Cyanex 272 as an extractant for the extraction of tetravalent hafnium from acidic chloride solutions

Cyanex 272 as an extractant for the extraction of tetravalent hafnium from acidic chloride solutions has been investigated. Increase of acid concentration decreases the percentage extraction of metal showing that the extraction, follows an ion-exchange mechanism. The plot of log D vs log [HCl] gave a straight line with a negative slope of 1.9 indicating the exchange of two moles of hydrogen ions for every mole of Hf(IV). Extraction of Hf(IV) increases with increase of extractant concentration. The plot of log D vs log [(HA)(2)], is linear with slope 1.8 indicating the association of two moles of extractant with the extracted metal species. Based on the results, the species extracted into the organic phase was postulated to be HfO(HA(2))(2). Addition of sodium salts enhanced the percentage extraction of metal and follows the order NaSCN > Na2SO4 > NaNO3 > NaCl. Stripping of metal from the loaded organic with different acids indicated sulphuric acid as the best stripping agent. Increase of temperature during extraction stage increases the metal transfer showing the process is endothermic. Regeneration and recycling capacity of cyanex 272, IR spectra of complex, extraction behavior of associated elements such as Zr(IV), Ti(IV), Al(III) and Fe(III) were studied.