METHOD FOR THE TREATMENT OF METALLIC PARTICLES AND OBJECTS 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

1-115. (canceled)

116. A method for the stabilization of substantially free-flowing metallic particles of a heavy metal, comprising the step of contacting the metallic particles with an agglomeration agent to substantially bind together at least a portion of the metallic particles and form at least a first metallic particle agglomerate and reduce the probability of the metallic particles being released to the atmosphere during handling and/or transportation of the metallic particles.

117. The method recited in claim 116, wherein the agglomeration 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.

118. The method recited in claim 117, wherein the agglomeration agent comprises a natural resin.

119. The method recited in claim 118, wherein the natural resin is selected from the group consisting of xanthan gum, guar gum, locust bean gum, diutan gum and welan gum.

120. The method recited in claim 116, wherein the metallic particle agglomerate comprises at least about 0.1 wt. % of the agglomeration agent.

121. The method recited in claim 116, wherein the metallic particle agglomerate comprises not greater than about 15 wt. % of the agglomeration agent.

122. The method recited claim 116, wherein the at least a first metallic particle agglomerate comprises not greater than about 10 wt. % of the agglomeration agent.

123. The method recited in claim 116, wherein the metallic particles comprise metallic lead particles.

124. The method recited in claim 116, wherein the metallic particles comprise metallic particles selected from the group consisting of metallic copper particles, metallic arsenic particles, and metallic antimony particles.

125. The method recited in claim 124, wherein the metallic particles comprise metallic lead particles and metallic copper particles.

126. The method recited in claim 116, wherein the agglomeration agent is in a substantially dry form, and the step of contacting the metallic particles with the agglomeration agent comprises mixing the substantially dry agglomeration agent with the metallic particles.

127. The method recited in claim 126, further comprising the step of adding a solvent to the mixture of the substantially dry agglomeration agent and the metallic particles.

128. The method recited in claim 127, wherein the solvent comprises water.

129. The method recited in claim 128, wherein the solvent consists essentially of water.

130. The method recited in claim 116, further comprising the step of applying a heavy metal stabilizing agent to the metallic particles.

131. The method recited in claim 130, wherein the step of applying the heavy metal stabilizing agent to the metallic particles occurs before the step of contacting the metallic particles with the agglomeration agent.

132. The method recited in claim 130, wherein the method comprises applying the heavy metal stabilizing agent and the agglomeration agent to the metallic particles substantially simultaneously.

133. The method recited in claim 132, wherein the heavy metal stabilizing agent and the agglomeration agent are combined before being applied to the metallic particles.

134. The method recited in claim 130, wherein the heavy metal stabilizing agent is a heavy metal stabilizing agent 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.

135. The method recited in claim 130, wherein the weight ratio of the heavy metal stabilizing agent to the metallic particles is at least about 0.5:1.

136. The method recited in claim 130, wherein the weight ratio of the heavy metal stabilizing agent to the metallic particles is at least about 1:1.

137. The method recited in claim 130, wherein the weight ratio of the heavy metal stabilizing agent to the metallic particles is at least about 2:1.

138. The method recited in claim 130, wherein the weight ratio of the heavy metal stabilizing agent to the metallic particles is at least about 3:1.

139. The method recited in claim 130, wherein the weight ratio of the agglomeration agent to the heavy metal stabilizing agent is at least about 0.005:1.

140. The method recited in claim 130, wherein the weight ratio of the agglomeration agent to the heavy metal stabilizing agent is at least about 0.01:1.

141. The method recited in claim 130, wherein the weight ratio of the agglomeration agent to the heavy metal stabilizing agent is at least about 0.1:1.

142. The method recited in claim 130, wherein the weight ratio of the agglomeration agent to the heavy metal stabilizing agent is at least about 0.15:1.

143. The method recited in claim 116, further comprising the step of recycling at least a portion of the metallic particles.

144. The method recited in claim 116, wherein the object further comprises a potentially explosive dry powder.

145. The method recited in claim 144, wherein the potentially explosive dry powder comprises gunpowder.

146. The method recited in claim 116, wherein the method comprises the step of applying a fire retardant to the object.

147. The method recited in claim 146, wherein the stabilizing composition comprises the fire retardant.

148-172. (canceled)

Description

[0063] FIGS. 1-5 illustrate various examples of process flows in accordance with the above description. FIGS. 1-5 are presented for the purposes of illustration, and are not intended to limit the present disclosure to any particular aspects illustrated therein.

[0064] FIG. 1 illustrates a process 100 for the treatment of a filter 102 that includes metallic lead particles, e.g., lead dust, deposited on a surface of the filter 102. The filter 102 may be categorized 104 as a pre-filter 106 (e.g., non-HEPA) or as a HEPA filter 114. If the filter 102 is categorized as a HEPA filter 114, a portion of the lead dust may be optionally removed 116 from the HEPA filter 114. After the optional removal 116 of lead dust, the HEPA filter may be treated 118a/118b with a phosphate solution, i.e., with a phosphate compound that is partially or fully dissolved in a liquid carrier. By treating 118a/118b the HEPA filter 114 with a phosphate solution, the solubilized phosphate will be able to contact the lead dust that is captured within the very fine pores of the HEPA filter 114.

[0065] Thereafter, a fixation agent 120a may be contacted with the treated HEPA filter 114. As is discussed above, in an alternative embodiment, the phosphate solution and the fixation agent (e.g., a gum) may be applied to the HEPA filter 114 simultaneously to enhance the wetting of the lead particles by the phosphate solution, in addition to adhering the phosphate to the filter 114. A TCLP test 122 may be performed to determine if the total leachable lead is less than about 5 ppm. If the treated HEPA filter passes the TCLP test 122, the treated filter may be disposed 124 in a non-hazardous waste landfill. If the treated filter does not pass the TCLP test 122, the treated filter may be disposed 126 in a hazardous waste landfill, or may be recycled 128.

[0066] In a similar manner, a pre-filter 106 may optionally have lead particles (e.g., loose lead dust) removed 108. The pre-filter 106 may be treated with a phosphate slurry and/or with a phosphate solution 110a/110b. That is, a pre-filter 106 may be amenable to treatment using a phosphate slurry, particularly if the phosphate slurry includes phosphate particles of a relatively fine particle size. Thereafter, a fixation agent may be added 112a/112b to the treated pre-filter. Thereafter, a TCLP test 122 may be performed to determine if the total leachable lead is less than about 5 ppm. If the treated pre-filter passes the TCLP test 122, the treated filter may be disposed 124 in a non-hazardous waste landfill. If the treated filter does not pass the TCLP test 122, the treated filter may be disposed 126 in a hazardous waste landfill, or may be recycled 128.

[0067] FIG. 2 illustrates a process 200 for the treatment of metallic particles, e.g., free-flowing metallic particles (e.g., lead dust) in accordance with an embodiment. The free flowing lead dust 202 may be dust that is physically removed, e.g., vacuumed 204 from an object into HEPA filter bag. The lead dust 206 may be treated with a stabilizing composition, e.g., a phosphate solution 208a and/or a phosphate slurry 208b to render at least a portion of the lead dust as non-leachable. Thereafter, the lead dust that is been treated with the stabilizing composition may be contacted with an agglomeration agent 210a/210b, e.g., with an agglomeration agent, to form agglomerates of the lead dust. Thereafter, a TCLP test may be performed 212 to determine if the total leachable lead from the lead agglomerates is less than about 5 ppm. If the lead agglomerates pass the TCLP test 212, the lead agglomerates may be disposed 214 in a non-hazardous waste landfill. If the treated lead dust agglomerates do not pass the TCLP test 212, the agglomerated lead dust may be disposed in a hazardous waste landfill 216 or may be recycled 218.

[0068] FIG. 3 illustrates another process 300 for the treatment of an object that is contaminated with heavy metal particles on a surface of the object. Once the object is obtained 302, a heavy metal stabilizing agent is dissolved 304 in a solvent to form a stabilizing composition and is applied 306 to the contaminated object to stabilize 308 the heavy metal particles. If a fire retardant is needed 310, e.g., where the object includes small amounts of a potentially explosive material such as gunpowder, then the fire retardant is contacted 312 with the treated object. Thereafter, a TCLP test may be performed 314. If the treated object passes the TCLP test 316 it may be disposed 318 in a non-hazardous waste landfill. If the object does not pass the TCLP test 316, then the object may be disposed in a hazardous waste landfill or may be recycled 320.

[0069] FIG. 4 illustrates a process 400 for the treatment of an object is contaminated with heavy metal particles by sealing the object. The object 402 may or may not require a stabilizing composition 404. If the object does not require a stabilizing composition 404, then the object may be directly treated by applying 412 a sealant (e.g., a fixation agent) to the object. If it is determined that a stabilizing composition 404 is needed to properly treat the object, then a heavy metal stabilizing agent, e.g., that has been dissolved 406 in a solvent to form a stabilizing composition may be applied 408 to the contaminated object to stabilize 410 the heavy metal particles prior to applying 412 a sealant to the treated object. After the sealant has been applied 412 to the object to bind 414 the metallic particles to the object, a fire retardant 418 may optionally be added, such as by coating the treated object with the fire retardant. In either case, a TCLP test may be performed 420 and if the treated object passes the TCLP test 422 the treated object may be disposed 424 in a non-hazardous waste landfill. If the treated object does not pass the TCLP test 422, the object may be disposed 426 in a hazardous waste landfill or may be recycled.

[0070] FIG. 5 illustrates a process 500 for the agglomeration of free-flowing metallic particles such as free-flowing metallic lead particles. Once the free-flowing metallic particles are obtained 502 they may be contacted with an agglomeration agent 504. The metallic particles may be contacted 504 with the agglomeration agent in a manner to form 506 agglomerates having a size of at least about 100 m. It may also be determined if a fire retardant is needed 508 and, if so, a fire retardant may be added 510 to the particle agglomerates. Thereafter, a TCLP test may be performed 512. If the agglomerated particles pass the TCLP test 514, the agglomerated particles may be disposed 516 in a non-hazardous waste landfill. If the agglomerated particles do not pass the TCLP test 514 the agglomerated particles may be disposed 518 in a hazardous waste landfill or may be recycled.

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 TCLP Pb Section Type Total Pb (ppm) (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 III for granulated rubber.

TABLE-US-00004 TABLE II Treatment Treatment Ratio TCLP 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 Treatment Ratio TCLP 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 Pb Filter Treatment Method Ratio (ppm) Box HEPA Filter Hybrid 10 wt. % 1.09 Spray On 10 wt. % 0.562 Hybrid + Spray On 20 wt. % 0.0817 Cylindrical HEPA Hybrid 10 wt. % 2.29 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 Rubber Treatment Method Ratio TCLP 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 Pb Dust Treatment Method Ratio (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 Fines 90 pbw TSP and 10 pbw MgO 10 wt. % 0.432 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.