Search Results (29)

To achieve the large-scale, high-value utilization of vanadium–titanium slag (VTS) in the metallurgical industry, this study replaces blast furnace slag (BFS) with VTS to construct a quaternary all-solid-waste cementitious system composed of VTS, BFS, steel slag (SS), and desulfurization gypsum (DG). It systematically investigates the effects of VTS content (0–60%) on the mechanical properties, leaching toxicity, and hydration heat behavior of the system. XRD, TG–DSC, and SEM–EDS techniques are employed to explore the influence of VTS on hydration behavior and microstructural evolution. The results show that when VTS replaces 30% of the BFS (A3, VTS:BFS:SS:DG = 3:3:3:1), the 28-day compressive strength reaches 31.33 MPa. The leaching concentrations of heavy metals in all specimens are far below the standards for drinking water quality. Hydration heat analysis reveals that the incorporation of VTS advances the acceleration period of hydration. The A3 specimen maintains a relatively high heat release rate in the middle and later stages (after 72 h), and its cumulative heat release is significantly higher than that of the system without VTS, revealing the “slow hydration” mechanism of VTS at later stages. The [SiO₄]–[AlO₄] bonds in VTS undergo a depolymerization–repolymerization process. In addition, an appropriate amount of VTS promotes the deposition of hydration products such as ettringite (AFt), C–S–H, and C–A–S–H gels through micro-filling effects and heterogeneous nucleation, thereby improving the microstructure of the system. However, excessive VTS (≥45%) significantly inhibits the hydration reaction and reduces gel formation due to the decrease in highly reactive BFS components and the increased TiO₂ content. This study provides new insights into the resource utilization of VTS in multi-solid-waste cementitious materials. In addition, VTS-based cementitious materials are suitable for practical scenarios with low early strength requirements, such as goaf backfilling. Therefore, future studies should further investigate the long-term sulfate resistance and carbonation resistance of these materials under real application conditions. Full article

This study addresses the challenge of achieving efficient separation of vanadium and chromium from vanadium–chromium slag (VCS) while simultaneously tackling issues related to artificial granite waste residue (AGWR), such as its substantial stockpiling and associated air pollution. AGWR was used as a substitute calcination additive for calcium carbonate to achieve efficient separation through a calcination-leaching process. Orthogonal experiments were conducted to investigate the effects of AGWR addition amount, calcination temperature, and calcination time on the leaching behavior of vanadium and chromium. During calcination, vanadium reacts with CaO (a decomposition product of AGWR) to form acid-soluble calcium vanadate. Concurrently, chromium hydroxide decomposes into chromium oxide, which is poorly soluble in dilute acid. Subsequent leaching of the calcination product with dilute sulfuric acid leaches vanadium (V) into the solution, while chromium (Cr) remains in the residue, thus achieving separation. The experimental results showed that under the conditions of 30% AGWR addition; calcination at 850 °C for 1 h; leaching at 90 °C for 2 h with a liquid-to-solid ratio of 10:1 and a sulfuric acid concentration of 50 g·L⁻¹; the leaching rate of vanadium reached 85.68%, whereas that of chromium was only 2.34%. These results demonstrate highly efficient separation of vanadium and chromium, offering valuable insights for resource recovery from both VCS and AGWR. Full article

While vanadium-extracted tailings contain valuable components, their utilization is difficult due to their high sodium content. In this work, a new oxygen-pressure calcification and alkaline leaching strategy to achieve barium orthovanadate vanadium precipitation is developed to realize the resourceful recycling and utilization of vanadium-extracted tailings. First, the preparation of barium orthovanadate via calcified alkaline leaching and vanadium precipitation was studied, and the effects of CaO addition, NaOH concentration, leaching temperature, and liquid–solid ratio on the leaching rates of sodium and vanadium were evaluated in single-factor experiments. Under the optimum leaching conditions (CaO addition of 20%, alkali concentration of 150 g·L⁻¹, leaching temperature of 180 °C, and liquid–solid ratio of 10:1), the leaching rates of vanadium and sodium reached 85.25% and 82.36%, respectively. Subsequently, the vanadium-containing leaching solution was subjected to a vanadium precipitation test, and the effects of pH, Ba(OH)₂ addition (expressed as ${\mathrm{n}}_{\mathrm{Ba}}/{\mathrm{n}}_{\mathrm{V}}$), vanadium precipitation temperature, and vanadium precipitation time on the vanadium precipitation rate were investigated. Under the optimum vanadium precipitation conditions (pH 14, ${\mathrm{n}}_{\mathrm{Ba}}/{\mathrm{n}}_{\mathrm{V}}$ = 1.5:1, temperature of 30 °C, reaction time of 60 min), a vanadium precipitation rate of more than 99% was achieved. The precipitated vanadium product of this reaction was confirmed to be Ba₃(VO₄)₂ with a purity of more than 99%. Notably, the wastewater generated during the test process can be mixed with an alkali and returned to the leaching process for reuse, and the dealkalized residue can be used as a raw material for ore reduction in iron smelting processes. Full article

Enhanced vanadium recovery from vanadium-bearing steel slag is essential in the sustainable use of metallurgical solid waste. This study uses microwave-assisted acid leaching on roasted clinker and systematically investigates it to enhance vanadium recovery; uses response surface methodology (RSM) to identify optimal parameters for leaching; and the influences of sulfuric acid concentration, leaching time, liquid-to-solid ratio (L/S ratio), and leaching temperature on vanadium dissolution are evaluated. The optimal leaching parameters are identified as an L/S ratio of 10:1, 41% sulfuric acid concentration, 65 min leaching time, and 92 °C leaching temperature, under which the highest vanadium extraction rate is 84.58%. Kinetic studies revealed that the leaching behavior during the initial 30 min followed a shrinking core model with fixed particle size. The vanadium microwave-assisted acid leaching process exhibited the observed activation energy (E_a) of 37.30 kJ·mol⁻¹, following a kinetic order of 1.5392 relative to sulfuric acid concentration, implying that ion transport across the solid phase formed during the reaction determined the step that limits the reaction rate. The semi-empirical kinetic equation established in this study accurately describes the leaching behavior under different conditions. This research establishes a theoretical framework and technical reference for boosting vanadium recovery from steel slag, which uses microwave-assisted leaching technology. Full article

This study proposed a selective leaching method to address the challenge of excessive iron (Fe) leaching during a sulfuric acid treatment of magnetite pellets, which complicates the subsequent extraction and precipitation of vanadium (V). The approach involved constant-pH sulfuric acid leaching of calcined and roasted vanadium–titanium (V–Ti) magnetite pellets to enhance V recovery while minimizing Fe dissolution. A comparison between constant-pH leaching and conventional heap leaching was conducted. The results showed that, under optimal leaching conditions, the V leaching rate remained largely unchanged, while the Fe leaching rate was significantly reduced compared with conventional heap leaching. Specifically, under optimal conditions—acid concentration of 2 mol/L, liquid–solid ratio of 1:3, temperature of 90 °C, and leaching time of 360 h—the V leaching rate reached 72.21%, while the Fe leaching rate remained as low as 0.91%. Additionally, the valence states of V and Fe in the pellets before and after leaching, as well as the main phase compositions during the leaching process, were analyzed. The results indicated that the primary phases in the calcined and roasted pellets remain unchanged before and after leaching, and most of the V and nearly all divalent Fe were effectively leached. Full article

Currently, Electric Arc Furnace Slag (EAFS) is undervalued and is therefore only used in road construction, while blast furnace slag (BFS) is used as an interesting alternative in construction materials to replace natural aggregates in the manufacture of concrete. Steel slag (SS) represents a promising secondary resource due to its high content of critical metals, such as chromium (Cr) and vanadium (V). These metals are essential for various strategic industries, making it crucial to consider slag as a resource rather than waste. However, the primary challenge lies in selectively recovering these valuable metals. In this work, we explore the development of a hydrometallurgical process aimed at efficiently extracting Cr and V from Electric Arc Furnace Slag (EAFS). The characterization of the investigated EAFS shows that the main crystalline phases contained in this heterogeneous material are srebrodolskite, larnite, hematite, and spinel such as probably magnesio-chromite. The targeted metals seem to be dispersed in various mineral species contained in the SS. An innovative hydrometallurgical method has been explored, involving physical preparation by co-grinding slag with alkaline reagents followed by treatment in a microwave furnace to modify the metal-bearing species to facilitate metal processing dissolution. The results obtained showed that the leaching rates of Cr and V were, respectively, 100% and 65% after 15 min of treatment in the microwave furnace, while, after 2 h of conventional heat treatment, as explored in a previous study, 98% and 63% of the Cr and V were, respectively, leached. Full article

The recovery of vanadium from titanium tetrachloride tail residue is a resource-efficient and environment-friendly method for treating hazardous vanadium-containing solid waste. In this study, to maximize the recovery rate of vanadium in the vanadium extraction process, the independent calcination and leaching factors were optimized using response surface methodology, in terms of calcination temperature (750–950 °C), calcination time (60–180 min), leaching liquid–solid ratio (5–25 mL/g), and leaching time (30–150 min). The results revealed that the calcination temperature was the most effective parameter for vanadium recovery, while the liquid–solid ratio was the least effective factor. Additionally, the optimal conditions were identified as a calcination temperature of 937 °C, a calcination time of 150 min, a leaching solid-to-liquid ratio of 17.4 mL/g, and a leaching time of 150 min. The maximum predicted recovery rate of vanadium by the model regression equation reached 93.1% and showed high credibility consistent with the experimental recovery rate of 93%. Full article

Vanadium is a significant metal, and its derivatives are widely employed in industry. One of the essential vanadium compounds is vanadium pentoxide (V₂O₅), which is mostly recovered from titanomagnetite, uranium–vanadium deposits, phosphate rocks, and spent catalysts. A smart method for the characterization and recovery of vanadium pentoxide (V₂O₅) was investigated and implemented as a small-scale benchtop model. Several nondestructive analytical techniques, such as particle size analysis, X-ray fluorescence (XRF), inductively coupled plasma (ICP), and X-ray diffraction (XRD) were used to determine the physical and chemical properties, such as the particle size and composition, of the samples before and after the recovery process of vanadium pentoxide (V₂O₅). After sample preparation, several acid and alkali leaching techniques were investigated. A noncorrosive, environmentally friendly extraction method based on the use of less harmful acids was applied in batch and column experiments for the extraction of V₂O₅ as vanadium ions from a spent vanadium catalyst. In batching experiments, different acids and bases were examined as leaching solution agents; oxalic acid showed the best percent recovery for vanadium ions compared with the other acids used. The effects of the contact time, acid concentration, solid-to-liquid ratio, stirring rate, and temperature were studied to optimize the leaching conditions. Oxalic acid with a 6% (w/w) to a 1/10 solid-to-liquid ratio at 300 rpm and 50 °C was the optimal condition for extraction (67.43% recovery). On the other hand, the column experiment with a 150 cm long and 5 cm i.d. and 144 h contact time using the same leaching reagent, 6% oxalic acid, showed a 94.42% recovery. The results of the present work indicate the possibility of the recovery of vanadium pentoxide from the spent vanadium catalyst used in the sulfuric acid industry in Jordan. Full article

Hydrothermal leaching vanadium using oxalic acid is a novel method reported recently to overcome the serious environmental problems caused by traditional extracting processes. In view of its promising application potential, the hydrothermal leaching kinetics of vanadium from a concentrate mainly composed of Fe_3−xV_xO₄ mineral via oxalic acid were investigated in this study. Firstly, the effects of the temperature and concentration of oxalic acid on the leaching behavior of vanadium were studied by measuring the leaching efficiency of vanadium at various times. Then, by fitting the measured leaching efficiency data to the proposed kinetic model, the leaching mechanism was analyzed and the rate-controlling step of the leaching process, the apparent activation energy, and the order of the chemical reactions were determined. Finally, a kinetic model was proposed to describe the present investigated leaching process. Detailed results are as follows: (1) an interfacial chemical reaction was the rate-controlling step of the present hydrothermal leaching process within temperatures ranging from 363 to 403 K, and the leaching efficiency was less than 85%; (2) the apparent activation energy of the interfacial chemical reaction was 45.6 kJ/mol; (3) the order of the interfacial chemical reaction to the concentration of oxalic acid was around 1.66. Full article

In the vitrification of high-level radioactive liquid waste (HLW), the separation of sodium-molybdate melts is a problem because it reduces the chemical durability of the vitrified waste. A glass with both high MoO₃ solubility and chemical durability is required for the safe disposal of radioactive waste. In this study, we investigate the effects of vanadium oxide on the phase separation of the molybdenum-rich phase and the water resistance of the resulting glass by phase equilibrium experiments and chemical durability test. Phase equilibrium experiments were performed on SiO₂-B₂O₃-Al₂O₃-ZnO-CaO-Na₂O-LiO₂-MoO₃ system glasses and on glasses with V₂O₅ added. The results showed that MoO₃ solubility increased when V₂O₅ was added. The increase in MoO₃ solubility in borosilicate melts may be associated with the viscosity-lowering effect of V₂O₅. Chemical durability tests were performed on borosilicate glass compositions obtained from phase equilibrium experiments. The normalized leaching rates of V₂O₅-bearing glasses were higher than those of other glasses. This is due to the higher network modifier/network former ratio of the glass tested. The normalized elemental mass loss of glass containing waste components increases with increasing leaching duration. This suggests that the waste component prevents the formation of a gel layer at the reaction front. Full article

This paper investigated a pellet ore production process in which vanadium was extracted from vanadium and titanium magnetite concentrates using sulfuric acid leaching. Calcium and magnesium were added to the iron ore concentrate during pellet production to produce calcium vanadate and magnesium vanadate after roasting. The pellets were leached with sulfuric acid solution to extract V⁵⁺. The resulting pellets had a compressive strength of 3375 N after primary roasting, a good pellet morphology after acid leaching, and simple liquid–solid separation. Under the optimal experimental conditions, the vanadium leaching rate in the pellets reached 77.86%, while the iron leaching rate was only 1.17%. The pellets did not fragment, which was an improvement upon existing vanadium extraction methods. The strength of the pellets after vanadium extraction decreased to 563 N, but after secondary roasting, the compressive strength of the pellets reached 2578 N, which was suitable for blast furnace ironmaking. The roasting and acid leaching experiments showed that the vanadium extraction process resulted in suitable pellet properties. The use of low compound additives can effectively improve the leaching effect, while avoiding the previous problems of too many additives, pellet iron grade reduction, or the pursuit of high vanadium extraction rate pellet breakage and serious high secondary use process costs. Full article

The conventional V₂O₅ preparation processes include ion exchange, chemical precipitation, solvent extraction, and other processes. Given the long process and complex operation nature of traditional V₂O₅ production methods, we herein developed a short-process, low-temperature, and convenient operation method of isolating vanadium (in the form of V₂O₅) from shale acid leaching solution. The acid leaching solution was oxidized with NaClO₃ and pH-adjusted with NaOH to form a vanadium-containing precipitate, which was mixed with AlCl₃ (V:AlCl₃ = 1:5, mol/mol) and roasted for 120 min at 170 °C to afford vanadium oxytrichloride (VOCl₃) with a purity of 99.59%. In addition, the vanadium-containing precipitate was mixed with AlCl₃ and NaCl (V:AlCl₃:NaCl = 3:12:8, mol/mol/mol) and roasted for 120 min at 170 °C to afford VOCl₃ with a purity of 99.94%. VOCl₃ (purity of 99.94%) was dissolved in ultrapure water, and the solution (32 g_vanadium/L) was treated with NH₃·H₂O (NH₃:V = 1.34, mol/mol) at 50 °C for 120 min. The obtained precipitate (vanadium precipitation rate = 99.28%) was roasted at 550 °C for 3 h to afford high-purity vanadium pentoxide (V₂O₅) with a purity of 99.86%. Compared with the traditional hydrometallurgical method of V₂O₅ preparation, our method avoided solvent extraction and other undesired processes and the overall process flow is greatly shortened, thus having high practical value. Full article

In this study, a clean pellet production method of calcium roasting and sulfuric acid leaching of vanadium from vanadium and titanium magnetite concentrates is proposed, which can effectively separate vanadium and iron, and the pellets after acid leaching and vanadium extraction can be used as raw material for iron making after secondary roasting. During the experiment, only 2% Ca(OH)₂ was added as the calcifier to make pellets, and vanadium was extracted by acid leaching after calcination. Under the optimum conditions, the vanadium leaching rate was 74.51%, and the iron leaching rate was only 1.05%. After secondary roasting, the compressive strength of the pellets was 2358 N, and the qualification rate was 97%. Additionally, after acid leaching and vanadium extraction, the impurities in the pellet were partially removed, and the iron content of the pellet increased by 6.6%, which is more conducive to subsequent ironmaking. The roasting and acid leaching experiments show that based on the production of iron smelting pellets, the use of pellets can better extract vanadium from the titanium magnetite concentrate, while avoiding the problems of excessive additives to reduce the iron grade of pellets. Or the pursuit of high vanadium extraction rate pellets, which can be seriously damaged and difficult to use later. This process can perform a comprehensive utilization of vanadium titanium magnetite, and has certain guiding significance for industrial production. Full article

Black shale ore contains rich strategic metal resources such as vanadium, nickel, and molybdenum, but due to its complex composition, it is currently only used in the vanadium extraction industry. Metals such as nickel and molybdenum have not been effectively recovered, resulting in environmental pollution and resource waste. Using mineralogical features and a combination of beneficiation and metallurgy-based tests, the present work carried out feasibility studies of the combined beneficiation and metallurgy processes. The mineralogical features of the stone coal sample were studied using chemical analysis, an automatic mineral analyzer (BPMA), etc., and we identified the main phase composition, embedded characteristics, and particle size distribution of the associated strategic metals, vanadium, nickel, and molybdenum. The results showed that the grade of V₂O₅ in the stone coal was 1.29%, which was mainly present in carbonaceous clay and mica minerals. The nickel grade was 0.53%, mainly in the form of nickel–magnesium spinel and a small amount of nickel-containing magnesite. The stone coal contained 0.11% molybdenum; the mineral particles were fine, mostly in the form of molybdenite, and some were associated with carbonaceous matter and carbonaceous clay minerals. Based on the mineralogical feature, we proposed using the scrubbing–desliming and flotation process to enrich vanadium, nickel, and molybdenum. Our preliminary experiments obtained two products: vanadium–molybdenum-rich sludge and nickel-containing tailings. The V₂O₅ and molybdenum grades in the sludge were 4.10% and 0.44%, respectively, and the recovery was 41.31% and 51.40%, respectively. The nickel grade in the tailings was 1.49%. These products were roasted and leached. The vanadium, nickel, and molybdenum in the stone coal were effectively recovered through the beneficiation–metallurgy combination process, and the comprehensive utilization rate of the stone coal was improved. Full article

Here, a process for leaching vanadium from calcified roasting pellets (CPVC) of vanadium–titanium-iron concentrate by a two-stage sulfuric acid cycle was proposed. The first stage of leaching was mainly for the removal of silicon from the pellet and leaching solution. After the second stage, the total leaching rates of vanadium and iron were 75.52% and 0.71%, respectively. The concentration of vanadium in the leaching solution reached 6.80 g/L, which can subsequently direct a vanadium precipitation process without extraction and enrichment. After the second roasting, the crushing strength of the pellets reached 2250 N, which met the requirement for blast furnace iron making. The Eh-pH diagrams of the V-Fe-H₂O system at different temperatures were plotted. Thermodynamically, it was difficult to selectively leach vanadium and iron by changing the conventional acid leaching conditions. In addition, the pellets before and after leaching were analyzed. The grade of iron in the pellets increased slightly after leaching, and the main phases in the pellets remained as Fe₂O₃ and Fe₉TiO₁₅. The S in the sulfuric acid solution entered the leached pellets during the acid leaching reaction and was removed by the second roasting of the leached pellets. Full article