Experimental Study on Ion Exchange Equilibria between Ilmenite Solid Solution (Fe²⁺, Mn²⁺, Mg)TiO₃ and Aqueous (Fe²⁺, Mn²⁺, Mg)Cl₂ Solution

Abstract

Ion exchange experiments between ilmenite solid solution (Fe²⁺, Mn²⁺, Mg)TiO₃ and 1 molal aqueous (Fe²⁺, Mn²⁺, Mg)Cl₂ solution were carried out using standard cold-seal type pressure vessels at 600°C and 1000kg/cm². The ion exchange reactions can be expressed as follows;FeTiO₃+MnCl_2aq=MnTiO₃+FeCl_2aqMnTiO₃+MgCl_2aq=MgTiO₃+MnCl_2aqand MgTiO₃+FeCl_2aq=FeTiO₃+MgCl_2aq. Under the experimental conditions, FeTiO₃, MnTiO₃ and MgTiO₃ make a perfectly continuous solid solution. Based on thermodynamic analysis using ternary solid solution model of Kakuda et al. (1991), interaction parameters (W_i) for the ternary ilmenite solid solution have been obtained to be W_FeFeMn=-0.02, W_FeMnMn=-0.19, W_MnMnMg=2.99, W_MnMgMg=3.34, W_MgMgFe=1.23, W_MgFeFe=1.03 and W_FeMnMg=1.83kcal/mol. FeTiO₃-MnTiO₃ solid solution is regarded as ideal solution, and MnTiO₃-MgTiO₃ and MgTiO₃-FeTiO₃ solid solutions show positive deviations from ideal solution. Ferrous ion is preferably partitioned into ilmenite solid solution. On the other hand, manganese ion tends to concentrate into aqueous chloride solution.