Free Reply to Response to Motion - District Court of Federal Claims - federal

Case 1:05-cv-01075-TCW

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Exhibit 17

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~N_N .~TED SOIL...~D SOLID WASTE

~12494774 .

FIELD O~._THE.~N~,ENTION The present invention relates to a method of fixing or immobilizing leachable lead in contaminated soil and solid waste materials. BACKGROUND OF THE INVENTION Lead contaminants are often .found in the soil around lead shelters, and battery recycling and manufacturing plants. This.occurs when leadzcontaining chemicals are used in the plant, and.waste water containing the lead-is al!owed to spil! over or drain into the soil. Some species of lead contaminants are mobile and leachable, and when present in soil and solid waste materials are considered "hazardous" to human health and the environment. The Resource Conservation and Recovery Act of 1976, commonly known.as RCRA, provided for federal classification ofhazardous waste. The statutory language defi~es "hazardous waste" as solid waste or combinations of solid wastes which pose a "substantial present or potentia! hazard . ... when improperly treated, stored, transported, ordisposed of, or otherwise mismanaged". Any solid waste that exhibits one 6f the hazard characteristics defined in Subpart C of Part 261, Volume 40, Code of Federal Regulations is, by definition, a hazardous waste. A solid waste is considered to be a hazardous waste if it exhibits characteristics of either ' ignitability, corrosivity, reactivity or EP toxicity (EPTOX). The core of the toxicity characteristic regulations is the extraction procedure (EP) test, which specifies laboratory steps to befollowed in analyzing samples. The test is aimed at identifying the tendency of

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wastes to generate a leachate with concentrations of contaminants greater than the values listed at Volume 40, Code of Federal Regulations, Part 261.24, page 406, revised July I, .1988. If concentrations of leachable, mobile lead are found to be less'than 5 mg/liter, the material is considered non-hazardous with respect to lead content. Various conventional methods have been used to remove leachable, mobile lead from soils and solid waste materials. Those methods include washing, leaching and extracting the lead. According to conventional practice, contaminated soil or solid waste material is excavated from the ground for processing. During washing, the contaminated material is immersed in water or other specified solutions while it is being agitated. Leaching involves the removal of lead from contaminated material by the use of water or.liquid chemicals at elevated temperatures. Extraction is a form of leaching wherein water or liquid chemicals are used at elevated temperatures and increased pressure to remove the lead. None of the prior art processes reduces the leachable lead content to below 5 milligrams of lead per liter in the extract from contaminated soil or solid waste material. Other methods for removing lead from contaminated soil or solid waste involve the use of water in the formation of slurries, which requires cumbersome equipment for the separation of lead from the waste material. The separated solids are usually wet and require further processing before disposal as a stabilized material. The additional steps required in the treatment by conventional. wet processing of contaminated soil and solid waste materials are so costly as to become prohibitive.

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-3Other conventional techni~es involve the chemical fixation oflead in contaminated soils and solid w~ste. One well-known technique involves the extraction of lead using nitric acid and/or aqua regia, and a subsequent purging of the resultant lead nitrate solution with hydrogen sulfide gas to precipitate the lead nitrate as lead sulfite. However, the use of noxious hydrogen sulfide gas necessitates specific health and safety measures. U.S. P~tent No. 4,687,373 describes a composition which encapsulates contaminants such as lead in soils, sludges, sedfment and ash. A cementitious matrix in the form of metal metasilicates is Zormed to encapsulate the contaminants; however, the metal metasilicates increase the volume and weight of the treated soil or solid waste material that must be disposed. U.So Patent No. 3,201,268 describes a method for stabilizing clay soils by mixing phosphoric acid and sulfuric acid with the soil, which is then further mixed with a water-soluble lead salt. The resulting composition may be compacted and cured to produce a stabilized mass having a significantly improved, unconfined compressive strength as compared with untreated soil. This method is suitable for the s~abili~ation of argillaceous soils and clays containing aggregates. U.S. Patent No. 4,028,130 describes a method for disposing and using municipal sewage plant waste materials, more particularly digestive sewage sludge. The sludge is treated with cementitious reactants, including calcium sulfate, to form a hardened product for subsequent disposal. The sewage sludge contains heavy metals, such as lead, which may be involved in the cementitious reaction. U.S. Patent No.'4,615,643 describes a method of sealing off a mass of stored waste in soil containing heavy

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metal cations. An additive is added to the soil which comprises cement, clay, silicone, sodium carbonate and alkali~metal pyroph0spha~e. The lead cation forms an insoluble compound upon reaction with the sodi~ carbonate and pyrophosphate.. The conventional processes,, typically, do not reduce levels of lead below the maximum concentration of contaminant for'the characteristic of EP toxicity. Moreover, some of the conventional methods involvewet processing which is burdensome and requires a considerable amount of equipment to separate the lead from the contaminated soil or solid waste material. Accordingly, a method is needed which fixes or immobilizes leachable lead in contaminated soil or solid waste materials and which brings the level of lead, after treatment, to that below the EPTOX limit. The method must also be relatively dry to provide for easy handling and must be inexpensive in all processing steps~ The method must also produce a stabilized treated material~ suitable for disposai, reduce the volume and/or weight of the treated material to minimize transportation costs, and be adaptable for in-situ treatment of contaminated soils~and solid waste materials. The method of the present invention meets these requirements. SUMMARY OF THE INVENTION The present invention relates-to a method of immobilizing leachable lead in contaminated soils and solid waste materials. The method comprises contacting lead in the contaminated soil or the solid waste material with a solid powder agent which includes one Or more reactive sulfate ions. The contact is maintained for a sufficient amount of time to convert a first portion of ihe lead, or a

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species of the lead reactive with sulfate ions, in the contaminated soil or solid waste, into a substantially insoluble form. A second step in the method comprises, contacting lead in the contaminated soil or solid waste materia~ with a phosphate supplying reagent, including one or more reactive phosphate ions. This contactis maintained for an effective amount of time to convert a second portion of the lead, or a species of thelead reactive with phosphate, in the contaminated soil or solid wastellnto a. substantially insoluble form. The solid powder and phosphate supplying reagent are typically contacted or mixed with the contaminated soil for a time period from about three to five hours. Five hours, is preferable particularly when the moisture content of the soil is low and ranges from about 15 percent to about 25 percent by weight. The relative order of addition of the solid powder and the phosphate supplying reagent is not critical. The phosphate supplying reagent may be added to the soil before the solid powder because each agent reacts with a specific portion of the leachable lead in-the soil. In a p~eferred embodiment, the solid powder includes one or more sulfate ions and comprises a sulfate salt. More particularly, the solid powder can comprise calcium sulfate or gypsum. The calcium sulfate converts the leachable lead to a hard sulfate mineral salt of the barite family, such as anglesite and calcium-substituted anglesite or mixed calcium anglesite of nominal formula, PbSO4,' Cao.05Pb0.95SO4, CaO.2Pb0..sS04, and Ca0.3Pbo.7SO4. It is also preferred that the phosphate supplying reagent, which includes one or more phosphate ions, be added to the contaminated soi! 6r_solid waste material in

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liquid form. The phosphahe supplying reagent is preferably phosphoric acid dissolved in water in amounts ranging from about 5 percent to about 25 percent by weight. Phosphate ~ons convert the second portion of lead to superhard mixed minerals of the apatite family, such as calcium substituted hydroxy lead apatite, lead hydroxy/chlor apitates, and. ~yromorphite. Presence of both excess sulfate and phosphate together results in formation of insoluable "hard" and "superhard" mixed minerals of lead, such as calcium lead phosphate sulfate; e.g., Ca0.05Pb0.95(PO4)o.5(S04)0.25 and Ca0.2Pb0.8(SO4)0.76(PO4)0.16. Trace amounts of organo-lead phosphate sulfate; are also formed. All these minerals of lead are heavy, with densities greater than 5.0, and usually do not dissolve in mild acid and/or water. The use of a combination of the sulfatE-containing solid powder and the phosphate supplying reagent as a liquid reduces the leachable lead content of the soil chemicallY. This method provides a stabilized soil that is within the standard criteria, for non-hazardous waste, set under the RCRA. BRIEF~ESCRIPTION OF THE DRAWINGS In the drawings, which comprise a portion of this disclosure: " Figure 1 is a block diagram of one embodiment of the method of the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The method according to the present invention includes a two-step process for treating contaminated soil ¯ or solid waste materials with chemical treating agents that convert leachable ~ead to synthetic (man-made) substantially

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insoluble or immobilized mineral crystals. As used herein, "substantially insoluble" means the leachable lead content in the sample is less than about 5.0 ppm.of EP toxic lead, The first step of thi~ innovative process c~mprises converting leachable lead in contaminated soil or solid waste materials with a solid powder. The solid powder includes one or more sulfate minerals, often referred to as "hard sulfates", which are insoluble in water. In this invention, dry calcium sulfate or gypsum powder is a preferred solid for'blendlng with lead contaminated materials. However, sulfuric acid and alum in liquid or powder form can also be used.. When used in the method of the present invention, calcium ions from the gypsum or other solid treating agent displace lead from soil complexes and organic micelles present in the contaminated soil and solid waste material. The following equations (I) and (2) describe[the reaction of, 'leachable lead with gypsum. Pb-Micelle +'CaSO4.2H20---~Ca-Micelle + ~bSO41 + 2B20 . . . {I) (2) Pb|HCO3)2 + CaSO4"2H20--------PbSO4 + CaCO3 + 3H20 + CO2 . . Anglesite The reaction of lead with gypsum forms a "hard sulfate" which crystallizes into mineral species of the barite family. Specifically, these mineral salts are anglesites and calclum-substitut~d anglesites which are insoluble in water. The solubility product of lead sulfate is 1.8 x 10-8,

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indicating that angelslte crystals would continue to develop over the geologic periods. After treatment with the solid powder, the 30 " contaminated soil or solid waste material is treated with a phgsphate supplying reagent which in contact with t~e soil reacts chem~cally to immobilize t~e remaining leachable lead. The phosphate supplying reagent includes any ..~

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phosphate ion source having one or more reactive phosphate ions; for example, phosphoric acid, trisodium phosphate, a potassium phosphate and mono basic or dibasic calcium phosphates. The lead, along with the calcium ions, binds with the phosphate to form insoluble "super-hard" phosphates or calcium substituted hydroxy lead apatites as shown in the following equation
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4PbCO3 + CaCO3 ÷ 3H3PO4------Pb4Ca(OH) (P04)3 + 5C02 + 4H20 . Hydroxy Lead Apltates

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The phosphate ion is added to the contaminated soil in solution form, for example, phosphoric acid may be added to water in amounts ranging from about 5 percent to about 25 percent by weight. It is preferred to have soil moisture at about15 percent to about 25 percent by weight to the soil in order to accelerate the fixation of the leachable lead with the phosphate ions. The solid sulfate powder and the phosphate supplying reagent are added to contaminated soil and solid waste material having a typical moisture content ranging from about 15 percent to about 25 percent by weight. At a moisture level within the foregoing range, the curing time of the treating agents ranges from about 3 to about 5 hours, which provides time for chemical reactions to precipitate and immobilize the leachable lead species. Crystals of various lead mineral species begin .to form and would continue to develop over the geological time frame. Under the foregoing conditions, the immobilization ofleachable lead occurs in a relativelY dry environment because no Wet materials, slurries and waste waters are produced by th9 process. The dryness of the material aids in the handling of the soil and ~e.waste materlal. The

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immobilized lead minerals synthesized .according~to the present method are stable, subst~ntially water insoluble and non-leachable under normal environmental conditions. A list of these synthetic leadmineral speqies and complexes is presented below (Table 1), in order of the relative abundance found during characterization of treated soil by x-ray fluorescence spectrometry,, polarized light microscopy and scanning electron microscopy. Table 1 Synthetic Mineral Species of Lead Detected in a Treated Sample (Listed in decreasing order of 9bundance)
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31-41%, Calcium Substituted Hydroxy Lead Apatites, ea0.5_l.sPb3os-4.5(OH)(PO4)3 28~9%, Mixed Calcium Lead Phosphate Sulfates, Ca0.05-0.2PbO.8-0.95(PO4)0.1S-0.5(SO4)O.25-O.7S 21-22%, Mixed Calcium Anglesites, Cao. OS_o.3Pbo.7_0.95SO4 3-6%, Anglesites, PbSO4

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2-7%, ' Lead Hydroxy/Chlor Apatite, Pb5(PO4)3(OH)0.5CI0.5 1-3%, Pyromorphite, Pb3(P04)2 I&2%, Organg-Lead Phosphate Sulfate, Humus-o-Pb3(P04)(S04) Some of the chemical reactions that-occur during the curing stage, and lead to development of.mixed minerals containing both sulfates a~d phosphates, are illustrated in equations (4) and (5).

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lSPbCO3 + 5CaSO4.2H20 + ~2H3PO4 Curing Time of 3 to 5 hours Ambient Temperature & Pressure 20Ca0.1Pb0.9(P04)0.5(S04)0.25 + Ca~(PO4)2 + 18CO2 + 28H20 .... Mixed Calcium Lead Phosphate Sulfate (4)

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-i06Pb[Humus] + 2CaSO4.2H20 + 3H3PO4 Curing Time of 3 to 5 hours Ambient Temperature& Pressure

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cagH[Humus]-Pb3~(P04)S04 + 2H20 ~ Ca0.3Pb0.7SO4 + .C.a0.TPb2.'~(P04)2 . . (5} Pyromorpb~te Organo-Lead phosphate Ca substituted (Ca suhsr.ituted)o sulfate Anglesite The foregoing treatment process also reduces the volume and mass of the waste materials. This is due to: (i) the evolution of carbon dioxide during the chemical degradation of carbonates and bicarbonates, upon reaction with the acidic components in the phosphate supplying reagent,, and (ii) hardening and compaction as a result of new minera! ~ynthesis which is associated with reduction of interstitial spaces. The reduction in mass and volume of the contaminated soil and the solid waste material makes the present method particularly convenient for off-site processing of waste materials. However, one practical advantage of the method of the present invention is that the method can be employed in-situ at a field location to immobilize leachable lead. The method of the present invention is schematically represented in Figure i. The contaminated soil and solid waste material i0 is subjected to grinding/mixing 12 and screening 14 through an appropriately sized mesh. The screening yields particles that are less than 3/8 inch in diameter for mixing with chemicals ,in conventional equipment. Gypsum or calcium sulfate powder (the solid powder 16) is added during the grlnding/mlxing step or alternatively (as shown by the dashed line) to the screened contaminated soil and solid waste material in" effective amounts as defined herein. The leachable lead is ,chemically bound and forms lead sulfate, which crys.tallizes

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to a synthetic nucleus of mixed calcium anglesite and pure anglesite minerals identified in the treated materia!. The gypsum-containing material is then transported to an area where an effective amount of a phosphate~ .
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s~pplying reagent 18; for e~ample, a phosphoric acid solution of various strengths in water 20, is added or sprayed just prior to thorough mixing in a puqmill 22. The material is mixed.thoroughly so that during the curing time of about-fiv~ hoursvarious "super-hard phosphate" mineral species such as calcium substituted hydroxy lead apatities, and mixed calcium lead phosphate-sulfate agglomerates and poorly de~eloped crystals (the treated soil or solid waste 24) are formed, immobilizing the leachable lead ~in the soi! completely. The proportions of waste materials and reagents used in the method of the present invention may be varied within relatively wide limits. For e~ample, the amount of solid powder shoul4 be an amount sufficient to produce lead sulfate in contaminated soil or s~lid waste material which has a moisture content of about 15 percent to about 25 percent by weight, when cured for a time period ranging from about 3 to about 5 hours. In addition, the amount of phosphate supplying reagent should be an amount sufficient to produce mineral species such as h~droxy lead apatite in contaminated soil or solid waste material having the foregoing moisture content and subjected to the same curing time as previously noted. The amount of the solid powder and the phosph~ate supplying reagent is dependent on the amount of contaminant present in the soil and solid waste material, whether the material is in-situ or is excavated and brought to an offsite facility for treatment. The following Example describes various ratios of the chemical reagents for.

SH039539

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application to excavated lead-contaminated soil in order to render the leachable lead substantially insoluble; i.e., to reduce the level of leachable lead to levels below 5.0 ppm of EP toxic lead. ~xamDle .The method of. the present invention was utilized' with three samples of soi! from B lead contaminated test site. Gypsum powder was used as the solid treating agent andphosphoric acid in wa~er at~concentrations of about 7, 15 and 22 percent byWeight was used as thephosphate supplying agent. The soil was measured for lead content in accordance with the Extraction Procedure (EP) Toxicity Test before and after treatment. A level of leachable lead below 5 milligrams per liter was considered non-hazardous according to this procedure. The results are shown in the fol!owing table. Table 2 EP Toxicity (Lead) Soil Gypsum Phosphoric acid Test Results (mg/l) (q/kq soil} SamPle ~{~/ku soil) Befor__~e After 30 '20 40 20 I0 30 61 8 3,659 < 0.i < 0.I 1.7

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The foregoing results demonstrate that the twostep method of the present invention provides treated.soil that is well within the standards prescribed by the EP toxicity testing procedures for. acceptable, or characteristically non-hazardous,.lead concentrations; From the foregoing, it can also be seen that the present provides an efficient, economical and ecologically acceptable method for treating leachable lead in contaminated soil and solid waste materials.

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--13It should be Understood that while the invention has been described with 9espect to particular compositions, it is not necessarily limited thereto. This specification should be construed as encompassing the invention in a scope that includes possible variations and modifications thereof as may be apparent to those skilled in the art.

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WHAT IS CLAIMED IS: I. A method of immobilizing leachable lead in substantially dry contaminated soil and solid waste materials comprises the steps of: contacting the contaminated soil or solid ~aste materials with a solid powder including one or more reactive sulfate ions for a piriod of time sufficient to convert a first portion of the leachable lead in the contaminated soil or solid waste materials into a substantia!ly insoluble form; and .contacting the contaminated soil or solid waste materials with a phosphate reagent including one or more reactive phosphate ions for a period of time sufficient to convert a second portion of the leachable lead in the contaminated soil or solid waste materials into a substantially insoluble form. 2. The method according to claim 1 wherein the solid treating agent comprises a sulfate salt. 3. The method according to claim 2 wherein the sulfate salt is selected from the gr6up consisting of calcium sulfate, gypsum, sulfuric acid, and alum in. liquid or powder form. 4. The method according to claim 1 wherein the first portion of leachable lead is converted to a substantiallyinsoluble sulfate species. 5. The method according to claim 4 wherein the first portion of leachable lead is converted to a synthetic mineral species selected from the group consisting of ¯ synthetic anglesite and calcium-substituted anglesites. 6. The method according to claim i wherein the phosphate supplying reagent is selected from the group consisting of phosphoric acid, trisodium phosphate, ~

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potassium phosphates and mono basic or dibasic calcium phosphates. 7. The method according to claim .6 wherein the soil or solid waste material includes about 15 percent'to about 25 percent water by weight after being contacted with the phosphate supplying reagent. 8. The method according to claim 6 wherein the phosphate supplying reagent comprises phosphoric acid dissolved in water. 9. The method according to claim 8 wherein the phosphoric acid is dissolved in water in an amount ranging from about 5 percent to about 25 percent by weight. i0. The method according to claim 1 wherein the second portion of leachable lead is converted to a substantially insoluble phosphate mineral species. ll. The method according to claim 1 wherein the second portion of leachable lead is converted to a superhard phosphate including calcium substituted hydroxy lead apitate, a lead hydroxy/chlor apitate and pyromorphite. 12. The method according to claim i wherein the period ~f time needed to convert the first and second portions of leachable lead to an insoluble form ranges from about 3 hours t6 about 5 hours. 13. The method according to clai~ 12 wherein the period of time needed to convert the first and second portions of leachable lead to an insoluble form is about 5 hours. 14. The method according to claim 12 wherein the moisture Content of the soil or solid waste material r~nges from about IS percent to.about 25 percent by weight.

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A~BSTRACT
A two-step method is provided for treating contaminated soil and solid waste material to immobilize leachable lead. The first step comprises contacting the leachable lead with a solid powder which includes o~e or more sulfate ions so that a substantially insoluble lead sulfate and calcium substituted lead sulfate minerals are the dominant species-formed. Th~ second step comprises contacting the leachable lead with a'phosphate ~pplying. reagent which includes one or more phosphate ions so that substantially insoluble phosphate minera! species are formed within about 3 to 5 hours. The method can be used with substantially dry contaminated soil or solid waste in-situ and with excavated waste materials.

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