Comparative study of tantalite dissolution using different fluoride salts as fluxes

•Fluoride salts were compared as fluxing reagents for tantalite dissolution.•KF·HF, KF and NH4F·HF are more efficient than NaF and HF·NaF in tantalite dissolution.•Nb2O5 dissolved more readily in the acidic fluoride matrix compared to Ta2O5.•Both H+ and F− are important for the complete dissolution of Nb2O5 and Ta2O5.

Six different fluoride salts, NH4F·HF, KF, KF·HF, CaF2, NaF and HF·NaF, were evaluated as fluxes in the fusion dissolution of Ta/Nb containing minerals, and compared with the commercially employed HF dissolution. The cold fusion products were dissolved in dilute H2SO4 for both the dissolution and matrix matching purposes. Analytical results indicated that the KF, KF·HF and NH4F·HF dissolution procedures were the most effective for dissolving and recovering the main elements from the tantalite mineral. CaF2, NaF and NaF·HF yielded the lowest recoveries of Ta and Nb from the tantalite mineral sample under study. This comparative study indicated that the dissolution and separation of Ta and Nb from one another and from other elements in minerals depended heavily on fluoride concentration, acidity as well as temperature for the formation of the metal–halogen complexes.Dissolution of the minerals using KF·HF and NH4F·HF as fluxes are recommended as alternatives to HF dissolution due lower energy demands, elemental recoveries, cost, separation efficiency and ease of the dissolution step.

Graphical abstractSix different inorganic fluoride salts, NH4F·HF, KF, KF·HF, CaF2, NaF and NaF·HF, were evaluated as flux-fusion reagents for dissolution of tantalite. Results indicated that quantitative recoveries were obtained for NH4F·HF, KF, KF·HF. Quantitative analyses of Ta2O5 and Nb2O5 in tantalite sample dissolved by HF/H2SO4 and flux fusion using five different fluoride fluxes at a sample:flux ratio of 1:20.Figure optionsDownload full-size imageDownload as PowerPoint slide