1995 Volume 59 Issue 5 Pages 532-539
The reductive stripping of Pd and Pt from Pd(II), Pt(II) and Pt(IV)-loaded organics was investigated using NaH2PO2. The organics employed in this study were TBP and Alamine 336 diluted in kerosene. The main findings are as follows: (1) Pd particles of around 1 μm can be effectively stripped from Pd(II)-loaded TBP solution by using an excess amount of NaH2PO2 of 5 molar equivalents. The addition of 0.1 kmol·m−3 NH3 to the aqueous NaH2PO2 solution enhances the precipitation efficiency. (2) Pd can be reductively stripped from Pd(II)-loaded Alamine 336 by mixing the organics with an aqueous NaH2PO2 solution, followed by the addition of NH3 prior to reagitating the solution. In order to quantitatively strip Pd(II) from this organic phase, the addition of NaH2PO2 of 7∼10 molar equivalents to Pd(II) and 1 kmol· m−3NH3 is required. Pd particulates are obtained by using less than 5 molar equivalents of NaH2PO2, while a further addition of NaH2PO2 forms film-like precipitates. (3) Pt precipitation reaction from the organics containing Pt(II) and Pt(IV) is impossible under the experimental condition suitable for the reductive stripping of Pd from the organics containing Pd(II). The authors also discussed the possible mechanisms of these reductive stripping reactions.
