Effects of mechanical activation modes on microstructural changes and reactivity of ilmenite concentrate

Abstract Mechanical activation of ilmenite in dry and wet milling modes was carried out by a planetary ball mill. Characterization of microstructural changes and their influences on the dissolution of Ti were studied. The characterizations were performed by XRF, EPMA, XRD, UV–Visible spectroscopy, SEM, particle size analysis and surface area measurement. The results showed that the dry milling mode after 45 min led to an intensive agglomeration of particles with available pores for nitrogen gas. The specific BET surface area was steadily increased to 10.77 m2/g after 150 min of dry milling. The maximum BET surface area of 12.06 m2/g was measured after 150 min of milling in wet mode. It was found that the dry mode of activation has a pronounced impact on structural changes compared with wet mode milling as a result of intensive stressing. The X-ray amorphization degrees of 95.03 and 68.60% were achieved after 150 min of dry and wet milling, respectively. A minimum volume weighted crystallite size equal to 8.01 nm and a maximum lattice strain equal to 1.43 × 10−2 were obtained for the dry mode of milling after 150 min of activation. It was concluded that the dry mode of activation generated a deeper and more intensive distortion in ilmenite bulk compared with the wet mode of milling. Dissolution experiments indicated that, in comparison to the specific surface area, the structural distortion had the predominant effect on the reactivity of ilmenite. According to the leaching results, dissolution rate in dry and wet milled ilmenites after 150 min of milling, has been increased by 58.43 and 14.66 times, respectively. In addition, Ti extractions of 93% and 70% were achieved after 150 min of activation in dry and wet modes, respectively.