Kinetics and Mechanisms of Carbothermic Reduction of Weathered Ilmenite Using Palm Kernel Shell Biomass

The kinetics and mechanisms of carbothermic reduction of a complex Kalimantan weathered ilmenite (FeTiO₃) using palm kernel biomass were investigated in the temperature range 1273–1473 K. The study included a combined thermodynamic assessment together with reduction experiments. Results were contrasted with data from similar experiments conducted using graphite as the reductant. Thermodynamic simulations showed that the major phases formed during reduction were pseudobrookite and metallic iron with reduction using biomass predicted to produce more metallic iron compared to the use of graphite in the same temperature range. Incomplete dissociation of ilmenite by biomass was noted at 1473 K and 30 min reaction time however increasing the reaction time to 180 min resulted in near complete ilmenite dissociation. The kinetic analysis indicated that the reduction process followed a diffusion-controlled mechanism. This was confirmed by a microstructural analysis that showed the reduced ilmenite grains had a three-layer structure. The microstructural analysis also revealed that pores and cracks present in the initial weathered ilmenite promoted metallic iron formation. The apparent activation energy for ilmenite reduction using biomass and graphite was determined to be 217.00 ± 0.06 kJ mol⁻¹ and 239.44 ± 0.06 kJ mol⁻¹, respectively. Based on the findings, a general micro-mechanism for the carbothermic reduction of weathered ilmenite was developed. Graphical Abstract: [Figure not available: see fulltext.]