An Energy Efficient Process for TiO₂ Synthesis from Indian Ilmenite Ore Using Alkali Decomposition: Thermodynamic Modelling and Experimental Studies

An energy efficient route of alkali decomposition of ilmenite ore followed by leaching to produce titania with higher yield and purity has been discussed. The evolution of phases during the process steps have been studied through thermodynamic modelling and SEM and XRD analysis. It is demonstrated that NaOH is more effective in ilmenite transformation compared to Na₂CO₃ and Na₂SO₄ during the decomposition process. The effective temperature and the molar ratio of NaOH to ilmenite for the optimal conversion of ilmenite are noted as 1073 K and 2.7 mol/mol, respectively. The major titanate phases formed in the ilmenite decomposition are Na₈Ti₅O₁₄, Na₂Ti₆O₁₃, Na₂Ti₃O_7, and Na₄TiO₄, which depended upon the alkali to ilmenite ratio and temperature. Further, it is demonstrated that the roasted product required two leaching steps (water and mild acid leaching) to separate titania from iron and other impurities. The experimental evidence obtained from the XRD patterns and SEM analysis also supported the present thermodynamic calculations. The total energy demand required for the proposed process circuit was calculated as 50 MJ/kg.