Solvent extraction of vanadium

The extraction of vanadium(IV) from aqueous acid and alkaline solutions by organophosphorus compounds and high-molecular-weight amines has been investigated in comparison with the results for the extraction of vanadium(V). As a result, it is suggested that the application of the solvent extraction method is very useful in the hydrometallurgy of vanadium metal. In extractions from hydrochloric acid solutions by neutral organophosphorus compounds, secondary and tertiary amines and quaternary ammonium salts, the distribution coefficients for vanadium(V) are 500 -- 100 times larger than those for vanadium(IV), although their extraction curves are analogous to every cases, showing maxima at [HCl] = 6 -- 8 M. It is seen that these extractants are suitable for the extraction of vanadium(IV), and that they are also applicable to the extraction of vanadium(V) from low acid and alkaline media. Vanadium(IV), on the other hand, is extracted effectively from low acid media by acid organophosphorus compounds, and from aqueous solutions in the presence of thiocyanate, by quaternary ammonium salts. (author)