Search Results (16)

This study developed a hydrothermal-crystallization coupling strategy for selective titanium extraction from low-grade titanium-bearing blast furnace slag. Systematic parametric optimization revealed that an optimum titanium extraction efficiency of 92.3% was achieved under mild hydrothermal conditions. Phase evolution analysis demonstrated that the leaching residues comprised commercially valuable calcium oxalate hydrate and amorphous silica aggregates, while titanium primarily existed as stable Ti(OH)₂(C₂O₄)₂²⁻ complexes in the leachate. Subsequently, 99.4% of titanium in the leachate was precipitated through the hydrothermal decomposition method, and mixed-phase titanium oxides with a grade of 90.5% were obtained through alkaline washing. Comparative analysis highlights three notable advantages over conventional metallurgical processes: (1) selective extraction specificity for low-concentration titanium minerals, (2) process intensification through integrated hydrothermal-crystallization operations, and (3) environmental benignancy via reagent recyclability. Full article

Ti-bearing blast furnace slag (TBFS) can be converted to impurity bearing TiOSO₄ solution for TiO₂ pigment production. However, the H₂TiO₃ (MTA) hydrolyzed from the solution has too high Fe/V impurity to meet the standard for TiO₂ pigment. In this study, we found that Fe³⁺ and V³⁺ were easily hydrolyzed and entered the MTA lattice, and hence could not be removed by washing. Furthermore, Fe/V was hard to co-remove by the traditional reduction method. Therefore, the Fe/V non-hydrolysis condition (Ti³⁺ = 0.01 M, F = 3.0, T = 130 °C; Ti³⁺ = 0.01 M, F = 3.5, T = 150 °C) was determined by thermodynamic calculations. However, at these conditions, the Ti hydrolysis ratio was low or the reaction time was long. Therefore, a new two-step hydrothermal hydrolysis process was proposed. Step 1 (130 °C, 2 h) ensured the non-hydrolysis of V³⁺, and Ti was partially hydrolyzed to increase the H₂SO₄ concentration. Step 2 (150 °C, 2 h) ensured a high Ti hydrolysis ratio (>0.95) and short total reaction time (4–6 h). Finally, a high-purity MTA was obtained (Fe = 21 ppm, V = 145 ppm). These results provide new insights into the control of the hydrolysis of impurity ions in solutions and help to optimize the process of TiO₂ pigment preparation from TBFS. Full article

A porous geopolymer with adsorption and photocatalytic degradation functions was successfully developed by utilizing Ti-bearing blast furnace slag (TBBFS) as the raw material. The prepared porous geopolymers were characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, and Fourier transform infrared spectrum. Selective crystallization, water quenching, and natural cooling methods were employed to investigate the influences of these modifications on the applicability of TBBFS as a precursor for geopolymer synthesis. Water-quenched slag with amorphous content was prone to alkali dissolution, and the resulting geopolymer exhibited the highest adsorption capacity (97.18 mg/g) for methylene blue (MB) removal. Selective crystallization at 1400 °C generated a hybrid microstructure consisting of a non-cementitious CaTiO₃ crystallization phase and a cementitious amorphous fraction. The retention of CaTiO₃ in the final geopolymer enables a bifunctionality in adsorption–photodegradation. Particularly, the adsorption and photodegradation processes under various conditions were investigated. The superior removal efficiency for MB could be attributed to the synergistic effects between the geopolymer matrix and CaTiO₃, leading to an enhancement in the formation of hydroxyl radicals. The conversion of TBBFS into porous geopolymer offers an efficient and straightforward solution for slag utilization and dye removal. Full article

The extraction of titanium-bearing components in the form of CaTiO₃ is an efficient utilization of blast furnace slag. The photocatalytic performance of this obtained CaTiO₃ (MM-CaTiO₃) as a catalyst for methylene blue (MB) degradation was evaluated in this study. The analyses indicated that the MM-CaTiO₃ had a completed structure with a special length–diameter ratio. Furthermore, the oxygen vacancy was easier to generate on a MM-CaTiO₃(110) plane during the photocatalytic process, contributing to improving photocatalytic activity. Compared with traditional catalysts, MM-CaTiO₃ has a narrower optical band gap and visible-light responsive performance. The degradation experiments further confirmed that the photocatalytic degradation efficiency of pollutants by using MM-CaTiO₃ was 3.2 times that of pristine CaTiO₃ in optimized conditions. Combined with molecular simulation, the degradation mechanism clarified that acridine of MB molecular was stepwise destroyed by using MM-CaTiO₃ in short times, which is different from demethylation and methylenedioxy ring degradation by using TiO₂. This study provided a promising routine for using solid waste to obtain catalysts with excellent photocatalytic activity and was found to be in keeping with sustainable environmental development. Full article

As the byproduct in the smelting process of vanadium titano-magnetite, titanium-bearing blast furnace slag (TBFS) can be converted to a titanyl sulfate (TiOSO₄) solution containing MgSO₄ and Al₂(SO₄)₃ impurities via dissociation by concentrated H₂SO₄ (80–95%) at 80–200 °C, followed by leaching with H₂O at 60–85 °C. In this study, hydrated TiO₂ was prepared by hydrothermal hydrolysis of a Mg/Al-bearing TiOSO₄ solution at 120 °C and the hydrolysis law was investigated. The experimental results indicate that MgSO₄ and Al₂(SO₄)₃ accelerated the hydrolysis and significantly affected the particle size (increasing the primary agglomerate size from 40 to 140 nm) and dispersion (reducing the aggregate size from 12.4 to 1.5 μm) of hydrated TiO₂. A thermodynamic equilibrium calculation showed TiOSO₄ existed as TiO²⁺ and SO₄²⁻ in the solution, and MgSO₄ and Al₂(SO₄)₃ led to little change of [TiO²⁺], but an obvious decrease of [H⁺], which favored the hydrolysis process. At the same time, the coordination–dissociation mechanism of SO₄²⁻ and Al(SO₄)₂⁻ facilitated the lap bonding of Ti-O-Ti, promoting the growth of hydrated TiO₂ synergistically. Full article

The viscosity of high-titanium blast furnace slag with different TiO₂ content, Al₂O₃ content, and basicity was measured at 1653–1773 K using the rotational cylinder method. The phase composition of the slag is measured by XRD. Phase diagram of the slags is calculated by FactSage software. Ionic network structure of the slags is analyzed by FT–IR. Results show that TiO₂ depolymerizes the silicate network structure, reducing viscosity at high temperature, while increasing Al₂O₃ content generates a more complicated silicate, increasing viscosity. Basicity affects viscosity, with higher basicity resulting in lower viscosity above 1733 K. Perovskite significantly affects the viscosity of slag. This study provides an in-depth understanding of the relationship between the composition and viscosity of high-titanium blast furnace slag, which is very important for improving production efficiency. Full article

Slag compositions are significant for the viscosity of blast furnace slag. An improved Urbain model (IUM) was proposed by introducing R₅ ((X(CaO) + X(MgO) + 2X(TiO₂))/(2X(SiO₂) + 3X(Al₂O₃))) and N (X(MgO)/3X(Al₂O₃)) as the model parameters. By comparing IUM with other models, the model parameters of R₅ and N are more reasonable and suitable for TiO₂-bearing blast furnace slag, and IUM for predicting viscosity has a higher precision, and its relative error is only 10%. The viscosity isolines of the CaO–SiO₂–15%Al₂O₃–MgO–2.5% TiO₂ system were plotted, and the results show that the viscosity center of the slag is between R_w2 (w(CaO)/w(SiO₂)) = 0.77–1.39 and N_w (w(MgO)/w(Al₂O₃)) = 0–1.37, the value of the viscosity center is 0.3 Pa·s, the viscosity increases gradually from the center to the outside, and the viscosity of the slag gradually decreases with the increase in N_w and R_w2. Furthermore, FTIR (Fourier Transform Infrared Spectroscopy) analysis was carried out in order to understand the mechanism between the slag structure and viscosity. With the increase in N_w and R_w2, the peak values of the symmetrical stretching vibration of non-bridging oxygen in the Si–O tetrahedral structure of slag decrease, and the slag structures depolymerize, which leads to the decrease in the viscosity of the slag. Full article

Blast furnace–basic oxygen furnace (BF–BOF) process is the predominant method for smelting vanadium titano-magnetite (VTM) in China. Hydrogen-rich (H₂-rich) gas injection in BF is considered as an important way to reduce CO₂ emission under the background of low carbon metallurgy. In this paper, the softening–melting behaviors of VTM sinter in H₂–rich gases were investigated by the method of determination of its reduction softening drippinger performance under load. The experimental results indicated that the permeability of VTM sinter during the softening–melting process was improved by increasing the H₂ content of the reducing gases. The maximum pressure drop of the burden decreased gradually from 29.76 kPa to 19.97 kPa, and the total characteristic value (representing the comprehensive softening–melting property) also decreased obviously from 2357.52 kPa·°C to 630.94 kPa·°C with the increase in H₂ content. The softening interval of the samples was widened, while the melting–dripping interval increased firstly and then decreased. In that case, the position of the melting–dripping zone in BF would move downwards, which was beneficial to smelting smoothly. The thermodynamic analysis indicated that Ti- and Fe-bearing phases were more difficult to be reduced than iron oxides, and H₂-rich gas is beneficial to the reduction of that kind of oxides. Titano-magnetite will be reduced stepwise to form Fe₂TiO₄, and then in the order of FeTiO₃→TiO₂→Ti(C,N). Wustite (FeO) was an important component during the slag-forming process, whose content increased firstly and then decreased. Perovskite and silicate were the main phases in the dripping slag samples. Full article

Preparing ceramic materials is a meaningful way to treat and utilize industrial slags. In this work, high-performance and low-deformation industrial slag ceramics were prepared from Ti-extraction blast furnace slag and illitic clay. The phase composition and contents, microstructure, physical properties, and pyroplastic deformation of ceramic samples were investigated. With the increasing proportion of illitic clay, the main crystalline phase of ceramic samples changed from akermanite to Fe-bearing diopside. Moreover, the minor crystalline phases changed from perovskite and spinel to anorthite and titanite. The proportion of illitic clay was linearly related to the amorphous phase content. The dense microstructure comprised concentrated short-columnar and granular grains with a few isolated pores, whereas plate-like grains destroyed their denseness. An appropriate proportion of illitic clay helped to improve the physical properties, increase the high-temperature viscosity and reduce the deformation of the ceramics. The optimal proportion of illitic clay was 30%, and the prepared ceramic sample had a dense microstructure and excellent physical properties. Its bulk density was 2.82 g/cm³, bending strength was 62.17 MPa, and water absorption was 0.21%. Full article

Ti-extraction blast furnace slag (EBFS) is a secondary slag produced by titanium extraction of titanium-bearing blast furnace slag (TBBFS), which is challenging to be used directly because of its residual carbon and chlorine. This study was performed to recover the residual carbon and remove chlorine from EBFS by froth flotation. The finely ground EBFS (FEBFS) contained graphitized carbon and khamrabaevite and had a 10.19% loss on ignition (LOI) and 5.52% Cl. The graphitized carbon was mainly recovered by flotation rather than khamrabaevite. Graphitized carbon appeared as flakes embedded in or stacked on the surface of the concentrate grains. The irregular-shaped particles were amorphous aluminosilicate glasses, whose presence adversely affected the quality and performance of the flotation concentrate. The Cl contents of the flotation concentrate and tailings obtained under the optimized flotation conditions were significantly reduced to 1.17% and 0.4%, respectively. The dechlorination efficiency reached 71.56%. Meanwhile, the LOI of flotation tailing was reduced to 1.32% and the carbon recovery was 84.79%. Froth flotation could recover residual carbon and remove chlorine from EBFS simultaneously, a novel way to deal with EBFS as a resource and harmless process. Full article

Titanium-containing carbide slag (TCS) is the product obtained by high-temperature carbothermal reduction in Titanium-bearing blast furnace slag (TBFS), which contains a large amount of TiC phase with excellent electrical conductivity. In this paper, conductive cement mortar was prepared with TCS as an aggregate and graphite as a conductive phase. The content of graphite on the compressive strength and electrical resistivity of the prepared cement mortar was investigated. The results showed that the replacement of standard sand with TCS as an aggregate not only significantly reduced the electrical resistivity of the cement mortar, but also improved its compressive strength. When the graphite content was 10 wt%, the cement mortar with TCS as the aggregate exhibited excellent comprehensive performance with the 28d compressive strength of 34.0 MPa and the electrical resistivity of 2.9 Ω m in dry condition, respectively. The results of this paper provided a new way both for the utilization of TBFS and the preparation of conductive cement mortars. Full article

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. Full article

To evaluate the crystallization behavior of Ti-bearing blast furnace slag-based glass ceramics, SiO₂-Al₂O₃-CaO-MgO-TiO₂ systems with various TiO₂ were investigated. The crystallization process and mechanical properties were analyzed. The results show that with TiO₂ increasing, exothermic peak temperature (T_p) decreases, and the crystallization is promoted by the introduction of TiO₂. A small amount of TiO₂ (≤4%) addition can significantly promote crystallization, and when TiO₂ continues to increase, the crystallization is decreased slightly. The Avrami parameter (n) of all samples is less than 4, indicating that in prepared glass-ceramics, it is hard to achieve three-dimensional crystal growth. The main crystalline phase is akermanite–gehlenite. The addition of TiO₂ has no obvious effect on the type of main crystalline phase. The prepared glass-ceramic with 4% TiO₂ show good mechanical properties with the hardness values of 542.67 MPa. The recommended content of TiO₂ is 4% for preparing glass-ceramics. Full article

In view of the fact that Ti–bearing blast furnace primary slag has been explored limitedly and its viscosity–structural property is not fully understood, the phase compositions, viscosity and structure of CaO–8%MgO–Al₂O₃–SiO₂–TiO₂–5%FeO slag are investigated by X-ray diffractometer, rotating cylinder method, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy respectively, considering the effect of Al₂O₃ and TiO₂. The critical temperature that is defined as the temperature below which the viscosity of slag increases quickly, could be explained by the relative amount of perovskite to melilite from phase compositions analysis. The slag viscosity first increases with increasing Al₂O₃ content from 10 to 15 mass%, and then decreases with the further increase of Al₂O₃ to 18 mass%. Increasing TiO₂ content continuously lowers the viscosity. FTIR and Raman spectra results show that increasing Al₂O₃ or decreasing TiO₂ content leads to complex Si–O and Ti–O networks structure, corresponding to the slag viscosity variation. The effect of weak linkages of Si–O–Al is more dominant when Al₂O₃exceeds 15 mass%, which results in the decrease of viscosity. Full article

The oxidation kinetics of low valence titanium and iron in Ti-bearing blast furnace slag were investigated, the activation energies were calculated, which are 461.1 and 437.3 kJ/mol, respectively. The results illustrate that the oxidation process of Ti³⁺ in the slag is controlled by chemical reactions. However, the chemical reaction between oxygen and iron, between slag and gas, is the determining step of the iron oxidation process. The effects of the isothermal oxidation on the content of Fe₂O₃, Fe_M, FeO, and Fe_T in the slag are discussed. The Fe²⁺ and Ti³⁺ in the molten slag were oxidized at high temperatures. Oxygen affinity of the slag can be described using oxygen capacity. The oxygen capacity of Ti-bearing blast furnace slag was investigated during the dynamic oxidation process, the results indicates that the oxygen capacity of the slag decreased with increasing oxidation time during the dynamic oxidation process. Full article