Патент USA US3072469код для вставки
United States Patent O?hce 1 > 3,072,459 Patented Jan. 8, 1963 2 3,072,459 PROCESS FOR PRODUCING FLUORIDE-FREE COLUMBIUM OR TANTALUM PENTOXIDE Raymond A. Foos, Freemont, Ohio, and Robert L. Ripley, Lockport, N.Y., assignors to Union Carbide Corpora HgTaFq in the ?uoride solution and at least 21/2 moles of sulfuric acid for each mole of H2CbOF5 in the ?uoride solution. Excesses of sulfuric acid over this amount may be advantageously employed in accordance with the dic tates of the economics of the process. When the ?uorine has satisfactorily been removed by volatilization as hydrogen ?uoride, precipitating reagent is added to precipitate the metal values as hydrated pent oxides substantially free from ?uoride contamination. This invention relates to a method for producing 10 The metal components of the solution which have been columbium and/ or tantalum pentoxides substantially free freed from ?uorine may be precipitated by adding a base tion, a corporation of New York No Drawing. Filed Dec. 30, 1959, Ser. No. 862,809 5 Claims. (Cl. 23-23) from ?uorine contamination. , In the puri?cation and separation of tantalum and columbium values, from solid starting materials such as such as ammonium hydroxide. However, if the amount of concentrated sulfuric acid employed is substantially in excess over that necessary to remove the ?uoride con the ores of these metals, it is common practice to ?rst 15 tamination, no further precipitating agent need be added. solubilize the metal values in an aqueous acid solution The precipitated material is then separated from the containing ?uorides. The tantalum and columbium mother liquor. values are then extracted from the acid solution with an To illustrate the process of the present invention 25 organic solvent; the extracted metal values are then milliliters of a hydro?uoric acid solution of 3.80 grams selectively stripped from the organic phase with an aque 20 of Ta2-O5 were digested with 5 milliliters of concentrated ous solution. The aqueous strip liquor is treated so as sulfuric acid. The mixture was boiled until the hydro to precipitate tantalum and columbium oxides. A typi gen ?uoride was completely volatilized. A stoichiometric cal analysis of a wet ?lter cake from a tantalum precipi amount of ammonium hydroxide was then added and 100 tate is 7 percent ?uorine, 3 percent ammonia, 40 percent percent recovery of tantalum as a hydrated oxide con 25 water and 50 percent tantalum pentoxide. A typical anal taining only 0.06 percent ?uorine was obtained. The ysis of a columbium wet cake is 4 percent ?uorine, 2 per ‘ precipitated hydrated oxide was calcined at about 500° C. cent ammonia, 60 percent water and 34 percent colum to insure elimination of any residual sulphur. Analysis 'bium pentoxide. of the calcined metal showed a sulphur content of less As may be seen from these analyses, the cakes contain 30 than 0.005 percent. a high percentage of ?uoride material. Before either of To illustrate the process wherein sulfuric acid is em the metal oxide materials can be. processed to the ele ployed as the precipitating reagent, a mixture consisting mental metal, the water of hydration and the ?uorides of 25 milliliters of concentrated sulfuric acid and 25 must be removed. The presence of ?uorine lowers the milliliters of an aqueous hydro?uoric acid solution of metal recovery and fouls and corrodes the reduction 35 3.80 grams of Ta2O5 was boiled to evolve gaseous hydro equipment. Further, for direct sale of the cake material, gen ?uoride. Once the ?uorine was eliminated, the tan a low ?uorine content is required, since the usual com talum automatically precipitated from the solution in the mercial ?uoride speci?cation for saleable oxides is a form of a hydrated oxide containing 1.9 percent ?uorine. 'maximum of 0.1 percent. The product was calcined and the calcined material was In the aqueous extracts and aqueous strip liquors ob 40 analyzed and found tov contain less than 0.005 percent 7‘. tained in the separation of columbium and tantalum the sulphur. columbium is generally present as HzCbFI] or H2CbOF5 Where the columbium or tantalum product is even and the tantalum as H2TaF7. The precipitated material tually to-be converted to the corresponding pentachloride generally contains ?uorine also and it is believed the up to about 2 percent ?uorine is not harmful. For the compounds precipitate as CbOFa and TaOF3. Many preparation of the pure pentoxide, however, the preferred attempts have been made to remove the ?uoride con 45 method of digesting with smaller quantities of sulfuric tamination but these methods ‘generally involve special equipment because of the corrosive nature of the ?uoride acid and precipitating with ammonium hydroxide is pre ferred. - ion. Other methods, for example washing with water, What is claimed is: have proven unsuccessful to obtain a ?uorine content of 1. A process for producing a substantially ?uoride~free 50 less than about 4 percent. pentoxide of at least one metal selected from the group Accordingly, it is an object of this invention to pro consisting of columbium and tantalum from an aqueous vide a process for the production of columbium and tan hydro?uoric acid solution containing a compound selected talum pentoxides by means of which columbium and tan from the group consisting of HzCbFq, H2CbOF5 and talum pentoxides containing less than about 0.1 percent of ?uoride contamination may be obtained. , 55 HzTaFq which process comprises adding at least 21/2 moles of sulfuric acid to said solution for every mole of Other objects will be apparent ‘from the subsequent dis H2CbF-7 and HzTaFq contained therein and at least 11/2 closure and appended claims. moles of sulfuric acid for every mole of H2CbOF5 con The process which satis?es the objects of the present tained therein; digesting the so-acidi?ed solution by boil invention comprises treating a ?uoride solution contain ing it whereby the combined ?uorine is dissociated from ing columbium values in the form of H2CbFq and 60 the metal compounds and volatilized during said diges H2CbOF5 and/ or tantalum values in the ‘form of HzTaFq tion as gaseous hydrogen ?uoride; continuing said diges with at least 21/2 moles of sulfuric acid for each mole of tion until the evolution of gaseous hydrogen ?uoride HzCbFq and HzTaFq in the ?uoride solution and at least from said solution has substantially subsided; and precipi 11/2 moles of sulfuric acid for each mole of H2CbOF5 in 65 tating said selected metal from the solution as a hydrated the ?uoride solution and digesting said acid treated solu pentoxide of said metal. tion by boiling it whereby the ?uorine is dissociated from 2. A process in accordance with claim 1 wherein the the metal compound and volatilized during the digestion amount of sulfuric acid added is insuf?cient for the pre as gaseous hydrogen ?uoride. , cipitation of the metal values and wherein ammonium ‘In the preferred form of the invention the ?uoride solu 70 hydroxide is added to the digested solution to precipitate tion containing the metal values is treated with at least the selected metal pentoxide. 31/2 moles of sulfuric acid for each mole of HzCbFq and 3. A process in accordance with claim 1 wherein at‘v 3,072,459 3 least 31/2 moles of sulfuric acid are added to said solution in the acidi?cation step for every mole of HzCbFq and H2TaF7 contained therein and at least 21/2 moles of sul furic acid for every mole of H2CbOF5 contained therein. 4. A process in accordance with claim 3 wherein the amount of sulfuric acid added is insuf?cient for the pre cipitation of the metal values and wherein ammonium hydroxide is added to the digested solution to precipitate the selected metal pentoxide. 5. A process in accordance with claim 3 wherein a sub 10 stantial excess of sulfuric acid is added to said solution in the acidi?cation step whereby the selected metal pent oxide precipitates from the digested solution without addi tional treatment. 4 References Cited in the ?le of this patent UNITED STATES PATENTS 2,795,481 2,819,146 2,819,945 2,950,966 2,953,453 2,980,496 Hicks et a1. __________ __ June 11, Ruhoff et a1. __________ __ Jan. 7, Ruhoff et a1. _________ __ Jan. 14, Foos _______________ __ Aug. 30, Foos _______________ .__ Sept. 20, Wettler ______________ __ Apr. 18, 1957 1958 1958 1960 1960 1961 OTHER REFERENCES Jacobson: “Encyclopedia of Chemical Reactions,” Reinhold Pub. Corp., New York, 1958, vol. 7, Reaction VII—690, page 166.