Solvent extraction of Fe 3+ from chloride solution by D2EHPA in kerosene

Abstract

The solvent extraction of Fe 3+ from chloride solution by di-2-ethylhexylphosphoric acid (D2EHPA, H 2A 2) dissolved in kerosene has been investigated over a wide range of aqueous acidity as a function of phase contact time, Fe 3+, HCl, H + and Cl − concentrations in aqueous phase, D2EHPA concentration in organic phase and temperature. The dependencies of the distribution coefficient on the concentrations of Fe 3+, H +, Cl − and D2EHPA vary with the extraction conditions used which indicates that the composition of Fe 3+ species in both the aqueous and the organic phases vary with the HCl or Cl − concentration in the aqueous phase. The experimental results are best fitted by the following equation: D=K 1x 0 [ H 2A 2 ] 3 ( O) [ H +] 3 +K 2x 1 [ H 2A 2 ] 2 ( O) [ H +] 2 +K 3x 2 [ H 2A 2 ] 1.5 ( O) [ H +] +K 4x 3[ H 2A 2 ] 1.5[ HCl] where, x 0, x 1, x 2 and x 3 are the fractions of Fe 3+, FeCl 2+, FeCl 2 + and FeCl 3 present in the aqueous phase at the particular HCl/Cl − concentration used; the values of K 1, K 2, K 3 and K 4 are found to be 1.315, 15, 12 and 320, respectively. The treatment of the temperature dependence data gives the apparent enthalpy changes (Δ H) of 125, 104, 20.8 and 33.3 kJ/mol for the extraction of the species Fe 3+, FeCl 2+, FeCl 2 + and FeCl 3, respectively. The loading of D2EHPA in the organic phase by Fe 3+ has also been investigated and the structures of the maximum loaded extracted species obtained at 0.05 and 1.0 M aqueous HCl concentrations have been demonstrated to be [FeCl(H 2O)A 2] and [FeCl 2·A·(HA) 2·(HA·HCl) 2], respectively.