VERFAHREN ZUR REINIGUNG VON UEBERGANGSMETALLE ENTHALTENDEN HYDROXIDEN VON NIOB UND TANTAL

Refining of either niobium hydroxide or tantalum hydroxide containing transition metals as impurities is accomplished easily and economically by dissolving the metal hydroxide in an aqueous solution of either hydrofluoric acid or oxalic acid, adjusting the pH of the solution to 1 to 4 and adding ammonium pyrrolidinedithiocarbamate (APDC) to the solution while maintaining the temperature of the solution below 60 DEG C. The addition of APDC causes the transition metals to simultaneously precipitate as coordination compounds. The minimum amount of APDC is 0.05 wt % of Nb2O5 or Ta2O5 that can be formed from Nb or Ta contained in the solution. After the treatment with APDC the pH of the solution is raised to 6 or above to precipitate the refined metal hydroxide.