Synthesis of titanium oxycarbonitride by carbothermal reduction and nitridation of ilmenite with recycling of polyethylene terephthalate (PET)

Abstract

An innovative and sustainable carbothermal reduction and nitridation (CTRN) process of ilmenite (FeTiO₃) using a mixture of polyethylene terephthalate (PET) and coal as the primary reductant under an H₂–N₂ atmosphere was proposed. The use of PET as an alternative source of carbon not only enhances the porosity of the pellets but also results in the separation of Fe from titanium oxycarbonitride (TiO _xC _yN _z) particles because of the differences in surface tension. The experiments were carried out at 1250°C for 3 h using four different PET contents ranging from 25wt% to 100wt% in the reductant. X-ray diffraction (XRD), scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX), and LECO elemental analysis were used to study the phases and microstructures of the reduced samples. In the case of 75wt% PET, iron distinctly separated from the synthesized TiO _xC _yN _z phase. With increasing PET content in the sample, the reduction and nitridation rates substantially increased. The synthesis of an oxycarbonitride with stoichiometry of TiO_0.02C_0.13N_0.85 with minimal intermediate titanium sub-oxides was achieved. The results also showed that the iron particles formed from CTRN of FeTiO₃ exhibited a spherical morphology, which is conducive for Fe removal via the Becher process.

Keywords

carbothermal reduction / nitridation / polyethylene terephthalate / titanium oxycarbonitride / ilmenite

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