Development of a separation process for the selective extraction of hafnium(IV) over zirconium(IV) from sulfuric acid solutions by using D2EHPA

• A new process for separation of Hf(IV) over Zr(IV) from H2SO4 solution was proposed.
• Hf(IV) was preferentially extracted over Zr(IV) from moderate H2SO4 solution by D2EHPA.
• Zr(IV) was selectively stripped over Hf(IV) by a strong H2SO4 solution with a separation factor of 10.
• Complete stripping of Hf(IV) from stripped D2EHPA was achieved by oxalic acid.
• Zr(IV) and Hf(IV) with high purity were obtained in raffinate and stripping solutions.

A new process for the separation of Zr(IV) and Hf(IV) from sulfuric acid solution by selective extraction and stripping was proposed. Firstly, Hf(IV) was preferentially extracted by di-2-ethylhexylphosphoric acid (D2EHPA) from moderate sulfuric acid solutions. From the loaded D2EHA, co-extracted Zr(IV) was selectively stripped by strong sulfuric acid solution with a separation factor of 10, leaving only Hf(IV) in the stripped D2EHPA. Hafnium(IV) was then completely stripped by oxalic acid solution and thus D2EHPA was regenerated. The McCabe–Thiele plots for the extraction and stripping isotherms were constructed and the results were verified by the simulated cross-current extraction and stripping experiments. Zirconium(IV) solutions of high purity were obtained in the extraction raffinate and sulfuric acid stripping solution, while Hf(IV) was present in the oxalic acid stripping solution.