High-efficient and selective extraction of Hf over Zr with DIBK-P350 synergistic extraction system

The combination of various organophosphorus extractants in di-isobutyl ketone (DIBK) has been investigated to selectively extract Hf over Zr. An obvious improvement of synergistic extraction efficiency was obtained when di-(1-methyl-heptyl) methyl phosphonate (P350) was added into DIBK-based extraction system. Hf extraction rate of 83.2%, separation factor of 17.6 and synergistic coefficient of 3.3 was achieved under the optimum conditions. The mechanism of synergistic extraction was elucidated by the slope method to study the extraction stoichiometry of the extracted complex for Hf. The structure of the extraction complex was determined as [H∙P350]∙[HfO(SCN)3]∙DIBK. Scrubbing and stripping experiments have been performed for the loaded organic phase. Firstly, co-extracted Zr was selectively scrubbed by the sulfuric acid solution. Hf was then effectively stripped by ammonium carbonate solution and thus the extractants were regenerated. Based on the above research, a novel process for the separation of Hf from Zr by selective synergistic extraction, scrubbing and stripping has been proposed.