High-efficient removal of tungsten from hafnium by TOA/XAD-7 extraction resin from HCl-HF media

For removal of the natural isobar 182W interference prior to ultra-trace 182Hf determination by accelerator mass spectrometry, an extraction chromatographic method for separation of Hf from W has been developed by using a newly synthesized tri-n-octylamine (TOA)/XAD-7 resin as the stationary phase and HCl-HF media as the mobile phase. Based on the TOA liquid-liquid extraction studies in HF and HCl-HF solutions at wide concentration range, a maximum separation factor of 8.6 × 103 for W/Hf was obtained in 8 M HCl-0.05 M HF solution. Subsequently, the macroporous organic polymer-based TOA/XAD-7 resin was prepared by vacuum impregnation technique and its morphology, chemical structure and composition were characterized by SEM, EDS, FT-IR, TG-DSC, and EA. The results showed the self-assembly TOA/XAD-7 resin uptakes about 50% of extractant and keeps intact binding characteristic for metal ions. Hence, this resin was employed to investigate the column chromatographic behavior of Hf and W with variable parameters of sample loading and column bed dimensions. As a result, a high yield of more than 99% for Hf and high decontamination factor of 3.2 × 105 for W were achieved under the optimal column condition. The strategy developed provides a simple and efficient alternative to sample preparation for 182Hf measurement.