LANDFILL DISPOSAL OF MATERIAL CONTAINING VANADIUM

Abstract: Materials containing vanadium values which are leachable by water are treated to reduce the leachability of vanadium to minimum practical values, thereby rendering the material suitable for disposal as landfill. Vanadium is insolubilized by adding a polyvalent metal salt which is capable of dissolving in water to form an acidic solution from which polyvalent metal cations are precipitated at a pH of 5, the polyvalent cations having a valence of +3 or higher or being a divalent metal that is oxidizable to a valence of +3 or higher. The salt-treated mixture is then neutralized by a base. The vanadium may be contained in a solid such as, for example, a spent cracking catalyst or a spent sorbent used in the upgrading of petroleum feedstock by selective vaporization or it may be contained in liquid material.

Description: This invention relates to disposing of contaminated material containing soluble vanadium as landfill. Examples of such vanadium contaminated materials are spent cracking catalysts and spent contact material used in a selective vaporization process for upgrading heavy petroleum crudes, resid fractions of petroleum crudes or the like. The Asphalt Residual Treating (ART sm ) Process is a decarbonizing and demetallization process that has been developed to treat residual stocks and heavy crudes for the removal of contaminants. The process is described in numerous publications, including "The ART Process Offers Increased Refinery Flexibility", R. P. Haseltine et al, presented at the 1983 NPRA Conference in San Francisco. See also U. S. 4,263,128 to Bartholic. The process is a non-catalytic technological innovation in contaminant removal and will typically remove over 95% of the metals, essentially all the asphaltenes and 30% to 50% of the sulfur and nitrogen from residual oil while preserving the hydrogen content of the feedstock. The process enables the subsequent conversion step in residual oil processing to be accomplished in conventional downstream catalytic processing units. The ART Process utilizes a fluidizable solid particulate contact material which selectively vaporizes the valuable, lower molecular weight and high hydrogen content components of the feed. The contact material is substantially catalytically inert and little if any catalytic cracking occurs when the process is carried out under selected conditions of temperature, time and partial pressure. Generally, suitable contact material has a relatively low surface area, e.g., 5 to 20 m²/g as measured by the BET method using nitrogen. Presently preferred contact materials are silica-aluminas produced by calcining microspheres containing kaolin clay. Heavy metals are deposited on the contact material and removed. High molecular weight asphaltenes also deposit on the contact material, some asphaltenes being converted to lighter products. Because the contact material is essentially catalytically inert, very little molecular conversion of the light gas oil and lighter fractions takes place. Therefore the hydrogen content of these streams is preserved. In other words, the lighter compounds are selectively vaporized. It is believed that the molecular conversion which does take place is due to the disproportionation of the heavier, thermo-unstable compounds present in the residual feedstock. The hydrogen content of the coke deposited on the contact material is typically less than four percent. Coke production is optimally equivalent to 80% of the feedstock Conradson Carbon Residue content. Heat from the combustion of coke is used internally within the ART system. Surplus heat may be recovered as steam or electric power. No coke product is produced. The ART Process is adapted to be carried out in a continuous heat-balanced manner in a unit consisting primarily of a contactor, a burner and an inventory of recirculating contact material. Chargestock is contacted with particles of hot fluidizable contact material for a short residence time in the contactor. In the contactor, the lighter components of the feed are vaporized; asphaltenes and the high molecular weight compounds, which contain metals, sulfur and nitrogen contaminants, are deposited on the particles of the contact material. The metals invariably include vanadium and nickel. Some of the asphaltenes and high molecular weight compounds are thermally cracked to yield lighter compounds and coke. The metals that are present, as well as some of the sulfur and nitrogen bound in the unvaporized compounds, are retained on particles of contact material. At the exit of the contacting zone, the oil vapors are rapidly separated from the contact material and then immediately quenched to minimize incipient thermal cracking of the products. The particles of contact material, which now contain deposits of metals, sulfur, nitrogen, and carbonaceous material are transferred to the burner where combustible contaminants are oxidized and removed. Regenerated contact material, bearing metals but minimal coke, exits the burner and circulates to the contactor for further removal of contaminants from the chargestock. In practice, the metals level of contact material in the system is controlled by the addition of fresh contact material and the withdrawal of spent contact material from the burning zone. Generally, metals accumulated on the contact material used in the ART Process tend to be less active in forming coke than metals accumulated on cracking catalyst. Thus, the ART Process is able to operate effectively when accumulated metals are present on the contact material at levels higher than those which are generally tolerable in the operation of FCC units. For example, the process has operated effectively when combined nickel and vanadium content substantially exceeded 2% based on the weight of the calcined kaolin clay contact material. The oxidation state of vanadium in the withdrawn particles will depend upon the conditions used in the burning zone. Typically, the vanadium is present in both V⁺⁵ and V⁺⁴ oxidation states even when the burner is operated with an excess of oxygen. A portion of the contact material with accumulated deposit may also be discharged with combustion gases and/or vaporized hydrocarbon product in the form of fines, i.e., particles not retained by cyclone separators in the contactor and/or burner zones. In prior commercial practice, the spent contact material has been discarded without removing metals. It has been proposed to leach spent contact material to remove at least part of the metal contaminants before recycling the contact material to the system. This can result in a by-product solution containing nickel and vanadium. Under some conditions it may be desirable simply to dispose of the resulting leachate without recovering all of the metal values or without removing any metals. Similarly, particles of spent fluid cracking catalysts will contain deposits of metal contaminants originating in the petroleum feedstock charged to the fluid catalytic cracking (FCC) unit. Spent catalyst particles are periodically withdrawn from the FCC regenerator in order to permit catalytic cracking units to operate at desirable activity and selectivity levels. See, for example, U. S. 4,268,188. The spent catalyst is frequently employed to start-up FCC units. Usually spent cracking catalyst particles, as well as fines discharged from FCC regenerators, are discarded and used as landfill. There has been a trend in recent years to charge FCC units with feedstocks which contain considerably higher levels of metal contaminants than the relatively "clean" gas oils heretofore used as FCC chargestock. Consequently, spent FCC catalysts may be expected to contain higher metals concentrations than were encountered in the past unless high catalyst replacement rates are used. When discarded materials or leachates are to be disposed of as landfill, it is desirable to minimize leaching of water soluble heavy metals contaminants. Such materials are likely to come into prolonged contact with rain and/or surface waters, resulting in possible pollution of the waters. Generally, such waters are mildly acidic, e.g., the pH is about 3-5. Further, it is desirable to accomplish this result while minimizing treatment costs associated with chemical additives and equipment. Also, it is advantageous to provide material intended for disposal as landfill in the form of a solid or semi-solid mass amenable to direct disposal without a downstream filtration or dewatering step. In addition to vanadium and nickel, metals originating in petroleum feedstocks may include one or more of the following as contaminants: chromium, cobalt, copper, arsenic, antimony, bismuth and barium. When present, these metals eventually form a deposit on spent cracking catalyst or spent contact material used in an ART unit. Constituents present in spent material that are leachable in water typically include V⁺⁵ and V⁺⁴ compounds. In some cases, nickel is also leachable. Generally, the leachates are mildly acidic, e.g., pH is 3 to 6. Thus, when such materials are disposed of as landfill, leaching of vanadium or vanadium and nickel is likely to occur. Processes capable of insolubilizing vanadium should also result in treated products in which leaching of the aforementioned other metals is minimal. The difficulty involved in insolubilizing vanadium in spent contact material or cracking catalysts is that vanadium, an amphoteric element, is soluble at acidic pH values and is still somewhat soluble at neutral and mildly alkaline pH values at which other heavy metals such as nickel and iron are insoluble or are low in solubility. Vanadium compounds increase in solubility at strongly alkaline pH values. The present invention provides a process of treating solid particulate vanadium-containing material to suit it for disposal (e.g. landfill disposal) which comprises reducing the leachability and/or solubility of vanadium component therein by steps comprising [a] contacting the material in the presence of water with at least one water soluble salt of polyvalent metal selected from such salts of iron, tin, titanium, zirconium, aluminium, and trivalent and quadrivalent rare earth metals and [b] thereafter increasing the pH of the resulting mixture, said salt being capable of forming an acidic aqueous solution and of forming hydroxide, oxide or hydrated oxide which is substantially insoluble at pH 5, said salt containing polyvalent metal ion selected from those having a valence of +3 or higher and those which are divalent and oxidisable to a valence of +3 or higher, and the amount of water employed being limited so that the material after step [b] is a solid or semi-solid mass. EP-A-0,149,501 adds a metal salt to a noxious waste water using a group VII or VIII acid solution which is precipitated as metal hydroxide, the precipitate including noxious metal(s) - principally cadmium - dissolved from the waste by the acid solution. There is no reference to vanadium or equivalent metal, and the hydroxide precipitation step does not result directly in a solid or semi-solid mass. In US-A-3,752,759, highly oxidized cobalt and vanadium and optionally iron in aqueous solution are removed by first adding a reducing agent to insolubilize highly oxidized vanadium and then cobalt is precipitated by adding base, forming a precipitate that is separated from the liquid; this process does not treat a solid particulate material to render all components insoluble by treatment which results directly in a treated solid or semi-solid mass without filtration. US-A-1,733,700 seeks to recover vanadium from ores and metallurgical products in which vanadium is solubilized as sulfate and impurities are then precipitated with base; it seeks to avoid loss of vanadium in the precipitated impurities. Thereafter the vanadium is precipitated from solution with a ferric compound and neutralized. This process does not convert a particulate solid containing soluble vanadium directly into a solid or semi-solid mass in which vanadium is insoluble. FR-A-629,790 deals with precipitating vanadium from acidic solution by adding a ferric salt, followed by neutralization with a base, using an oxidation treatment if the vanadium is in +4 state. It is not concerned with insolubilizing vanadium in a particulate solid by a treatment which gives directly a disposable solid or semi-solid product. US-A-2,749,211 uranium and vanadium are separately recovered from acid solutions in which vanadium is precipitated as a compound of iron and vanadium to form ferric vanadate which is precipitated at pH 2.2 to 3.5 and separated by filtration. It is not concerned with insolubilizing vanadium in a particulate solid by a treatment which gives directly a disposable solid or semi-solid product. The present invention treats the problem of reducing the leachability of normally leachable vanadium compounds to practical levels by addition of certain polyvalent ions which result in the conversion of the vanadium values to compounds that are insoluble at moderately acidic pH values, e.g., pH 5, at which other heavy metals are insoluble or substantially so. Prior to disposing of material comprising one or more water-soluble vanadiferous compounds as landfill, the leachability of the vanadium is reduced, preferably to minimum practical levels, by contacting the vanadiferous material in the presence of water with one or more of water soluble acidic salts of certain polyvalent metals, hereinafter described. The resulting mixture is then neutralized with base. The polyvalent salt (or salts) is preferably present in amount at least sufficient to provide at least one equivalent of cation in the salt per equivalent of leachable vanadium. A feature of the invention is that contaminant metals associated with vanadium, for example nickel, also have very limited solubility after undergoing the treatment. Polyvalent metal salts useful in practice of the invention are those that are capable of dissolving in water to form an acidic solution and which are capable of forming hydroxides, oxides or hydrated oxides which are substantially insoluble at pH 5, said polyvalent metal having a valence of +3 or higher or being a divalent metal that is oxidizable to a valence of +3 or higher. Metal sulfate, chloride and nitrate salts selected from the following divalent and trivalent metal cations are suitable: Fe⁺²; Fe⁺³; Mn⁺², Mn⁺³, Zr⁺⁴, Ti⁺⁴, Al⁺³ and trivalent or quadrivalent rare earth or mixtures of rare earths. An advantageous feature of the process is that the weight added to the material as a result of the insolubilization treatment may be minimal because relatively small amounts of chemical additives and water are needed. Most preferably, a minimum amount of water is introduced during the treatment and a solid or semi-solid mass, essentially free from solubles, is provided. Such material is amenable to direct disposal as landfill without further treatment. In the treatment of a typical solid residue, the weight of the treated product is only about 1 1/2 times the weight of the material being processed. Another advantage is that it is not necessary to add heat during treatment. It will be noted, however, the mixture undergoes an increase in temperature which may be significant during the neutralization step which is exothermic. Another advantage of the process is that the salt can be added in excess, even substantial excess, because excess salt will be neutralized during the second phase of treatment. Most preferably, the anion of the metal salt is a sulfate and neutralization is carried out entirely with a calcium-containing base such as lime. By using such combinations of reagents, insoluble calcium sulfate is a reaction product, and no soluble or potentially soluble chemicals are introduced during the treatment. While anions other than sulfate can be present in the salt reagent, it is obvious that sulfite and formate salts, for example, would produce undesirable discharges into streams. For this reason, reducing anions such as nitrites may be undesirable. Other anions also undesirable for discharge into streams include halides, fluoroborates and fluorosilicates. Also, many organic materials such as citrates and acetates, which promote biological action in water, may be undesirable. It is not presently understood how the presence of polyvalent metal salt contributes to the insolubilization of vanadium but it is believed that the anion of the salt does not play a role other than providing the polyvalent metal cations in initially soluble forms. The present invention in especially preferred aspects is a simple and economical procedure for treatment of spent ART Process fluidizable contact material or spent fluid cracking catalyst to render such materials suitable for direct disposal without the need for prior extraction of metals. The ART Process is described in U. S. 4,263,128,to which attention is directed for further information. A presently preferred contact material is a catalytically inert solid obtained by spray drying an aqueous slurry of kaolin clay and calcining the resulting microspheres to cause the kaolin clay to dehydrate and pass through the characteristic exothermic reaction. Present day fluid cracking catalysts contain a zeolitic molecular sieve component and a matrix-diluent which is an inorganic oxide, usually silica-alumina. An especially preferred treatment of the present invention comprises the steps of: (a) contacting spent fluidizable contact material or spent cracking catalyst contaminated with metals in the presence of water with: (i) ferrous sulfate acidified with sulfuric acid or (ii) ferrous sulfate alone or (iii) ferric sulfate or (iv) aluminum sulfate or (v) mixtures of aluminum and iron sulfates; and (b) pugging the material treated in step (a) with sufficient calcium hydroxide to raise the pH to at least 7 (or at least 8 when nickel is also present), and, preferably, to at least pH 10. The amounts of any water added in steps (a) and (b) should be the minimum consistent with adequate wetting of the solids so as to produce a final product of minimum weight for disposal. Tests were carried out on various samples of spent ART contact material containing vanadium. The fresh contact material had been produced by calcining microspheres of kaolin clay. An amount of ferrous sulfate of 5 parts by weight FeSO₄·7H₂O per 100 parts by weight of the spent contact material adequately suppressed vanadium leach- ability in all samples tested, although smaller additions could be used in some cases. Acidification of the ferrous sulfate appears to be unnecessary, but, where applied (with the intent of reducing any V⁺⁵ material to less soluble V⁺⁴ form), the sulphuric acid addition was about 1 part per 100 parts spent material. Final weight for disposal averaged 166% of the weight of spent material treated. Based on a large batch made in a mechanical pug mill, this weight was reduced to 152%. Using unacidified ferrous sulfate would reduce processing costs by only a small amount due to omission of H₂SO₄ and the reduction in the amount of Ca(OH)₂ to 1.3 parts per 100 of spent material from 2.3 parts per 100. It was found that where ferric sulfate was used, the requirements were the same as for ferrous sulfate (5 parts per 100 parts by weight of contact material) when using Fe₂(SO₄)₃xH₂O, containing 72% Fe₂(SO₄)₃ (which is the same for the laboratory grade as for the commercial grade). It may be noted that this material has the same Fe content (about 20%) as FeSO₄·7H₂O. Lime requirements were the same as for acidified ferrous sulfate as was the final weight of disposal material. When 5 parts by weight per 100 parts by weight of either ferrous or ferric sulfate were used, there was found to be a reduction in leachability of nickel from those samples which, without prior treatment, showed higher leachability of nickel (2.6 to 4 ppm). Nickel leach levels were reduced to 2 ppm or less. Ferric chloride/lime has been shown to be as effective as ferric or ferrous sulfate. Lime and salt costs would be about the same, but with the disadvantage of generating a calcium chloride waste stream. However, this finding demonstrates that the sulfate ion is not an essential ingredient in the insolubilization of vanadium. Aluminum sulfate has been shown to be effective at about the same addition levels as ferrous or ferric sulfate and with about the same lime requirements and final weight generation, so that costs would be substantially equal to those for the iron systems. There is an indication that vanadium leach levels may be reduced by incorporation of a small proportion of ferric sulfate along with aluminum sulfate and that, with or without ferric sulfate, the alum system may give reduced nickel leaching. However, these finds are based on only one sample of spent contact material. The use of lime alone, in the absence of an inadequate amount of soluble polyvalent metal such as iron and aluminum, has been found to be ineffective in suppressing leaching of vanadium. The following examples are given for illustrative purposes and are not to be construed as limiting the invention unless otherwise indicated. In illustrative examples, the terms "KNV" and "CAL" refer to samples of spent contact material removed from the burners of two different ART units. The letter following the term "KNV" or "CAL" refers to specific batches of spent contact material. For example, KNV/A and KNV/E refer to different samples of spent material from the same unit but obtained at different times and, therefore, having different compositions reflecting differences in feedstock to the ART units, different temperatures in the ART burner, as well as different metal levels. The fresh contact materials (material charged to the ART units) were composed of calcined kaolin clay and were obtained by the procedures described in U. S. 4,263,128. More specifically, deflocculated aqueous slurries of high purity Georgia Kaolin clay were spray dried in commercial spray dryers and the resulting microspheres classified to obtain fluidizable particles and then calcined at a temperature and time sufficient to undergo the characteristics kaolin exotherm without substantial formation of mullite. These examples refer to an "EPA" leach test. The Environmental Protection Agency (EPA) has provided a procedure to extract solid waste with water to determine whether toxic substances can enter ground water that is used as drinking water. This extraction procedure hereinafter has been published in the Federal Register, Vol. 43, No. 243, pp. 58956-7 (Monday, December 18, 1978). By this procedure, determination of leachability is determined at pH 5.0 ± 0.2, using 0.5 N acetic acid to adjust pH. The E.P.A. leach test requires that the sample leached should be at least 100 grams. Since the material used in some of the examples was of particle size less than 100 µm it was considered justifiable to use substantially smaller sample weights. These are recorded in the examples and where weights of less than 100 grams were used the ratio of sample weight to weight of leach water used was always the same as that required in the E.P.A. test. To verify the validity of leach tests based on less than 100 grams sample weight, a disposal material was prepared by treatment of a sample spent ART contact material KNV/M) with acidified ferrous sulphate followed by lime neutralization, and three samples were leached by the E.P.A. test method except that sample weights of 20,50 and 100 grams were used, respectively. In carrying out the tests, 150 g KNV/M was mixed with 3.0 g FeSO₄.7H₂O and 5.58 g 10% H₂SO₄ dissolved in water. A total of 70 ml H₂O was added to make a mixable paste. Ca(OH)₂ was added in amount of 1.71 g, resulting in a pH of 11.7. The weight of the treated sample of KNV/M was 230.3 g. Samples of the treated material were then subjected to the E.P.A. leach test. From the data, shown below, it was concluded tht the V and Ni contents of the leachates were independent of the sample weight within the range of 20 g to 100 g. Sample Weight E. P. A. Leachates (ppm) g V Ni 20 30 1.7 50 32 1.5 100 31 1.7 Other methods to test leachability of the material treated by the process of the invention can be selected by one skilled in the art. Generally, such methods should result in determinations of leachability at pH 5.0. It is necessary to ensure compliance with whatever law, local or other, which may be applicable to the presence of the contaminants and/or the substances used in the process of the invention. We believe that leachable vanadium in material used as landfill should be less than 10 ppm, preferably 5 ppm or below, as determined by the E.P.A. test published in Vol. 43 of the Federal Register. However, we are not aware of federal regulations that are applicable to vanadium or nickel. In all the examples, analyses of Ni and V in spent contact materials were made by fusion with sodium carbonate and sodium tetraborate and dissolution in hydrochloric acid, the metals being then determined by atomic absorption spectrometry. All analyses of metals in leachates were carried out by atomic absorption spectrometry. Where values are below atomic absorption detection limits, they are: V < 1 ppm Ni < 0.3 ppm Values reported are considered accurate to: V up to 10 ppm ± 1 ppm above 10 ppm ± 10% of value reported Ni up to 5 ppm ± 0.3 ppm above 5 ppm ± 10% of value reported In carrying out the tests described in these examples, it was desired to reduce leachability of vanadium to 10 ppm of below, preferably below 3 ppm. Figures given in the examples for "E.M.F." indicate the E.M.F. as measured between platinum and silver/silver chloride electrodes. A value of about -400 mv. indicates that all the vanadium is tetravalent and iron is divalent. When all the vanadium is pentavalent, the E.M.F. is about -900 mv. Intermediate values indicate mixtures of valence states. EXAMPLE I This example, in conjunction with subsequent examples, demonstrates the necessity of adding a polyvalent metal to spent contact material in order to minimize the leachability of vanadium. A. Treatment of Spent ART Process Material with Ca(OH)₂ Only : One hundred (100)g of KNV/E (V - 1.94%, Ni, 0.38%) were pugged with 50g H₂O, giving a pH of 6.2. Ten (10)g Ca(OH)₂ and 10g H₂O were pugged in to give a paste of pH 12.3. An E.P.A. leach test gave: V - 250 ppm, Ni - 3.6 ppm, indicating that lime alone was ineffective in suppressing leaching of vanadium. B. Treatment with Ca(OH)₂ Alone After Acidifying with H₂SO₄ : Fifty (50)g of KNV/M (V - 1.73%, Ni - 0.41%) were pugged with 25g H₂O giving pH 6.2. Addition of 2.68 g 20% H₂SO₄ reduced the pH to 1.5. Addition of 1.2 g Ca(OH)₂ raised the pH to 11.8. An E.P.A. leach test gave: V - 100 pm, Ni - 3 ppm, indicating that acidification (without introduction of polyvalent cations) plus lime treatment was ineffective in suppressing leaching of vanadium. A similar experiment using KNV/PD 1 (V - 0.85%, Ni - 0.22%) gave the following leach values: V - 55 ppm, Ni <0.3 ppm. EXAMPLE II Various spent ART Process materials were pugged with solutions of acidified ferrous sulfate and then neutralized with lime. Details and results appear in Table I. EXAMPLE III The procedures of Example II were repeated using lower levels of ferrous sulfate than in Example II. Details and results appear in Table 2. EXAMPLE IV Procedures of Examples II and III were repeated to optimize proportions of reagents. Details and results are reported in Table 3. EXAMPLE V A. Ferric sulfate was used instead of ferrous sulfate in experiments similar to those described in previous examples. See Tables 4 and 5. B. Ferric chloride was used in similar tests. Fifty (50)g KNV/PD-1 (V - 0.85%, Ni - 0.22%) were pugged with 1g FeCl₃·6H₂O dissolved in 25g H₂O and a further 8.5 g H₂O added (pH 1.5, EMF 700 mv); 0.87 g Ca(OH)₂ was added to pH 10.5. Weight of the resulting paste was 85.4g. The amount of FeCl₃ used was of Fe content equal to that of 1g of Fe₂(SO₄)₃·XH₂O. An E.P.A. leach test gave: V - 2 ppm, Ni <0.3 ppm, indicating that ferric chloride was effective. EXAMPLE VI Spent ART Process contact material was rendered amenable to disposal as landfill by addition of aluminum sulfate and lime or mixtures of aluminum and ferric sulfate and lime. See Table 6. It should be noted that when aluminum salts other than the sulfate are used in practicing the invention that pH should be in the range of 8 to 10 after neutralization in order to avoid solubilization of aluminum which may occur at pH above 10, e.g., pH 12. EXAMPLE VII Spent ART process contact material was rendered amenable to disposal by addition of mixed rare earth chlorides and lime. Fifty (50)g of spent contact material CAL-#5 (V 0.98%, Ni 0.39%) were mixed with 6g of a solution of rare earth chlorides and 26.7g of H₂O. The solution of mixed rare earth chlorides contained 23.1% total rare earths having the following composition (calculated as oxides): CeO₂ Sm₂O₃ La₂O₃ Y₂O₃ Nd₂O₃ Pr₆O₁₁ wt. % 3.67 0.11 12.84 <0.01 4.70 1.77 Ca(OH)₂ was then added to pH 10.0 (0.96g added and 2.3g H₂O). The total paste (86.0g) was leached at pH 5.0 ± 0.2 according to the E.P.A. test method The leachate contained <1 ppm V, and 1 ppm Ni, indicating that rare earth chlorides are an effective treatment agent. EXAMPLE VIII This example is similar to the previous example except that ceric sulfate was used instead of mixed rare earth chlorides. Fifty (50)g CAL-#5 were mixed with a solution of 2.0g Ce(SO₄)₂ and 2.0g 20% H₂SO₄ diluted with 25 ml H₂O. 1.45g Ca(OH)₂ was added to raise the pH to 10.7, an additional 2.6g H₂O being added. The total paste (83.1g) was leached by the E.P.A. method. The leachate contained <1 ppm V, 2 ppm Ni, showing that ceric (Ce+4) sulfate is as effective as the mixed trivalent rare earth chlorides. EXAMPLE IX Experiments were carried out to determine which metal salts other than those of Fe and Al and rare earth could be used to treat spent ART contact material followed by lime neutralization. The results are reported in Table 7. The results shown in Table 7 indicate that salts of quadravalent tin, titanium and zirconium may be used in place of iron or aluminum salts or rare earth salts and are equally effective. Stannous chloride (Sn⁺²) was also effective but would have been oxidized to Sn⁺⁴ by V⁺⁵. Salts of divalent metals not oxidizable and shown to be ineffective are Zn, Sr, Ca and Mg. Divalent metals which were effective in suppressing leachability of vanadium are Cu and Ni; however, these salts led to high concentrations of Cu and Ni, respectively, in the leachate. Nickel (Ni⁺²) can be oxidized to Ni⁺³ and copper might be converted by V⁺⁵ to CuO₂ (Cu⁺⁴). Mn⁺² effected some reduction of leachability of vanadium but gave a high Mn content in the leachate; oxidation of Mn⁺² to Mn⁺³ or Mn⁺⁴ is possible. EXAMPLE X Another experiment was made to establish that the neutralization could be partially effected with CaCO₃ to pH of 5 to 6 followed by completion of neutralization with Ca(OH)₂ to pH of about 10. The details of this experiment are as follows: Twenty five (25.0)g spent contact material CAL-#5 were mixed with 1.25g Fe₂(SO₄)₃·xH₂O (72% Fe₂(SO₄)₃) dissolved in 12.0g H₂O and 5.7g H₂O added to produce a stirrable paste; 1.25g of CaCO₃ ("Chemstone" limestone, 90% minus 44 µm)were added to raise the pH to 5.6 and then 0.26g Ca(OH)₂ were added to pH 10.0, an additional 0.5g H₂O being added. The total weight of the neutralized paste was 46.0g. The leachate from an E.P.A. test on the whole of the paste contained V, <1 ppm and Ni 1 ppm. These results show that neutralization can be partially effected with CaCO₃ and completed with Ca(OH)₂. EXAMPLE XI Tests were carried out to demonstrate the effectiveness of bases other than those containing calcium in the neutralization step. In each case, 50g of spent ART Process material (CAL-#5) were mixed with 2.5g FeSO₄·7H₂O dissolved in 25g H₂O, additional water being added as required. The mixture was neutralized to pH ≧8 with Mg(OH)₂ or NaOH or Na₂CO₃. Results are summarized below: Neutralizing Reagent Added (g) Additional H₂O(g) to Final pH Total wt. of paste g EPA Leachate (ppm) Mg(OH)₂ NaOH Na₂CO₃ Acid Mix Neutralized Mix V Ni 1.60 --- --- 2.3 3.0 8.8 84.4 <1 1 --- 0.70 --- 2.6 3.6 11.5 84.4 1 1.2 --- --- 1.76 3.2 2.7 9.2 85.2 <1 1 The results show that bases other than those containing calcium can be used in the neutralization step to minimize leachability of vanadium and nickel. However, soluble salts (magnesium sulfate or sodium sulfate) are produced and may result in leachates undesirable for some disposal situations. EXAMPLE XII Tests were carried out to determine the efficiency of the process of the invention in minimizing leachability of vanadium in spent samples of commercial fluid zeolitic cracking catalysts withdrawn from FCC units. Analyses of vanadium and nickel in the equilibrium catalyst samples are given below as are also the results of a direct leach test on each sample. Cracking Catalyst Sample No. Analysis (ppm) EPA Leachate (ppm) V Ni V Ni A 3250 1700 8 <0.3 B 4050 2000 15 <0.3 C 3400 1700 1 1 In accordance with this invention, 50g of each of fluid cracking catalysts A & B were mixed with 2.5g FeSO₄·7H₂O in 25g H₂O and neutralized with lime to pH ≧ 10 and leached by the EPA test method. Results are summarized below. Ca(OH) Added (g) Additional H₂O Added (g) Total wt. of Paste (g) pH of Paste EPA Leachate (ppm) To Acid Mix To Lime Mix V Ni A 0.85 10.0 2.3 90.7 12.0 <1 <0.3 B 0.76 8.8 3.0 90.1 10.2 <1 <0.3 Since Sample C contained minimal amounts of leachable vanadium and nickel, the treatment was not used. EXAMPLE XIII This example illustrates practice of the invention with liquid solutions. The waste liquor (Solution A) used in this example contained: V 14.0 gpl Al 5.82 gpl Ni 3.55 gpl Fe 0.24 gpl approx. 30% Free H₂SO₄ at least 90% of the V in solution A was present as V⁺5. In a control test, 50 ml of Solution A were stirred at ambient temperature while calcium hydroxide was added until the final pH of the slurry was 11.1; additional water was added to thin the slurry as required. This was filtered and washed. The filtrate and washing contained 54 ppm V and <0.3 ppm Ni. A sample of the moist filter cake was leached at pH 5.0 ± 0.2. The leachate contained 11 ppm V and 37 pm Ni. This example was carried out exactly as the control except that 5g FeSO₄·7H₂O were dissolved in the 50 ml of Solution A before adding calcium hydroxide to a final pH of 11.7. The filter wash contained 1 ppm V and <0.5 ppm Ni indicating that addition of ferrous sulfate was effective in insolubilizing vanadium. The leachate contained 3 ppm V and 22 ppm Ni, showing that leaching of vanadium was reduced by the introduction of ferrous sulfate. EXAMPLE XIV Example XIII describes the use of the process to treat a waste liquor containing V and Ni; in the solution at least 90% of the V was present as V⁺⁵. A similar solution (Solution B) was made up but with all the V as V⁺⁴. On neutralizing with lime the filter wash contained 1 ppm V and <0.3 ppm Ni (cf. Example XIII in which the filter wash analyzed V 54 ppm, Ni <0.3 ppm). An E.P.A. leach of the filter cake gave in the leachate: V 95 ppm, Ni 8 ppm. (cf. Example XIII V 11 ppm, Ni 37 ppm) In a similar experiment using the same V⁺⁴ solution, 5g FeSO₄·7H₂O were added before lime neutralization, as in Example XIII. The filter wash contained 7 ppm V, <0.3 ppm Ni (cf. Example XIII, V 1 ppm, Ni <0.3 ppm). The E.P.A. leachate of the filter cake contained 9 ppm V, 17 ppm Ni (cf. Example XIII, 3 ppm V, 22 ppm Ni). Another experiment was made with the V⁺⁴ solution with the addition of 5g Fe₂(SO₄)₃ 2H₂O. In this case the filter wash contained 9 ppm V, <0.3 ppm Ni. The E.P.A. leachate contained 4 ppm V, 11 ppm Ni. It may be concluded that: 1. When V is present as V⁺⁵, the filter wash from lime neutralization contains much V but when FeSO₄ is added before neutralization the filter wash contains no significant V. When V is present as V⁺⁴ there is no significant V in the filter wash without or with FeSO₄. Presumably V⁺⁴ is much less soluble than V⁺⁵ at pH about 11. 2. Leaching at pH 5 extracted much more V from the V⁺⁴ material than from the V⁺⁵ material, presumably due to greater solubility of the V⁺⁴ species at this pH. 3. Addition of either ferrous or ferric sulphate is effective in reducing leaching of V to acceptable levels from V⁺⁴ material. This suggests that conversion of Fe⁺² to Fe⁺³ by V⁺⁵ is not a necessary condition, unless in the course of the filtration some Fe(OH)₂ became oxidized to Fe(OH)₃. EXAMPLE XIV Since the nickel levels in the leachates in EXAMPLE XIII were higher than normally encountered when applying the disposal method to ART Process contact materials, it was thought that this might be due to calcium carbonate present in the calcium hydroxide of which a much larger relative proportion was required for the strongly acid waste liquor than for treatment of the only slightly acid contact materials. To test this possibility, Example XIII (including the control) was repeated except that the calcium hydroxide was freshly prepared by calcination of the hydroxide at 980°C (1800°F) to remove CO₂ and reslaking with water to reconvert to hydroxide free of carbonate. The results were as follows: FeSO₄·7H₂O Added Analysis of Filter Wash Analysis of E.P.A. Leachate V Ni V Ni None 11 ppm <0.3 ppm 21 ppm 21 ppm 5.0g 1 ppm <0.3 ppm 2 ppm 10 ppm The results again show the effectiveness of ferrous sulfate in suppressing leaching of vanadium. They also show that ferrous sulfate promotes a significant reduction in leaching of nickel and that the reduction is greater when calcium hydroxide free of carbonate is used. Reasonable variation and modification are possible within the scope of the foregoing disclosure and the appended claims to the invention. The term "Leachability" as used in the claims refers to such property as determined by the procedure published in the Federal Register, Vol. 43, No. 243.

Claims: A process of treating solid particulate vanadium-containing material to suit it for disposal (e.g. landfill disposal) which comprises reducing the leachability and/or solubility of vanadium component therein by steps comprising [a] contacting the material in the presence of water with at least one water soluble salt of polyvalent metal selected from such salts of iron, tin, titanium, zirconium, aluminium, and trivalent and quadrivalent rare earth metals and [b] thereafter increasing the pH of the resulting mixture, said salt being capable of forming an acidic aqueous solution and of forming hydroxide, oxide or hydrated oxide which is substantially insoluble at pH 5, said salt containing polyvalent metal ion selected from those having a valence of +3 or higher and those which are divalent and oxidisable to a valence of +3 or higher, and the amount of water employed being limited so that the material after step [b] is a solid or semi-solid mass. A process according to claim 1 wherein the pH in step [b] is increased to at least 7, preferably at least 8. A process according to claim 2 wherein the pH in step [b] is increased by adding basic material, preferably basic calcium. A process according to any preceding claim wherein said salt is selected from chlorides, nitrates and sulphates. A process according to any preceding claim wherein the amount of said metal salt employed is such as to provide at least one equivalent of said polyvalent metal ion per equivalent of leachable or soluble vanadium in said material. A process according to any preceding claim wherein the weight of the particles after step [b] is about 1.5 times the weight of the original particles. A process according to any preceding claim wherein the material to be treated comprises spent contact material previously used for selective vaporisation or fluid catalytic cracking of hydrocarbon feedstock. A process according to any preceding claim wherein the material to be treated contains at least nickel as additional contaminant whose leachability and/or solubility is simultaneously reduced. A process according to any preceding claim wherein the polyvalent metal salt comprises sulphate, and sufficient basic calcium compound is added in step [b] to precipitate sulphate ions as calcium sulphate.

Inventors: HEMSTOCK, GLEN A., MOSELLE, INEZ L., PITTS, FRANK
Applicants: ENGELHARD CORPORATION
Application year: 1987
Main classification: A62D3
IPC codes: C22B34, A62D101, C02F1, A62D3, B09B3, C02F9