Ti-bearing Blast Furnace Slag Research Articles

The hollow spherical nano-TiO2 particles synthesized from Ti-bearing blast furnace slag and the reaction model analysis

The hollow spherical nano-TiO2 was successfully synthesized by carbon spheres as the template and Ti-bearing blast furnace slag as the Ti source. The SEM and TEM results showed that the as-synthesized TiO2 consist of uniform separated hollow spheres, and the sphere wall was composed of nanoparticles. The XRD result showed that the crystallized phase was rutile. Almost complete extraction of Ti from slag was achieved in NaOH-NaF molten salt. The kinetic analysis indicated that the slag decomposition was applied to control of chemical reaction of the reactionless core-shrinking model, and the apparent activation energy was39.54 kJ mol-1 .

Extraction of valuable metals from Ti-bearing blast furnace slag using ammonium sulfate pressurized pyrolysis–acid leaching processes

Abstract A novel method of extracting valuable metals from Ti-bearing blast furnace slag (TBBF slag) via pressure pyrolysis of recyclable ammonium sulfate (AS)–acid leaching process was proposed. The results show that when pressurized roasting at an AS-to-slag mass ratio 3:1 and 370 °C for 90 min, the extraction rates of titanium, aluminum and magnesium reached 94.5%, 91.9% and 97.4%, respectively. The acid leaching solution was subjected to re-crystallization in a boiling state to obtain a titanium product having a TiO2 content of 94.1%. The above crystallization mother liquor was adjusted to pH=6 and pH≥12.2, respectively, and then qualified Al2O3 and MgO products were obtained. The analysis through XRD and SEM–EDS proves that the main phases in roasted samples were NH4AlSO4, CaSO4 and TiOSO4. The thermodynamic analysis presents that the main minerals of perovskite, spinel and diopside in raw ore could spontaneously react with the intermediate produced by AS under optimal conditions.

Effect of rutile crystal shapes on its settlement

Abstract The effect of rutile crystal shapes on its settlement in a modified slag was studied by theoretical analysis, FactSage simulation, X-ray diffraction and scanning electron microscopy. The results show that the settling velocities of spherical rutile crystals are faster than those of other shapes of rutile crystals under the same volume conditions, and the shape transformation of rutile crystals from rod to sphere can be achieved by adding titanium slag to Ti-bearing blast furnace slag. The volume fractions of the rutile crystals in the upper and lower parts of the modified slag are 30% and 71% when the added titanium slag increases to 278 g, indicating that rutile settling is obvious. Due to the rutile settling, half shaker sorting task is saved, and the recovery rate of TiO2 is significantly increased. The TiO2 content of rutile is greater than 93%, and the total content of CaO and MgO is less than 0.4%, meeting the requirements for the raw materials of titanium white in the chloride process.

Ti3O5 and Al2TiO5 Crystals Flotation Characteristics from Ti-bearing Blast Furnace Slag: A Density Functional Theory and Experimental Study

Anosovite crystalline is an ideal mineral for flotation from the Ti-bearing blast furnace (TBBF) slag. Ti3O5 crystal and Al2TiO5 crystal are two kinds of anosovites, and the Al element significantly affects the electronic structure and flotation performance of anosovite. The floatability of Ti3O5 and Al2TiO5 crystals were studied by Mulliken populations, energy bands, and density of states (DOS). In addition, the flotation experiment of the two kinds of anosovite crystals (Ti3O5 and Al2TiO5) was conducted and proved that the density functional theory (DFT) calculation results were accurate. Compared with Ti3O5 crystal, the Fermi energy level of Al2TiO5 crystal shifts around 2 eV in a negative direction by DOS analysis, which is beneficial to flotation. And Al2TiO5 crystal possesses a larger value of bond population, which is 0.41, for Ti-O bonds than Ti3O5 crystal and the bond length of Ti-O in Al2TiO5 crystal is shorter, therefore Al2TiO5 crystal shows a stronger covalency. The changes of the Fermi energy level and the covalency bonds in Al2TiO5 crystal both demonstrated that doping the Al component into the Ti3O5 crystal was beneficial to improve the flotation effect. Moreover, the Al2TiO5 crystal had a higher flotation efficiency compared to the Ti3O5 crystal when the dosages of salicylhydroxamic acid (SHA) and sodium oleate were the same. Therefore, both DFT calculation and experiment show that the flotation effect of the Al2TiO5 crystal is better than that of the Ti3O5 crystal.

Determination of dielectric properties of titanium carbide fabricated by microwave synthesis with Ti-bearing blast furnace slag

The preparation of functional material titanium carbide by the carbothermal reduction of Ti-bearing blast furnace slag with microwave heating is an effective method for valuable metals recovery; it can alleviate the environmental pressure caused by slag stocking. The dynamic dielectric parameters of Ti-bearing blast furnace slag/pulverized coal mixture under high-temperature heating are measured by the cylindrical resonant cavity perturbation method. Combining the transient dipole and large n bond delocalization polarization phenomena, the interaction mechanism of the microwave macroscopic non-thermal effect on the titanium carbide synthesis reaction was revealed. The material thickness range during microwave heating was optimized by the joint analysis of penetration depth and reflection loss, which is of great significance to the design of the microwave reactor for the carbothermal reduction of Ti-bearing blast furnace slag.

Removal of arsenic in groundwater using Slag based calcined layered double hydroxides (CLDHs) with dual functions of adsorption and photo-catalysis

We employed Ti-bearing blast furnace slag (Ti-BFS) as raw material to prepare calcined TiO2-loaded layered double hydroxides (TiO2-CLDHs) through acidolysis-alkali precipitation coupled with pyrolysis strategy. During the pyrolysis process, the involvement of TiO2 and LDHs made the TiO2-CLDHs composites have superior photocatalytic ability and abundant porosities, resulting in highly-efficient removal of arsenic (As) from groundwater. Meanwhile, OH played crucial role in the As(III) oxidation process through the results of Electron-spin resonance spectroscopy (ESR) and X-ray photoelectron spectroscopy (XPS) measurements. In addition, the co-existing of humic acid in groundwater was found to compete for OH and adsorption sites of TiO2-CLDHs, leading to a decrease in As removal. This study not only provided a novel strategy for Ti-BFS disposal, but also evaluated the application of TiO2-CLDHs in the treatment of As contaminants in groundwater environment.

An approach for simultaneous treatments of diamond wire saw silicon kerf and Ti-bearing blast furnace slag

Both diamond wire saw silicon kerf (DWSSK) and Ti-bearing blast furnace slag (TBBFS) are largely accumulated industrial wastes and important resources of Si and Ti. Currently, both are treated using independent approaches. In this study, a novel approach is proposed to simultaneously extract Ti from TBBFS to prepare TiO2 and recycle Si from DWSSK to prepare high-purity Si. Firstly, DWSSK (86.9 % Si) was employed as a reductant to extract Ti from TBBFS to prepare bulk Si-Ti alloys, and the largest extraction rate was 99.4 %. Secondly, Si and Ti in the bulk Si-Ti alloy were separated using a HF-containing acid solution. Ti in the Si-Ti alloy dissolved into the HF-containing acid solution, and high-purity Si was obtained after acid leaching. The purity of Si in DWSSK increased from 86.9% to 99.94%. Thereafter, a NaOH solution was used to precipitate Ti(OH)4 from the HF-containing acid solution, and TiO2 was prepared by roasting Ti(OH)4. Notably, the new approach had the advantage of concurrently eliminating impurities while recycling DWSSK. Finally, NaOH and HF solutions were used to prepare high-purity NaF (>98 %) to treat the waste solutions. The results of this study provides a new and sustainable technology for clean utilization of DWWSK and TBBFS.

Mechanochemical activation of titanium slag for effective selective catalytic reduction of nitric oxide

Ti-bearing blast furnace slag was usually recycled by acid leaching. For the first time, a catalyst was synthesized from the slag by wet ball-milling. During this process, no waste was produced. When the activated slag was used in selective catalytic reduction of nitric oxide (NO), 80.5 ± 1.2% of NO (990 ppm) was removed at 350 °C. The catalyst steadily removed 91.0 ± 1.3% of NO for 900 min at 400 °C. On the contrary, the slag without activation showed almost no catalytic activity at these temperatures. The enhanced activity was mainly attributed to the following characterizations. After wet ball-milling, specific surface area of the slag was increased from 2.595 to 26.497 m2/g; surface acid sites were amplified by 15 times; Fe/Ti ratio on surface was enhanced from 0.20 to 1.10. At the same time, surface Fe2+/Fe3+ was regulated from 0.43 to 0.53. The above enhanced properties were attributed to the mechanochemical activation, which dissolved and re-deposited active species on particle surface as well as reinforced the effect between Fe and Ti species. The main result of this work put forward a green method for the direct utilization of industrial waste without generating by-products.

Reinforce of hydrotalcite-like loaded TiO2 composite material prepared by Ti-bearing blast furnace slag for photo-degradation of tetracycline

In this study, a composite material of hydrotalcite-like loaded TiO2 (TiO2@Mg-Al LDH) was prepared from Ti-bearing blast furnace slag (Ti-BFS) and used for photo-catalytic degradation of tetracycline (TC) in aqueous solution. The results of SEM, XRD, XRF, FT-IR, BET and UV-Vis DRS showed that photocatalytic TiO2@Mg-Al LDH was layered double hydroxide loading TiO2 structure and doped with metal elements, which could effectively induce the excitation wavelength of TiO2 to extend from UV to visible region. At the initial TC of 20?mg/L, the removal rate of TC and TOC were more than 90% and 72% within 120?min using UV in combination with TiO2@Mg-Al LDH. The radical quenching tests and EPR analysis indicated that TC degradation and mineralization were attributed to production of abundant OH• radicals, •O2- and h+ under UV conditions, which performed different proportion of removal, compared with adsorption experiment under non-light irradiation. Qualitative analysis of the by-products showed the aromatic ring of TC was opened, which effectively reduced the virulence of by-products. It indicated that the synergistic effect of hydrotalcite-like structure and photocatalysis could achieve efficient photodegradation of TC by TiO2. TiO2@Mg-Al LDH synthetized by high Ti-bearing blast furnace slag presented a good prospect of removing trace organic pollutants under synergistic effect of adsorption and UV photo-catalytic.

Combined Effect of SiO2 and O2 on the Crystallization Behavior of Modified Ti-Bearing Blast Furnace Slag.

FactSage simulation, X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled to energy-dispersive spectroscopy (EDS) analyses were performed to explore the combined influence of SiO2 and O2 on the crystallization behavior of modified Ti-bearing blast furnace slag. The results of FactSage simulation showed that an increase in the added amount of SiO2 was beneficial to the conversion of Ti-bearing minerals into simple titanium oxides. An increase in oxidation time was conducive to the transformation of low-valent titanium oxides to tetravalent titanium oxide. Therefore, Ti components were precipitated only in the form of rutile under the optimal added amount of SiO2 (40 g) and the optimum oxidation time (126 s). The results of XRD and SEM analyses were well in agreement with the results of FactSage simulation. Moreover, the mechanism of formation of rutile and glassy phases was discussed.

Novel approach for clean utilization of complex low-grade metal resources using silicon as metal getter

A method to utilize complex low-grade metal resources cleanly is necessary for the sustainable development of resources and the environment. Si is a widely consumed material in the semiconductor and photovoltaic industries; however, its purity must be upgraded for specific uses. In this study, inexpensive low-purity Si (∼99.32%) was employed as a metal getter to clean accumulated low-grade metal resources by extracting valuable elements from the low-grade resources and to make the manufacture of high-purity Si (∼99.99%) possible. Two common low-grade metal resources were employed in the study as examples: 1) a Ti-bearing blast furnace slag containing Ti and V and 2) a spent automotive catalyst containing Zr, rare-earth elements (Ce, Nd, and La) and platinum group metals (Pt, Pd, and Rh). First, the valuable elements were extracted from the low-grade metal resources using Si to prepare the Si–valuable-element alloy. The extraction process released no carbon gas, because Si acted as both a reductant and a metal getter. Then, the extracted valuable elements were observed to concentrate at the grain boundaries of Si crystals during the solidification process. Finally, the concentrated valuable elements were completely discharged into lixiviants with a minor loss of the Si matrix, i.e., the concentrated valuable elements could be completely separated from the Si matrix through acid leaching. The purity of the Si matrix was significantly enhanced after acid leaching, and high-purity Si was prepared. The high-purity Si, an important high-value byproduct, can be utilized in the semiconductor and photovoltaic industries after further purification or recycled again as a metal getter to treat low-grade metal resources repetitively. This new approach is a promising method for the large-scale treatment of other complex low-grade metal resources.

Recovery of rutile from Ti-Bearing blast furnace slag through phase transformation and super-gravity separation for dielectric material

High-purity rutile (TiO2) possessing favorable dielectric properties was sustainably recovered from Ti-bearing blast furnace slag through phase transformation and super-gravity separation in this study. Firstly, the phase transformation behavior of Ti was studied, the favorable conditions for transformation from perovskite to rutile were determined, and the Ti elements were efficiently enriched into rutile in the Ti-bearing blast furnace slag. Subsequently, the condition for solid and liquid phases of rutile and slag in coexistence was acquired by high-temperature CSLM, the rutile was effectively recovered from the Ti-bearing blast furnace slag through super-gravity separation, and its high purity was verified by the results of XRD, SEM-EDS, XRF, EPMA and Raman. Moreover, the rutile ceramic was prepared, and its dielectric properties were investigated, the dielectric constant was up to around 200, and the dielectric loss was as low as 0.0047 at about 900 Hz. The excellent frequency stability, high dielectric constant and low dielectric loss of the rutile recovered from Ti-bearing blast furnace slag reflect its favorable energy storage capability for dielectric material.

The Online Research of B2O3 on Crystal Behavior of High Ti-Bearing Blast Furnace Slag

The existence and phase structures of high Ti-bearing blast furnace slag at a high temperature are the key issue to flow performance and reaction temperature. It is essential to evaluate the physical-chemical properties, such as viscosity and melting point In this work, a new method of online research of B2O3 on crystal behavior of high Ti-bearing blast furnace slag is proposed. By ultrahigh-temperature confocal laser scanning microscope and area scanning analysis, it can be concluded that the effect of B2O3 additives on the viscosity has a more obvious effect among the low-temperature region of the slag. Compared to the samples without B2O3 additives, the liquid phase of Ti-bearing slag with B2O3 additives appears earlier at the same experimental temperature, and the solid particles floating on the surface of liquid slag become less. Moreover, the B2O3 additives can promote the migration of titanium elements from the high melting point phase to the low melting point phase, and the transferring quantity increases with the addition of the amount of B2O3 additives. These results demonstrate that B2O3 additives can restrain the appearance of the perovskite phase, decrease the apparent viscosity, and promote the metallurgical properties of Ti-bearing blast furnace slag.

1250°C liquidus for the CaO–MgO–SiO2–Al2O3–TiO2 system in air

Ti-bearing blast furnace slags have been regarded as an important secondary material in modern society, and the efficient recycling of Ti oxides from it is of key interest. For this reason, more thermodynamic data is needed regarding the phase relations in different composition ranges and sections. Therefore, the equilibrium phase relations of CaO–MgO–SiO2–Al2O3–TiO2 system in a low w(CaO)/w(SiO2) ratio of 0.6–0.8 at 1250 °C in air and fixed concentrations of MgO and Al2O3, were investigated experimentally using a high temperature equilibration and quenching method followed by SEM-EDS (Scanning Electron Microscope and Energy Dispersive X-ray Spectrometer) analyses. The equilibrium solid phases of perovskite (CaO·TiO2), a pseudo-brookite solid solution (MgO·2TiO2, Al2O3·TiO2)ss, and anorthite (CaO·Al2O3·2SiO2) were found to coexist with the liquid phase at 1250 °C. The calculated results of Factsage and MTDATA were used for comparisons, and significant discrepancies were found between predictions and the experimental results. The 1250 °C isotherm has been constructed and projected on the CaO–SiO2–TiO2-8 wt.% MgO-14 wt% Al2O3 quasi-ternary plane of the phase diagram. The obtained results provide new fundamental data for Ti-bearing slag recycling processes, and they add new experimental features for thermodynamic modeling of the high-order titanium oxide-containing systems.

Titanium Recovery from Ti-Bearing Blast Furnace Slag by Alkali Calcination and Acidolysis

This research mainly focuses on recovery of titanium from Ti-bearing blast furnace slag using the process of alkali calcination, water leaching, and acid hydrolysis. The Ti-bearing blast furnace slag contained approximately 24% SiO2, 12.73% Al2O3, and 20.74% TiO2. The main minerals in the slag were perovskite, diopside, and spinel. In the calcination process, the chemical products were NaAlO2, Na2SiO3, Na2CaSiO4, and Na2TiO3. In the leaching process, NaAlO2 and Na2SiO3 dissolved in water, Na2CaSiO4 remained in the water-leached product, and Na2TiO3 was hydrolyzed to an amorphous state. After alkali calcination and water leaching, 45% of SiO2 and 83% of Al2O3 were removed, while the TiO2 content increased to 36.13%. The extraction rate of titanium was 91.21% after hydrolysis by dilute sulfuric acid at 120°C for 2 h of the water-leached product, and nano-anatase TiO2 was obtained by hydrolysis and calcination of the resulting titanyl sulfate solution.

A novel approach to prepare high-purity Si and Si/TiSi2 materials simultaneously using Ti-bearing blast furnace slag

A new approach was proposed to prepare multi-products, high-purity Si powders, bulk Si, and Si/TiSi2 materials (eutectic Si-Ti), simultaneously using inexpensive low-purity Si (99.3%) and metallurgical waste—Ti-bearing blast furnace slag. TiO2 in Ti-bearing blast furnace slag was first reduced by Si to form a Si-Ti alloy which was then separated into high-purity bulk Si (99.97%) and Si/TiSi2 materials (99.4%) using directional solidification. The bulk Si could be repeatedly recycled as a reductant, or further upgraded to prepare super-pure Si powders (99.995%) after acid leaching. The new approach shows many sustainable and economic benefits, such as no carbon gas emission, low acid consumption and Si loss, recyclable Si reductant, widely-used multi-products employing one approach, and rapid consumption of accumulated Ti-bearing blast furnace slag.

Conversion of CaTi1–xMnxO3–δ-Based Photocatalyst for Photocatalytic Reduction of NO via Structure-Reforming of Ti-Bearing Blast Furnace Slag

In this work, a novel low-cost and robust approach is developed to covert Ti-bearing blast furnace slag (Ti-slag) to the main feed stock of photoassisted NH3 selective catalytic reduction (Photo NH...

Effects of different substrates on nitrogen and phosphorus removal in horizontal subsurface flow constructed wetlands.

This study aimed to explore the nitrogen and phosphorus removal performance of the horizontal submerged constructed wetland (HSCW) with Ti-bearing blast furnace slag (T). Another two HSCWs, with the converter steelmaking slag (G) and the stone (S) as wetland substrates, respectively, were simultaneously running as control. The results showed that the nitrogen and phosphorus removal capacities of the T-HSCW were generally better than those of another two HSCWs. When the hydraulic retention time (HRT) was 6days, the effluent concentrations of ammonia nitrogen (NH4+-N) and total nitrogen (TN) were 6.66mgL-1 and 14.02mgL-1, respectively, and the removal rates of NH4+-N and TN reached 77.54% and 71.07%, respectively. The T-HSCW had better removal efficiency of phosphorus. The effluent concentration of total phosphorus (TP) was lower than 0.3mgL-1, and the maximum removal rate could reach 98%. Through the characterization of the three substrates before and after experiments, it was found that the removal of nitrogen and phosphorus by T and G mainly relied on chemical adsorption, while S mainly relied on physical adsorption. Ti could also promote the absorption of nitrogen by plants and increase the nitrogen removal capacity of T-HSCWs.

An approach to employ titanium-bearing blast-furnace slag to prepare Ti and Al–Si alloys

Ti-bearing blast-furnace slag is a metallurgical waste but a promising Ti resource. In this study, Ti and Al–Si alloys can be prepared directly by separating a Ti–Si–Al alloy that was prepared by reducing Ti and Si from Ti-bearing blast-furnace slag with Al. The technology of directional solidification with electromagnetic force was employed to carry out the separation of the Ti–Si–Al alloy. When additions of CaO and Al were 24 wt% and 40 wt%, respectively, the composition of the obtained Ti–Si–Al alloy was 31.8 wt% Ti, 22.7 wt% Si, 28.5 wt% Al, and 10.2 wt% Fe. Ti5Si4, TiSi, Al–Si–Ti (τ2), Al–Si–Fe (τ4), and Al–Si alloys were prepared in sequence after separating the Ti–Si–Al alloy using directional solidification with electromagnetic force. However, when the composition of the Ti–Si–Al alloy was changed to 21.2 wt% Ti, 48.5 wt% Si, 19 wt% Al, and 6.8 wt% Fe, the TiSi2, Si, Al–Si–Fe and Al–Si alloys were prepared in sequence. This study will propose an approach to employ the metallurgical waste, titanium-bearing blast-furnace slag, to prepare Ti and Al–Si alloys.

Phase Equilibrium Investigation for CaO-SiO<sub>2</sub>-5wt.%MgO-20wt.%Al<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> System Relevant to Ti-bearing Slag System

In order to resolve the lack of thermodynamic information for the comprehensive unilization of Ti-bearing blast furnace slag, the phase diagram relevant to the Ti-bearing slag composition was widely investigated. In the present work, the phase equilibrium relationships were investigated for the CaO-SiO2-5wt.%MgO-20wt.%Al2O3-TiO2 phase diagram system. The equilibrium phases were experimentally determined at 1300°C and 1400°C using the high temperature equilibrium technique followed by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscope (EDX) analysis. The liquid phase (L), melilite solid solution ((2CaO·MgO·2SiO2, 2CaO·Al2O3·SiO2)ss) phase, perovskite (CaO·TiO2) phase, Al–Ti diopside phase and pseudobrookite solid solution (MgO·TiO2, Al2O3·TiO2)ss phase were found. Based on the experimental results, the 1300°C to 1500°C liquidus lines and phase diagram were constructed for the specified region of the CaO-SiO2-5wt.%MgO-20wt.%Al2O3-TiO2 system.