A comparison of the extraction of carrier-free 176,177W and 99Mo with that of U, Th, Am, Cm, La, Ce, Tm, Yb, Lu, and Hf into tri-n-octyl amine in toluene from nitric, phosphoric, and sulphuric acid media

The extraction of carrier-free tungsten and molybdenum from nitric, phosphoric and sulphuric acid with 0.05 M TOA (tri-n-octyl amine, R3N) in toluene and 2.5% by volume 1-dodecanol has been studied. Their extraction behaviour has also been compared to hafnium, some trivalent lanthanides (lanthanum, cerium, thulium, ytterbium and lutetium) and some actinides (thorium, uranium, americium and curium). The extraction of these metal ions decreases in the order M4+ > MO22+ > M3+ from > 1 M nitric acid solutions, if hafnium, which is on the form HfO2+, is disregarded. At low nitric acid concentrations tungsten and molybdenum are most likely extracted as tungstate or molybdate ions (R3NH)2.MO4, while at higher concentrations they are most likely extracted similar to uranium, i.e. on the form R3NH.MO2(NO3)3. Further, the extraction from phosphoric acid solutions decreases in the order M4+ > MO22+ > M3+, if the elements which are easily hydrolysed, hafnium, molybdenum and tungsten, are disregarded. The major extracted complex of tungsten contains one TOA and the minor two TOA. The extracted complex with one TOA is probably (R3NH).WO2(H2PO4)3 or R3N.WO2(H2PO4)2, while that with two TOA more likely is (R3N)2H.WO2(H2PO4)3 or even the more hydrolysed species of tungsten (R3NH)2.WO4. For molybdenum, the extracted complexes seem reasonably similar. Disregarding HfO2+ the extraction decreases in the order MO22+ > M4+ > M3+ for the chosen range of sulphuric acid concentration. (orig.)