Selective recovery of neodymium from oxides by direct extraction method with supercritical Co₂containing TBP–HNO₃complex

Abstract

A method for the direct extraction of a metal utilizing supercritical CO 2 containing tri-n-butylphosphate (TBP)-HNO 3 (TBP), which is the TBP solution of TBP -HNO 3 complex, has been developed for the recovery of Nd from its oxide. This method was applied using a flow reactor to several oxides (Nd 2 O 3 , ZrO 2 , MoO 3 , and RuO 2 ), and binary mixtures of the oxides (Nd 2 O 3 -ZrO 2 , Nd 2 O 3 -MoO 3 , and Nd 2 O 3 -RuO 2 ). Neodymium (Nd) was extracted almost quantitatively from 0.01 mol Nd 2 O 3 powder with supercritical CO 2 containing TBP -HNO 3 (TBP) at 313K and 12 MPa, while Zr, Mo, and Ru were hardly extracted from their oxides and remained in the reactor. Nd was extracted quantitatively and selectively also from the binary mixtures of the oxides. From these results, it is found that the supercritical CO 2 extraction process using TBP -HNO 3 (TBP) as reactant is feasible for the selective recovery of lanthanides directly from the various oxide mixtures. 1153

Study on Properties of TBP‐HNO3 Complex Used for Direct Dissolution of Lanthanide and Actinide Oxides in Supercritical Fluid CO2

“…Figure 4 shows the density of the TBP-HNO 3 complex increases with increase of the concentration of HNO 3 in the TBP-HNO 3 complex from 1.95 to 5.89 mol/L. The density of the TBP-HNO 3 complexes is higher than that of the pure TBP liquid (0.975 g/cm 3 , 15 ℃). The density of water saturated TBP is 0.997 g/cm 3 (15 ℃).…”

“…The density of the TBP-HNO 3 complexes is higher than that of the pure TBP liquid (0.975 g/cm 3 , 15 ℃). The density of water saturated TBP is 0.997 g/cm 3 (15 ℃). Figure 5 shows that the viscosity of the TBP-HNO 3 complex decreases from 4.57×10 -3 to 2.73×10 -3 Pa•s with increase of the concentration of HNO 3 in the TBP-HNO 3 complex from 1.95 to 5.89 mol/L, and is higher than that of the pure TBP liquid (2.72×10 -3 Pa•s, 25 ℃).…”

“…The nitric acid peak in CDCl 3 tends to shift upfield with increasing HNO 3 concentration in the acid solution. The peak at δ 11.97 in Figure 10 is the peak representing the averaged protons of HNO 3 and H 2 O in the complex. The NMR results obtained from the CDCl 3 -TBP-HNO 3 complex system, though qualitative in nature, demonstrate the formation of nitric acid droplets from the TBP-HNO 3 complex when dissolved in a low dielectric constant solvent as a result of an antisolvent effect.…”

“…[2][3][4][5] The U(IV) in solid UO 2 is possibly oxidized to U(VI) by HNO 3 in the TBP-HNO 3 complex and dissolves in SCF-CO 2 as UO 2 (NO 3 ) 2 •2TBP. The metallic nitrate complex with TBP is finally recovered by depressurizing to atmospheric pressure.…”

Dissolution Behavior of Uranium Oxides with Supercritical CO2Using HNO3-TBP Complex as a Reactant

“…The authors have studied the dissolution behavior of lanthanide oxides, zirconium oxide, strontium oxide, etc. 2,7,15) with the supercritical CO 2 containing the HNO 3 -TBP complex as a reactant, and a method has been developed for the removal of the uranium oxides from the solid samples named supercritical fluid leaching (SFL) method, which was reported preliminarily in Ref. 12).…”