscale, i.e. 10 nanometers up to about 1 micron in micro scale, i.e. From 1 microns to approximately 5 microns. Zero-valent iron within its ranges of measurements is generally commercially available. Preferably, the suspension includes a zero-valent iron in an aqueous solution of sodium persulfate (Na 2 S 2 O 8). The concentration of zero-valent iron in the suspension can vary from 1 to about 1000 ppm in metal base. The peroxygen compound and the zero-valent iron can be mixed together and the composition supplied or stored before being combined with water in the same container before the injection. The peroxygen and iron compound solutions can be injected simultaneously or sequentially in which the case of the composition is formed in an ambient environment. If injected sequentially, it is preferable that the iron be injected first. In another modality, zero-valent iron can be in a permeable reaction barrier (PRB, for its acronym in English) and persulfate introduced into the environment at the highest level since the PRB. It is also preferred that sufficient peroxygen compound is injected to satisfy the oxidant demand of the soil, compensates for any decomposition and oxidizes and destroys most but all organic compounds. The demand for soil oxidant (SOD, for its acronym in English), is the loss of persulfate due to the reaction with the components of the soil matrix as well as through the self-decomposition of persulfate, as well as the chemical oxidant demand, and to compensate for any decomposition of the peroxygen compound. A method for calculating the preferred amount of peroxygen compound to be used per unit mass of soil (for an identified volume of soil at the site) is to first determine the minimum amount of peroxygen compound that is needed to Totally satisfy the oxidant demand of the soil per unit mass of soil without contamination. A sample of soil contaminated from the identified volume of soil is then treated with the predetermined amount (per unit mass) of peroxygen compound; and the minimum amount of peroxygen compound required to remove the organic compounds in the treated sample is then determined. The chemical reaction stoichiometry handles the mass / mass ranges and in this way the total amount required to achieve the desired result. In actuality the amount of peroxygen compound injected into several places in a single contaminated site will depend on what is learned from core samples and other techniques to track what is believed to be surface conditions. SOD can also be calculated according to the formula ("): SOD = V * (CQ-Cf) / ms (I) Where V = volume of groundwater used in the sample C0 = initial concentration of persulfate in time 0 Ct = persulfate concentration after 48 hours Ms = mass of soil used in the sample Depending on the type of soil, target compounds, or other oxidant demand at the site, the concentrations of peroxygen compound in the solution used in this invention can vary from 0.5 mg / L to approximately more than 250,000 mg / L. Preferred concentrations are a function of soil charactercs including demands for specific oxidants at the site.The hydrogeological conditions indicate the range of movement of chemicals through the soil, and these conditions should be considered along with soil chemy to understand how it is best to carry out the injection. and carrying out the injections are well known in the art. For example, wells or boreholes can be in various locations in and around the possible contaminated site, to determine, as close as possible, where the contamination is located. The base samples can be suspended, being careful to protect the samples from atmospheric oxidation. The samples can then be used to determine the oxidant demand of the soil, the chemical oxidant demand (VOC) and the stability of the existing oxidant in the subsurface. The precise chemical compounds in the soil and their concentration can be determined. Contaminated groundwater can be collected. Oxidants can be added to groundwater collected during laboratory experiments to determine which compounds are destroyed, in what order and to what degree, in groundwater. Then you can determine if the same oxidants are capable of destroying chemicals in the soil environment. The objective is for the concentration of peroxygen compound in the injected solution to be sufficient to result in the reaction of the peroxygen compound passing through the contamination area which requires treatment in sufficient quantity to oxidize the contaminants present. (The zone of saturated soil is the zone of soil which is under the portion of water and is completely saturated, this is the region in which the groundwater exists and flows). In some saturated zones where the natural velocity of the groundwater is too slow for the purpose of treatment within a certain time, the velocity of the groundwater can be increased by increasing the flow rate of the injected persulphate solution or installation. of groundwater extraction wells to direct the fl ow of the injected peroxygen compound solution. Some soils to be treated may be in unsaturated zones and the peroxygen compound injection method may be based on the infiltration of the peroxygen compound solution in the subsurface to provide sufficient contact of soils with the chemicals introduced. Some soils and conditions will require large amounts of peroxygen compound to destroy the demand for soil oxidant, while other soils and conditions may not require it. For example, sandy soils that have a large amount of grain may have a very small surface area, very few oxidizing compounds and thus very little demand for soil oxidant. On the other hand, soils with silty clay or clay, which have fine grains, will have a long surface area by volume. These may also contain large amounts of oxidizing compounds, and may also cause a higher degree of decomposition of peroxygen compound and thus have a more complete demand for soil oxidant. For in situ soil treatment, the injection ranges can be chosen based on geological conditions, that is, the ability of the oxidant solution to displace, mix or disperse with existing groundwater and move through the soil. In addition, the injection ranges can be sufficient to satisfy the demand for soil oxidant and the chemical oxidant demand in real time. It is an advantage to clean the site effectively in cost and time. Careful evaluation of site parameters is crucial. It is well known that soil permeability can change rapidly as a function of depth and lateral dimension. In this way, injection well locations are also site-specific. The proper application of any remediation technology depends on the knowledge of subsurface conditions, both chemical and physical, and this process is not different in this respect. Any solid phase water soluble persulfate compound can be used including monopersulfates and dipersulfates. Dipersulfates are preferred because they are not as expensive and survive for long periods in unsaturated groundwater under typical site conditions. These compositions of the present invention comprise a solid state, the peroxygen compound soluble in water and zero-valent iron can also be used off-site to treat quantities of contaminated soil, which were removed from the soil. According to the method of the present invention the contaminants are treated in an environment. As used herein, "environment" refers to a medium where contaminants are found including, without limitation, soil, rock, groundwater, contaminated columns, process water, waste water, and the like. The process of the present invention can be carried out in situ or ex situ. In situ treatment is carried out in the physical environment where the contaminants are found. The ex situ treatment includes the elimination of the contaminated medium from the place where it is located and the treatment in a different place. In order to describe the invention in more detail, the following examples are established: EXAMPLE 1 Stability of Persulphate / Zero-valent Iron The stability of persulfate in the presence of zero-valent iron (ZVI) was demonstrated by the following procedure. The following abbreviations are used to identify the materials / equipment: ZVI-zero-valent iron Fe (0) FeEDTA-Fe (ll) chelated with ethylenediaminetetraacetic acid VOA-flasks used for Dl-deionized volatile organic analysis Experimental procedure: • One liter of water DI was added to each vial VOA • Sodium persulfate was added to VOA bottles in three different dosages: 1, 3 and 5 grams • FeEDTA was added to a set of three bottles containing three different dosages of persulfate in a concentration of 0.2 g of Fe in each bottle. > ZVI was added to a set of three bottles containing three different dosages at a concentration of 0.2 g of Fe in each vial > A set of three bottles in three different dosages of persulfate were not dosed with iron > Persulfate concentrations were measured after one and two weeks via standard analysis methods. The percentage of persulfate remaining (as an average of three dosages of persulfate for this period of time) after these times is shown in Table 1 As can be seen in Table 1, the persulfate showed approximately equivalent stability in the presence of ZVI in presence of FeEDTA.

Example 2 Treatment of Organic Compounds The effectiveness of using a combination of persulfate and zero-valent iron for treating various organic compounds was shown by the following procedure. The following # abbreviations are used to identify materials / equipment: ZVI-zero-valent iron Fe (0) 20 FeEDTA-Fe (ll) chelated with ethylenediaminetetraacetic acid (EDTA) VOA-flasks used for Dl-deionized volatile organic analysis The following contaminants organics were used: "Chlorinated-tin", "chlorhetene", refers to a mixture of tetrachloroethene, trichlorethene, cis-1, 2-dichloretene, and 1,1-dichloretene, -BTEX refers to a mixture of benzene, toluene, ethylbenzene and xylene 5-chlorinated benzenes, or "chlorobenezenes", refers to a mixture of chlorobenzene, 1,2-dichlorobenzene, and 1,3-dichlorobenzene • - "Oxygenates" refers to ethers that include methyl tert-butyl ether (MTBE) 10 Survival procedure: • One liter of DI water was added to each VOA flask • 1.0 g of sodium persulfate was added to each flask VOA • The flasks were dosed with 15 ZVI ammonium sulfate, Fe (ll) or FeEDTA to get 0.5 gd Faith in the vial. For ZVI / Fe (ll) combinations, equal amounts were used to obtain 0.5 g of Fe • The bottles were dosed with a concentrated matrix solution of the contaminants identified above to obtain a contaminant dosage of approximately 10-20 mg / L. • The VOA bottles were filled until there was no space • The bottles were stored at room temperature for 7 days. After 7 days of reaction period, the bottles were stored at 4 ° C for analysis. The analyzes were carried out in a gas mass spectrometer / chromatograph using USEPA SW-846, Method 8260B. The results in ug / L are shown in the Table compared to the initial concentration indicated by Time = 0: # As can be seen in Table 2, the combination of persulfate and ZVI was effective in treating the indicated organic compounds. Example 3 Treatment of organic compounds The procedure described in Example 2 was used to evaluate the efficacy using a combination of persulfate and zero-valent iron to treat organic compounds. In addition to the compounds of Example 2, the following organic contaminants were used: 1, 1, 1 TCA refers to 1,1,1-trichloroethane 1. 1 DCA refers to 1,1-dichloroethane 25 1 .2 DCA refers to to 1, 2-dichloroethane The results are shown in Table 3.

As can be seen in Table 3, activated persulfate with ZVI destroyed a wide range of contaminants. Also, ZVI can be used in combination with Fe I I to activate persulfate. # twenty # 25

Claims (10)

1. A method for oxidizing a contaminant present in an environmental environment, said method comprises contacting the contaminant with a composition comprising a peroxygen compound soluble in water and zero-valent iron.

2. A method according to claim 1, wherein the environment is selected from soil, groundwater, process water or waste water.

3. A method according to claim 1, wherein the contaminant is an organic compound selected from the group consisting of volatile organic compounds, semi-volatile organic compounds, aromatic hydrocarbons, polychlorinated biphenyls, pesticides and herbicides.

4. A method according to claim 1, wherein the peroxygen compound is a dipersulfate.

5. A method according to claim 4, wherein the dipersulfate is selected from sodium, potassium or ammonium persulfate or a combination thereof.

6. A method according to claim 1, wherein the peroxygen compound is a monopersulfate.

7. A method according to claim 6, wherein the monopersulfate is selected from sodium and potassium monopersulfate.

8. A method according to claim 1, wherein the peroxygen compound is a combination of dipersulfate and monopersulfate.

9. A method according to claim 1 wherein the zero-valent iron has a nanoscale particle size from about 10 nanometers to about 1 micron.

10. A method according to claim 1 wherein the zero-valent iron has a micro scale particle size from 1 micron to about 5 microns. eleven . A method according to claim 1, wherein the concentration of the peroxygen compound is from 0.5 mg / L to about 250,000 mg / L. 12. A method according to claim 1 wherein the zero-valent iron is from 1 ppm to about 1000 ppm based on metal. 13. A method according to claim 1 wherein the oxidation is carried out in situ or ex situ. 14. A method according to claim 1, wherein the water-soluble peroxygen compound is sodium persulfate. 5. A method according to claim 1 wherein the zero-valent iron and the sodium persulfate are present in a suspension. 16. A method according to claim 3 wherein the organic compound is selected from the group consisting of trichlorethylene (TCE), vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichloroethane, 1, 1, 1 -troterlorethane (TCA), carbon tetrachloride, chloroform, chlorobenzene, benzene, toluene, xylene, ethyl benzene, ethylene dibromide, 5 methyl tertiary butyl ether, aromatic hydrocarbons, polyaromatic hydrocarbons, polychlorinated biphenyls, phthalates, 1,4-dioxane , nitrosodimethylamine, and methyl tertiary tert-butyl ether. • 1 7. A method according to claim 1 wherein the contaminant is present in soil or water 10 underground. 18. A composition suitable for use in the treatment of a contaminant present in an environmental environment, this composition comprises peroxygen compound soluble in water and zero-valent iron. 19. A composition according to claim 18 wherein the peroxygen compound is a monopersulfate or dipersulfate. 20. A composition according to claim 1 wherein the peroxygen compound is sodium persulfate. twenty #