Separation of Hf(IV) and Zr(IV) using di(p-tert-octylphenyl) phosphate in sulfuric acid medium
摘要
Efficient separation of nuclear-grade zirconium (Zr) and hafnium (Hf) remains a significant challenge in the nuclear industry. In this study, a novel extractant, di(p-tert-octylphenyl) phosphate (DTOPPA), was designed and synthesized. DTOPPA demonstrated preferential extraction of Hf over Zr in sulfuric acid media, surpassing the performance of conventional extractants such as D2EHPA and PC88A. Under optimized conditions, Hf(IV) extraction achieved 90.7% with a separation factor SF(Hf/Zr) of 13.4. Density functional theory (DFT) calculations and acid–base titration indicated enhanced dissociation of DTOPPA, attributed to the electron-withdrawing phenoxy group, which facilitates cation exchange. Slope analysis, saturation capacity measurements, and Fourier-transform infrared spectroscopy (FTIR) identified the extracted species as Zr(Hf)OA2·2DTOPPA, involving cation exchange and P=O coordination. Selective stripping of Zr was accomplished using dilute sulfuric acid, while oxalic acid efficiently stripped Hf. A two-stage countercurrent extraction process yielded nuclear-grade Zr with stable organic phase recycling. This novel extractant provides an environmentally friendly and efficient method for Zr/Hf separation with significant potential for industrial application.