In this work, the effects of temperature, acid concentration, and mechanical activation on dissolution of ilmenite were studied using the statistical design of experiment technique. Mechanical activation was carried out using a planetary ball mill in dry mode, and the resulting structural changes were characterized by the particle size analysis, specific surface area measurements, and X-ray diffraction method. The results obtained indicated that intensive milling led to a significant decrease in the ilmenite particle size and that after 20 minutes, particles tended to agglomerate. However, after 90 minutes, the BET specific surface area increased to 9. 36 m2/g. In addition to surface changes, mechanical activation led to intense changes and disorders in the crystal structure of ilmenite as amorphization degree increased to 94. 30% and the volume weighted crystallite size and lattice strain changed from 346 nm and 0. 13% to 14 nm and 1. 44%, respectively. The results of the dissolution tests in the form of experimental design indicated that a suitable model could fit the experimental data in 95% confidence level. The coefficient factors for acid concentration, mechanical activation, and temperature were 3. 75%, 33. 04%, and 9%, respectively. Mechanical activation had the highest effect on titanium extraction in comparison to the other factors involved. Also in addition to its dominant effect on ilmenite dissolution, it also weakened the temperature effect. However, the results of the kinetic tests proved that mechanical activation led to promotion of the temperature effect on increasing the dissolution reaction rate in the initial stages. Finally, a dissolution yield of more than 98% was achieved through 90 minutes of activation at 95° C and 55 wt. % acid concentration.

Beneficiation of ilmenite and preparation of synthetic routile from ilmenite concentrates was used in different countries. In this work we have used a hydrometallurgical method for preparation of synthetic routile from Kahnoj (Kerman, Iran) concentrate. For removal of FeO from ilmenite crystal network (FeO.TiO2), the HSAB (Hard and Soft Acid and Bases) principle was used. Thus, the leaching of ilmenite concentrate was done with mixture of mineral acids, such sulfuric and hydrochloric acids, and hydroxylic compounds, such as methanol, ethanol and ethylene glycol. The synthetic routile with 75%purity was a result of this work.

Al2O3/TiC composites are used as cutting tools for machining gray cast iron and steels. The addition of iron improves the toughness of Al2O3/TiC composites. Ilmenite, aluminum and graphite can be used to produce in-situ Al2O3/TiC–Fe composites. However, the formation mechanism and reaction sequences of this system are not clear enough. Therefore, the present research is designed to determine the reactions mechanism of the first step of reactions that may be occurred between raw materials. In this research, pure ilmenite was synthesized to eliminate the effects of impurities available in the natural ilmenite in the system. The milled and pressed samples, prepared from the synthesized ilmenite, aluminum and graphite mixture with a molar ratio of 1:2:1, were heat treated at 720oC for 48h. In addition, two samples one containing ilmenite and aluminum with a molar ratio of 1:2 and ilmenite and graphite with a molar ratio of 1:1 were heat treated at 720°C for 48h. The final products were analyzed with XRD. It was found that at 720°C, aluminum reacts with FeTiO3, forming Fe, TiO2 and Al2O3. Since the aluminum content used in the mixture was more than the stoichiometry for reaction of ilmenite and aluminum, some unreacted aluminum remains. Therefore, the residual aluminum reacts with the reduced Fe to form Fe2Al5.

Structural changes of mechanically-activated ilmenite during milling by a planetary mill are monitored and determined as a function of the milling time. The maximum specific BET surface area of 10. 76 m2/g is obtained after 150 min of milling. The results obtained indicate that agglomeration of the particles occurs after 45 min of milling. The maximum X-ray amorphization degree of ca. 95% has been calculated after 150 min of milling. Estimation of the stored energy reveals that the X-ray amorphization degree has a dominant contribution to the excess enthalpy of the activated materials. The surface-weighted crystallite size in the ground ilmenite reaches 4. 45 nm, which corresponds to the volume-weighted crystallite size of 8 nm and 11. 18 nm obtained by the Williamson-Hall and Rietveld methods, respectively. After 150 min of mechanical activation, the root mean square strain, , increases to 0. 78%, which corresponds to the strains of 1. 43% and 1. 04% obtained from the Williamson-Hall and Rietveld methods, respectively. Reduction in the crystallite size leads to the contraction of the ilmenite unit cell after 150 min. The reaction rate constant of the ilmenite dissolution increases by over 58 times after 150 min of milling. Activation energy of the dissolution reaction decreases from 57. 45 kJ/mol to 41. 09 kJ/mol after 150 min of milling.

In this research, the first step of reactions in ilmenite-aluminum-graphite system for the formation of Al2O3-TiC/Fe composites was investigated by the study of the binary system of aluminum and ilmenite. The milled and pressed samples prepared by the synthesized ilmenite and aluminum powders having the molar ratio of 1:2 were heat treated at the critical temperatures obtained from DTA analysis. It was found that a transient Fe phase is formed along with TiO2. The spherical shaped Fe2Ti phase was then formed in the matrix consisting of TiO2 and Al2O3.

The aim of this work was to synthesize TiC reinforced coating on carbon steel via reduction of ilmenite powder. A mixture of ilmenite and graphite was pre-placed on AISI 1020 steel surface. The effect of the addition of excess graphite amounts on the progress of the synthesis of carbide particles was studied. The evolution of phases in different coatings was analyzed via X-ray diffraction and scanning electron microscopy. Then, the initial powder mixtures were mechanically activated for various durations, to accelerate the reactions in the transient melt pool. Finally, the Fe-TiC hard coating was successfully synthesized by carbothermic reduction of ilmenite through laser surface treatment. Moreover, it is proved that combination of mechanical activation with additive laser melting effectively improves the level of ilmenite reduction, besides enhancing the distribution of hard particles and the hardness of the coatings to more than 1300 HV.

The effects of surface dissolution by oxalic acid were investigated on the flotation kinetics and kinetics of collector adsorption in ilmenite flotation in the presence of olivine-pyroxene, tremolite-clinochlore and quartz. Fitting of first order kinetic model on the results of flotation before and after surface dissolution showed that flotation kinetic constant (K) and ultimate recovery (R∞, ) of ilmenite is increased after surface dissolution and they are decreased for gangue minerals. The results showed that kinetic selectivity index of ilmenite in the presence of olivine-pyroxene, tremolite-clinochlore and quartz are increased from 1. 28 to 1. 98, 1. 42 to 3. 02 and 3. 58, respectively, after surface dissolution indicating the positive effect of surface dissolution process. Investigating the kinetics of collector adsorption showed that the collector adsorption is conforming to second order kinetic model. After surface dissolution, the kinetics of collector adsorption and initial rate of collector adsorption on ilmenite surface is increased from 3. 85 to 8. 44 g. mol-1 min-1 and it is decreased for olivine-pyroxene, tremolite-clinochlore and quartz from 6. 33 to 5. 03, 7. 3 to 6. 22 and 7. 77 to 7. 37 g. mol-1 min-1, respectively. These results are in good agreements with the results of collector adsorption via UV analysis which the collector adsorption on ilmenite surface is increased and it is decreased for gangue minerals after surface dissolution. The results of SEM showed that the surface of ilmenite becomes smoother and uniform and about the gangue minerals, some cavities are produced due to dissolution of surface cations.