METHOD FOR THE TREATMENT OF AN OBJECT CONTAMINATED WITH METALLIC PARTICLES

Abstract

Methods for the treatment of metallic particles such as heavy metal particles and objects contaminated with the metallic particles. For the treatment of objects contaminated with the metallic particles, a stabilizing composition may be applied to the object with or without a fixation agent. For the treatment of free-flowing metallic particles, an agglomeration agent may be used with or without a stabilizing agent.

Claims

1. A method for the treatment of an object that is contaminated with metallic particles of a heavy metal deposited on a surface of the object, comprising the step of applying a stabilizing composition to the object, where the stabilizing composition comprises a liquid carrier and a heavy metal stabilizing agent.

2. The method recited in claim 1, wherein the metallic particles comprise metallic lead particles and metallic copper particles.

3. The method recited in claim 1, wherein the concentration of metallic particles on the object is at least about 5 wt. %.

4. The method recited in claim 1, wherein the median (D50) particle size of the metallic particles on the surface of the object is not greater than about 200 m.

5. The method recited in claim 1, comprising, before the step of applying the stabilizing composition, removing a portion of the metallic particles from the object.

6. The method recited in claim 1, wherein the heavy metal stabilizing agent comprises a compound or a precursor to a compound that is selected from the group consisting of a phosphate compound, a silicate compound, a carbonate compound, a sulfide compound, a hydroxide compound and combinations thereof.

7. The method recited in claim 6, wherein the heavy metal stabilizing agent comprises magnesium hydroxide and/or a precursor to magnesium hydroxide.

8. The method recited in claim 6, wherein the heavy metal stabilizing agent comprises a phosphate compound.

9. The method recited in claim 1, wherein the stabilizing composition comprises at least about 20 wt. % of the heavy metal stabilizing agent.

10. The method recited in claim 1, wherein the liquid carrier comprises water.

11. The method recited in claim 10, wherein the heavy metal stabilizing agent is at least partially solubilized in the liquid carrier.

12. The method recited in claim 11, wherein the heavy metal stabilizing agent has a solubility in the liquid carrier of at least about 10 g/100 ml.

13. The method recited in claim 11, wherein at least about 90 wt. % of the heavy metal stabilizing agent is solubilized in the liquid carrier.

14. The method recited in claim 11, wherein the heavy metal stabilizing agent comprises a phosphate compound that is selected from the group consisting of dipotassium phosphate, phosphoric acid, and combinations thereof.

15. The method recited in claim 10, wherein the liquid carrier comprises an acid.

16. The method recited in claim 1, wherein the stabilizing composition is a slurry comprising the liquid carrier and particulates of the heavy metal stabilizing agent dispersed in the liquid carrier.

17. The method recited in claim 1, comprising applying a fixation agent to the object.

18. The method recited in claim 17, wherein the fixation agent is selected from the group consisting of an adhesive, a binder, a resin, a thickener, an elastomeric polymer, waxes, paints, polyaspartic compounds/coatings, polyurethanes, varnish, shellac, lacquer, a cementitious material and combinations thereof.

19. The method recited in claim 18, wherein the fixation agent comprises a resin.

20. The method recited in claim 19, wherein the resin comprises a gum.

21. The method recited in claim 1, comprising applying the stabilizing composition and the fixation agent to the object substantially simultaneously.

22. The method recited in claim 21, wherein the fixation agent comprises at least about 0.1 wt. % of the stabilizing composition and not greater than about 40 wt. % of the stabilizing composition.

23. The method recited in claim 17, wherein the method comprises first applying the stabilizing composition to the object and, after applying the stabilizing composition to the object, applying the fixation agent to the object.

24. The method recited in claim 1, wherein the object is a filter.

25. The method recited in claim 1, wherein the object comprises rubber.

26. The method recited in claim 1, wherein the object is obtained from a firing range.

27. The method recited in any of claim 26, wherein the object further comprises a potentially explosive dry powder deposited on the surface of the object.

28. The method recited in claim 27, comprising applying a fire retardant to the object.

29. A method for the treatment of a filter that is contaminated with metallic lead particles deposited on a surface of the filter, comprising the step of applying a stabilizing composition to the filter, where the stabilizing composition comprises a liquid carrier and a heavy metal stabilizing agent that is at least partially solubilized in the liquid carrier, wherein the heavy metal stabilizing agent has a solubility in the liquid carrier of at least about 10 g/100 mL.

30. A method for the treatment of rubber that is contaminated with metallic lead particles deposited in a surface of the rubber, comprising the step of applying a stabilizing composition to the filter, where the stabilizing composition comprises a liquid carrier and a heavy metal stabilizing agent, and applying a fixation agent to the rubber.

Description

EXAMPLES

Firing Range Materials

[0071] Several different types of filters are obtained from indoor firing ranges, including box HEPA filters, cylindrical HEPA filters and pre-filters. The box HEPA filters are procured from an air-mover used in an indoor firing range. The cylindrical HEPA filters are procured from a decelerator that is part of a steel trap system in an indoor firing range. The pre-filters are also procured from an indoor firing range.

[0072] In addition to the filters, three different types of rubber contaminated with metallic lead particles are obtained from backstop berms acquired from indoor firing ranges. The three types of rubber are granulated rubber, DURA-BLOC rubber (Range Systems, New Hope, Minn., USA) and rubber strips.

[0073] In addition, two lead dust samples are also procured from indoor firing ranges. One sample comprises primarily lead dust collected from a dust containment unit (DCU) and the other sample comprises heavily contaminated fine rubber particles from a backstop berm that is collected during range maintenance cleaning.

[0074] A copper metal particle sample is also prepared using a 99% reagent grade powder having a median average particle size of less than about 75 m.

[0075] To obtain baseline values for each of these objects, total lead is measured using the EPA's SW486 Method 6010D, which uses Inductively Coupled Plasma-Optical Emissions Spectrometry to detect concentrations of metals. In addition, the samples are analyzed using the EPA's SW846 Method 1311, the Toxicity Leaching Procedure (TCLP). The total lead and TCLP lead baseline values for each material are listed in Table I.

TABLE-US-00003 TABLE I Total TCLP Section Type Pb (ppm) Pb (ppm) Filter Box HEPA 134,000 1620 Cylinder HEPA 247,000 5960 Pre-Filter 155,000 1519 Rubber Granulated 146,000 749 Strips 112,000 827 DURA-BLOC 216,000 1430 Dust DCU Dust 967,000 8640 Rubber Fines 171,000 1310

[0076] The copper (Cu) particle sample (high purity copper dust) is also subjected to a TCLP extraction and analyzed for leachable copper. The TCLP Cu value was 8.10 ppm.

Treatment Applying Prior Art Methods

[0077] The following prior art methods are selected based on existing, traditional soil remediation and solid hazardous waste treatment methods. These methods are referred to herein as Conventional Technology. Typically, conventional environmental treatment methods use additives in the range of 2 to 5 wt. % and hazardous waste treatment methods use additives in the 5 to 10 wt. % range. Due to the extremely high concentration of elemental lead in the foregoing objects (Table I), each treatment method is carried out here using about 100 wt. % of the additive. The additives include triple superphosphate (TSP), phosphoric acid (H.sub.3PO.sub.4), calcium sulfate (CaSO.sub.4), aluminum chloride solution (AlCl.sub.3, 0.16 molar), magnesium oxide (MgO), and/or Portland cement. Although the phosphoric acid is initially selected, due to the low pH of below pH 2.0 being classified as hazardous under RCRA, it is eliminated from further consideration, as using a hazardous material to treat a hazard is not suitable for field use. The remaining additives are selected for their known ability to treat soil and hazardous waste contaminated with lead compounds, and the non-hazardous nature of the additives.

[0078] The TCLP Pb values using the conventional technology are illustrated in Table II for cylindrical HEPA filters and in Table Ill for granulated rubber.

TABLE-US-00004 TABLE II Treatment TCLP Treatment Ratio Pb (ppm) TSP 100 wt. % 2300 TSP + CaSO.sub.4 100 wt. % 335 H.sub.3PO.sub.4 + AlCl.sub.3 100 wt. % 2570 TSP + MgO 100 wt. % 1430 Portland Cement 100 wt. % 19.4

TABLE-US-00005 TABLE III Treatment TCLP Treatment Ratio Pb (ppm) TSP + CaSO.sub.4 100 wt. % 990 H.sub.3PO.sub.4 + AlCl.sub.3 100 wt. % 39 TSP + MgO 100 wt. % 187 Portland Cement 100 wt.% 965

[0079] Despite the use of a high concentration of additive (i.e., about a 1:1 ratio of additive to metallic particles), all TCLP values listed above are in excess of the RCRA TCLP nonhazardous lead threshold of 5.0 ppm, and also generate 100% more weight than the untreated filter or rubber.

Treatment According to the Present Disclosure

[0080] Two different stabilizing compositions according to the present disclosure are used for the treatment of filters and rubber that are heavily contaminated with metallic lead. A first method, referred to herein as a Spray-On method, uses a stabilizing composition that comprises suspended solids and a highly adhering resin in a liquid carrier, e.g., in the form of a slurry. Specifically, the Spray-On method includes the use of a combination of monocalcium phosphate, tricalcium phosphate, magnesium hydroxide and magnesium oxide as the heavy metal stabilizing agents, and vinyl acetate ethylene resin (WACKER VINNOL 728, Wacker Chemical Corp., Allentown, Pa.) as the fixation agent. The stabilizing composition comprises 22 wt. % of the heavy metal stabilizing agents and 18 wt. % of the fixation agent, the balance being water. The stabilizing composition is applied to the object by spraying through a spray nozzle.

[0081] The second stabilizing composition is a solution of a heavy metal stabilizing agent in water that has a low viscosity to penetrate the pores and folds of a filter, and a resin to promote adherence of the heavy metal stabilizing agent to the object, a method referred to herein as a Hybrid method. Specifically, the stabilizing composition comprises about 49 wt. % of phosphoric acid and dipotassium phosphate as the heavy metal stabilizing agents and 12 wt. % of a vinyl acrylic copolymer resin (DSM Haloflex 202, from DSM Coating Resins, B.V., Netherlands) as the fixation agent.

[0082] The TCLP Pb values from these experiments are listed in Table IV and Table V. For one experiment with the cylindrical HEPA filter, Portland cement is added post treatment as a drying agent.

TABLE-US-00006 TABLE IV Treatment TCLP Filter Treatment Method Ratio Pb (ppm) Box HEPA Filter Hybrid 10 wt. % 1.09 Spray On 10 wt. % 0.562 Hybrid + Spray On 20 wt. % 0.0817 Cylindrical Hybrid 10 wt. % 2.29 HEPA Filter Hybrid + Spray On 20 wt. % 0.313 Hybrid + Portland Cement 15 wt. % 2.00 Pre-Filter Hybrid 20 wt. % 2.82 Spray On 20 wt. % 0.331 Hybrid + Spray On 20 wt. % 3.14

TABLE-US-00007 TABLE V Treatment Treatment TCLP Rubber Method Ratio Pb (ppm) Granulated Hybrid 20 wt. % <0.1 Granulated Spray On 20 wt. % 0.353 Strips Hybrid 20 wt. % 4.94 Strips Spray On 20 wt. % 0.649 DURA-BLOC Hybrid 20 wt. % 1.92 DURA-BLOC Spray On 20 wt. % 0.361

[0083] All methods successfully reduce the TCLP Pb value to below the RCRA criteria of 5.0 ppm.

Firing Range Lead Dust

[0084] In addition to RCRA, lead dust having a particle size of less than 100 m is classified as hazardous under the Department of Transportation (DOT) classification of scrap metal (22 CCR 66260.10), as well as an Occupational Safety and Health Administration (OSHA) hazard to workers by potentially exceeding the permissible exposure limit (PEL). Not only does the lead dust need to be treated, but the particle size needs to be increased for the material to be rendered non-hazardous for transportation and worker safety. Not only is the lead dust a problem, but also copper dust generated from non-lead bullets or reduced lead bullets that are becoming increasingly popular. For the dust samples, an agglomeration agent was needed that did not affect treatment as well as increased the particle size of the material to greater than about 100 m.

[0085] Several agglomeration and treatment agents according to the present disclosure are tested. The TCLP Pb values for the agglomerated and treated Pb dust samples are listed in Table VI. A pure copper dust sample is also treated, agglomerated, and analyzed for leachability using TCLP.

TABLE-US-00008 TABLE VI TCLP Dust Treatment Method Ratio Pb (ppm) DCU TSP.sup.1 200 wt. % 26.3 DCU Hybrid 500 wt. % 1.33 DCU 90 pbw TSP and 10 pbw MgO 100 wt. % 0.843 with 5 pbw Xanthan Gum Rubber 90 pbw TSP and 10 pbw MgO 10 wt. % 0.432 Fines with 5 pbw Xanthan Gum .sup.1Prior Art Technique

[0086] Following treatment, all lead dust samples are agglomerated into large hardened agglomerates and all TCLP lead values are reduced to below the RCRA criteria of 5.0 ppm. The dust collection unit (DCU) dust included 96.6% lead, therefore higher concentrations of heavy metal stabilizing agent are required. The leachability of the copper dust sample was reduced from 8.10 ppm to 7.04 ppm and the dust was agglomerated.

[0087] Methods using current technology for the HEPA filters and other contaminated objects do not successfully treat to the RCRA criteria of 5.0 ppm. In regards to the lead contaminated dust, even if treatment is successful, the material is still considered hazardous due to the small average particle size. HEPA filters and dust contaminated objects are successfully treated to below the RCRA TCLP Pb criteria of 5.0 ppm. In addition, the successfully treatment of lead dust to below RCRA TCLP Pb criteria of 5.0 ppm while increasing particle size to above 100 m to satisfy the additional DOT requirement.

[0088] The conventional technology for treatment of lead-contaminated soils and the like does not successfully apply to firing ranges. Due to the extreme level of contamination from the metallic lead being so much greater, and the matrix being so different than that of soils and typical hazardous lead-contaminated waste, a new method was needed. The present disclosure demonstrates the successful treatment of different types of actual firing range filters and other contaminated objects such as rubber. RCRA TCLP Pb threshold of 5.0 ppm may be achieved. In the case of the lead dust, it may be both treated and agglomerated, and therefore rendered non-hazardous by both RCRA and DOT regulations. Copper powder samples are also agglomerated and the leachability is reduced. Using the treatment methods disclosed herein, firing ranges can significantly reduce the amount of hazardous waste that is generated, provide a safer environment, and allow for ease of transportation, all at a substantial cost savings.

[0089] While various embodiments of methods for the treatment of objects that include metallic particles, and for treating metallic particles, have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.