Migration and Enrichment Behaviors of Ca and Mg Elements during Cooling and Crystallization of Boron-Bearing Titanium Slag Melt

Synthetic rutile was prepared from titanium slag melt with low energy consumption and a small amount of additive (B2O3) in our previous work. The modification mechanism of titanium slag was not clear enough. The migration and enrichment behaviors of Ca and Mg elements during cooling and crystallization of boron-bearing titanium slag melt were characterized by XRF, FESEM, EMPA, and XPS. Results show that when additive (B2O3) is added, Ti elements are migrated and enriched in the area to generate rutile, while Ca, Mg, and B elements are migrated and enriched in another area to generate borate. With the additive (B2O3) amount increased, Ca and Mg element migration is complete and more thorough. Additive (B2O3) promotes rutile formation and inhibits the formation of anosovite during cooling and crystallization of titanium slag melt. With the additive (B2O3) amount increasing from 0% to 6%, the proportion of Ti3+ in the modified titanium slag reduces from 9.15% to 0%, and the proportion of Ti4+ increases from 90.85% to 100% under the same cooling and crystallization condition. The result will lay the foundation for the efficient preparation of synthetic rutile by adding B2O3 to the titanium slag melt.

A comparative study on the chloride effectiveness of synthetic rutile and natural rutile manufactured from ilmenite ore

Studies on continuous and selective chlorination by using ilmenite have been actively conducted because the efficient removal of FeO from ilmenite(FeTiO3) ore using selective chlorination not only improves the reaction purity of TiCl4 but it also leads to price competitiveness compared to TiCl4 synthesized from natural rutile. The chlorination of synthetic rutile with FeO removed was compared with that of natural rutile to examine the reaction efficiency. The selective chlorination efficiency depends on the input amounts of coke and Cl2, as shown by thermodynamic calculation, when FeO is selectively removed. It was found that manufacturing of TiCl4 was easier by using the synthetic rutile, because it had greater porosity than natural rutile. Relatively greater pore volumes were found in the synthetic rutile than in natural rutile. It was confirmed that the reaction efficiency of chlorination for TiCl4 production was directly related to the difference in the porosity distribution between the titanium ores, as verified by a kinetic comparison of synthetic and natural rutiles.

Direct electrochemical production of pseudo-binary Ti–Fe alloys from mixtures of synthetic rutile and iron(III) oxide

Combining the FFC-Cambridge process with field-assisted sintering technology (FAST) allows for the realisation of an alternative, entirely solid-state, production route for a wide range of metals and alloys. For titanium, this could provide a route to produce alloys at a lower cost compared to the conventional Kroll-based route. Use of synthetic rutile instead of high purity TiO2 offers further potential cost savings, with previous studies reporting on the reduction of this feedstock via the FFC-Cambridge process. In this study, mixtures of synthetic rutile and iron oxide (Fe2O3) powders were co-reduced using the FFC-Cambridge process, directly producing titanium alloy powders. The powders were subsequently consolidated using FAST to generate homogeneous, pseudo-binary Ti–Fe alloys containing up to 9 wt.% Fe. The oxide mixture, reduced powders and bulk alloys were fully characterised to determine the microstructure and chemistry evolution during processing. Increasing Fe content led to greater β phase stabilisation but no TiFe intermetallic phase was observed in any of the consolidated alloys. Microhardness testing was performed for preliminary assessment of mechanical properties, with values between 330–400 Hv. Maximum hardness was measured in the alloy containing 5.15 wt.% Fe, thought due to the strengthening effect of fine α phase precipitation within the β grains. At higher Fe contents, there was sufficient β stabilisation to prevent α phase transformation on cooling, leading to a reduction in hardness despite a general increase from solid solution strengthening.

Removal of Metallic Iron from Reduced Ilmenite by Aeration Leaching

Aeration leaching was used to obtain synthetic rutile from a reduced ilmenite. The reduced ilmenite, obtained from the carbothermic reduction of ilmenite concentrate in a rotary kiln at about 1100 °C, contained 62.88% TiO2 and 28.93% Metallic iron. The particle size was about 200 μm and the size distribution was uniform. The effects of NH4Cl and HCl concentrations, stirring speed, and aeration leaching time on the extent of removal of metallic iron from the reduced ilmenite were studied at room temperature. The results revealed that aeration leaching is feasible at room temperature. When using the NH4Cl system, the metallic iron content was reduced to 1.98% in synthetic rutile, but the TiO2 content only reached 69.16%. Higher NH4Cl concentration did not improve the leaching. Using 2% NH4Cl with 3% HCl, we were able to upgrade the synthetic rutile to 75%, with a metallic iron content as low as 0.14% and a total iron content of about 4%. Synthetic rutile could be upgraded to about 90% using HCl solution alone. HCl and NH4Cl are both effective on the aeration leaching process. However, within the scope of this experiment, hydrochloric acid is more efficient in aeration leaching.

The Manufacture of Synthetic Rutile by Solvent Extraction of Tri-Alkyl Phosphine Oxide from HCl Leaching Solution of Soda-Roasted Ilmenite Ore

To manufacture TiO2, a high-purity synthetic rutile, the recovery of Ti was investigated using a hydro-metallurgical process. Using a feed solution containing 32050 mg/L Ti, 110 mg/L Si, 88 mg/L Nb, 2614 mg/L Fe, and 130 mg/L Zr, solvent-extraction experiments were conducted with alkyl phosphine oxide in conjunction with diluents such as kerosene and xylene. The results showed that the extraction mechanism of both diluents was very similar to slope analysis, which had a value of 1.9; however, the extraction equilibrium constant value of organic–metallic species in xylene as a diluent was lower than in kerosene as a diluent. This result affected the stripping efficiency of Ti in particular; therefore, xylene was selected as a diluent. To recover Ti ion from a leaching solution, a series of experiments was conducted, such as the McCabe–Thiele method and countercurrent simulation test for extraction and stripping of Ti. As a result, Ti and impurities such as Fe and Zr were extracted to 99.9% from Si and Nb under optimal conditions using countercurrent four-stage extraction, with 1 M Cyanex 923 at a ratio of organic phase/ aqueous phase=3. In the stripping test, Ti was selectively stripped to 90.1% from Fe and Zr in the organic phase by 1 M HCl. The obtained powder, which was hydrolyzed from an impurity-free solution, was analyzed to a purity of 99.9% by inductively coupled plasma. The TiO2, which has a spherical shape and a diameter of approximately 2 µm according to SEM, was evident by XRD.

The Upgrading of Ha Tinh Ilmenite to Synthetic Rutile by Becher Process

Becher process was applied for upgrading Ha Tinh ilmenite concentrate (54-55% TiO2) to synthetic rutile. The process includes reduction of ilmenite concentrate using anthracite coal as reductant, followed by aeration of reduced ilmenite in ammonium chloride solution (NH4Cl). The controlled parameters were temperature and NH4Cl concentration. The results showed that the degree of iron metallization was 83% after 4 hours of reduction at 1150 °C. Most of the metallic iron (98%) was successfully rust after 9 hours of aeration at 70°C, 7/1 of liquid/solid ratio (L/R), 4 liter/minutes (L/min) of air flow rate and 0.5% of NH4Cl concentration. The addition of acetic acid or citric acid in to the aeration solution has facilitated the aeration process. The aeration time could be vastly reduced when ammonium chloride solution used in aeration was replaced by the mixture of CH3COOH 0.075M and CH3COONa. Leaching with H2SO4 15% has improved TiO2 content from 82% in the aerated ilmenite to approximately 89% in synthetic rutile. The research work has proved that Becher process is applicable for the beneficiation of Ha Tinh ilmenite concentrate.