Solvent extraction of tetravalent titanium from chloride solution by di-2-ethylhexyl phosphoric acid in kerosene

Abstract

The solvent extraction of Ti 4+ from chloride solution by di-2-ethylhexyl phosphoric 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, Ti 4+, H + and Cl − concentrations in aqueous phase, D2EHPA concentration in organic phase and temperature. The equilibrium is reached within 2 h. The distribution coefficient is found to be independent of Ti 4+ concentration at least up to 1 g/l Ti 4+ in the aqueous phase. The pH and log extractant concentration dependences are approximately −2 and 2, respectively. The extraction is independent of Cl − concentration. These results suggest that extraction occurs via the following reaction: TiO 2++2H 2A 2(O)⇌[TiO(HA 2) 2] (O)+2H +. The temperature dependence data give Δ H values of 30 kJ/mol in the higher temperature region (>30°C) and 78 kJ/mol in the lower temperature region (∼15°C) under investigation. The equilibrium constant, K ex at lower loading is 1×10 3.95 with a standard deviation of log K ex of 0.023. The loading capacity of D2EHPA for Ti 4+ is 7.31 g Ti(IV)/100 g D2EHPA. The loading study suggests that a variation of the extraction equilibrium reaction occurs during the course of loading. At high loading Ti 4+ is extracted by the reaction: TiO 2++H 2A 2(0)⇌[TiOA 2] (0)+2H +. The structure of the solid complex prepared from the high loaded organic phase has been established by determining the Ti/P ratio and using infrared spectroscopy.