Selective Extraction of Zr(IV) over Hf(IV) from Aqueous Hydrochloric Acid with p-tert-Butylcalix[4]arenediphosphonic Acid

p-tert-Butylcalix[4]arenediphosphonic acid (L) extracts Zr(IV) and Hf(IV) from aqueous HCl, H2SO4, and H3PO4. In the extraction from aqueous HCl of different concentrations, the percentage of extra...