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Vanadium(V) and chromium (Cr) are important strategic resources due to their outstanding physicochemical properties. Due to their similar physical and chemical properties, V and Cr are often associated and coexist in many minerals. This review highlights the significance of V and Cr extraction and separation from high-chromium vanadium slag, emphasizing the key separation techniques. Current strategies for vanadium–chromium separation include separation during the extraction process, that is selective extraction of one of the elements from the slag and co-extraction of vanadium and chromium into solution followed by separation of vanadium and chromium from the solution. Both strategies are pivotal for optimizing the extraction process and enhancing industrial applications. This comprehensive review provides insights into the separation methods, addressing the challenges and advancements in the field. The elucidation of the importance of vanadium and chromium, coupled with a detailed analysis of high-chromium vanadium slag and current separation techniques, contributes to the utilization of vanadium–titanium-bearing magnetite resources with a high content of chromium and also evolves the knowledge in this critical area. [ABSTRACT FROM AUTHOR]

This study investigated the impact of BaO/Al2O3 molar ratio on the electrical conductivity and Al coordination state of CaO–MgO–SiO2–Al2O3–BaO slag using four-electrode technique and 27Al MAS-NMR spectroscopy, respectively. With an increasing BaO/Al2O3 molar ratio from 0.14 to 0.36, BaO preferentially participated in charge compensation of Al3+, which facilitated the transition from AlO5 and AlO6 structures to AlO4 structure and increased the stability of AlO4 tetrahedra, thus enhancing the slag's polymerization and reducing its electrical conductivity. However, once the compensation achieved equilibrium, remaining BaO was involved in depolymerizing the tetrahedral structure and promoting the formation of AlO5 and AlO6 structures. Consequently, the decreased degree of polymerization and increased concentration of free ions together led to an increase in electrical conductivity. However, the increased migration resistance due to the large radius of Ba2+ ion is responsible for the electrical conductivity minimum near the molar ratio of 0.43. [ABSTRACT FROM AUTHOR]

Sulfide capacity is one of the essential properties of molten slag, which determines the sulfur content in the hot metal during the smelting process. In the present study, an artificial neural network model was developed to predict the sulfide capacity of molten slag over a wide range of components and temperature. A CaO–SiO2–MgO–Al2O3–FeO–TiO2–MnO slag database for sulfide capacity covering most of the previous confident literature was constructed. The influence of activation function, optimization algorithm, and various hidden layers on the performance of the models on sulfide capacity were studied using ten-fold cross-validation. The developed model shows excellent prediction performance, which is capable of accurately predicting complex slag systems, especially TiO2-bearing slag systems. The accuracy and nonlinear prediction ability of the model are verified by experiments, and the iso-sulfide capacity diagrams of CaO–SiO2–Al2O3, CaO–SiO2–TiO2–8 wt pct MgO–14 wt pct Al2O3, and CaO–SiO2–30 pct wt pct TiO2–MgO–14 wt pct Al2O3 slag systems at 1773 K were established with the model. [ABSTRACT FROM AUTHOR]

To increase the utilization of V-Ti-Magnetite ore in the burden of a blast furnace, we investigated replacing CaO with MgO. The high fraction of TiO2-bearing raw materials leads to a super-high TiO2 content in the blast furnace slag, typically above 30 wt pct, which affects normal blast furnace operation. The present study focuses on the sulfide capacity of slag containing a super-high TiO2 content. The effects of TiO2 content and the ratio of MgO to CaO (M/C) on the sulfide capacity of slag were examined using a gas-slag equilibrium method. In the CaO-SiO2-TiO2-MgO-Al2O3 slag system, as the content of TiO2 in the slag increased from 20 to 34 wt pct, the sulfide capacity decreased from 6.25 × 10−5 to 2.86 × 10−5. Above 30 wt pct TiO2, the influence of TiO2 content on the sulfide capacity became negligible. Increasing the (M/C) ratio induced a non-monotonic trend in the sulfide capacity, which first increased and then decreased. Thermodynamic and structural analyses were employed to characterize the experimental results. Thermodynamically, decreasing the CaO activity reduced the free oxygen in the slag with increasing TiO2 content. Furthermore, an increase of titanium suboxide slowed the reduction of the sulfide capacity. Mass substitution mainly influenced the availability of free oxygen in the slag, and then the sulfide stability and oxygen concentration worked together, resulting in a non-monotonic sulfide capacity when MgO was substituted for CaO. In addition, the sulfide capacity was dependent on the effect of both the quaternary molar basicity and the binary molar basicity. Finally, the structural analysis revealed that for a super-high TiO2 content in the slag, both the structure of Ti and the depolymerization reaction of Ti had an extremely important effect on desulfurization. [ABSTRACT FROM AUTHOR]

The Special Issue on "Metallurgical Slag" is a collection of 23 original articles dedicated to theoretical and experimental research works providing new insights and practical findings in the field of metallurgical slag-related topics. 10.3390/cryst10110971 6 Shi G.Y., Zhang T.A., Dou Z.H., Niu L.P. Dissolution Behavior of Al2O3 Inclusions in CaO-Al2O3 Based Slag Representing Aluminothermic Reduction Slag. 10.3390/cryst11060583 3 Xu Y., Song P., Cao W., Li H., Liang J. Effect of Al2O3-SiO2 Addition on Gehlenite Growth and the Mechanical Performance of Steel Slag. Further examples of hydrometallurgy are given by Li et al. [[15]] who designed an electrochemical method that could be used to remove impurities in zinc leaching night and enrich zinc ferrite in the ammonia leaching residue of the solution, and that of ammonia leaching slag after ammonia leaching of zinc hypoxide. [Extracted from the article]

As the titanium industry rapidly develops, low-grade ilmenite resources are drawing global attention. The direct use of low-grade ilmenite can result in low production efficiency and heavy pollution. In addition, the production of high-titanium slag via electric furnace melting consumes significant energy and possesses low production efficiency. Therefore, a novel process with low energy consumption is necessary for producing ultra-grade slag (UGS) for chlorination. For low-grade ilmenite, semi-molten reduction and magnetic separation were suggested in this study. The effects of carbon content, reduction time, and Na2CO3 addition on the reduction and separation behavior were studied. The results showed that the addition of Na2CO3 favored the formation of a semi-molten state, which was more conducive for the diffusion, aggregation, and growth of the metal phase. In this regard, excess carbon was not helpful, and it weakened the growth of the metal phase. Wet grinding and magnetic separation were used for beneficiation of the reduced sample for efficiently separating the slag iron and preventing the formation of agglomerates between slag and metal. For the sample with a carbon dosage of 13 pct, Na2CO3 dosage of 8 pct, reduction temperature of 1673 K (1400 °C), and 90 minutes holding time, high-titanium slag with a TiO2 grade of 81.63 pct and iron content of 4.53 pct was produced, with the TiO2 recovery rate of 93.43 pct and the yields of 55.37 pct. High-titanium slag can be used as a high-quality raw material to produce UGS for chlorination by leaching. [ABSTRACT FROM AUTHOR]

TiO2-FeO-Ti2O3 slag system is the dominant system for industrial high-titania slag production. In the present work, viscosities of TiO2-FeO and TiO2-FeO-Ti2O3 systems were experimentally determined using the concentric rotating cylinder method under argon atmosphere. A viscosity model suitable for the TiO2-FeO-Ti2O3 slag system was then established based on the modification of the Vogel-Fulcher-Tammann (VFT) equation. The experimental results indicate that completely melted high-titania slags exhibit very low viscosity of around 0.8 dPa s with negligible dependence on temperature and compositions. However, it increases dramatically with decreasing temperature slightly below the critical temperature. Besides, the increase in FeO content was found to remarkably lower the critical temperature, while the addition of Ti2O3 increases it. The developed model can predict the viscosities of the TiO2-FeO-Ti2O3 and TiO2-FeO systems over wide ranges of compositions and temperatures within experimental uncertainties. The average relative error for the present model calculation is < 18.82 pct, which is better than the previously developed models for silicate slags reported in the literature. An iso-viscosity distribution diagram was made for the TiO2-FeO-Ti2O3 slag system, which can serve as a roadmap for the Ilmenite smelting reduction process as well as the high titania slags tapping process. [ABSTRACT FROM AUTHOR]

To elucidate the effects of FeS on the carbothermic reduction of ilmenite, a series of tests were conducted using non-isothermal thermogravimetric analysis at heating rates of 10°C/min, 15°C/min, 20°C/min, and 25°C/min. The Malek method was used to analyze the reduction mechanism and obtain a kinetic model, and the Starink method was used to calculate the apparent activation energy. The morphology of the reduction products was examined by scanning electron microscopy. A complementary series of isothermal carbothermic reductions tests was also performed in a vertical tube furnace to study the effect of FeS on the metallization of Fe and TiO2 grade in the slag phases. The results show that the carbothermic reduction of the ilmenite concentrate in the presence of FeS proceeds in four stages. FeS showed a negative effect to the carbothermic reduction of ilmenite as its addition of 2.5 wt.% increased the apparent activation energy from 486 kJ mol−1 to 565 kJ mol−1 and decreased metallization by 11.1% and TiO2 grade in the slag phases by 7.2%. [ABSTRACT FROM AUTHOR]

To increase the utilization fraction of V-Ti-Magnetite ore in the burden of the blast furnace over 80 pct, the technology of "replacing CaO with MgO" was discussed. The high content of TiO2-bearing raw materials leads to a super high TiO2 content in the blast furnace slag, which affects the normal operation of the blast furnace ironmaking process. The physicochemical properties of TiO2-bearing blast furnace slag such as viscosity are fundamentally determined by the high temperature and structure of the slag. In this study, Raman spectroscopy focusing on the effect of TiO2 and MgO/CaO ratio on the structure of super high TiO2-bearing blast furnace slag was performed. The results indicate that most of the Ti4+ ions are in the tetrahedron unit, and a few of Ti4+ ions are in the octahedron unit with a coordination number of six; this is confirmed by the presence an emission spectrum related to Ti-O stretching vibrations at wavenumbers less than 700 cm−1. The mole fraction of the band below 700 cm−1, which is related to the coupling of Al-O stretch vibration and the Ti-O stretch vibrations of Ti4+ in sixfold coordination, increased from 0.14 to 0.19 as the TiO2 content in CaO-SiO2-TiO2-MgO-Al2O3 slag increased from 20 to 34 mass pct. The (Q3)2/(Q2) ratio that is proposed as an index for the degree of polymerization (DOP) of melts decreased from 5.72 × 10−3 to 1.0 × 10−3 as the TiO2 content increased. Increasing the MgO/CaO ratio caused a slight decrease in the fraction of the bands below 700 cm−1 and resulted in the decrease of the (Q3)2/(Q2) ratio; thus, the DOP of the melts increased with increasing MgO/CaO ratio. The quantitative relationship, ln(η) = 0.91 + 0.11·ln((Q3)2/(Q2)), between the high-temperature structure information and the viscosity of TiO2-bearing blast furnace slag was established. [ABSTRACT FROM AUTHOR]

To increase the utilization fraction of vanadium titano-magnetite in the blast furnace burden to > 80 pct, a new slag zone with high MgO was found. The effect of the TiO2 content and MgO/CaO mass ratio on the viscosity and liquidus temperature of the high TiO2-bearing blast furnace slag was investigated in the present work. The results indicated that at a fixed CaO/SiO2 ratio of 1.1, the viscosity decreases with increasing TiO2 content at a range of 20 to 34 mass pct. Conversely, increasing the MgO/CaO ratio from 0.32 to 0.65 causes a slight increase in the slag viscosity. The activation energy may show a concomitant variation corresponding to the viscosity of slag. The liquidus temperature first increases and then slightly decreases with TiO2 content. However, the liquidus temperature first decreases and then increases with the MgO/CaO ratio, similar to the variation of the thermodynamic calculation using FactSage software. Various viscosity models were employed to predict the viscosity, and Yan's model was found to be the most reliable in predicting the viscosity in the present study. In addition, the iso-viscosity distribution diagram was obtained using Yan's model calculation. It may have potential for application in the blast furnace ironmaking process with super-high (> 80 pct) vanadium titano-magnetite. A suitable slag composition was found to satisfy the smelting process in a blast furnace with super-high TiO2 content at low temperature by using more MgO and less CaO content. [ABSTRACT FROM AUTHOR]

The electric conductivity of high-titania slag of TiO2-Ti2O3-FeO-CaO-SiO2-Al2O3-MgO slag system was measured by means of four-electrode alternating current (AC) impedance method. The results show that high-titania slag exhibits a good electric conductivity, around 45 to 141 S cm−1 with slight dependence on the temperature, which is of several orders of magnitude higher than that of the silicate slags. Further, electric conductivity of high-titania slag decreased with the increasing FeO content, whereas, the increasing Ti3+/Ti4+ and TiO2 contents caused a significant increase in the electric conductivity. Based on the experimental results and the calculated results, the conductive mechanism of high-titania slag was discussed in detail. It can be concluded that the high-titania slag exhibits a characteristic of electronic–ionic mixed conductivity, but the effect of electronic conduction dominates above the liquidus temperature; however, with the decreasing temperature, the electronic conductivity was gradually weakened. The mechanism was postulated to be a random walk of electrons between tetravalent titanium and trivalent titanium dispersed in the melt. [ABSTRACT FROM AUTHOR]

Stabilizing the toxic element chromium and improving vanadium recovery are crucial for the economic and efficient treatment of high chromium-bearing vanadium slag. This study employed mechanical activation to enhance vanadium extraction from high chromium-bearing vanadium slag through a low-sodium salt roasting-water leaching process. The effects of Na 2 CO 3 addition, roasting temperature, and roasting time were investigated to determine the optimal roasting parameters. Subsequently, the effects of mechanical activation on the morphological and microstructural changes were characterized using a laser diffraction particle size analyzer, a micropore physisorption analyzer, scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. The effects of mechanical activation on the extraction of vanadium and chromium were determined by leaching the roasted samples after varying activation times. The results indicated that mechanical activation decreased particle size, increased surface area, and enhanced the activity of the samples. The leaching results demonstrated that mechanical activation enhanced the leaching efficiency of vanadium by 5 %, reduced the optimum roasting temperature by 50 ℃, and slightly increased the leaching efficiency of chromium by 0.5–1 %. [Display omitted] • High Chrome Vanadium slag requires mechanical activation. • The leaching rate of V reached 94 % and the leaching rate of Cr was less than 7 %. • A significant amount of Cr is stabilised in the vanadium tailings in a non-water soluble state. • Effective in reducing environmental pollution from V and Cr. [ABSTRACT FROM AUTHOR]

A novel method of smelting a mixture of two types of laterite ore (saprolitic and limonitic) to prepare ferronickel has been investigated. Thermodynamic analysis revealed that the melting temperature of the slag phase dropped below 1400°C with increasing FeO content, which can be regulated by adjusting the ratio of limonite and the carbon content. The experimental results also proved that the melting degree of the reduced pellets increased with increasing limonitic laterite ratio and that the reduction as well as magnetic separation was enhanced when the reduction was carried out in the presence of limonitic laterite ore. A ferronickel product with 8.08 wt.% Ni, 80.09 wt.% Fe, and 3.75 wt.% C was prepared by heating the mixture to 1380°C in the presence of 6 wt.% carbon content and 5 wt.% limonitic laterite ore, followed by magnetic separation. The Ni and Fe recoveries were 89.26% and 81.64 wt.%, respectively. [ABSTRACT FROM AUTHOR]

Oxygen potential of TiO2-FeO-Ti2O3 ternary slags was determined by the electromotive force (EMF) method based on the solid electrolyte oxygen sensor at 2003 K (1730 °C). The effect of FeO content and Ti3+/Ti4+ mass ratio on the oxygen potential of the high-titania slag was also studied. At a fixed Ti3+/Ti4+ mass ratio of 3.11, the oxygen potential increased with increasing FeO content. Increase of Ti3+/Ti4+ mass ratio from 2.29 to 3.60 caused a significant decrease in the oxygen potential of the slag. Comparing measured oxygen potential with the calculated values indicated that the oxygen potential of the slag might be determined by FeO/Fe equilibrium reaction rather than TiO2/Ti2O3 reaction. In addition, the experimentally measured oxygen potential values were modeled by multiple linear regression analysis, and a semi-empirical mathematical correlation was established between the oxygen potential and slag compositions. The iso-oxygen potential distribution diagram based on the mathematical model was obtained for the high-titania slag. [ABSTRACT FROM AUTHOR]

A structure-based viscosity model has been developed for the CaO-MgO-FeO-SiO2-Al2O3 system and its subsystems. A critical analysis of the experimental data for iron oxide aluminosilicate systems has been conducted and used in the optimization of a model, which provides a link between the viscosity and the structures of the melts. The structural characteristics of aluminosilicate melt can be described by four types of oxygen: bridging oxygen Oi0, non-bridging oxygen Oj-, free oxygen O2−, and excess bridging oxygen O*. The present model is capable of predicting the viscosities in the CaO-MgO-FeO-SiO2-Al2O3 system and its subsystems over wide ranges of composition and temperature above the liquidus within experimental uncertainties, and the average of relative errors for this model was found to be 19.94 pct. This model includes FeO-SiO2, CaO-SiO2-FeO, Al2O3-SiO2-FeO, MgO-SiO2-FeO, CaO-SiO2-MgO-FeO, CaO-SiO2-Al2O3-FeO, and CaO-MgO-SiO2-Al2O3-FeO. It was found that the effects of different metal cations on the viscosity can be determined, and the ability to reduce viscosity in the silicate melts follows the order: FeO > CaO > MgO. In the present model, the predicted viscosity decreased when CaO was initially initial added to the Al2O3-MgO-FeO-SiO2 system at a fixed SiO2 content because Ca2+ has the highest priority for charge compensation and FeO is the strongest modifier for this slag. [ABSTRACT FROM AUTHOR]

Ultrasonic vibration was applied to the solidification process of calcium ferrite (CF) to modify the grain size and improve the homogeneity of the solidified microstructure. The effects of ultrasound on microstructure, density, compressive strength, and reducibility were studied. The acoustic pressure decreased and then increased along the axis symmetry due to the attenuation of acoustic pressure and reflection of ultrasonic waves in the melt under a fixed power. When the ultrasonic power was increased, the general acoustic pressure increased, which was beneficial to the avoidance of macropores and to improvement of the microstructure. Coarse acicular CF grains were significantly refined; the grain size decreased from 1967 to 442 μm when the ultrasonic power was increased from 0 to 300 W. The density of the samples increased from 4370 to 4680 kg/m3 due to cavitation and acoustic streaming effects. Ultrasonic vibration greatly improved the ultimate compressive strength of CF; the values were 41.8 ± 2.1 to 67.3 ± 3.4 MPa for ultrasonic powers of 100 to 300 W, respectively. Without ultrasonic treatment, it was only 37.4 ± 1.9 MPa. Ultrasonic vibration also influenced the reduction time of CF due to the composition segregation in the slag during solidification. [ABSTRACT FROM AUTHOR]

The recycling of metallic iron is commonly the first step to fully use the converter slag, which is the biggest waste discharge in the steelmaking process. This study presents a proposed improved process of separating metallic iron from vanadium-bearing converter slag more efficiently. The mineralogical and morphological characteristics of the converter slag were first investigated, and the results showed that most of the iron was incorporated in the spinel and olivine. Grinding, sieving and magnetic separation were combined to recover metallic iron from the converter slag, and yielded approximately 41.5% of iron in which the iron content was as high as 85%, and the non-magnetic concentrate contains 8.56% vanadium with a yield of 95.3% and 8.63% titanium with a yield of 85.3%. The magnetic part can be used as the raw materials in the steel making process, whereas the non-magnetic part can be used as the raw materials for the further extraction of vanadium. [ABSTRACT FROM AUTHOR]

The wetting behaviors of a TiO2 substrate by calcium ferrite (CF) series slags were investigated using an improved sessile drop method at 1523 K (1250 °C). The initial contact angles were in the range 35 to 50 deg, the final equilibrium apparent contact angles were < 20 deg, and the spreading durations were in the range 75 to 180 seconds. The CF-TiO2 system showed reactive wetting, which was categorized into four dynamic stages. Stage I: physical spreading, stage II: slow linear spreading, stage III: fast linear spreading, and stage IV: equilibrium. Interfacial reactions yielded CaTiO3 during reactive spreading, thereby transitioning TiO2 wetting into CaTiO3 wetting and then forming Fe2TiO5 and FeTiO3 owing to the excess Fe2O3 and FeO that had accumulated in the interfacial zone. Although stage III spreading was faster than stage II spreading, adding MgO to the slag slowed stage III spreading. The interfacial microstructure of the residual slag was roughly divided into three layers owing to the different densities of the slag and solid products. The top layer was composed of CaTiO3 and Fe2O3, the middle one was composed of CaTiO3 and Fe2TiO5, and the bottom one was composed of Fe2TiO5 and FeTiO3. Adding TiO2 to the slag produced a dense CaTiO3-containing interfacial layer, resulting in CF being detected in the residual slag. [ABSTRACT FROM AUTHOR]

Because of its potential to achieve a high recovery rate of vanadium, the mechanical activation pretreatment of vanadium-bearing converter slag followed by calcification roasting at low temperature and a two-step leaching process may be a viable alternative to the present roasting and one-step leaching process for vanadium extraction. The object of this study is to enhance the leaching efficiency of vanadium by mechanical activation and two-step leaching methods. The effects of solution acidity, liquid/solid ratio, particle size of the roasted slag, stirring speed, leaching temperature and time were investigated. The first stage leaching liquor was recycled in order to improve vanadium content in the leaching solution and reduce leaching solution consumption and wastewater discharge. Experimental results showed that approximately 81.8% vanadium was dissolved in the first stage of the leaching process with a solution pH of 2.5, and approximately 8.1% vanadium was dissolved in the second stage of the leaching process with a solution pH of 0. In the first stage, the vanadium leaching efficiency was significantly hindered by long recycle times, though this property also increased the content of vanadium in the leaching solution and greatly decreased the water consumption. In addition, mineralography and microstructures of the solid samples were studied by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to help understand the mechanism. [ABSTRACT FROM AUTHOR]

In this paper, a novel process was studied for the recovery of iron and titanium from ilmenite concentrate. The ilmenite powders first underwent an oxidation pretreatment and were reduced isothermally at 1350–1450 °C by graphite with the addition of Na 2 SO 4 . The influence of temperature, C/O molar ratio and the dosage of the added Na 2 SO 4 on the metallization ratio, phase transformation and titanium grade were studied. The results demonstrated that Na 2 SO 4 not only significantly promotes the aggregation and growth of metallic iron-grain particles but also enhances the reduction ability. Under the promotion of added Na 2 SO 4 , the highest metallization ratio reached 94%, and the theoretical calculation of the highest grade of titanium dioxide is approximately 75%. The Na 2 SO 4 additive decreases the melting point of the slag and metal, resulting in the effect of semi-melting reduction. The carbothermic reduction order of phase transitions of pre-oxidized ilmenite concentrate was also discussed. [ABSTRACT FROM AUTHOR]

The effect of AlO and AlO/SiO ratio on the sulfide capacity of the molten aluminosilicate CaO-SiO-AlO-MgO-TiO slag system with high AlO content was measured at 1773 K (1500 °C) using a metal-slag equilibration method. The sulfide capacity between silicate-based and aluminate-based slag was also compared based on the thermodynamic analysis and structural characteristics of melts. At a fixed CaO/SiO ratio of 1.20, the sulfide capacity decreases with increasing AlO content primarily due to the decrease of free oxygen (FO) and the activity of O. Increasing the AlO/SiO ratio from 0.47 to 0.79 causes a significant increase in the sulfide capacity of the slags, and a slight increase is found when the AlO/SiO ratio is more than 0.79. The effect of the substitution of silica by alumina on the sulfide capacity of the slags was not only due to an increase in the activity of basic oxides ( $$ a_{{{\text{O}}^{2 - } }} $$ ) but also to a decrease in the stability of sulfide ( $$ \gamma_{{{\text{S}}^{2 - } }} $$ ). Moreover, $$ a_{{{\text{O}}^{2 - } }} $$ and $$ \gamma_{{{\text{S}}^{2 - } }} $$ increase in a similar degree, and the weaker binding electronegativity of Al with oxygen atoms results in a slight increase in the final sulfide capacity in the aluminate-based slag system with AlO ↔ SiO substitution. Five different sulfide capacity models were employed to predict the sulfide capacity, and the iso-sulfide capacity distribution diagram based on the Young's model was obtained in the high AlO corner of the diagram. [ABSTRACT FROM AUTHOR]

The high roasting temperature and low leaching efficiency of vanadium from vanadium-bearing converter slag are regarded as the main factors significantly influencing the application of calcification roasting-acid leaching processes in the cleaner production of vanadium. In this study, a mechanical activation treatment was performed to enhance the extraction of vanadium from converter slag. The enhancement effects obtained from mechanical activation were comprehensively evaluated through indices such as the roasting temperature and leaching efficiency. The effects of mechanical activation time, roasting temperature, leaching temperature, solid to liquid ratio, particle size, and acid concentration on the leaching efficiency were investigated. Microstructure morphology and elemental analyses of the raw materials and leaching residue were also investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results demonstrated that the mechanical activation significantly decreased the optimum roasting temperature from 1173 K to 1073 K (900 °C to 800 °C) and increased the leaching efficiency from 86.0 to 90.9 pct. [ABSTRACT FROM AUTHOR]

Calcium ferrite is the main binding phase for high-basicity sinter. The production and structure of calcium ferrite greatly influence the quality of the sinter. With the change in gangue composition, MgO becomes an important factor in the generation of calcium ferrite. In this study, the rotating cylinder method was used to study the dissolution kinetics of MgO into CaO-MgO-FeO melt. The experimental variables included the temperature, the initial composition of the melt, the FeO/CaO mass ratio, the rotation time, and the rotation speed. The results indicate that the dissolution rate increases with increasing dissolution time, temperature, and rotation speed but decreases with increasing MgO content and FeO/CaO mass ratio in the initial slag. The dissolution rate was observed to increase and then decrease with the addition of SiO in the initial slag. The activation energy and diffusion coefficient for MgO dissolution were found to range from 117.31 to 234.24 kJ mol and from 1.03 × 10 to 1.18 × 10 cm s, respectively. The concentration difference between the solid and liquid phases is the main driving force for dissolution, but the viscosity and magnesium ion diffusivity of the melt also affect the process. [ABSTRACT FROM AUTHOR]

To determine the effect of AlO content and AlO/SiO mass ratio on the structure of molten aluminosilicate systems, CaO-SiO-AlO-MgO-TiO systems were investigated by conducting molecular dynamics (MD) simulation and Raman spectroscopy. The capabilities of different elements to attract O on the basis of bond length are ranked as follows: Si > Al > Ca. The CN (approximately 4) and the average CN (approximately 4.09) demonstrate that the [AlO] tetrahedron is not as stable as the [SiO] tetrahedron and that some highly coordinated Al units exist in the slags. Non-bridging oxygen prefers to be coordinated with Si, and Al tends to be localized in polymerized environments as a network intermediate phase. In addition, Ca is more energetically active than Mg as the charge compensation ion. MD results and Raman analysis show that an increase in AlO content complicates the structure at a fixed CaO/SiO ratio. In addition, the viscosity of the sample may increase with increasing AlO content but is also influenced by polymerization strength. The substitution of AlO for SiO simplifies the structure of the slag at a fixed CaO concentration when AlO/SiO is less than 0.92, as indicated by the (Q + Q)/(Q + Q) ratio of Al and the structure complexity. The results of MD and Raman analysis agree with those of viscosity measurement. [ABSTRACT FROM AUTHOR]

High-basicity sinter is the predominant Fe-bearing material used in blast furnace process in East Asia. The dissolution of SiO into molten calcium ferrite influences the assimilation process. In this study, a rotating cylinder method was used to explore the dissolution kinetics of SiO into CaO-FeO-SiO slag. The influencing factors, including temperature, rotating time and speed, and initial composition of the slag, were considered. Results showed that the dissolution rate increased with increasing rotation speed and temperature, whereas the increase in ω(SiO) or ω(FeO)/ ω(CaO) ratio in the initial slag composition decreased the dissolution rate. The diffusion coefficient and activation energy of SiO during the dissolution process ranged from 2.09 × 10 to 6.40 × 10 cm s and 106.62 to 248.20 kJ mol, respectively. Concentration difference between the boundary layer and bulk phase was the primary driving force of the dissolution process; however, this process was also influenced by the slag viscosity and ion diffusivity. [ABSTRACT FROM AUTHOR]

The crystallisation behaviour of perovskite in liquid synthesised titanium-bearing blast furnace (BF) slag (TiO2-SiO2-Al2O3-MgO-CaO) was observed in situ with a confocal scanning laser microscope (CSLM). Perovskite crystals were dendritic columnar crystals that nucleated on the crucible bottom (and wall) and grew to the centre and surface of liquid slag. The CSLM result that perovskite grew along straight lines through the successive appearances of quasi-particles on slag surface reflected the growth process of dendrites beneath the surface. The formation of perovskite required the diffusion of TiO2 and CaO to the solid interface at the dendrite tips and the rejection of SiO2, Al2O3 and MgO from the interface. [ABSTRACT FROM AUTHOR]

Ilmenite produced from the Panxi area in China has high impurities such as Ca and Mg. High-grade titanium (Ti) slag can be obtained by the electric arc furnace process, a traditional method of treating ilmenite. Thus, Ti slag prepared from the Panxi ilmenite contains high CaO and MgO, exceeding 5 pct of the slag content. This high CaO and MgO content confers considerable difficulty in producing titania (TiO) white using fluidizing chlorination. In this study, a new process named vacuum separation was found to produce high-grade TiO materials. The effects of separation temperature and time on the TiO grade were studied. The high-grade TiO slag, which has 93 pct TiO, <0.1 pct MgO, <1.2 pct SiO, and <0.5 pct CaO, can be produced at 1823 K (1550 °C) in 45 minutes through the proposed method. [ABSTRACT FROM AUTHOR]

The isothermal phase composition of high-titanium-bearing slag (23 mass pct TiO) under an argon atmosphere during cooling process from 1723 K (1450 °C) was calculated by FactSage.6.3 (CRCT-ThermFact Inc., Montréal, Canada). Three main phases, which were perovskite, titania spinel, and clinopyroxene, could form during the cooling process and they precipitated at 1713 K, 1603 K, and 1498 K (1440 °C, 1330 °C, and 1225 °C), respectively. The nonisothermal crystallization process of perovskite in synthesized high-titanium-bearing slag was studied in situ by a confocal scanning laser microscope (CSLM) with cooling rate of 30 K/min. The results showed that the primary phase was perovskite that precipitated at 1703 K (1430 °C). The whole precipitation and growth process of perovskite was obtained, whereas other phases formed as glass under the current experimental conditions. Perovskite grew along a specific growth track and finally appeared with snowflake morphology. The growing kinetics of perovskite formation from molten slag were also mentioned. [ABSTRACT FROM AUTHOR]

The particle size and metallization ratio of iron in reduced ilmenite have an important function in separating the metal from TiO2-rich slag in the electric arc furnace process. In this study, an ilmenite concentrate supplied by Panzhihua Iron and Steel (Group) Co. was reduced at 1380°C in an electric resistance furnace. The effects of Fe-Si addition and reduction time on the particle size and metallization ratio of iron in the reduced sample were analyzed. The metallization ratio of iron significantly increased with increasing Fe-Si amount and reduction time, and reached ≈90% after 40 min. However, the metallization ratio of iron was about 85% without Fe-Si addition. Meanwhile, the iron particle size increased with increasing Fe-Si amount; the growth was obvious with the addition of 1% Fe-Si. Moreover, the growth rate of the iron particle size also increased with increasing reduction time. The TG-DTG curves indicated that the mass loss with Fe-Si addition was less than that without Fe-Si addition, and the temperature at which the maximum rate of mass loss rate was achieved was lower than that without Fe-Si addition. [ABSTRACT FROM AUTHOR]

Blast furnace slag is the main byproduct in the ironmaking process, which contains large amounts of sensible heat. In addition, it's the major raw material for cement. However, the sensible heat is wasted not only without any recovery in the traditional water granulation process at this present. The main challenge is to granulate the slag at a high cooling rate while the heat is also being recovered. This paper describes the hot experiments where a rotating multi-nozzle cup atomizer (RMCA) is used to atomize the molten blast furnace slag without water impingement. The atomization process shows good agreement with Rayleigh's mechanism. The particle size of the slag particle is strongly controlled by the rotating speed and the nozzle diameter, and the higher rotating speed and smaller nozzle diameter are beneficial for obtaining smaller and more uniform slag particles. Moreover, the slag particle still has a high content of glass, which is suitable for cement manufacture. [ABSTRACT FROM AUTHOR]

Blast furnace (BF) slag, which is the main byproduct in the ironmaking process, contains large amounts of sensible heat. To recover the heat, a new waste heat-recovery system-granulating molten BF slag by rotary multinozzles cup atomizer and pyrolyzing printed circuited board with obtained hot BF slag particle-was proposed in this study. The feasibility of the waste heat-recovery system was verified by dry granulation and pyrolyzation experiments. The energy of hot BF slag could be converted to chemical energy through the pyrolysis reaction, and a large amount of combustible gas like CO, H, CH, and CH can be generated during the process. [ABSTRACT FROM AUTHOR]

In order to remove impurity elements from molten aluminum, many processes, such as using inert gas, reactive gas, reactive powders, unreactive powders, slag, or their combinations, have been used during the past 30 years. In the current paper, mathematical models on the removal of impurity elements from molten aluminum for these processes were extensively developed, and validated by industrial measurement from literatures. Special parameters were introduced to express the refining efficiency. Mathematical models for the combined processes like inert gas mixed with reactive gas purging, reactive powders injection with inert gas as carrying gas, were also developed. The removal efficiency of impurity elements for batch reactor and continuous reactor were derived for these processes, either the single method or the combined method. The effects of gas flow rate, impellor rotating speed, fraction of reactive gas, injecting rate of reactive powders, and temperature on the removal of impurity elements were discussed. [ABSTRACT FROM AUTHOR]

In this paper, the effect of titanium carbonitride (Ti(C,N)) on the viscosity of high-titanium-type blast furnace slags was investigated. The different Ti(C,N) contents were achieved by adjusting the reduction degree of TiO2 to reflect the real characteristics of the high-titanium slag. The results show that the viscosity of the slag increased with the increasing Ti(C,N) content and decreased with the rising temperature. A deviation between the measured and the fitted viscosity appeared as the content of the Ti(C,N) was beyond 4 wt%. Furthermore, the apparent viscous flow activation energy of the slag ranged from 106.13 kJ/mol to 235.46 kJ/mol by varying the Ti(C,N) contents from 0 wt% to 4.97 wt%, which was evidently different from the results of previous studies. The optical microscope and energy dispersive X-ray spectroscopy (EDS) analysis show that numerous bubble cavities were embedded in the slags and the Ti(C,N) particles agglomerated in the solidified samples. This phenomenon further indicates that the high-titanium slag is a polyphase dispersion system, which consists of liquid slag, solid Ti(C,N) particles and bubbles. [ABSTRACT FROM AUTHOR]

A multistage utilization process was developed to fully recover valuable metals from vanadium-bearing converter slag and reduce the content of hazardous elements, such as vanadium and chromium, in the tailings. A mechanical activation–calcification roasting–acid leaching process was firstly employed to recover vanadium. This process generated two products, viz. a V-bearing solution accounting for ∼95% V recovery and vanadium tailings with Fe and Ti contents of 31.85% and 8.94%, respectively. Then, based on theoretical calculations and physical measurements, a coal–based direct reduction–magnetic separation process and a hydrochloric acid leaching process were employed for the stepwise recovery of iron and titanium, respectively, from the vanadium tailings. Iron was recovered in the form of high chromium–vanadium iron with 81.53% Fe, 1.31% Cr, and 2.04% V, and titanium was recovered as titanium dioxide pigment with 85–90% yield. Such a comprehensive and clean utilization of vanadium-bearing converter slag has great potential for practical application. [ABSTRACT FROM AUTHOR]

In this study, the effect of the CaO/SiO 2 mass ratio on the viscosity, free running temperature, electrical conductivity and structure of high-titanium CaO-SiO 2 -10 wt%MgO-13 wt%Al 2 O 3 -4 wt%FeO-40 wt%TiO 2 slag was investigated. The results revealed that viscosity and free running temperature monotonically decreased with an increasing CaO/SiO 2 ratio from 0.1 to 0.8, whereas the electrical conductivity followed a trend of first increasing, then decreasing, and ultimately increasing again. XRD analysis revealed only a small amount of Ti-related phases in the quenched slag. This ensured that the high-temperature state structure of the slag was largely preserved. Molecular dynamics simulations, FTIR, and Raman results indicated that Ti-based structural units predominated in the slag. With an increasing CaO/SiO 2 ratio, the [SiO 4 ] tetrahedral and Ti-based structures progressively simplified, while the [AlO 4 ] tetrahedral and Si-O-Al structures showed a tendency of complexity followed by simplicity. However, the overall degree of polymerization of the slag decreased, leading to the viscosity reduction. The degree of polymerization and the migration capacity of ions and electrons together contributed to complex changes in electrical conductivity. A comprehensive analysis indicated that the slag composition with a CaO/SiO 2 mass ratio of 0.4 is more favorable for the smelting of vanadium-titanium magnetite in the pre-reduction electric furnace process. • Higher basicity improves high-titanium (40 wt% TiO 2) slag's fluidity. • Electrical conductivity of slag is determined by the migration of ions and electrons. • Precipitation of CaTiO 3 phase affects the trends in electrical conductivity. • The [TiO 6 ] unit dominates the microstructure of high-titanium slags. • Basicity of about 0.4 is more favorable for smelting VTM in electric furnace. [ABSTRACT FROM AUTHOR]

• Higher basicity enhances slag fluidity. • With increasing basicity, free running temperature first rises and then falls. • Degree of polymerization is the main factor influencing the slag's viscosity trend. • MD simulations reveal two interruption mechanisms of bridging oxygen. Slag regulation is crucial for achieving smelting of high-alumina iron ore in blast furnaces. This study investigated the fluidity and structure of CaO-SiO 2 –10 wt.%MgO-30 wt.%Al 2 O 3 slag by varying the CaO/SiO 2 ratio (1.0–2.0). The results revealed that viscosity decreased with increasing CaO/SiO 2 ratio, while the free running temperature, defined as the temperature at which the slag can flow freely, initially increased and then decreased, peaking at the range of 1.2–1.6. Interestingly, the free running temperature of slag at basicity 2.0 (1392 °C) was lower than that at basicity 1.0 (1398 °C). Spectroscopic analysis demonstrated that increasing basicity facilitated greater charge compensation of Al3+ ions, resulting in an increased amount of [AlO 4 ] tetrahedra. Moreover, increasing free oxygen promoted the depolymerization of [SiO 4 ] and [AlO 4 ] tetrahedra, reducing bridging oxygen and increasing non-bridging oxygen. Consequently, the slag's overall polymerization degree decreased. Furthermore, MD simulations identified two distinct fracture mechanisms of bridging oxygen within the Si-O-Si structure. [ABSTRACT FROM AUTHOR]

• Viscosity first decreases and then increases with increasing MgO/CaO ratio. • The free running temperature decreases significantly with increasing MgO/CaO ratio. • Degree of polymerization of slag is the main determinant of viscosity change. • Connected forms of the slag microstructure are clearly observed by MD simulations. In this study, the effect of MgO/CaO mass ratio on the flowability and structure of CaO-28 wt.%SiO 2− MgO-22 wt.%Al 2 O 3 slag was investigated. It was found that the viscosity first decreased and then increased with increasing MgO/CaO ratio, while the free running temperature monotonically dropped. FTIR and Raman analyses indicated that the [AlO 4 ] and [SiO 4 ] tetrahedral structures underwent a change from complex to simple and back again as the MgO/CaO ratio increased. XPS analysis confirmed that the bridging oxygen first decreased and then increased with increasing MgO/CaO ratio, whereas the free oxygen and non-bridging oxygen presented the opposite trend. Molecular dynamics simulations demonstrated that the Al atoms mainly existed in the form of [AlO 4 ] and [AlO 5 ], and the [AlO 4 ] unit first decreased and then increased upon increasing the MgO/CaO ratio. Both spectral analysis and simulations indicated that the degree of polymerization of the slag structure is a key factor in determining the viscosity variation. [ABSTRACT FROM AUTHOR]

This study investigated the effects of equimolar substitution of BaO for CaO and Al 2 O 3 for SiO 2 on the viscosity and structure of CaO-SiO 2 -MgO-Al 2 O 3 -BaO slag. In slags containing 2 mol.% Al 2 O 3 , introducing BaO disrupted the bridging oxygen bonds, leading to an increase in non-bridging oxygen and the depolymerization of the tetrahedral structure. Consequently, viscosity decreased with increased BaO substitution. However, for slags with 5 mol.% Al 2 O 3 , the synergistic effects of preferential charge compensation by Ba2+ for Al3+ and structural depolymerization by BaO led to the initial stabilization of tetrahedral structures, followed by destabilization. This resulted in the viscosity first increasing and then decreasing with higher BaO substitution levels. With the gradual replacement of SiO 2 by Al 2 O 3 , a significant increase in [AlO 4 ] tetrahedra relative to the decrease in [SiO 4 ] tetrahedra could be observed. Concurrently, a reduction in free oxygen and non-bridging oxygen content was observed, ultimately leading to an increase in viscosity. • Variation of slag viscosity with BaO replacing CaO depends on the Al 2 O 3 content. • Charge compensation of Ba2+ for Al3+ equilibrates at BaO/Al 2 O 3 molar ratios < 0.5. • Substituting Al 2 O 3 for SiO 2 increases the slag viscosity and bridging oxygen. • Degree of polymerization of slag is the main determinant of viscosity change. [ABSTRACT FROM AUTHOR]

[Display omitted] Given the high chloride ion content in chlorinated tailings that harm the surrounding environment cannot be directly utilized, a new process for the deep removal of chloride ions from chlorinated tailings with additives was proposed. The products obtained included tailing slag, which can be used as a building material, and salt, which can be used in industry. Theoretical calculations and experiments were performed to determine the feasibility of the new process. The results showed that the chloride ions from the chlorinated tailings and sodium ions from the additives formed NaCl, which could be removed during water leaching. NaOH served as a better additive than sodium sulfate. An increase in the molar ratio and the prolongation of ball-milling was beneficial for the dechlorination of the water leaching residue. An increase in the roasting temperature leads to an increase in particle size, which worsens the kinetics of subsequent leaching and reduces the leaching rate. The developed process can obtain tailings with chloride ion content of less than 0.1%, which meets the standard for building materials applications. Meanwhile, NaCl with a purity greater than 99% could be obtained, preventing chloride ion pollution of water resources and the comprehensive utilization of chlorinated tailing. [ABSTRACT FROM AUTHOR]

Blast furnace process is the main approach for utilizing vanadium–titanium magnetite (VTM) and VTM pellet is an important burden due to its excellent performance. In this paper, the softening–melting behavior of VTM pellets was investigated. The softening, melting temperature interval and permeability index were obtained as 75 °C, 181 °C and 507 kPa·°C, respectively. Ti–bearing components in pellets were transformed in the order of Fe 2 TiO 5 → Fe 3-x Ti x O 4 → FeTiO 3 → Mg x Ti 3-x O 5 and TiC. Hematite was reduced stepwise to metallic iron entering metallic fraction while most of titanium entered the slag phase. Wustite was an important component during slag evolution. The slag phase mainly consisted of spinel, silicates and wustite, in which the FeO content gradually decreased during the slag evolution process. Anosovite and silicate were the main phases in the slag fraction at the dripping temperature of 1441 °C. Titanium carbide (TiC) was also verified, which was an unfavorable product for the slag properties. [Display omitted] • The characteristic temperatures and temperature intervals of softening and melting are obtained. • The phase transformation of VTM pellets during softening–melting process is investigated. • The morphology transition and slag evolution process is discussed. • The migration behavior of titanium during softening–melting process is revealed. [ABSTRACT FROM AUTHOR]

• A novel process for extraction titanium from high Ti-BF slag has been proposed. • The effects of Fe 2 O 3 , urea and sawdust additives on the reaction have been studied. • The proposed novel recycling process has been assessed. • The novel recycling process showed many potential advantages and great feasibility. The recycling of high-titanium-bearing blast furnace slag (TiO 2 > 23 wt.%) is an urgent problem that has attracted global research attention. To achieve high-efficiency, low-consumption, clean, and high value-added recycling utilization, a new process is proposed herein, which entails reacting a CH 4 -H 2 -N 2 gas mixture with the titanium-bearing blast furnace slag to initially produce Ti(C, N, O) at a low temperature, whereafter the product is purified and chlorinated. The effects of Fe 2 O 3 , urea, and sawdust on the reduction and carbonitriding characteristics are also investigated. The results indicate that the Fe 2 O 3 additive can promote the formation of Ti(C, N, O), while urea and sawdust are instrumental for enhancing gas diffusion in solid powders. The proposed novel recycling process was assessed and it evinced many advantages and great feasibility. [ABSTRACT FROM AUTHOR]

• Viscosity first increases and then decreases with increasing BaO/Al 2 O 3 molar ratio. • The maximum viscosity occurs near the BaO/Al 2 O 3 molar ratio of 0.36. • Charge compensation of Ba2+ for Al3+ equilibrates near the BaO/Al 2 O 3 ratio of 0.36. • Degree of polymerization of slag is the main determinant of viscosity change. In this study, the effect of BaO/Al 2 O 3 molar ratio on the viscosity and structure of CaO SiO 2 MgO Al 2 O 3 BaO slag was investigated. The results revealed that the viscosity first increased and then decreased with increasing the BaO/Al 2 O 3 ratio, and the transition point occurred at the ratio of 0.36. Deconvolution of Raman spectra showed that the Q3 unit first increased and then decreased with increasing the BaO/Al 2 O 3 ratio, while the Q0, Q1 and Q2 units presented the opposite trend. FTIR and XPS analyses indicated that the [SiO 4 ] and [AlO 4 ] tetrahedra polymerized due to the charge compensation of Al3+ by Ba2+ and the increase in bridging oxygen prior to increasing the BaO/Al 2 O 3 ratio to 0.36. However, once the BaO/Al 2 O 3 ratio further increased, the tetrahedra gradually depolymerized owing to the interrupting effect of BaO and the increase in non-bridging oxygen. Spectral analysis demonstrated that the degree of polymerization of slag was the main factor affecting viscosity. [ABSTRACT FROM AUTHOR]

• Grinding together with alkali activation improve the reactivity of CBA and TS. • TS used as calcium source improves the properties of alkali-activated CBA binder. • 20% TS in the binder reduced the setting time and improved the strength development. In this study, ground coal bottom ash (CBA) and titanium-extraction tailing slag (TS) were used as source materials to prepare alkali- activated materials (AAMs). The effects of grinding time on the properties of CBA and TS were investigated, and it was found that the optimum reactivity of CBA and TS appeared at specific surface areas of 700 ∼ 800 m2/kg. The influence of alkali content and modulus of water glass, water–solid mass (w/b) ratios and TS content on the fresh and hardening properties of AAMs were investigated. Furthermore, the reaction process of the binder was conducted by using XRD, FT-IR, SEM and hydration heat. Results showed that increasing the alkali content, reducing modulus of water glass, and adding TS into system could promote the reaction of AAM. A binder with more desirable properties was prepared at alkali content of 12%, water glass modulus of 1.2, w/b ratio of 0.45 and TS content of 20%. Its compressive strength at 7 d and 28 d was 20.8 MPa and 25.9 MPa, respectively. Microstructure analysis showed that the reaction products of binder contained AFm, N-A-S-H gel, C-S-H gel and C-A-S-H gel. This research tried to provide a fundamental basis for preparing clinker-free cement concrete from local industrial wastes to achieve sustainable development. [ABSTRACT FROM AUTHOR]

A cleaner process is tremendously required to deal with the vanadium tailings, which may cause serious environmental problem due to the high content of water soluble hazardous elements such as V and Cr. This problem can be possibly solved by proposed high temperature reduction–magnetic separation process, in which, V, Cr and Fe can be recycled as ferroalloy. The thermodynamic calculation results reveal that a higher temperature (>1127.8 °C) promotes the reduction of Fe, V and Cr, and improves the recovery rates of V and Cr in liquid iron. The reduction behavior of vanadium tailings was investigated using XRD, TG/DSC, SEM, EDS and ICP-OES techniques. The EDS results show that a small portion of V was remained in the slag phase when roasted at 1300 °C, while nearly all of V and Cr can concentrate in ferroalloy at 1400 °C. Approximatly 90% of V and 95% of Cr recovery in magnetic fraction can be obtained for the magnetic separation step. A small portion of V and Cr is remained in the non-magnetic final tailings, however, the hazardous potential assessments results indicate that such kind of tailings can safely use as secondary materials or stockpiled as an end-waste. [ABSTRACT FROM AUTHOR]

Vanadium slag (V-slag) is an important secondary V source, but other valuable elements are discarded in the tailings in industry. Herein, a green nitridation–corrosion process is proposed for the comprehensive recovery of valuable elements (V, Ti, Cr, Fe) from V-slag without producing hazardous waste. Thermodynamic results indicate that ammonia gas (NH 3) can selectively reduce Fe and nitride V, Cr, and Ti. The main phase composition of the nitrided V-slag included metallic Fe, nitrides, and diopside under optimal conditions, and their relative contents were 42.5, 26.2, and 31.3%, respectively, after roasting at 1000 °C for 6 h. The effects of the main parameters on corrosion test were investigated, and the highest weight-gain ratio attained was 19.6%. FeOOH crystallizes on the surface of the nitrided V-slag due to the oxidization of metallic Fe. The phase evolution during the entire process is spinel/olivine/diopside → Fe/nitrides/diopside → FeOOH/nitrides/diopside. Owing to finer particle sizes, most FeOOH is separated by wet sieving (<1400 mesh). The purity of the enriched nitrides attained was 43% after pickling to remove excess Fe. The total recovery rates of Fe, V, Ti, Cr were 87.76%, 95.92%, 92.92%, 92.11%, respectively. This paper provides a sustainable strategy for the comprehensive utilization of V-slag, and guides the cleaner treatment of other similar minerals. [Display omitted] • The NH 3 -based nitridation–corrosion process to recover V, Ti, Cr, and Fe from V-slag is proposed. • The reaction mechanism of reduction–nitridation process is revealed. • The optimal parameters during the nitridation–corrosion processes are investigated. • Enrichment of V, Ti, Cr nitrides and separation of Fe are realized. [ABSTRACT FROM AUTHOR]