What is it about?
This paper deals with the solubility of Nb(V) and Ta(V) at pH > 8. The results show that niobium pentoxide (Nb2O5,nH2O) is slowly transformed into sodium hexaniobate (Na7HNb6O19_15H2O), even at room temperature and at pH < 12. Similar phase transition is expected to take place between Ta2O5·nH2O(s) and Na8Ta6O19·mH2O(s), but at pH higher than 12.
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Why is it important?
The solubility product of Na7HNb6O19,15H2O has been determined for the first time. The results show that the solubility of Na7HNb6O19,15H2O could be increased in the presence of potassium ions. Hexaniobate ions play a major role in the solubility of Nb(V) but the current solubility model for Nb(V) doesn't take these ions into account.
Perspectives
The implication of these results concerns Nb and Ta recovery processes and also the storage of nuclear wastes that contain the isotopes 94Nb and 93mNb since most of them are subject to be stored under high pH conditions. The enhancement of the solubility of Na7HNb6O19,15H2O, observed in the presence of K+ ions, could be of interest for the development of new hydrometallurgical processes.
Dr Gauthier J-P. Deblonde
Lawrence Livermore National Laboratory
Read the Original
This page is a summary of: Solubility of niobium(V) and tantalum(V) under mild alkaline conditions, Hydrometallurgy, July 2015, Elsevier,
DOI: 10.1016/j.hydromet.2015.05.015.
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