Process for the recovery of hydrofluoric acid and depositable residues during treatment of niobium- and/or tantalum-containing raw materials

In a process for treating tantalum- and/or niobium-containing raw materials by dissolving them in hydrofluoric acid and sulfuric acid mixtures, separating the niobium and tantalum elements by liquid-liquid-extraction, and subsequently re-extracting said elements as complex fluoroacids from the organic phase in aqueous solutions, the improvement which comprises

• (a) decomposing said obtained aqueous solutions containing fluoroacid complexes of niobium and/or tantalum and small amounts of free hydrofluoric acid by pyrohydrolysis within a temperature range of from 60.degree. to 600.degree. C., calcinating within a temperature range of from 600.degree. to 1500.degree. C., converting the complex fluoroacids of niobium and/or tantalum to pure oxides of niobium and/or tantalum, and recovering the hydrofluoric acid separated during pyrohydrolysis in its pure reusable form with a hydrogen fluoride content of from 1 to 80 percent by weight, by condensation or scrubbing of the exhaust gas, and
• (b) decomposing by pyrohydrolysis extracted niobium- and/or tantalum-free raffinate solution comprising dissolved metalloids as well as still free sulfuric acid and hydrofluoric acid in the mixture, and calcinating, recovering the hydrofluoric acid and the sulfuric acid as a condensate in a reusable mixture, and recovering the metalloids as oxides not comprising water-soluble constituents as deposable waste products.