A New Approach to Processing Rutile from Ilmenite Ore Utilizing the Instability of Pseudobrookite

Naoki Kumagai, Takehito Hiraki, Uday B. Pal, Eiki Kasai, Tetsuya Nagasaka

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Rutile (TiO2) is a vital industrial material used in pigments and in many other valuable chemicals. A new production process to synthesize rutile from natural ilmenite ore and therefore overcome the environmental problems associated with conventional rutile extraction processes was developed. Because the simple phase separation of ilmenite (FeTiO3) into Fe2O3 and TiO2 occurs due to air oxidation, extracting TiO2 by removing Fe2O3 may be possible if pseudobrookite (Fe2TiO5), known as a stable compound in the Fe2O3-TiO2 system at higher temperatures, is of unstable phase in the lower-temperature range. In order to clarify the potential of this new approach, the phase stability of pseudobrookite in the lower-temperature range is discussed. The free energy of formation of pseudobrookite from the respective pure oxides was measured at temperatures ranging from 1073 K to 1473 K by the chemical equilibrium technique using Al2O3 as the reference oxide. The observed free energy is given as a function of temperature: ∆G0 = 7715 − 7.7T (J/mol). The results indicate that pseudobrookite has an unstable phase below 929 K. This has important industrial implications as a new approach to producing synthetic rutile from ilmenite ore by oxidation at low temperatures and acid leaching.

Original languageEnglish
Pages (from-to)2278-2284
Number of pages7
JournalMetallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
Issue number5
Publication statusPublished - 2018 Oct 1


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