Catalytic leaching of ilmenite using hydrochloric acid: A kinetic approach

• The chemical kinetics of ilmenite leaching with hydrochloric acid was studied under different conditions.
• The enthalpy and entropy of the reaction were calculated.
• The positive value of ΔH indicates the endothermic reaction.
• The negative value of ΔG the spontaneous nature of the reaction.
• The addition of gypsum enhances the leaching process.

The iron content present in the ilmenite is removed by leaching the ore with hydrochloric acid. The enriched TiO2 mineral thus obtained is called synthetic rutile (SR) or beneficiated ilmenite (BI). The quality of the synthetic rutile (in terms of TiO2 content) mainly depends on the condition of leaching process. The present study envisages the effect of acid concentration, temperature, and agitation speed on the leaching of the ore. The kinetics of the leaching reaction follows the first order at normal and stimulated leaching conditions. The highest rate constant value of 5.18 × 10− 3 min− 1 was observed for leaching the ilmenite with 30% hydrochloric acid under 700 rpm and at 70 °C. The enthalpy of the reaction (ΔH) was calculated as 24.157 kJ/mol and the entropy of the reaction (ΔS) was calculated as 26.25 J/mol/K. The positive value of ΔH indicates the endothermic nature of reaction. The value of ΔG at different temperature was found to be negative indicating the feasibility of the process and the spontaneous nature of the reaction. The addition of gypsum enhances the leaching process. The rate constant increases with the increase in the gypsum concentration in leaching process. The rate constant increased to 6.15 × 10− 3 min− 1 by introducing 100 mg of gypsum in the leaching process carried out with 30% hydrochloric acid at 70 °C and 500 rpm.

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