Extraction Performance of Aminophosphorus Extractants Containing Cyclohexyl or Benzyl Group Towards Zirconium and Hafnium in Sulfate Medium

In this work, the aminophosphonate extractants bis(2-ethylhexyl)((cyclohexylamino)methyl) phosphonate (CAMP) and bis(2-ethylhexyl)((benzylamine)methyl) phosphonate (BAMP) were synthesized, and the performance of these two extractants in extracting and separating zirconium and hafnium in H2SO4 solutions was investigated. The effects of oscillation time, extractant concentration, H2SO4 concentration, and temperature on the extraction of zirconium and hafnium were systematically investigated. It was found that the reaction of extracting zirconium and hafnium by CAMP and BAMP could reach equilibrium within 1 min, and the temperature hardly affected the extraction process in the range of 289.45-318.75 K. The extraction process was an entropy- driven spontaneous reaction. With the increase of H2SO4 concentration, the extraction rate of zirconium and hafnium by CAMP and BAMP decreased, and the extraction rate of zirconium by CAMP was more obviously affected by the H2SO4 concentration. The maximum separation factors ( beta( Zr)/(Hf )) of CAMP and BAMP were 14.21 and 18.68 respectively. According to the slope analysis, it was inferred that the molecular formula of the complex formed by the extraction of zirconium and hafnium by CAMP and BAMP was MO(HSO4)(2)<middle dot>2L (where"M"was Zr or Hf, and"L"was the extractant molecule). The saturated loadings of 30% (V/V)CAMP for zirconium and hafnium were 28.2 g/L and 24.1 g/L, while those for 30% (V/V) BAMP were 27.7 g/L for zirconium and 22.2 g/L for hafnium. Additionally, 0.5 mol/L HCl could completely strip the hafnium from the loaded organic phase.