Thermodynamics, phase transformations, and theoretical perspective of roasting kinetics during sulfurization and carbothermic reduction of Ilmenite

Global demand for titanium-based materials requires more sustainable and cost-effective upgrading routes for ilmenite. This study presents a thermodynamic, phase transformation, and theoretical kinetic analysis of ilmenite roasting via combined sulfurization and carbothermic reduction, uniquely employing coconut-shell-derived biochar as a low-cost, renewable carbon source. Thermodynamic modelling identifies the stability regions of iron sulphides and titanium oxides, showing that carbothermic reactions become spontaneous above 500–600 °C with ΔG values of − 116.3, − 52.3, and − 64.1 kJ/mol at 1000 °C, while sulfurization reduction is thermodynamically feasible throughout 0–1500 °C with ΔG = − 201.6 kJ/mol at 800 °C. Experimental roasting and Rietveld phase analysis quantify the evolution of Fe- and Ti-bearing phases, and kinetic trends are discussed in terms of temperature dependence. The findings provide fundamental insights into the thermodynamics, phase evolution, and reaction trends during ilmenite carbothermic and sulfurization reduction. Further studies, including pilot-scale testing and process optimization, are necessary to assess industrial applicability and to develop a scalable, sustainable ilmenite upgrading route.