Characterisation of the reactive test system ZnSO4/D2EHPA in n-heptane

The equilibrium behaviour in n-heptane of ZnSO4/di-2-ethylhexyl phosphoric acid (D2EHPA), the reactive test system of the European Federation of Chemical Engineering has been investigated in this study at changing loading conditions. The existence of two competitive zinc-complex species ZnR2RH and ZnR2 in the organic phase has been identified using Fourier transformed infrared (FT-IR) spectroscopy method. Analysis of FT-IR spectra of the organic phase indicates the complex ZnR2RH predominates at low loading conditions while both complexes ZnR2RH and ZnR2 co-exist at intermediate and high loading conditions.