Stoichiometry and structural studies of Fe(III) and Zn(II) solvent extraction using D2EHPA/TBP

• Adding Cyanex 272 to D2EHPA enhanced separation V (IV) from Ni (II).
• Increasing Cyanex 272 to D2EHPA increased RV of vanadium and decreased RNi.
• Addition of TBP as a modifier raised separation factor of V (IV) over Ni (II).
• McCabe-Thiele diagrams showed two extraction stages for V (IV) and Ni (II).

The extraction equilibrium of Zn(II) and Fe(III) from chloride solution by the mixture of TBP (tri-n-butyl phosphate) and D2EHPA (di(2-ethylhexyl) phosphoric acid), diluted in kerosene was studied. The results show that in TBP to D2EHPA volume ratio of 3:1 (0.55 M TBP:0.15 M D2EHPA) ΔpH0.5 increased to about 2.5 and Fe(III) and Zn(II) extracted separately with the percentage extraction of 99% and 80%, respectively. The Fourier transform infrared (FTIR) measurements were used in order to find the possible structural functionalities of extracted species in the organic phase. Moreover, the FTIR measurements indicated that there was a hydrogen bond between TBP and D2EHPA molecules. According to FTIR studies and slope analysis method, the reaction between TBP, D2EHPA and zinc was determined and the FTIR-ATR (attenuated total reflectance) method was also employed to verify the stoichiometry of Zn(II) - organic complexes in the organic phase. Both FTIR-ATR and slope analysis methods provided the same results that the ZnA2AH·TBP was probably the extracted specie in the organic phase.