Patent ID: 6592830
Filing Date: 2003-07-15
Classification: C22B,Y02P

Abstract:
A process for the treatment of raw material containing tantalum and/or niobium and other admixture elements comprising the following steps:A. the raw material is decomposed by a solution containing ammonium fluoride at the boiling point of reaction mixture for not more than 10 hours; said tantalum and niobium and other admixture elements of said raw material are converted into ammonium fluoride complex compounds; exhaust gases from said decomposition consist of ammonia and ammonium fluoride which are recovered by condensation and scrubbing the exhaust gases; B. the mixture obtained as a result of decomposition stage according to step A is leached with water or a solution containing ammonia at a temperature below 100Â° C. to remove said ammonium fluoride complex compounds into said water or a solution containing ammonia and leaves insoluble oxides, oxide fluorides and fluorides of admixture elements; C. the mixture obtained after step B is filtered giving a main filtrateâ€”ammonium fluoride solution containing tantalum and niobium and a sediment of compounds of the admixture elements; the said sediment is washed with ammonium fluoride solution or water, or ammonium solution; D. the main filtrate from step C is mixed with a solution of NH3 to precipitate the tantalum and niobium; E. a sediment containing tantalum and niobium precipitated during step D is separated from ammonium fluoride solution by filtering and is than dried and calcined at a temperature not higher than 450Â° C. for not more than 2 hours to remove ammonia and ammonium fluoride which is recycled for decomposition of raw material according to step A; F. the sediment containing tantalum and niobium after step E is then dissolved in a solution containing fluoride ions and hydrofluoric acid to prepare a hydrofluoric acid solution containing said metal; G. subjecting the solution obtained from step F to extraction separation to produce separate aqueous solutions of niobium fluoroacid complex and tantalum fluoroammonium complex H. addition of ammonia to each of the separate aqueous solutions of niobium fluoroacid complex and tantalum fluoroammonium complex produced in step G to precipitate niobium hydroxide and tantalum hydroxide respectively; I. the sediment of niobium hydroxide precipitated during step H is separated from ammonium fluoride solution by filtering and the sediment of tantalum hydroxide precipitated during step H is separated from ammonium fluoride solution by filtering; ammonium fluoride solutions are used for decomposition of raw material according to step A; and J. the niobium hydroxide from step I is calcined giving a product containing more than 99% of niobium oxide and the tantalum hydroxide from step I is calcined giving a product containing more than 99% of tantalum oxide; and ammonium fluoride is recovered from exhaust gases by scrubbing them.