Basic hydrolysis of Nb(V) and Ta(V) fluorides in HF-acqueous solutions

Abstract Composition and structure of fluoride complexes of Nb and Ta in neutral and basic aqueous solutions of HF have been studied by 19 F NMR. It is shown that in acid solutions of HF (pH=2) with ratio F:Nb=5, Nb exists predominantly in the form of NbOF 4 (H 2 O) - . With The increasing of the basicity the equilibrium is displaced towards NbOF 2- 5 as a result of the increasing of F - activity; accordingly the hydrolysis is extended and NbOF 3 (H 2 O) 2 is formed. While the hydrolysis of Nb(V) fluorides leads to formation of double bonding Nb=o, the hydrolysis of Ta(V) fluorides proceeds via formation of Mechanisms of extraction of fluoride compounds of Ta and Nb with tributylphosphate from the neutral and basic aqueous solutions were studied. The influence of the extraction process on equilibrium between fluoride complexes of Ta and Nb in acqueous solution has been studied.