Aug. 25, 1964 J. D. MOORE ETA 3,146,063 PROCESS FOR SEPARATING SCANDIUM 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 RecyRecycle 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 fluoride 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 potassium fluoride 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 ammonium bifluoride 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 fluorides 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.