Abstract:
The solvent extraction of niobium(V) from hydrofluoric acid solutions has been studied with decanol and tri-n-butyl phosphate (TBP). The effects of various parameters such as concentration of hydrofluoric acid (3-8 M) and sulphuric acid (3-8 M) and their mixtures, decanol and TBP concentrations, number of extraction stages, temperature (301-321 K), recycling of extractants, mixing of extractants and addition of foreign ions on niobium (V) extraction were determined. The absorption and infrared spectra of the aqueous and organic phases of niobium(V) extracted from 3 M HF/3 M H2SO4 and 4 M HF/4 M H2SO4 solution with decanol and TBP were also measured. It was observed that optimum percentage extraction (E %) of 75.0 % was attained by decanol at HF concentration of 3 M, and 53.3 % was attained by TBP at HF concentration of 4 M. Change in temperature showed an irregular variation in the percentage extraction for the extractants at 301, 306, 311, 316, and 321K with the percentage extraction (E %) using decanol being 77.0, 35.5, 75.0, 73.0 and 72.0 % respectively, while for TBP were 90.0, 85.0, 70.3, 23.6 and 52.0 % . In the recycling of extractants, the optimum percentage values of extraction were 77.0 % for decanol and 86.0 % for TBP at first stage. Sixth and fourth stages of extraction with decanol and TBP reduced niobium(V) to minimal amount in the aqueous phase. The mixture of Methyl Trioctyl Ammonium Chloride (TOMAC) (20 %v/v) and decanol (80 %v/v) had the least percentage of 26.1 % for niobium(V) extraction. All the foreign ions added (Mn2+, V5+, Fe2+, Zr4+ and Ta5+) to decanol at the concentration range of 0.001-0.003M decreased the percentage extraction of Nb (V) except V (V) ion of 0.002 M that has 91.1 %, and V (V), ion of 0.001 M and Mn (II), ion of 0.003 M that have the same percentage extraction of 77.0 % compared with when no ion was added with decanol.
