WO1989000463A1

WO1989000463A1 - Method for sequestering polyhalogenated biphenyls within solid waste

Info

Publication number: WO1989000463A1
Application number: PCT/US1988/002387
Authority: WO
Inventors: P. G. Johansing, Jr.; Kasi Viswanath Gabbita
Original assignee: Johansing P G Jr; Kasi Viswanath Gabbita
Priority date: 1987-07-15
Filing date: 1988-07-14
Publication date: 1989-01-26
Also published as: AU2314788A

Abstract

An improved, low cost method for reducing the detectable level of polyhalogenated biphenyls in solid wastes is provided which permits treatment of heretofore intractable waste such as non-metallic ''fluff'' resulting from the shredding of electrical appliances. The method preferably includes the steps of initially applying an agent to the solid waste which includes humic substances (e.g. humic acid or salts thereof), followed by thoroughly mixing the solid waste and applied treating agent, with adjustment of the moisture content to achieve a level of at least about 20 % by weight moisture therein. Advantageously, the humic treating agent is selected from the group consisting of solid, particulate lignite, leonardite, coal and mixtures thereof. Further advantages are obtained by the application of a base such as sodium hydroxide with or subsequent to the humic treating agent, followed by a set time of from one to five days. The final step in the most preferred process involves application of a material such as gypsum to lower the pH and fix the inhibited biphenyls to prevent subsequent leachout thereof.

Description

METHOD FOR SEQUESTERING POLYHALOGENATED

BIPHENYLS WITHIN SOLID WASTE

Background of the Invention 1. Field of the Invention

The present invention is broadly concerned with a method for reducing the detectable amount of polyhalogentated biphenyls contained in solid waste in order to reduce the environmental harm caused by such chemicals. More particularly, it is concerned with such a method which is particularly designed to reduce detectable polychlorinated and polybroraonated biphenyls (PCB's and PBB's) in solid wastes by contacting such wastes with an agent including humic substances (e.g. humic acid or salts thereof); the most preferred treatment agent is selected from the group consisting of lignite, leonardite, coal and mixtures thereof.

2. Description of the Prior Art

Polyhalogentated biphenyls, and most commonly PCB's, have been used in electrical equipment such as transformers and capacitors such as nonflammable dielectrics. In view of the long standing use of PCB's in this context, there is a substantial volume of these materials still in use or in dump sites. This is particularly troublesome inasmuch as the Environmental Protection Agency has determined that PCB's present a distinct hazard to the environment, in that they exhibit decided carcinogenic, teratogenic and mutagenic properties. Considerable research has been conducted in the past in an effort to find ways of properly and inexpensively reducing or destroying PCB's. Prior techniques have involved pyrolysis of PCB- impregnated solids and liquids, as well as various proposals for filtration and/or chemical modification thereof. A number of such prior attempts are disclosed in U.S. Patents Nos. 4,610,729, 4,526,677, 4,601,817, 4,581,130 and 4,246,255.

While a number of PCB destruction methods have been employed for removing PCB's from water or other liquids, a distinct problem is presented by solid waste materials which include substantial PCB's. For example, many waste disposal sites which handle worn out appliances are plagued by extremely large quantities of so-called "fluff", which comprises non-metallic wastes such as insulation, seals, synthetic resin parts and incident dirt and debris. Such "fluff" can contain objectionable amounts of PCB's by virtue of absorbing the same from electrical equipment during the waste disposal and recovery process (50 parts per million of PCB's is presently considered to be the legal maximum). Indeed, the problem of PCB reduction in such "fluff" is so formidable that at present large quantities of the material are sitting in open air sites and cannot be normally disposed of in Class 3 landfills. In short, operators of affected disposal facilities simply have no solution to the problem.

Summary of the Invention

The present invention overcomes the problems described above and provides a greatly improved method for reducing the detectable amount of polyhalogentated biphenyls within solid waste, at a relatively low cost in both terms of materials and methodology. Broadly speaking, the method of the present invention involves applying to a quantity of polyhalogentated biphenyl-carrying solid waste an agent which includes humic substances as at least a part thereof. Advantageously, the humic substances may be in the form of humic acid or a salt thereof, and the applied agents may be selected from the group consisting of lignite, leonardite, coal and mixtures thereof.

After application, the solid waste and agent are thoroughly mixed, and the moisture content of the mix is adjusted as necessary to achieve a level of at least about 20% by weight moisture. In this fashion the polyhalogentated biphenyls within the solid waste are inhibited to the point that the detectable amount of such objectionable chemicals is significantly reduced. Although the exact mechanism of such inhibition is not perfectly understood, it is presently believed that the reduction in detectable polyhalogentated biphenyl level obtains by virtue of a complexation or sequestration of the biphenyls.

In particularly preferred forms of the invention wherein the solid waste is in the form of "fluff" or polyhalogentated biphenyl-impregnated earth, the following method is followed. First, the solid waste material is treated by applying thereto an agent which includes humic substances, and most typically this would be solid, particulate lignite having a mesh size of from 150-250. The lignite would be added at a level to obtain a ratio of from about 10:1 to 20:1 (w/w) of solid waste material to lignite, normally by simply spreading the particulate lignite over the affected solid waste. The next step involves application of a base such as sodium hydroxide (e.g., 1 N NaOH) and moisture as necessary to the solid waste, followed by thorough mixing. The final step would include application of a material such as powdered gypsum to the mix in order to lower the pH thereof. Actual practice with such a method has demonstrated that a substantial reduction in 'detectable polyhalogentated biphenyls can be achieved.

Description of the Preferred Embodiments

As indicated above, the preferred treating agent in accordance with the present invention includes a substantial portion of humic substances. Such humic substances are broadly found in nature and are defined as a general category of naturally occurring, biogenic heterogeneous organic substances that can generally be characterized as being yellow to black in color, of high molecular weight, and refractory (Aiken, et al., Humic Substances in Soil, Sediment and Water, p. 651, John Wiley & Sons, 1985). One of the most preferred humic substances useful in the present invention, i.e., humic acid, is defined as that fraction of humic substances that is not soluble in water under acid conditions (below pH 2), but becomes soluble at greater pH, Ibid 651. Another reference, Youngs et al., Humic Acids from Leonardite; A Soil Conditioner and Organic Fertilizer, Proceedings of North Dakota Academy of Science, Vol. XVII, pp. 76-82, 1963, defines humic acids as yellow-brown to black-brown substances of unknown constitution, formed in nature by decompo sition of organic materials under atmospheric influence or in the laboratory by chemical action; humic acids can split off hydrogen ions and form typical salts with strong bases and usually are insoluble in water, soluble in alkali, and reprecipitated by acid. Humic acids are not chemically uniform substances, but are hydrophilic, reversible colloids with molecular weights varying from 300 to as high as 10,000 units. Their micelles carry a negative charge. The alkali solubility of humic acid is due, to carboxyl and phenolic hydroxyl groups which account for about 22% of the weight of the molecule.

As further indicated, in the preferred practice of the invention the treating agent is a naturally occurring material which includes humic substances. Such naturally occurring agents include lignite, defined as a low rank of coal between peat and sub-bituminous coal, Ibid, Aiken et al. at 652, and leonardite, defined as naturally oxidized lignite containing up to 36% humic acids on a moisture- and ash-free basis, Ibid, Youngs et al. at 77. Further, low grade coals containing humic substances also find utility in the invention. It will of course be appreciated that the practice of the invention is not limited to the preferred materials, but rather any agent having the requisite humic substances as a portion thereof can be used in the invention. For reasons of ease of handling and application, solid particulate or granulated treating agent should be employed, and lignite in such form can be readily obtained at a reasonable price, inasmuch as it is presently in use as a commercial soil additive. In the preferred method of the invention a base such as a monovalent cation hydroxide is added with or subsequent to the application of the humic treating agent. Typical bases useful in this context include ammonium hydroxide, and the alkali metal hydroxides such as sodium hydroxide. The purpose of base addition is to elevate the pH and form the appropriate salts. Thus, where sodium hydroxide is added, sodium humate is formed in situ. The base may most easily be employed as a liquid which is sprayed onto the solid waste with or after application of the humic treating agent. The pH of the mixture should be above about 8, and more preferably from about 9-12 after base addition and appropriate mixing.

It is important in the practice of the present invention to thoroughly mix the starting solid waste and humic treating agent (and base if such is employed), so as to achieve an intimate and substantially homogeneous mix. This ensures maximum contact between the objectionable polyhalogenated biphenyls within the solid waste and the active ingredients of the treating agent. In the case of solid waste "fluff", large commercial mixing/tilling equipment can be used to thoroughly agitate and mix the solid waste and humic treating agent. Such equipment can be of the type typically used for the incorporation of clays into reservoir bed soils.

Although it is contemplated that sufficient moisture would be added to the solid waste with the aqueous base, in instances where no base is added, or additional water is needed, such can be added at any time, either prior to application of the treating agent, with such application, or subsequently thereto. The only real requirement is that the final mix of treated waste have a moisture level of at least about 20% by weight therein. More preferably, this moisture level should be in the range of 20-40% by weight. The function of moisture in this context is to enhance the reactivity between the polyhalogenated biphenyls and the humic substances.

After the mixing step is completed, the treated solid waste should be allowed to remain undisturbed for a period of time to ensure complete reaction between the polyhalogenated biphenyls and the humic subs tances . This period mus t be determined on an essentially eraperical basis, inasmuch as this time varies depending upon the humic substance content of the treating agent, particle sizes, pH, moisture content, and degree of mixing. As a guideline in this respect, it is believed that a setting time of from about 1 to 5 days would be adequate, and most preferably about 3 days.

After the set time has elapsed, it is desirable to then add an acidic ingredient to lower the pH of the treated solid waste. A wide variety of materials can be used for this purpose, such as any one of a number of acids or most preferably powdered gypsum. Here again, where a particulate ingredient is employed it is desirable to spread the material over the waste followed by mixing to complete the process. The purpose of pH depression is to "fix" the inhibited polyhalogenated biphenyls and to prevent unwanted leaching thereof through the action of rain or ground water passing through the solid waste. E X A M P L E

In order to demonstrate the method of the present invention, five separate bags of PCT- impregnated shredder "fluff" were obtained from a solid waste disposal facility in Orange County, California. The contents of each of these bags were put into a large drum and mixed thoroughly. A large sub-sample was taken from this mixed sample and cut into five identical piles, each containing representatives from all facets of the sample matrix. An equal portion was taken from each of these piles and combined into a single sample from which 50 grams was used for analysis. The remaining "fluff" was split in half, one-half being retained by a testing laboratory and the other half treated in accordance with the present invention.

Specifically, the treated half was placed in a vessel and an amount of solid particulate lignite was appliad thereto to achieve a ratio of 10:1 (w/w) of "fluff" to lignite. The lignite was commercially obtained from Los Angeles Chemical Company, and was reported to contain approximately 50% humic acid (agricultural grade). The treated "fluff" was mixed by hand and, during the mixing procedure, 1 N NaOh was added to obtain a moisture level of about 40% by weight.

The treated and pH-adjusted "fluff" was then allowed to sit in the treating vessel for a period of three days to ensure reaction between the polyhalogenated biphenyls and humic treating agent. The treated "fluff" was then sent to the laboratory for a determination of detectable biphenyls. The untreated "fluff" was analyzed to contain 89 ppm of Arachlor 1242 and 25.2 ppm of Arachlor 1260. The treated material on the other hand was analyzed to contain 48.1 ppm of Arachlor 1242 and 11.0 ppm of Arachlor 1260.

It is believed that the results of the foregoing test could be measurably improved by the addition of an ingredient to lower the pH, such as gypsum. This subsequent treatment is believed to fix the inhibited biphenyls within the solid waste and to thereby prevent subsequent leaching thereof.

The present Example demonstrates the efficacy of the method of the present invention in reducing the detectable polyhalogenated biphenyls content of solid waste. Although it is known that technical grade humic acid will adsorb PCB's in a laboratory context (Haque et al., Studies Of The Adsorption Of Selected Polyhalogenated Biphenyl Isomers On Several Surfaces, J. Environ. Sci. Health, B11(2), 129-137.(1976)), it is also well established that the reactivity of humic substances cannot be in any fashion predicted. Thus, in Youngs et al. Ibid. at p. 232, it is noted that "The wide variety of potential humic interactions with organic pollutants, coupled with a paucity of studies of their salinity dependence, render impossible any generalizations regarding this subject. Humic interactions with both metals and organic pollutants should have an important influence on transport and immobilization of these materials in estuaries. However, very few field data are available to test the implications of the largely experimental nature of studies carried out to date." Thus, it was quite surprising and unexpected to discover that humic substances of variable and unknown composition could be used to effectively reduce detectable levels of polyhalogenated biphenyls in solid waste, and that such substances contained no substantially interfering components.

Claims

1. A method of reducing the detectable amount of polyhalogenated biphenyls within solid waste materials, comprising the steps of: providing a quantity of solid waste material having an undesirably high content of polyhalogenated biphenyls therein; applying to said waste material an agent which includes humic substances as at least a part thereof; and thoroughly mixing said waste material and said applied agent, and adjusting as necessary the moisture content of the mix to achieve a level of at least about 20% by weight moisture therein.

2. The method of Claim 1, said agent being selected from the group consisting of lignite, leonardite, coal and mixtures thereof.

3. The method of Claim 2, said agent being lignite.

4. The method of Claim 2, including the step of applying a base with or subsequent to application of said agent.

5. The method of Claim 4, said base being selected from the group consisting of alkali metal hydroxides.

6. The method of Claim 4, said base being applied in an amount such that the pH of said mix is above about 8.

7. The method of Claim 6, said p H being from about 9-12.

8. The method of Claim 1, including the step of adding an ingredient to said mix to lower the pH thereof, after said mixing step.

9. The method of Claim 8, said ingredient being acidic.

10. The method of Claim 8, said ingredient being powdered gypsum.

11. The method of Claim 1, said agent being in the form of a particulate solid having a mesh size in the range of from about 150 to 250.

12. The method of Claim 1, said waste material comprising non-metallic waste from appliances.

13. The method of Claim 1, said waste material comprising polyhalogenated biphenyl- impregnated earth.

14. The method of Claim 1, said agent being selected from the group consisting of solid particulate lignite, leonardite, coal and mixtures thereof, and being applied to said waste material to achieve a ratio of from about 10:1-20:1 (w/w) of solid waste material to said substance.

15. The method of Claim 1, the moisture content of said mix being from about 20 to 40% by weight moisture.

16. The method of Claim 1, including the step of allowing said mix to sit for a period of from about one to five days.

17. The metood of Claim 16, said period being about three days.