WO1996024442A1

WO1996024442A1 - Reagent for treating a contaminated waste material and method for same

Info

Publication number: WO1996024442A1
Application number: PCT/US1995/001192
Authority: WO
Inventors: Doyle H. Beckham; Harry E. Robson
Original assignee: Beckham Doyle H; Robson Harry E
Priority date: 1992-11-03
Filing date: 1995-02-07
Publication date: 1996-08-15

Abstract

A reagent material useful for converting a contaminated waste material, which is environmentally unacceptable, to a relatively harmeless granular substance which is environmentally acceptable. The reagent material is comprised of an effective amount of alumina, silica, a hydroxide, or hydroxide precursor, of an alkali metal, calcium oxide, and a medium to large pore zeolitic material. The method involves blending an effective amount of said reagent material with said waste material and allowing it to dry without setting, thereby resulting in an environmentally acceptable particulate substance.

Description

DESCRIPTION

REAGENT FOR TREATING A CONTAMINATED WASTE MATERIAL

AND METHOD FOR SAME

TECHNICAL FIELD The present invention relates to a reagent material useful for converting a contaminated waste material, which is environmentally unacceptable, to a relatively harmless granular substance which is environmentally acceptable. The reagent material is comprised of an effective amount of alumina, silica, a hydroxide, or hydroxide precursor, of an alkali metal, calcium oxide, and a zeolitic material . The method involves blending an effective amount of said reagent material with said waste material and allowing it to dry without setting, thereby resulting in an environmentally acceptable particulate substance.

BACKGROUND ART

All industrial societies are faced with significant environmental problems associated with industrial waste materials, many of which are hazardous to both animal and plant life. Examples of such waste materials include sludges which settle as sedimentation layers at the bottom of the sea, lakes, and rivers; effluent sludges discharged from various industries including pharmaceutical, tanning, paper and pulp manufacturing, wool washing, fermenting, food processing, metal surface processing, plating, ore dressing, coal washing, and fume desulfurizing; as well as other wastes such as sewage sludges discharged from sewage processing stations, and those resulting from the refining of petroleum products. Such wastes are often contaminated with substances which can have an adverse effect on the ecological system. Contaminants found in such wastes often include unacceptable levels of heavy metals such as copper, lead, cadmium, arsenic, mercury, hexavalent chromium. Also found are other chronically toxic compounds such as PCB, PCP, DDT, 2-BHC, Dieldrin, Chlordecone, Mirex, Parathion, cyanic compounds, alkyl-mercur compounds, dioxins, furans; and the like. These waste material are sometimes referred to herein as environmentally unacceptable The treatment and handling of such contaminated wast materials, many of which can be classified as hazardous, i strictly regulated by one or more governmental agencies because o their potential harm to the public welfare. As such, a great dea of work has been done in recent years in developing methods fo safely handling these materials and for neutralizing thei troublesome characteristics so they can be safely discarded.

Non-limiting examples of methods which have been developed an which have met with varying degrees of success, include sorption adsorption, volatilization, biodegradation, chemisorption passivation, ion-exchange, encapsulation, and embedment throug solidification into a monolith structure, as well as stabilizatio of chemical constituents. Sorption involves adding a solid to th hazardous waste material to soak-up any liquid which is present Non-biodegradable materials are typically used as the sorbent Such materials include activated carbon, anhydrous sodium silicate various forms of gypsum, celite, clays, bottom ash, fly ash, fl dust, kiln ash, and cement kiln dust. Biodegradable materials ca also be used, such as peat moss, rice hulls, sawdust, and the like These treatments primarily use biodegradation for reducing organi constituents of the waste material. The sorbent may interac chemically with the waste material, or it may simply be wetted b the liquid portion which is retained in the sorbent as a capillar liquid. Sorption generally cannot be used with many types o hazardous waste, such as those which contain potentially hazardou components, because they can often be easily leached from th sorbent. This is because sorption typically only requires that i be mixed with the waste. Further, as governmental regulation become ever stricter, sorption becomes less and less attractive for meeting such regulations.

Another method for treating hazardous waste involves the consolidation and solidification of the waste into a solid block of material that has relatively high structural integrity. The resulting block is often called a monolith. The monolith can be as small as the contents of a steel drum, or it can encompass the entire waste disposal site, called a monofill . The components of the monolith do not necessarily interact chemically with the reagents, but are usually mechanically locked within a solidified matrix, called microencapsulation. Contaminant loss is primarily limited by decreasing the surface area which is exposed to the environment and/or isolating the contaminants from environmental influences by encapsulating the waste particles. Wastes can also be microencapsulated. That is, bonded to, or surrounded by, an impervious coating.

While solidification can be very effective for treating some hazardous wastes, recently passed governmental regulations are placing greater demands on this technology. This is because of the ever stricter limitations relating to acceptable levels of leachates from the solidified block. Also, the block must withstand ever greater physical pressures without cracking and exposing contaminants to environmental influences.

Other methods of hazardous waste treatment include inorganic and organic stabilization. Unlike solidification processes which convert wastes into a solid mass, stabilization processes can reduce the solubility or chemical reactivity of the waste. Stabilization processes typically include adjusting pH, converting metals to hydroxides, and/or establishing oxidation-reduction conditions to prevent solubilization or leaching of contaminants into ground water. The most commonly used inorganic stabilization processes include mixing the waste product with inorganic materials such as fly ash, cement kiln dust, lime kiln dust, hydrated lime, Portland cement, or other pozzolanic materials. Stabilizatio processes, like solidification, are being pushed to meet th stricter governmental regulations. A typical stabilization process is taught in U.S. Patent Nos 4,781,842 and 4,902,431 wherein a sewage sludge is stabilized an converted to fertilizer by mixing the sludge with an alkalin material which is sufficient to raise the pH to at least 12. Th mixture is then allowed to dry for at least one day. The alkalin material is selected from cement, kiln dust, and lime dust, t achieve chemical stabilization. Bulking materials, such as sla fines, fly ash, gypsum, etc. may also be added. Such a process i primarily a drying process to eliminate offensive odors an pathogenic microorganisms. The process is not capable o generating a substantial amount of heat to destroy many of th contaminants .

Also, U.S. Patent No. 4,859,367 teaches a waste solidificatio method wherein toxic mine tailings are incorporated into a cemen mixture which contains a mineral binder selected from the class o alkali-activated silico-aluminate geopolymers which is stated t be related to natural and synthetic zeolites and feldspathoids.

Although a significant amount of work has already been don to treat contaminated waste materials, there is still considerable need in the art for improved methods for treating an neutralizing such materials.

DISCLOSURE OF THE INVENTION

In accordance with the present invention, there is provide a reagent material for treating environmentally unacceptable wast materials, which reagent material, by weight, is comprised of: (i) 1 part alumina; (ii) 1 to 3 parts of a silica having surface area of at least about 10 m²/g; (iii) 0.5 to 3 parts of hydroxide, or hydroxide precursor, of an alkali metal; (iv) 2 to 5 parts of CaO; (v) 2 to 5 parts of a zeolitic material having a pore diameter equal to or greater than 4A, and an Si0₂ to Al₂0₃ ratio greater than or equal to 2.5. Also in accordance with the present invention is an innocuous solid waste mixture which may be safely disposed of in a landfill comprising:

(a) a reagent material comprised of: (i) 1 part alumina; (ii) 1 to 3 parts of a silica having a surface area of at least about 10 m²/g; (iii) 0.5 to 3 parts of a hydroxide, or hydroxide precursor of an alkali metal; (iv) 2 to 5 parts of CaO; and (v) 2 to 5 parts of a zeolitic material having a pore diameter equal to or greater than 4A, and an Si0₂ to Al₂0₃ ratio greater than or equal to 2.5; and (b) a waste material, which prior to a reaction with said reagent material, contains unacceptable levels of one or more contaminants selected from the group consisting of heavy metals and organic components.

Also in accordance with the present invention, there is provided a method for treating an environmentally unacceptable contaminated waste material to convert it to an environmentally acceptable material, which method comprises mixing said contaminated waste material with an effective amount of a reagent material comprised of: (i) 1 part alumina; (ii) 1 to 3 parts of a silica having a surface area of at least about 10 m²/g; (iii) 0.5 to 3 parts of a hydroxide, or hydroxide precursor, of an alkali metal; (iv) 2 to 5 parts of CaO; and (v) 2 to 5 parts of a zeolitic material having a pore diameter equal to or greater than 4A, and an Si0₂ to Al₂0₃ ratio greater than or equal to 2.5. In a preferred embodiment of the present invention, the alkali metal hydroxide is NaOH, and the zeolite is a zeolite material which is iso-structural to a zeolite selected from clinoptilolit and chabazite.

In other preferred embodiments of the present invention, th reagent material is comprised of: (i) 1 part alumina; (ii) 1.5 t 2.5 parts of a silica having a surface area of at least about 1 m²/g; (iii) 0.5 to 1.5 parts of a hydroxide of an alkali metal; (iv) 2.5 to 3.5 parts of CaO; and (v) 2.5 to 3.5 parts of zeolitic material having a pore diameter equal to or greater tha 4A, and an Si0₂ to Al₂0₃ ratio greater than or equal to 2.5. In yet other preferred embodiments of the present invention, the contaminated waste material is selected from the grou consisting of sewage sludge; a biologic organic waste material; non-biologic waste material; waste resulting from the drilling, production, and processing of petroleum, such as tanker bottoms; and waste contaminated with a naturally occurring radioactiv material .

BEST MODE FOR CARRYING OUT THE INVENTION

Any contaminated waste material may be treated in accordanc with the present invention so long as it is a solid a liquid, o combination thereof. A typical waste stream which can be treate in accordance with the present invention is in the form of sludge. The term "sludge", as used herein, means a material whic is flowable at ordinary temperatures and at about atmospheri pressure, but which has a relatively high solids content, and whic can typically be pumped by conventional pumping means. Non limiting examples of such wastes included sludges which settle a sedimentation layers at the bottom of the sea, lakes, and rivers effluent sludges discharged from various industries includin pharmaceutical, tanning, paper and pulp manufacturing, woo washing, fermenting, food processing, metal surface processing plating, ore dressing, coal washing, and fume desulfurizing; an still other wastes, such as sewage sludges discharged from sewage processing stations, and those resulting from the drilling, production, and processing of petroleum. Such wastes are often contaminated with substances which have an adverse affect on the ecological system. Non-limiting examples of such substances include heavy metals, such as copper, lead, cadmium, arsenic, mercury, hexavalent chromium; and other chronically toxic compounds such as PCB, PCP, DDT, 2-BHC, Dield in, Chlordecone, Mirex, Parathion, cyanic compounds, alkyl-mercury compounds, dioxins, furans; and the like. It is also within the scope of the present invention to treat a waste material which is contaminated with naturally occurring radioactive materials.

The term "contaminated waste", as used herein, means any waste material which is environmentally unacceptable. By "environmentally unacceptable", we mean those materials which governmental regulations define as being harmful, or potentially harmful, to the ecological system pertaining to the environment and which must be disposed of in accordance with governmental laws and/or regulations. In accordance with the present invention, the contaminated waste material to be treated, will typically not meet environmental laws and/or regulations. After treatment, the waste is converted to a relatively innocuous granular substance. That is, a substance which will meet such regulations, and which will thus be environmentally acceptable. The resulting innocuous material is a granulated, or particulate substance, which when mixed with soil, will support the growth of vegetation. Furthermore, the method of the present invention can be performed on-site; thus, not requiring the transportation of contaminated substances which may be subject to even more restrictive regulations.

The waste material to be treated is placed into a containing means. Any suitable containing means may be used. Non-limiting examples of suitable containing means include earthen pits, barges, drums, as well as any relatively large metal container, such as those used to haul trash and soil. The particular containing mean used will depend on such things as economics of the job, the waste to be treated, and the amount of waste to be treated.

An effective amount of reagent material is mixed with the waste to be treated. An effective amount will typically be that minimum amount needed to contact an effective amount of the waste material to an innocuous material. That is, enough which will contact at least that fraction of the waste material which must be treated to render the entire volume of treated waste material environmentally acceptable. Of course, it is most preferred t contact substantially all of the waste. For typical treatments an wastes, a preferred ratio of reagent material to waste material will range from about 10/1 to 1/10, more preferably from about 5/1 to 1/5, most preferably 2/1 to 1/2, particularly about 1/1. Of course, the level of contamination of the waste, the treatin environment, and equipment used, will have an effect on the degre of mixing of reagent material and waste which can be achieved. It is especially preferred to achieve a substantially homogeneou mixture. Of course, water may be added to enhance mixing.

The reagent material of the present invention is comprised of: (i) 1 part alumina; (ii) 1 to 3 parts, preferably 1.5 to 2.5 part silica; (iii) 0.5 to 3 parts, preferably 1 to 2 parts of hydroxide, or hydroxide precursor, of an alkali metal; (iv) 2 t 5 parts, preferably from about 2.5 to 3.5 parts of CaO; (v) and to 5 parts, preferably from about 2.5 to 3.5 parts of a zeoliti material. It is also preferred that the silica material have surface area of at least about 10 m²/g, preferably at least abou 50 m²/g. The preferred hydroxide is NaOH. It is understood tha hydroxide precursor materials may also be used. None limitin examples of NaOH precursors include Na₂0, NaAl0₂, and Na₂0^» (Si0₂) _x. Preferred zeolitic materials are those having an average pore diameter equal to or greater than 4 A, preferably equal to or greater than 5 A. The more preferred are zeolitic materials which are iso-structural to a zeolite selected from clinoptilolite and chabazite. It is also understood that precursors of both alumina and silica may be used. For example, bauxite, kaolin, NaAl0₂, and A1₂0₃ • 3H₂0 are preferred materials for the alumina component of the reagent material of this invention. Preferred silica materials include: silica gel, silica smoke, volcanic ash, kaolin, and sodium silicate (water glass) .

The reagent material of the present invention, which will typically be in particulate or granular form, is used by mixing an effective amount of it with the waste material. As previously stated, it is preferred that the two be mixed as homogeneously as possible. The mixture of waste material and particulate reagent material will need to reach an effective temperature in order to initiate a chemical reaction between the reagent mixture and some of the contaminants in the waste material. An effective temperature can often be reached by merely mixing the reagent material with the waste material, particularly if the waste material contains water, thereby causing an exothermic reaction. If necessary, the mixture can be heated by an external heating means to achieve the effective temperature. It will be understood that the temperature of the mixture should not be allowed to reach a temperature at which undesirable, or toxic, gases evolve. Acceptable temperatures for most waste materials will range from about 50°C to about 250°C, preferably from about 100°C to about 200°C.

After the desired temperature is reached, and held there for an effective amount of time, the mixture is allowed to dry without setting. This ensures that a granular, or particulate, product is produced. Such a product can be mixed with soil and used t support the growth of vegetation.

The following examples are presently for illustrative purpose only and should not be taken as limiting the present invention i any way.

Example 1

A sample (236 gm) of a soil/sludge from a contaminated sit near Manvel, Texas, was treated with 236 gm of a reagent mixtur of the present invention having the composition set forth in Tabl I below. Mixing was conducted by use of a mortar and pestle an the resulting mixture was held at 175°C in an oven for 24 hours. After this treatment, the resulting dry sample was found to hav lost 58 gm, which was assumed to be water because neither odor no smoke was observed during heating. The texture of the treate material was observed to be a fine powder containing a few friabl lumps. Analyses of the treated and untreated materials are give in Table II below.

Example 2

A sample (200 gm) of a soil/tar from a contaminated site nea Mayfield, Texas, was treated with 200 gm of the same reagen material which was used in Example 1 above. Mixing was agai achieved by use of a mortar and pestle and the resulting mixtur was heated at 175°C in an oven for 24 hours. After this treatment the dried sample was found to have lost 151 gm, which was assume to have been water because neither odor nor smoke was observe during heating. The texture of the treated material was also foun to be a fine powder containing a few friable lumps. Analyses o the treated and untreated materials are set forth in Table I below. TABLE I

Composition of the Reagent Material

Component t.% Parts

alumina trihydrate 8.7 1.00 sodium hydroxide 10.0 1.15 silica 20.0 2.30 zeolite* 28.0 3.22 dolomite oxide 33.3 3.83

Total 100.0 11.50

*Clinoptilolite comprised of 84 wt.% clinoptilolite, 12 wt . volcanic glass, 3 wt .% feldspar, and 1 wt . % hematite.

TABLE II

Example 1 Example 2

Analysis As received Treated AS Received Treated

Aromatic volatile org.

(microσrams/Kσ)

xylenes 3570 BDL 3820 BDL acetone BDL 920 10,000 8900 toluene BDL BDL 3830 BDL

2-butanone BDL 1300 BDL 680

Base neut . /

Acid Extract

2-methyl- naphthalene 25,700 BDL BDL BDL phenanthrene BDL BDL 91 BDL

BDL = below detectable limit

Example 3 A sample (100 gm) of contaminated soil from a site near Mexico City was mixed with 100 gm of the reagent material used in the previous two examples . The two were mixed with a spatula in a stainless steel bowl. Water (61 gm) was added and blended into the sample resulting in a relatively stiff mud-like substance. After treating the mixture for 24 hr. at 175°C, the sample appeared to be powdery with only a few soft granules being present . There was n smoke or vapor evolution during heating, thus it was assumed tha the weight loss was due to loss of water. The dry weight was foun to be 174 gm. Analyses of the treated and untreated samples ar given in Table III below.

TABLE III

Analysis As received Treated

Total volatile petroleum hydrocarbons (mg/Kg) 3600 <5

Total Extractable Petro¬ leum hydrocarbons (mg/Kg) 32,000 25

BTEX Analysis (μg/Kg) benzene <500 26 toluene 570 67 ethylbenzene 10,000 5.3 xylenes 68,000 28

Organic Lead (mg/Kg) 1.0 <0.3

Example 4

A sample (100 gm) of contaminated soil from Chemical Pollutio Control of New York, New York, was treated with 100 gm of th reagent material of Example 1 above. The waste and reagen material were mixed with a mortar and pestle and placed in a 175° oven for 24 hr. The resulting dry sample appeared to be a powde and had a dry weight of 180 gm. The weight loss was assumed to b water because no odor or smoke was observed during heating Analyses of the treated and untreated materials are given in Tabl IV below. TABLE IV

Analysis As received Treated

Total volatile petroleum hydrocarbons (mg/Kg) 22,000 23

Total Extractable Petro¬ leum hydrocarbons (mg/Kg) 23,000 410

BTEX Analysis (μg/Kg) benzene 47,000 <50 toluene 1,100,000 820 ethylbenzene 370,000 350 xylenes 2,700,000 2,500

Claims

__J_S.We claim :

1. A reagent material for treating contaminated wast materials, which reagent material is comprised of: (i) 1 part alumina; (ii) 1 to 3 parts of a silica havin a surface area of at least about 10 m²/g; (iii) 0.5 to 3 parts o a component selected from hydroxide, and hydroxide precursors, o an alkali metal; (iv) 2 to 5 parts of CaO; (v) 2 to 5 parts of zeolitic material having an average pore diameter of about 4 A, an an Si0₂ to A1₂0₃ ratio greater than or equal to 2.5.

2. The reagent material of claim 1 wherein the alkal metal component is selected from the group consisting of NaOH, Na₂0, NaAl0₂, and Na₂0« (Si0₂)_x.

3. The reagent material of claim 2 wherein the alkal metal component is NaOH.

4. The reagent material of claim 2 wherein the zeoliti material has an average pore diameter greater than 5 A.

5. The reagent material of claim 4 wherein the zeoliti material is iso-structural with a zeolite selected from the grou consisting of clinoptilolite and chabazite.

6. The reagent material of claim 4 wherein from abou 1.5 to 2.5 parts of silica; about 1 to 2 parts of said alkali meta component; about 2.5 to 3.5 parts of CaO; and about 2.5 to 3. parts of zeolitic material are present.

7. The reagent material of claim 2 wherein the source of alumina is selected from the group consisting of Al₂0₃, bauxite, kaolin, NaAl0₂, and Al₂0₃ • 3H₂0.

8. The reagent material of claim 2 wherein the source of silica is selected from the group consisting of silica gel, silica smoke, volcanic ash, kaolin, and sodium silicate.

9. The reagent material of claim 2 wherein the zeolitic material has an average pore diameter greater than 5A; the source of alumina is selected from the group consisting of Al₂0₃, bauxite, kaolin, NaAl0₂, and Al₂0₃ • 3H₂0; and the source of silica is selected from the group consisting of silica gel, silica smoke, volcanic ash, kaolin, and sodium silicate.

10. An innocuous waste mixture which may be safely disposed of in a landfill comprising: (a) a reagent material comprised of: (i) 1 part alumina; (ii) 1 to 3 parts of a silica having a surface area of at least about 50 m²/g; (iii) 0.5 to 3 parts of a component selected from hydroxides and hydroxide precursors of an alkali metal; (iv) 2 to 5 parts of CaO; (v) and 2 to 5 parts of a zeolitic material having an average pore diameter of at least about 4 A, and an Si0₂ to Al₂0₃ ratio greater than or equal to 2.5; and (b) a waste material, which prior to a reaction with said reagent material, contains unacceptable levels of one or more contaminants selected from the group consisting of heavy metals and organic components.

11. The mixture of claim 10 wherein the alkali metal component is selected from the group consisting of NaOH, Na₂0, NaAl0₂, and Na₂0» (Si0₂)_x.

12. The reagent material of claim 11 wherein the alkal metal component is NaOH.

13. The mixture of claim 12 wherein the zeolitic materia has an average pore diameter greater than about 5A.

14. The mixture of claim 12 wherein the zeoliti material is iso-structural to a zeolite selected from the grou consisting of clinoptilolite and chabazite.

15. The mixture of claim 12 wherein from about 1.5 to 2. parts of silica; about 1 to 2 parts of said alkali metal component about 2.5 to 3.5 parts of CaO; and about 2.5 to 3.5 parts o zeolitic material are present per 1 part of Al₂0₃.

16. The mixture of claim 12 which contains contaminant selected from the group consisting of heavy metals, dioxins, an furans.

17. The mixture of claim 15 wherein the zeolitic materia has an average pore diameter greater than about 5A, the source o alumina is selected from the group consisting of Al₂0₃, bauxite kaolin, NaAl0₂, and Al₂0₃ • 3H₂0; and the source of silica i selected from the group consisting of silica gel, silica smoke volcanic ash, kaolin, and sodium silicate.

18. A method for treating an environmentall unacceptable contaminated waste material to convert it to a environmentally acceptable material, which method comprises mixin said contaminated waste material with an effective amount of reagent material comprised of: (i) 1 part alumina; (ii) 1 to parts of a silica having a surface area of at least about 50 m²/g (iii) 0.5 to 3 parts of a component selected from the hydroxides, and hydroxide precursors, of an alkali metal; (iv) 2 to 5 parts of CaO; and (v) 2 to 5 parts of a zeolitic material having an average pore diameter equal to or greater than 4A, and an Si0₂ to Al₂0₃ ratio greater than or equal to 2.5.

19. The method of claim 18 wherein the alkali metal component is selected from the group consisting of NaOH, Na₂0, NaAl0₂, and Na₂0« (Si0₂)_x.

20. The method of claim 19 wherein the alkali metal component is NaOH.

21. The method of claim 19 wherein the zeolitic material has an average pore diameter greater than about 5A.

22. The method of claim 16 wherein the zeolitic material is iso-structural to a zeolite selected from the group consisting of clinoptilolite and chabazite.

23. The method of claim 20 wherein from about 1.5 to 2.5 parts of silica; about 1 to 2 parts of said alkali metal component; about 2.5 to 3.5 parts of CaO; and about 2.5 to 3.5 parts of zeolitic material are present per 1 part of Al₂0₃.

24. The method of claim 18 which contains contaminants selected from the group consisting of heavy metals, dioxins, and furans .

25. The method of claim 18 wherein the waste material is mixed with said reagent material at a temperature from about 50°C to about 250°C.

26. The method of claim 25 wherein said temperature i from about 100°C to about 200°C.

27. The method of claim 19 wherein the waste materia is mixed with said reagent material at a temperature from abou 100°C to about 200°C.

28. The method of claim 27 wherein water is added to th mixture to raise its temperature to about 50°C to about 250°C.