Patent Number: 052681289
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is suitable for treating various types of particulate materials, and especially contaminated soil, but it can also be used to treat sludges, sediments, scrap yard dust and the like. These particulate materials can be contaminated with heavy metals, organics and radioactive species either alone or in combination. FIG. 1 illustrates a first embodiment of the invention. Initially, the excavated soil is processed to remove large rocks and debris. This step is not shown in FIG. 1. The soil is then processed in a mechanical size separator 10 such as for instance a rotating drum or vibrating screen device to sort and prewash the feed soil with a contaminant mobilizing solution, provided through line 12. Large pieces of soil, for instance larger than 5 mm are washed with the contaminant mobilizing solution, rinsed with water supplied through line 14, checked for residual contaminants, and returned to the site as recovered soil. The contaminant mobilizing solution (or process stream) used to wash the soil will be dependent upon the contamination to be removed. For soluble contaminants, the solution will contain a leaching agent. Many suitable leaching agents are known and common leaching agents suitable for leaching radioactive compounds include for example potassium carbonate, sodium carbonate, acetic acid, sodium hypochloride, and others. Leaching agents for contaminants typically found in contaminated soils and the like are well known. For dispersible contaminants, the contaminant mobilizing solution contains a suitable surfactant. Again, suitable surfactants for dispersing contaminants such as oil, grease, polychlorinated biphenyls, etc., are also known. The contaminant mobilizing solution may contain various combinations of leaching agents and surfactants, again, depending on the contaminants in the soil to be cleaned. The effluent of soil particles smaller than 5 mm and contaminant mobilizing solution discharged from the mechanical separator 10 through line 16 is then processed in a countercurrent flow size separator such as the mineral jig 18. In the jig 18, additional contaminant mobilizing solution supplied through line 13 flows upwardly countercurrent to the effluent. The fines are carried upwardly with the upward flow of contaminant mobilizing solution to form a slurry which is discharged through a line 20. These fines typically include heavy metal particles. The velocity of the upward flow of contaminant containing solution in the mineral jig 18 is set to separate fines of a desired size, for example fines smaller than 60 microns in diameter. The slurry discharged in the line 20 includes, in addition to the fines, contaminant mobilizing solution which contains leached and dispersed metals and organics. Heretofore, mineral jigs such as that disclosed in U.S. Pat. No. 4,783,253, have only been operated in a concurrent flow mode. We operate the mineral jig 18 in a countercurrent flow mode. For such countercurrent flow operation, the jig can be operated with a stroke length of 1/2 to 3/4 inch, a pulse frequency of 300 to 400 per minute, an upflow rate of contaminant mobilizing solution of 1 to 8 liters per minute an underflow rate of 1 to 3 liters per minute, with one layer of balls 3/16 inch in diameter or greater to provide a soil under flow of 80 to 95 percent and soil over the top of 20 to 5 percent. The intermediate sized particles between 5 mm and 60 microns in diameter, which are discharged from the bottom of the mineral jig 18, are abraded in an attrition scrubber 22 which dislodges mineral slime or fines from them. The intermediate sized particles and the dislodged fines discharged from the attrition scrubber 22 through line 24 are rinsed in a second countercurrent flow size separator such as the second mineral jig 26 operated in the manner discussed above in connection with jig 18. The countercurrent flow in the second mineral jig 26 is wash water which flows upwardly at a velocity again selected to separate the dislodged fines, typically of 60 microns in diameter and smaller. The slurry of fines and wash water is discharged through line 28. The remaining intermediate sized particles discharged from the second mineral jig 26 are processed in a density separator such as a cross-current flow jig 30 to extract higher density heavy metal solid waste particles. The mineral jig 30, which is similar to the jigs 18 and 26 is operated in the cross-current flow mode with a stroke length of 1/8 to 3/16 inch, a pulse frequency of 100-400/min, a water upflow rate of 1 to 8 liters/min, one to three layers of balls less than 3/16 inch to provide soil over the top of 80 to 95 percent and a soil underflow of 20 to 5 percent. The cross-current flow carrying the intermediate sized soil particles is discharged through a line 32 into dewatering apparatus such as, for instance, a clarifier 34 or a hydroclone. Sludge from the clarifier 34 is pumped by a pump 36 onto a drying pad 38. The dried particles recovered from the drying pad are checked for cleanliness and returned to the site as additional cleaned soil. Water removed by the clarifier 34 is circulated by a pump 40 through a line 42 as the countercurrent wash water for the second mineral jig 26, and through line 44 as the cross-current flow for the density separator jig 30. The two waste slurry streams in the lines 20 and 28 from the first and second mineral jigs 18 and 26, respectively, are discharged into precipitation equipment 46 to which is added a precipitant to precipitate the dissolved metals. A sulfide or other suitable agent can be used to precipitate the dissolved metals present in a particular contaminated soil. These precipitates and fine soil particles will be highly contaminated with organics and heavy metals. A flocculant, such as for example Nalco 7182, an anionic polymer that does not interfere with trace metal absorption and co-precipitation, supplied by the Nalco Chemical Company, Naperville, Ill., is added to the precipitates and fines conveyed from the precipitation equipment 46 through a line 48 to dewatering apparatus 50 which may include for instance Bardles-Mozley concentrator 52 which separate micron size particles of high specific gravity. Simultaneously, fine particles are washed by the high shear, orbital shaking of the table. Fine soil solution which is washed from the table is passed through high intensity matrix magnetic separators which remove micron sized particles coated with weakly paramagnetic hydroxides containing inorganic contaminants. Solids from the remaining solution are then separated from the stream by either filtration or flocculation settling and pelletizing in apparatus 54. The organically contaminated fractions can be further treated biologically, chemically or thermally and returned to the site. Concentrated solids removed by the Bartles-Mozley concentrator 52 can be disposed of or sold as a concentrate. The filtrate is passed through the line 55 to an activated carbon bed 56 to remove all organics before being sent through line 58 for recycling. The recycled solution is discharged in the one of two contaminant containing solution makeup tanks 60 and 62 which is not currently being used to feed the process. Makeup chemicals 61 may be supplied to the makeup tanks 60 and 62. The contaminated activated carbon in the bed 56 can be thermally or chemically treated or buried. The recycled contaminant mobilizing solution is analyzed and an active component such as caustic or emulsifier are made up on a batch basis in the off-line makeup tank 60 or 62. Contaminant mobilizing solution from the active one of the tanks 60 and 62 is pumped by the pump 64 or 66, respectively, through the line 12 to the mechanical size separator 10 and through the line 13 to the first mineral jig 18. FIG. 2 illustrates a modified embodiment of the invention in which the contaminated soil, after large pieces have been removed, is fed to a mechanical size separator in the form of the screw washer/classifier 68 where the soil is washed with the contaminant mobilizing solution supplied through a line 70, and where the larger particles are rinsed with a water based cleaning solution introduced through line 72 and discharged as clean large solids. The intermediate sized particles and fines are passed through a line 74 to a first attrition scrubber 76 where attached fines are dislodged from the intermediate sized particles. The abraded particles are then discharged into a countercurrent flow size separator in the form of a first mineral jig 78. The countercurrent flow in mineral jig 78 is provided by contaminant mobilizing solution supplied through the line 79. A slurry of fines and contaminant mobilizing solution containing dissolved and or dispersed contaminants is discharged from mineral jig 78 through the line 80. The intermediate sized particles are passed through a second attrition scrubber 82 where they are again abraded to dislodge additional attached fines, and a second countercurrent flow size separator in the form of a mineral jig 84 which uses an upward flow of wash water to separate the additional dislodged fines in a waste slurry which is discharged through line 86. The remaining intermediate sized particles are dewatered in a hydroclone 88 and then clarified in a tank 90. Sludge from the tank 90 is deposited through a line 92 on a drying bed 94 by a pump 93 to produce additional cleaned soil to be returned to the site. Water removed by the cyclone 88 is recycled as the wash water through line 96 to the second mineral jig 84. Makeup water is added as required through line 97. The two waste slurry streams in lines 80 and 86 are delivered through line 98 to dewatering apparatus which includes hydroclones 100. The cleaned fines from the hydroclones 100 are discharged through a line 102 into a precipitation reactor 104 to which a flocculant is added. Dewatered fines can be removed from the reactor 104 for disposal, or for further treatment. Overflow solution from the tank 104 and discharged from the cyclone 100 is recycled. Where the contaminants include radioactive compounds or heavy metals, the recycled solution can be passed through an ion exchange bed 106 to remove the soluble metals before being discharged into the contaminant mobilizing solution makeup tanks 108 and 110. Again, while makeup chemicals 61 are being added to one makeup tank 108 or 110, contaminant mobilizing solution is being pumped by a pump 109 or 111 from the other tank to the screw washer/clarifier 68 and the first mineral jig 78. FIG. 3 illustrates yet another embodiment of the invention. This embodiment utilizes a screen/washer mechanical size separator 112 similar to that used in the first embodiment to wash the feed soils with contaminant mobilizing solution supplied through line 113 and to separate and rinse with water provided through line 115 the large particles such as those over 5 mm. The intermediate sized particles and fines are then carried through a line 114 to a first attrition scrubber 116 which dislodges attached fines from the intermediate sized particles. The fines including those dislodged in the attrition scrubber 116 are then separated from the intermediate sized particles in a countercurrent flow size separator such as the first mineral jig 118 where the countercurrent flow is contaminant mobilizing solution provided through the line 120. The waste slurry containing the fines and solubilized and dispersed contaminants is discharged through the line 122. The remaining particles are passed through a second attrition scrubber 124 and then through a line 126 to a second mineral jig 128 for size separation by the countercurrent flow of rinse water. The waste slurry containing the fines is discharged from the second mineral jig 128 through line 130. The intermediate sized particles discharged from the second mineral jig 128 are passed through a classifier or gravity separator such as a cross-current flow jig 132 to remove heavy metal particles for disposal. The remaining intermediate sized particles are dewatered such as in clarifier 134. Again, the sludge from the clarifier 134 is discharged by pump 136 onto a drying pad 138 to produce additional clean soil. Water removed in clarifier 134 is recirculated by the pump 140 through a line 142 to supply the countercurrent flow to the second mineral jig 128 and through a line 144 to the cross-current flow jig 132. As in accordance with the invention, the waste slurry stream in lines 122 and 130 is treated to remove the contaminants and recirculate the contaminant mobilizing solution. The particular treatment of this waste slurry depends on the type of contaminants extracted from the soil. In the embodiment shown in FIG. 3 dissolved metal contaminants are precipitated in reactor 146 and the resulting precipitants and fines are separated by dewatering which includes the addition of a flocculant. The dewatering apparatus 148 may comprise the apparatus used in the embodiments in FIGS. 1 and 2 or other dewatering apparatus. Organic contaminants are removed from the recycled contaminant mobilizing fluid in a carbon bed 150 while the soluble radioactive contaminants which were not removed by precipitation are extracted in an ion exchange bed 152. Again, the recycled contaminant mobilizing solution is returned to the one of two makeup tanks 154 and 156 which is not currently in use, and is pumped by a pump 158 or 160 from the active tank to the screen/washer 112 and the first mineral jig 118. Makeup chemicals 155 may be supplied to the makeup tanks 154 and 156. In a preferred embodiment of the invention, the contaminant mobilizing solution, or process stream, is provided with an oxidizing or reducing agent, for example, selected from the group Cl.sub.2, ClO.sub.2, O.sub.3, which increase the solubility of the contaminants, most particularly the metal contaminants, in the process stream. This, in turn, assists in removing such contaminants from the feed soils, or contaminated particulate material fed to the soil washing system. A preferred embodiment of this aspect of the invention is illustrated in FIG. 9. As illustrated, feed soils, or contaminated particulate material 200 is fed to a soil washing process, 201, which may be any of the processes described herein, as well as those known in the art. The contaminated particulate material may contain various heavy metals, such as Hg, U, Pb, Ag, As, Cd, Cr, Cu, Ra, Th as well as organics, such as oils, PCBs, flue soot and radioactive compounds. The contaminants are removed from the particulate material by a contaminant mobilizing solution or process stream 202, contained in a makeup tank 210, which may contain a leachate and/or surfactant as previously described. Preferably, the process stream, which at this point has a pH of 6-10, contains an oxidizing agent or a reducing agent, for example, Cl.sub.2, ClO.sub.2, O.sub.3 or H.sub.2, which increases the solubility of at least one of the contaminants in the process stream, thereby effecting more efficient removal of the contaminants from the contaminated particulate matter and also improving the mobility of the contaminants through the process. Most preferably, when the heavy metal component is to be removed, an oxidant such as Cl.sub.2 is used in a high pH stream (8-10, preferably 9), which favors Cl.sub.2 absorption. In this case, a precipitant, such as Na.sub.2 SiO.sub.3 is used to precipitate the heavy metals, which remain in solution in said process stream following removal of clean particulate matter therefrom. The precipitant may also flocculate any precipitated heavy metal hydroxides, fines and/or precipitated soaps. Referring now to FIG. 9, the process stream 202 passes through the soil washing process 201, and clean soil or particulate matter 203 is removed from the process stream 202. If surfactants are used, and are not to be recovered for recycle, a surfactant precipitating agent 204, such as CaCl.sub.2 or other soluble calcium salt, is introduced to the process stream 202 at a surfactant removal system 211 following removal of the clean particulate material 203, and contaminated surfactants 205 are removed from the process stream 202 for further treatment or disposal. If the surfactants are to be recovered for recycle, or if no surfactants are used, no surfactant precipitating agent is introduced to the process stream 202. At this point in the process, fines may be removed via a fixed removal means 206. Fines removal may be by known methods, such as electro-coagulation, for example, using an ACE Separator manufactured by Electro-Pure Systems, Amherst, N.Y., followed by cyclones, which separate the contaminated, coagulated fines from the process stream. As fines removal generally requires adjusting the pH of the process stream to 5.5-6, and precipitation of heavy metals occurs generally at a higher pH, the pH is preferably adjusted to 8-10, preferably 9 for metals precipitation, for example by adding NaOH to the process stream 202, along with the addition of a precipitant, such as Na.sub.2 SiO.sub.3. The precipitated metals are removed from the process stream, via a precipitant removal means 207, for example, by electro-coagulation followed by cyclones, or filtration, classification, centrifugation or high efficiency cyclones. An advantage of the invention is that it does not require large, permanent settling ponds, rather, can utilize portable equipment which can be moved from one job site to another. The precipitated heavy metals may be re-dissolved in NaOH solutions to recover the heavy metal and regenerate the Na.sub.2 SiO.sub.3, as disclosed in U.S. Pat. No. 5,077,020, which issued on Dec. 31, 1991, from U.S. patent application Ser. No. 652,475, filed Feb. 8, 1991, which is a continuation of U.S. patent application Ser. No. 453,744, filed Feb. 20, 1989, and now abandoned. Following removal of the heavy metal precipitants, the process stream becomes a recycle stream 208, which may be used to recycle leachate and/or surfactants for washing of additional contaminated particulate matter. In the case where all contaminated surfactants have been removed from the process stream 202, the recycle stream 208 may be recycled directly to the soil washing process after addition of makeup chemicals, such as leachates and/or surfactants, if any. In the case where the recycle stream contains organics and/or surfactants, it is desirable to add oxidizing agent and/or reducing agent 209 to the recycle stream for the destruction of such organics using an organic destruction system 212. The preferred oxidizing agent is Cl.sub.2, which is highly absorbed in the high pH recycle stream. The preferred reducing agent is H.sub.2. Preferably, H.sub.2 may be used to reduce all organics contaminants, while Cl.sub.2, ClO.sub.2 and O.sub.3 are used to oxidize non-aliphatic organic contaminants preferentially to the surfactants. The oxidizing and/or reducing agent may be added to the process stream at any convenient point in the process. Preferably when Cl.sub.2 is used it is introduced to the recycle loop, after removal of particulate matter, under pressure through a diffuser which assists in dissolving the Cl.sub.2 into the process stream. When H.sub.2 is used, it is preferably introduced to the process stream via a catalytic bed, which assists in dissolving the H.sub.2 into the process stream. The amount of oxidizing/reducing agent used depends upon a variety of factors, including the concentration of contaminants in the process stream, the nature of those contaminants and the rate at which they use up the oxidizing/reducing agent(s). Of course, it is necessary to use the oxidant and reducing agent in separate treatment steps, if both are used in the process, for example by using the oxidizing agent first to remove the heavy metals and then removing any remaining oxidizing agent, and then use the reducing agent in the process stream to treat the organics. Reducing agents are especially useful in treating organics which are resistant to oxidation, such as PCB's. If the surfactants are to be recovered for recycle, it is preferred that aliphatic surfactants be used. If the surfactants are not to be recovered for recycle, aromatic surfactants may be used, preferably with H.sub.2 reduction, and aliphatic surfactants may be used preferably with oxidation. As can be readily appreciated, there are numerous possible combinations of the process of the present invention. Several of these these combinations are summarized in Table 1 below. TABLE 1 __________________________________________________________________________ Various Configurations Of This Process Contaminant Recover Metal Recover Surfactant Recover Fines __________________________________________________________________________ Metal No-precip. with Na.sub.2 SiO.sub.3 No-remove with precipitated metals Metal No-precip. with Na.sub.2 SiO.sub.3 Yes-remove before precipitated metals Metal Yes-precip. with Na.sub.2 SiO.sub.3 No-remove before precipitated metals Metal Yes-precip. with Na.sub.2 SiO.sub.3 Yew-remove with precipitated metals Organic No-precipitate with CaCl.sub.2 No-remove with precipitated surfactant Organic Yes-treat with H.sub.2 or oxidant No-remove before H.sub.2 /oxidant treatment Organic No-precipitate with CaCl.sub.2 Yes-skim precipitated surfactant Organic Yes-treat with H.sub.2 or oxidant Yes-remove before H.sub.2 /oxidant treatment Metal/Organic No-precip. with Na.sub.2 SiO.sub.3 No-precipitate with CaCl.sub.2 No-remove with precip. metals/surfactants Metal/Organic No-precip. with Na.sub.2 SiO.sub.3 Yes-treat with H.sub.2 or Cl.sub.2 No-remove before H.sub.2 /oxidant treatment Metal/Organic No-precip. with Na.sub.2 SiO.sub.3 No-precipitate with CaCl.sub.2 Yes-skim precipitated surfactant Metal/Organic No-precip. with Na.sub.2 SiO.sub.3 Yes-treat with H.sub.2 or Cl.sub.2 Yes-remove before precipitated metals Metal/Organic Yes-precip. with Na.sub.2 SiO.sub.3 No-precipitate with CaCl.sub.2 No-remove before precipitated metals Metal/Organic Yes-precip. with Na.sub.2 SiO.sub.3 Yes-treat with H.sub.2 or Cl.sub.2 No-remove before precipitated metals Metal/Organic Yes-precip. with Na.sub.2 SiO.sub.3 No-precipitate with CaCl.sub.2 Yes-skim precipitated surfactants Metal/Organic Yes-precip. with Na.sub.2 SiO.sub.3 Yes-treat with H.sub.2 or Cl.sub.2 Yes-remove before precipitated __________________________________________________________________________ metals In general, there are three primary cases which may be employed in practicing the invention, which include: (1) leached metal is to be recovered separately from fines; (2) metal and fines are recovered together; and (3) organics are recovered with the fines and metal may be covered separately from the fines or together with the fines and organics. The first case is used when it is desired to recover the leached metal separately from the fines. In this case, the fines are sent to either a high efficiency cyclone or to a filter or are electro-coagulated and cycloned for removal from the process stream. The cleaned process stream is then pH adjusted to about 9 using sodium hydroxide or other suitable base. Sodium silicate or other precipitant is then added to precipitate the heavy metal and to flocculate the metal hydroxides which precipitated due to the pH adjustment. The precipitated metals are then removed, for example, using either filtration, clarification, centrifugation or a cyclone. The treated water is then chlorinated to regenerate the required active chlorine level, pH adjusted to 6-10 and recycled to the soil washing process. The second case is used when the metal is not to be recovered separately from the fines. In this case, the process stream (after removal of clean particulate material, but not fines) is pH adjusted to about 9 using sodium hydroxide or other suitable base. Sodium silicate or other precipitant is then added to precipitate the heavy metal and to flocculate the metal hydroxides which precipitated due to the pH adjustment as well as the fines. The precipitated metals and fines are then removed from the process stream, for example, using either filtration, clarification, centrifugation or a cyclone. The treated water is then chlorinated to regenerate the required active chlorine level, pH adjusted to 6-10 and recycled to the process. The third case is used when an organic contaminant has been removed from the soil or particulate material and is not to be recovered separately from the fines. In this case, the process stream is pH adjusted to about 9 (following removal of clean particulate material) using calcium chloride plus sodium hydroxide or other suitable base. If heavy metals are not to be recovered separately from the fines, sodium silicate or other precipitant is then added to precipitate the heavy metal and to flocculate the metal hydroxides which precipitated due to the pH adjustment as well as the fines and precipitated soaps. The precipitated metals, soaps and fines are then removed, for example, using either filtration, clarification, centrifugation or a cyclone. The treated water, or recycle stream, is then chlorinated to regenerate the required active chlorine level, pH adjusted and recycled to the process. If the metals are to be recovered separately from the fines, the sodium silicate is added after the fines and precipitated soaps are removed. After sodium silicate is added the metal precipitate is removed before the process stream is chlorinated, pH adjusted and recycled to the process. The precipitates and fines will generally be highly contaminated with organics and heavy metals. Using the process described above, a variety of treatment methods are available for concentrating or recovering the metals from the organics or non-contaminated fines. These methods include, but are not limited to, shaking table, high gradient magnetic separation, or sodium dissolution of the silicate. The organically contaminated fraction can then be further treated biologically, chemically or thermally and returned to the site. The heavy metal fraction can be leached and returned to the site, disposed of or sold as a concentrate. There are several advantages attendant the preferred embodiments of the invention. The first is the lower chemical costs. Due to the use of chlorine oxidant, chemical transportation costs are reduced as compared to the use of hypochlorite-containing chemicals. In addition, the use of chlorine minimizes the use of both the NaOH and HCl, further reducing chemical costs. Sodium silicate and calcium chloride are also available as highly concentrated solutions in bulk quantities in trailer trucks at low cost. For example, in a recent case in which uranium and mercury were to be removed from a soil, the use of chlorine instead of either sodium or calcium hypochlorite reduced the cost of chemicals 50%. A second advantage is the character of the sodium silicate-heavy metal precipitate which is produced by this process. This precipitate has been shown in both laboratory and production application to be dissolvable in 50.degree. C. NaOH solutions. This dissolution process leaves behind a sludge with a very high concentration of the heavy metal which was removed from the soil, and allows the sodium silicate to be reused. This sludge is often high enough in concentration to allow use as a feed stock in mining/smelting operations. This approach changes a potentially hazardous material (the heavy metal precipitate) into a valuable feedstock which reduces the future liability of the owner of the decontaminated soils or particulate material. Another advantage of the invention is that it permits the selective removal of heavy metals and organics, thereby allowing mixed wastes, such as those containing both metals and organics, to be effectively treated. Finally, if the precipitated solids must be disposed of, the washed precipitates which result after dissolution of the waterglass are low in sodium. This sludge results in a more leach-resistant matrix when mixed with concrete, glass or other fixative material, since the amount of leachable sodium is low. Examples of soil cleanup using the various embodiments of the invention follow. The standards for these examples were the toxic chemical leaching procedures (TCLP) established for the particular site by the Environmental Protection Agency. For the first three examples, the results are illustrated in line graph form to show a continuum of the effect of the settings of the countercurrent flows in the mineral jigs which determines the size of fines removed, and consequently the percentage of the feed soil recovered. EXAMPLE 1 Industrial site soil contaminated with about 11,000 ppm of copper was treated in accordance with the embodiment of the invention set forth in the flow chart of FIG. 1. The contaminant mobilizing solution was a one percent by weight aqueous solution of acetic acid which was used in the initial wash phase in the screen/washer 10 and in the first mineral jig 18. Water recovered from the clarifier 34 was used as the rinse in the second mineral jig 26 and the cross-current density separator 30. The results of the tests are shown in FIG. 4. The untreated soil is represented by the trace 162, the results of soil washed only with water shown by the trace 164 and the results of the use of acetic acid as the contaminant mobilizing solution which dissolves the copper which is then carried off with the waste slurry from the mineral jigs 18 and 26 is shown by the trace 166. While the initial contamination was about 11,000 ppm of copper, it can seen that with the use of the invention, most of the copper was removed. The clean soil limit for this site was 250 ppm. It can be seen that by adjusting the countercurrent flow in the mineral jigs so that 80% of the initial soil was recovered that this clean soil limit was satisfied. Even at 90% recovery, the residual copper contamination was only 50 ppm above the clean soil limit. EXAMPLE 2 Soil contaminated with 69 ppm of radium was treated according to the embodiment of the invention shown in FIG. 2 using a 0.1 molar aqueous solution of potassium carbonate and a 0.1 molar solution of sodium carbonate as the contaminate mobilizing solution. The rinse water was the water recovered by the dewatering hydroclone 88. In FIG. 5, which illustrates the results of this example, the trace 168 represents the untreated soil, trace 170 represents soil washed only with water, and the trace 172 shows the results of the soil treated with the potassium carbonate and sodium carbonate chemical wash and rinsed with water. It can be seen from FIG. 5 that most of the contamination resides in the fine fraction so that even untreated soil from which only about 25% of the smaller particles are removed meets the clean soil limit of 42 ppm of uranium shown by the dotted line. With the invention, over 90% of the soil was recovered within the clean soil limit of 42 ppm of uranium. EXAMPLE 3 Soil contaminated with approximately 295 ppm of polychlorinated biphenyls was treated according to the embodiment of the invention illustrated in FIG. 2. The contaminant mobilizing solution in this example was a one percent by weight solution of NP90 a surfactant produced by Henkel Corporation together with a one percent by weight solution of Adsee 799, a surfactant supplied by Witco Corporation. The results of the test are shown in FIG. 6 where trace 174 is the untreated soil, trace 176 is soil washed only with water, and the cross hatched area 178 shows the results of soil washed with the surfactant solution. As can be seen, only soil treated in accordance with the invention met the clean soil limit of 25 ppm shown by the dashed line, and virtually all of the soil was recovered by this process. EXAMPLE 4 Sewer sediment having the following initial contaminant levels: ______________________________________ Uranium 140 to 200 ppm Mercury 900 to 1000 ppm PCBs 5 to 10 ppm ______________________________________ the remediation requirements were: ______________________________________ Uranium 50 ppm Mercury 12 ppm PCB 2 ppm Pass TCLP ______________________________________ The sewer sediment was treated by attrition scrubbing and initial fines separation using a sodium hypochloride solution (20 g/l), washing with water and density separation using the embodiment of the invention illustrated in FIG. 3. The results of the test are shown in the bar chart of FIG. 7. The uranium target of 50 ppm was easily met using the invention. The chemical limit of 12 ppm of mercury was not met. However, this limit was arbitrarily set on the assumption that the mercury contamination was in the form of elemental mercury. In fact, the mercury was in the form of an intermetalic amalgam of uranium and mercury which is highly insoluble. As a result, the mercury level achieved passed the TCLP. EXAMPLE 5 Oil land farm soil with the following initial contamination levels: ______________________________________ Uranium 120 ppm PCB 7 to 14 ppm Oil/Grease 3 to 6 wt. % ______________________________________ was treated according to the embodiment of the invention shown in FIG. 3. The remediation requirements were as follows: ______________________________________ Uranium 80 ppm PCB 2 ppm Pass TCLP Test ______________________________________ The contaminant mobilizing solution was a surfactant mixture of 0.1 wt. % APG--325 available from Henkel Corporation and 0.1 wt. % ASO available from Witco Corporation. This surfactant mixture was mixed with a leaching solution containing sodium hypochloride (20 g/l) and sodium carbonate (21 g/l). The results of this example for virtually 100% recovered soil were: ______________________________________ Uranium 60 ppm PCB &lt;2 ppm Passed TCLP ______________________________________ The uranium levels for untreated soil, water washed soil and soil treated in accordance with the invention are shown in FIG. 8. From the above, it can be seen that the invention provides a versatile method and apparatus for treating various types of particulate materials contaminated with various substances. While specific embodiments cf the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope cf the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.