Aug. 25, 1964 J. D. MOORE ETA 3,146,063 PROCESS FOR SEPARATING FROM, MIXTURES CONTAINING SCANDIUM AND THORIUM WALUES Filed Jan. 3, 1961. "RECOVERY OF MINERAL VALUES."

Acidified leoch Orgonic K OH Liquor Solvent

(II) (14) EXTRACTION METATHESIS -Roffinole . (5) to Woste FILTER - Filtrote to Wostel (2) O LOOded HMO -- HC Ear UOs Loaded S-se -STRIPPING HCl to (16) Uronium Production KOs. ODATE PRECIPITATION NHF, HF -- (3) (7) X Thorium Precipitate SCANDUM-THORIUM. FTER 8& PRECIPITATION 4Th (OKIOI8HO (18) AqueousFluoride Solvent RecycleRecy his Neutralization Solution N - (3a) Sc - Th (19) FLTERFILTER Precipitate- FILTER Filtrate to Waste

NHs Fitroe HC s (3b) (2O) NEUTRALIZATION HCOaaa-2?o (2) FLTER filtrate to Waste (3.c) - FILTER Titoniumis (22) Precipitote CACNE

- HF lsco ar HsO. Sces INVENTORS, JAMES D. MOORE 8 A76 f By NORMAN N. SCHIFF 0.4 k, losin-ka their a/VOAWAYS

- 3,146,063 United States Patent Office Patented Aug. 25, 1964 2 (NHF.HF) to precipitate and remove the thorium so 3,146,063 as to permit recycling of the organic solvent to the first PROCESS FOR SEPARAiNG SCANDUM FROM extraction operation previously described. Other mineral MIXTURES CONTAINING SCANDUM AND THORUM WALUES acid solutions of a salt may be used with the James D. Moore and Norman N. Schiff, Salt Lake City, proper amount of free fluoride. The insoluble thorium Utah, assignors to Vitro Corporation of America, New fluoride is removed by filtration while the soluble titani York, N.Y. um ion remains in solution. Filed Jan. 3, 1961, Ser. No. 80,260 According to the present invention, it has been dis 4 Claims. (CI. 23-4.5) covered that substantial and recoverable amounts of 0 scandium may be produced in the thorium fluoride pre This invention relates to a process for recovering scan cipitate by selecting a uranium ore containing even trace dium from mixtures with other metals, more particularly amounts of scandium and treating such ore by the pro with recovering scandium from mixtures of scandium cedure described above. and thorium. The scandium-thorium fluoride precipitate normally Scandium is a valuable and rare metal which generally 5 contains from about 5 to about 20% scandium and from occurs in ores in such a low concentration that it is very about 10 to about 40% thorium on a dry weight basis. difficult to isolate and purify. Of course, these values will vary depending upon the Accordingly, one object of the invention is to provide particular ore used in the leaching operation. The scan a source and method for producing scandium substantially dium-thorium fluoride precipitate is agitated in the pres isolated from other metals. 20 ence of a strong solution of an alkali metal hydroxide, Another object of the invention is to separate scandium Such as potassium hydroxide (six normal), at a tempera from thorium, a metal with which it is frequently asso ture and for a time sufficient to convert the fluoride to ciated. the insoluble hydroxides. With six normal potassium Other objects and advantages of the invention will hydroxide, heating at 70 to 90° C. for about four hours appear from the description. 25 generally completes the replacement of fluoride with hy It has been found according to the present invention droxyl ions. The insoluble hydroxides are then filtered that scandium occurs in Small amounts in certain uranium and the fluoride is removed as in the ores which are processed for the production of uranium, filtrate. The alkali solubilizes those metals that form thorium and titanium. The uranium ores pitchblende, amphoteric hydroxides and those that form soluble fluo autunite, uraninite, and coffinite are produced in various 30 ride complexes in an alkaline solution. These impurities mining districts throughout Utah, Colorado, Nevada, are removed with the filtrate. Wyoming, Idaho, New Mexico, Arizona, and Canada The precipitate is dissolved in a strong acid such as and to a lesser extent from other fringe areas. Such nitric acid (three normal). Presumably any mineral acid ores are usually crushed and then fine ground to ap in all concentration ranges can be used, however, we be proximately below 20 mesh in either ball mills or rod 35 lieve that 3 NHNO3 is optimum. A sufficient excess of mills in closed circuit with appropriate classification equip acid is used to insure that the solution has a three nor ment. The ground ore in water slurry is then fed to a mal concentration of nitric acid. An alkali metal or am series of agitator leach tanks where sulfuric acid is added monium iodate such as potassium iodate (KIO) is then to solubilize the uranium. Various conditions such as added to effect the formation of a complex and the pre residence time, acid concentration, oxidation state and 40 cipitation of the thorium as a complex thorium alkali elevated temperatures are maintained depending upon the metal iodate, e.g., 4Th (IO). KIO-18HO. Preferably amenability characteristics of the ore being processed. an excess of a saturated solution of potassium iodate is Following the leaching step, the slurry may be de-watered used which has been made slightly acidic with nitric acid. by any of the commonly known processes such as filtra Potassium iodate is added to the nitric acid solution in tion or decantation to produce a “pregnant' solution con 45 a 50% excess of that amount theoretically required to taining the desired uranium. Depending upon the urani precipitate the complex. Thus, a 50% excess would re um concentration in the ores treated and the amount of quire about 6.4 moles of potassium iodate for each mole wash water used, the uranium concentration of pregnant of thorium present. The use of potassium iodate in its liquor may vary from about 0.5 to 2.0 grams per liter Solid form is undesirable since the precipitate tends to of U3O8. 50 form around the iodate crystals and an excessive amount The acidified leach liquor produced by the method de of reagent is consumed. For maximum efficiency, a scribed has been treated by an extraction process with an Saturated solution of potassium iodate is used. In order organic solvent. The organic solvent used can be the to maintain the acid concentration of the solution con commonly known organo phosphates in a hydrocarbon taining soluble scandium and thorium, enough nitric acid diluent such as kerosene. Di-2-ethylhexyl phosphoric 55 is added to the saturated iodate solution to insure a total acid, or heptadecylphosphoric acid or dodecylphosphoric nitric acid concentration of three normal in the final acid may be used. However, a preferred organic solvent solution. This phase of the process is preferably car is 3% by volume solution of dodecyl phosphoric acid in ried out at about room temperature. The insoluble kerosene diluent. thorium iodate complex is removed by filtration. The The spent aqueous phase is discarded and the organic 60 reaction described above evidently takes place between phase, now containing the mineral values, is routed to a the iodate ion and the metallic (alkali metal and thorium) Second extraction operation wherein the mineral values ions to produce the complex metallic iodate. Nitric acid are removed by extraction with strong mineral acid, such is the preferred reagent but other acids may be utilized. as hydrochloric acid. This removes uranium from the The use of hydrochloric acid is to be avoided however, organic solvent and the acid solution is directed to fur 65 since reactions may occur between the acid and the iodate. ther processing for the production of uranium concen Since thorium sulphate is somewhat insoluble under cer trates. tain conditions, the use of sulphuric acid is also unde The organic solvent previously stripped with aqueous sirable. It should be realized that the solution of the hydrochloric acid, which is now substantially devoid of hydroxide precipitate by other acids requires an excess uranium but which still contains thorium, has then been 70 of reagents and usually produces less than optimum re extracted with acidified solution Sults. It is apparent moreover, that the process described

3,146,063 3 4. may be used in separating scandium from thorium de fied ammonium bifluoride solution at a volume ratio of rived from other sources. organic to aqueous phases of 10 to 1. The stripped sol After the thorium iodate has been precipitated and re Vent is recycled to the first extraction operation for fur moved, the filtrate is neutralized with an excess of am ther recovery of values from the aqueous acid feed solu monia preferably in the presence of excess ammonium tion. The aqueous solution used contains 5% fluoride chloride to precipitate insoluble hydroxides, consisting ion as NH4FHF with a pH adjusted to 5.0 with sul mainly of scandium hydroxides and small amounts of furic acid. The insoluble of scandium and impurities. The ammonium chloride is an optional re thorium are removed by filtration at 13a. The filtrate is agent and is added prior to precipitation to increase the adjusted to a pH of 8.0 with ammonia or ammonium solubility of the alkali and alkaline earth metal impuri O hydroxide at 13b and insoluble titanium hydroxide pre ties present. To obtain complete precipitation of the cipitates, which is removed by filtration at 13c. The fil hydroxides, an excess of ammonia is used. The pH of trate is fortified by the addition of hydrofluoric acid to the filtrate should be at least six and not more than about 5% free fluoride ion concentration and is acidified with nine. Practically speaking, a pH of seven to eight will Sulfuric acid back to a pH of 5.0. This solution is then suffice to insure essentially complete precipitation. The 5 available for recycle and recovery of additional values. hydroxide precipitates are recovered by filtration while The insoluble scandium-thorium fluoride from 13a is the filtrate is discarded. agitated with a solution of six normal potassium hydrox The hydroxide precipitate is dissolved in strong mineral ide at 14 for four hours at a temperature within the range acid such as hydrochloric acid (1.5 normal) preferably of 70 to 90° C., thus completing the replacement of the at an elevated temperature in the approximate range of 20 fluoride with hydroxyl groups. The insoluble hydroxides 70° to 90° C. Presumably any concentration can be are filtered at 15 and the filtrate containing soluble fluo used, however, we believe 1.5 NHCl is optimum. Other rides is withdrawn. To the precipitate is added sufficient acids may be used to dissolve the scandium hydroxide but three normal nitric acid to completely dissolve the hy hydrochloric acid is preferred since the oxalate precipi droxides and give a solution having a three normal nitric tation is more complete if carried out in a hydrochloric 25 acid concentration. A 50% excess of a saturated potas acid solution. Sufficient acid should be added to dis sium iodate solution containing sufficient nitric acid to solve the hydroxide and produce a 1.5 normal hydro maintain the acid concentration of the solution is there chloric acid solution. Scandium is precipitated from the upon added at 16 to precipitate the complex thorium solution by adding oxalic acid. The solution is boiled to iodate, 4Th (IO3)4. KIOa. 18HO. It should be obvious complete the precipitation. Preferably, an excess of ox 30 that the amount of potassium iodate reagent added de alic acid, e.g., 100% excess of the stoichiometric quantity pends upon the concentration of thorium in the acidic is used to decompose any small remaining amounts of each liquor. A ratio of about 6.4 moles of potassium potassium iodate. More complete precipitation can be iodate per mole of thorium should suffice to complete the obtained by allowing the solution to stand for several precipitation. The treatment and precipitation are car hours, for example, up to about eight hours. 35 ried out at room temperature and the insoluble thorium The precipitated Scandium oxalate is recovered by fil iodate complex is removed by filtration at 17. tration and the precipitate is calcined to the oxide by The filtrate containing the desired scandium ion is heating in a furnace in an oxidizing atmosphere at a tem neutralized with ammonia to a pH of 8.0 at 18, excess perature high enough and for a time sufficient to bring ammonium chloride having been added previously to about substantially complete oxidation of the organic 40 Increase the solubility of the alkali and alkaline earth matter. Heating at a temperature of 800° C. for about ions. The hydroxide precipitates, including scandium one hour is satisfactory. hydroxide, are recovered by filtration at 19, and the Although the procedure has been described in con filtrate is discarded. The precipitate is dissolved in 15 nection with the recovery of scandium from uranium normal hydrochloric acid at an elevated temperature Ores, and the isolation of a mixture of scandium and on the order of 70° to 90° C., sufficient acid being added thorium produced from such ores, it will be apparent to yield a solution having a 1.5 normal hydrochloric acid that the principle of the invention may be applied to the concentration. One hundred percent (100%) stoichio Separation and recovery of scandium from scandium metric excess (based on formation of scandium oxalate) thorium mixtures derived from other sources. Follow of Oxalic acid is then added at 20 and the solution is ing is an example of a procedure for carrying out the boiled to complete the precipitation of scandium oxalate. process of the present invention using materials derived The Solution thereafter is allowed to stand for eight from the refining of uranium ores. hours to effect precipitation of the maximum amount of FIGURE 1 is a schematic diagram illustrating the se Scandium oxalate. The precipitate is filtered at 21 and quence of operating steps carried out in the example. calcined in a muffle furnace 22 at a temperature of 800 The parts expressed are by weight unless otherwise 5 5 C. for one hour. The recovery of based indicated. on the content of the original acid leach liquor is about An acidified leach liquor obtained by the treatment of 85%. Analysis of the product showed it to be over uranium ore having a pH of about 1.0, said leach liquor 99% pure Sc2O3. It should be obvious that particular containing from 0.5 to 2.0 grams per liter of UOa and steps in the purification procedure may be repeated to on the order of about 0.001 gram per liter of scandium, 60 further purify the product. about 0.002 gram per liter of thorium and trace amounts Although specific and preferred embodiments of the of titanium are treated in a stagewise countercurrent invention have been described herein, we intend that all (four stages) operation at 11 with a 3% by volume solu modifications and equivalents thereof be included within tion of dodecylphosphoric acid in kerosene diluent. The the Scope of the appended claims. spent aqueous phase is discarded while the organic phase, 65 We claim: which now contains the desired mineral values, is routed 1. The process for separating scandium from a mix to a Second extraction operation 12 where the values are ture of Scandium and thorium, which comprises precipi removed by a stagewise (five stages) and countercurrent tating the thorium as the insoluble iodate from a mineral treatment with strong hydrochloric acid. This removes acid solution containing ions of scandium and thorium the uranium from the organic solvent and the acid solu 70 by adding a soluble iodate ion in aqueous solution, said tion is directed to further processing for the production mineral acid being free of ions which would prevent the of uranium concentrates. iodate precipitaion, separating the precipitate from the The organic solvent is then charged to a conventional liquid, adding an aqueous solution of ammonia as a mixer settler extraction unit 13, where it is treated in a Source of hydroxide ions to said liquid to produce a countercurrent stagewise process (two stages) with acidi 75 Solution having a pH of about 6 to about 9 to precipitate 3,146,063 6 selectively the scandium as scandium hydroxide and to hydroxide in nitric acid and treating said solution with increase the solubility of any alkali and alkaline earth potassium iodate thereby to convert the thorium to an metal ions present, and removing the scandium hydroxide. insoluble complex of thorium-potassium iodate retaining 2. A process for separating scandium from a mixture most of the other components in solution, separating said of scandium fluoride and thorium fluoride which com insoluble complex from the liquid, treating the latter prises treating said mixture with a strong aqueous solu liquid with ammonium chloride and free ammonia to tion of potassium hydroxide thereby to convert the scan produce a solution having a pH of about 6 to about 9 dium and thorium to their hydroxides, removing the in and thereby to precipitate selectively the scandium as soluble hydroxides from the solution, treating said in scandium hydroxide retaining most of the impurities in soluble hydroxides with nitric acid and potassium iodate 0 solution, separating said scandium hydroxide from said thereby to convert substantially all of the thorium to an solution, treating said scandium hydroxide with a strong insoluble thorium-potassium iodate complex while re mineral acid to dissolve the scandium ions, treating said taining substantially all of the scandium ions in solution, scandium ions in aqueous solution with oxalic acid removing the said insoluble complex from the solution, thereby to precipitate selectively scandium oxalate re adding ammonia and ammonium chloride to said last 5 taining most of the remaining impurities in solution, sep named solution to produce a solution having a pH of arating said scandium oxalate from said last-mentioned about 6 to about 9 and to substantially neutralize the Solution, and calcining said scandium oxalate in an oxi same and cause substantially complete precipitation of dizing atmosphere thereby to convert it to scandium. scandium hydroxide while retaining most of the impuri oxide. ties in solution, removing the scandium hydroxide from 20 4. A process for recovering scandium from ores con the solution, forming a solution of said scandium hy taining scandium and thorium, which comprises treating droxide by treatment with a strong mineral acid, treating acid leach liquor from the acid leach of crushed ore with said scandium ions in an aqueous solution with oxalic an organo-phosphate solvent to extract the scandium acid thereby to precipitate scandium oxalate from the and thorium ions, treating the organo-phosphate solvent solution, and removing said precipitate from the solution. 25 with a mineral acid to extract any metal cations soluble 3. A process for recovering scandium from a uranium in said mineral acid, adding an acid solution of a fluoride ore containing thorium, titanium, at least a trace amount to the stripped organic solvent to precipitate scandium of scandium and other impurities, which comprises treat fluoride and thorium fluoride, converting the mixture of ing acid leach liquor from the acid leach of crushed ore scandium and thorium fluorides to an acid-soluble precip with an organic solvent capable of extracting uranium, 30 itate by adding an alkali metal hydroxide and dissolving thorium, titanium, and scandium ions from said acid the precipitate in a mineral acid capable of dissolving leach liquor, stripping said organic solvent with an aque said precipitate and free of ions which would prevent ous mineral acid solution thereby selectively to extract iodate precipitation, precipitating the thorium by adding uranium ions therefrom, treating the stripped organic soluble iodate ion to the acid solution, neutralizing the solvent with an aqueous acid solution of a fluoride there 35 solution containing scandium ion to a pH of about 6 to by to precipitate selectively scandium fluoride and tho about 9 to precipitate scandium hydroxide, and calcining rium fluoride with some impurities, retaining a major the scandium hydroxide to produce scandium oxide. amount of titanium ions in solution, separating the pre cipitated scandium fluoride and thorium fluoride from References Cited in the file of this patent the liquid, treating the scandium fluoride and thorium 40 fluoride and impurities with a strong aqueous alkali metal NSA 1: 4057 (Nuclear Science Abstracts, vol. 7, Ab hydroxide solution thereby to convert most of the scan stract No. 4057), 1953. dium fluoride and thorium fluoride to scandium hydroxide Nuclear Science Abstracts, vol. 14, abstract No. 268, and thorium hydroxide and most of the impurities to January 15, 1960 abstracting "Separation of Scandium soluble ions, separating the insoluble scandium hydroxide 45 From the Rare Earths and Zirconium,” Moskalkavs et al., and thorium hydroxide from the liquid containing im Trudy Radievogo Inst. im V.G. Khlopina 7, 141-3 purities, dissolving said scandium hydroxide and thorium (1957).