Recovery of vanadium from calcification roasted-acid leaching tailing by enhanced acid leaching

Vanadium extraction from steel slag: Generation, recycling and management

The metal vanadium has superior physical and chemical properties and has a wide range of applications in many fields of modern industry. The increasing demand for vanadium worldwide has led to the need to guarantee sustainable vanadium production. The smelting process of vanadium and titanium magnetite produces vanadium-bearing steel slag, a key material for vanadium extraction. Herein, vanadium production, consumption, and steel slag properties are discussed. A detailed review of methods for extracting vanadium from vanadium-bearing steel slag is presented, including the most commonly used roasting and leaching method, and direct leaching, bioleaching and enhanced leaching methods are also described. Finally, the rules and regulations of steel slag management are introduced. In general, it is necessary to further develop environmentally friendly vanadium extraction methods and technologies from vanadium containing solid wastes. This study provides research directions for the technology of vanadium extraction from steel slag.

A theoretical analysis of the vibrational modes of ammonium metavanadate

Vanadium(v) is an extremely rare and precious metal, mainly used in aerospace equipment and new energy construction. However, an efficient, simple, and environmentally friendly method for separating V from its compounds is still lacking. In this study, we used first-principles density functional theory to analyse the vibrational phonon density of states of ammonium metavanadate and simulated its infrared absorption and Raman scattering spectra. By analysing the normal modes, we found that the V-related vibration has a strong infrared absorption peak at 711 cm^-1, while other significant peaks above 2800 cm^-1 are from N-H stretching vibrations. Therefore, we propose that providing high-power terahertz laser radiation at 711 cm^-1 may facilitate the separation of V from its compounds through phonon-photon resonance absorption. With the continuous progress of terahertz laser technology, this technique is expected to be developed in the future, and it may offer new technological possibilities.

Removal of Sodium from Vanadium Tailings by Calcification Roasting in Reducing Atmosphere

Vanadium tailings from vanadium extraction by a sodium roasting process are solid waste and cannot be used in sintering and ironmaking due to their high sodium content. In this paper, a calcification and reduction roasting process was proposed to remove sodium from vanadium tailings. The effects of Ca(OH)₂ addition, reduction temperature, and roasting time on the sodium removal behavior and compression strength of pellets were studied. The addition of Ca(OH)₂ and the reduction of iron oxides promoted the sodium-containing phases to transform to be simpler, which could enhance sodium removal. The sodium removal rate was up to 93.47% and the compression strength of the reduced products was 4497 N/P, and the metallized ratio of the product was higher than 70% under the optimal conditions: roasting at 1200 °C for 2 h with the Ca(OH)₂ addition of 35%. The treated product after removing sodium can be recycled in the ironmaking process in a steel company.

Analysis of Influencing Factors of Cementitious Material Properties of Lead-Zinc Tailings Based on Orthogonal Tests

At present, the treatment of tailings is mostly carried out in the form of stacking in tailings ponds, resulting in a huge waste of mineral resources and a major threat to the environment and ecology. Using tailings instead of a part of the cement to make cementitious materials is an effective way to reduce the accumulation of tailings. In this paper, lead-zinc tailings-based cementitious materials were prepared by using lead-zinc tailings, fly ash, and ordinary Portland cement, and the effects of four factors on the mechanical properties of lead-zinc tailings, as well as fly ash content, cement content, and water-binder ratio were studied by orthogonal experiments. The corresponding relationship between the factors and the properties of cementitious materials was determined, and the optimization and prediction of the raw material ratio of lead-zinc tailings-based cementitious materials were realized. The test showed the ratio of raw materials to be at the lowest price ratio. Synchronously the ratio that meets the minimum strength requirements was predicted. When the proportion of fly ash:lead and zinc tailings:cement = 30:40:30 and the water-binder ratio was 0.4, the predicted compressive strength of the prepared cementitious material achieved 22.281 MPa, which meets the strength requirements, while the total content of lead-zinc tailings and fly ash was the highest at this time.

The impacts of aging pH and time of acid mine drainage solutions on Fe mineralogy and chemical fractions of heavy metals in the sediments

Fe (oxyhydr)oxides are the main components that accumulate heavy metals (HMs) in the acid mine drainage (AMD) sediments, but how the aging pH and time of AMD solution affects the Fe mineralogy and HMs speciation remains ambiguous. Herein, we determined the impacts of aging pH and time on the Fe mineralogy and chemical fractions of HMs in the sediments from Dabaoshan mining area using mineral characterizations, chemical extraction, and AMD solution incubation. For the natural AMD sediments, jarosite and goethite are the major Fe (oxyhydr)oxides in sample S1 with solution pH 2.68, while schwertmannite is dominant in sample S2 with solution pH 6.78, co-existing minor ferrihydrite. With increasing the AMD solution pH, the total contents of HMs (expect for As) and the reducible fraction of HMs (expect for Pb) in the sediments both increase. The HMs of Mn, Zn, Ni, and Cd are mainly associated with Fe (oxyhydr)oxides, while Pb possibly exists as Pb-bearing minerals (e.g., PbSO₄) in the sediments. The oxidizable fraction of all HMs is negligible in both sediments. When the AMD solution of S1 was aged at different pHs, schwertmannite is dominant initially at all pHs, with a higher crystallinity being at a lower pH. With increasing aging time, the pre-formed schwertmannite transforms to goethite and jarosite at pH ≤ 3, while it keeps stable at pH 5 and 7 due to the accumulation of more HMs. These new insights are essential to assess the mobility and availability of HMs in the AMD-affected areas.

Mineralogical Properties of a Refractory Tantalum-Niobium Slag and the Effect of Roasting on the Leaching of Uranium-Thorium

In order to realize sustainable development, it is beneficial to explore an appropriate process to recover the radionuclides contained in tantalum-niobium slag. By micro-mineralogical analysis and roasting experiments, the effect of uranium-thorium leaching from a refractory tantalum-niobium slag is investigated. The uranium and thorium content in the slag is 2.26 × 10³ mg/kg and 7.84 × 10³ mg/kg, which have large recovery value. As the surface area and pore size of the slag are very small, the leaching agent cannot fully penetrate the particles. Various methods of characterization are used to analyze the mineralogical properties of roasted slag at different temperatures. The leaching ratio of U-Th is 90.84% and 96.62% at the optimum roasting temperature of 500 °C, which are about 39% and 27% higher than original samples. The oxidants Fe³⁺, O₂ and Mn can also promote the conversion of insoluble U(IV) to soluble U(VI). Roasting reduces the content of organic C and S, thereby preventing reduction of U(VI), and increasing pore size as well as specific surface area also promote radionuclide leaching. Thus, the roasting method at 500 °C can destroy the surface wrapping structure of radionuclides, reduce the internal density of minerals, and improve uranium-thorium leaching ratio significantly. It is of great practical significance to reduce the radioactive hazard of waste tantalum-niobium slag and to strengthen the sustainable utilization of resources by suitable process improvement techniques.

Mechanism on the Separation of Vanadium and Titanium from Vanadium Slag by Roasting with Ammonium Sulfate

The technology of simultaneously recovering V and Ti from vanadium slag via ammonium salt roasting has proven to be an efficient route. However, due to the phase stability and complex chemical composition of vanadium slag, intermediate materials containing Fe, V, Ti and Mn are difficult to be characterized critically. This work aims to investigate the decomposition and transformation of vanadium slag during ammonium salt roasting, using a combination of FT-IR, XRD, XPS and SEM techniques. It was found that the lattice structure of Fe-contained spinel would be transformed from FeV2O4 to Fe2+VnFe2−nO4 (0 < n < 2) during directly roasting in the air. However, there is no obvious change for Ti-contained and Mn-contained spinel. Using NH4HSO4 (ABS) as an additive and roasting the slag in the N2 atmosphere, those spinels would be decomposed into various sulfate salts. Meanwhile, when the slag was roasted with NH4HSO4 in the air, a part of Fe(II) in (NH4)2Fe(SO4)2 would be transferred into Fe(III), but V(III), Ti(IV) and Mn(II) from those salts would remain the same valance state. Ultimately, about 88% V and 81% Ti were recovered, when vanadium slag was roasted at 663.15 K with a 1:5 ratio of slag-to-NH4HSO4 and followed by 8 vol.% H2SO4 leaching.

Soil indigenous microorganisms alleviate soluble vanadium release from industrial dusts

Vanadium-bearing dusts from industrial processes release abundant toxic vanadium, posing imminent ecological and human health concerns. Although the precipitation of these dusts has been recognized as the main source of soil vanadium pollution, little is known regarding the interrelationships between industrial dusts and soil inherent compositions. In this study, the interactions between dusts from vanadium smelting and soil indigenous microorganisms were investigated. Soluble vanadium (V) [V(V)] released from industrial dusts was reduced by 41.5 ± 0.39% with soil addition, compared to water leaching. Reducible fraction accounted for the highest proportion (55.1 ± 1.73%) of vanadium speciation in the resultant soils, while residual vanadium fraction increased to 83.7 ± 3.22% in the leached dusts. Functional genera (e.g., Aliihoeflea, Actinotalea) that transformed V(V) to insoluble vanadium (IV) alleviated dissolved vanadium release. Nitrate/nitrite reduction and glutathione metabolisms contributed to V(V) immobilization primarily. Structural equation model analysis indicated that V(V) reducers had significant negative impacts on soluble V(V) in the leachate. This first-attempt study highlights the importance of soil microorganisms in immobilizing vanadium from industrial dusts, which is helpful to develop novel strategies to reduce their environmental risks associated to vanadium smelting process.

Will Vanadium-Based Electrode Materials Become the Future Choice for Metal-Ion Batteries?

Metal-ion batteries have emerged as promising candidates for energy storage system due to their unlimited resources and competitive price/performance ratio. Vanadium-based compounds have diverse oxidation states rendering various open-frameworks for ions storage. To date, some vanadium-based polyanionic compounds have shown great potential as high-performance electrode materials. However, there has been a growing concern regarding the cost and environmental risk of vanadium. In this Review, all links in the industry chain of vanadium-based electrodes were comprehensively summarized, starting with an analysis of the resources, applications, and price fluctuation of vanadium. The manufacturing processes of the vanadium extraction and recovery technologies were discussed. Moreover, the commercial potentials of some typical electrode materials were critically appraised. Finally, the environmental impact and sustainability of the industry chain were evaluated. This critical Review will provide a clear vision of the prospects and challenges of developing vanadium-based electrode materials.

A comparative study on adsorption behavior of iodinated X-ray contrast media iohexol and amidotrizoic acid by magnetic-activated carbon

As persistent and ubiquitous contaminants in water, iodinated X-ray contrast media (ICM) pose a non-negligible risk to the environment and human health. In this study, we investigated the adsorption behavior of two typical ICM compounds, iohexol (IOH) and amidotrizoic acid (DTZ), on magnetic activated carbon. Theoretical investigations, using density functional theory, identified the molecule structures and calculated the molecular diameters of IOH (1.68 nm) and DTZ (1.16 nm), which revealed that ICM could be adsorbed by mesopores and larger micropores. Therefore, magnetic activated carbon with a porous structure was prepared by the co-precipitation method to investigate the adsorption mechanism of IOH and DTZ. MAC--5 (magnetic activated carbon with a theoretical iron oxide content of 37%) showed the best adsorption ability for both IOH and DTZ, with maximum adsorption capacities of 86.05 and 43.00 mg g^-1, respectively. Adsorption kinetics and isotherm models were applied to explore the mechanisms involved, and the effects of solution pH, initial concentration, temperature, ionic strength, and natural organic matter were also investigated. The pore filling effect, π-π stacking, hydrogen bonding, and electrostatic interaction, were found to be the main adsorption mechanisms. The co-adsorption data showed that competition may occur in ICM coexisting environments. Interestingly, the used MAC--5 could be successfully regenerated and its adsorption efficiency did not decrease significantly after five cycles, indicating that it is a promising adsorbent for ICM. The results from this study provide some new insights for the treatment of water containing ICM.

Solidification/stabilization of heavy metals and its efficiency in lead-zinc tailings using different chemical agents

Lead-zinc tailings are generated during the mining process which is considered as hazardous solid waste due to its high heavy metal content and leachability in the natural state. At present, the most effective technology for disposing heavy metals in solid wastes is the solidification/stabilization (S/S) technique. In terms of S/S technology, chemical stabilization is one of the most potential and practical method. This paper aims to investigate the S/S property of four typical chemical agents (Na₂S, NaH₂PO₄, TMT and Na₂EDTA) on the heavy metals in lead-zinc tailings. The results reveal that the heavy metals lead and zinc in tailings are stabilized more effectively by using chelating agents TMT than by using inorganic chemical agents Na₂S and NaH₂PO₄. When the dosage of TMT reaches 4%, the leaching concentration of lead and zinc is 0.18 and 14.60 mg/L according to toxicity characteristic leaching procedure (TCLP), and the stabilization efficiency of lead and zinc is 99.31% and 80.92%, respectively, while the leaching concentration of lead and zinc just drops to 0.41 and 16.00 mg/L with addition of 10% NaH₂PO₄. Furthermore, the leaching concentration of heavy metal lead in tailings treated by 4% Na₂EDTA increases to 53.44 mg/L which far exceeds the standard of pollution control. Therefore, considering stabilization efficiency and dosage, TMT is the preferred agent for solidifying heavy metals in lead-zinc tailings.

Dynamics of vertical vanadium migration in soil and interactions with indigenous microorganisms adjacent to tailing reservoir

Severe vanadium pollution in deep soil through surface infiltration during mining activities has been particularly concerned, but little is known about vanadium migration dynamics in vertical soil profile. Indigenous microorganisms widely exist in soil, however, their functions and suffered impacts during vertical vanadium migration have rarely been investigated. In this study, 100 cm height columns were constructed with undisturbed soil around vanadium tailing reservoir were constructed to describe vertical vanadium transport process and corresponding interactions between vanadium and indigenous microorganisms. 91 d continuous leaching with pentavalent vanadium [V(V)] showed that V(V) gradually downward migrated. Soil microorganisms slowed down vertical V(V) migration rate by transferring V(V) to insoluble tetravalent vanadium. Enriched Gemmatimonadaceae and Actinobacteria were identified to contribute to microbial V(V) transformation. Co-existing nitrate weakened the soil's ability to intercept V(V) via electron competition. Microbial communities were reshaped by vanadium during leaching, while enzyme activities increased slightly due to vanadium stimulation. This work advances the understanding of vertical vanadium migration characteristics in soil, which is essential to risk management and effective remediation of vanadium-polluted sites.

Efficient Recovery of Vanadium from High-Chromium Vanadium Slag with Calcium-Roasting Acidic Leaching

High-chromium vanadium slag (HCVS) is an important by-product generated during the smelting process of high-chromium-vanadium-titanium-magnetite. Direct acid leaching and calcium-roasting acid leaching technology were applied to recover vanadium and chromium from HCVS. The effects of experimental parameters on the leaching process, including concentration of H2SO4, reaction temperature, reaction time, and liquid-to-solid ratio, were investigated. The XRD and UV-Vis DRS results showed that vanadium and chromium existed in low valence with a spinel structure in the HCVS. The Cr-spinel was too stable to leach out; no more than 8% of the chromium could be leached out both in the direct acid leaching process and calcium-roasting acid-leaching process. Most low valence vanadium could be oxidized to high valence with calcium-roasting technology, and the leaching efficiency could be increased from 33.89% to 89.12% at the selected reaction conditions: concentration of H2SO4 at 40 vt.%, reaction temperature of 90 °C, reaction time of 3 h, liquid-to-solid ratio of 4:1 mL/g, and stirring rate of 500 rpm. The kinetics analysis indicated that the leaching behavior of vanadium followed the shrinking core model well, and the leaching process was controlled by the surface chemical reaction, with an Ea of 58.95 kJ/mol and 62.98 kJ/mol for direct acid leaching and roasting acid leaching, respectively.

Innovative method for minimization of waste containing Fe, Mn and Ti during comprehensive utilization of vanadium slag

More than 1.2 million tons of tailings containing approximately 30 wt% of Fe from traditional vanadium extraction processes are discarded every year as solid waste, which waste resources. In order to achieve effective and green utilization of waste, a novel process was proposed to keep Cr and V at Cr³⁺ and V³⁺ during extraction by using AlCl₃-NaCl-KCl molten salt in Ar gas atmosphere to control the valuable elements (Cr, V, Mn and Fe) from oxidized. The morphological features of vanadium slag reacted in the temperature range from 200 °C to 800 °C and volatilization of samples under different AlCl₃/slag ratios were analyzed. Meanwhile, the chlorinated kinetics of V, Cr, Mn and Fe in vanadium slag were systemically investigated in temperature range of 850 °C-950 °C. The kinetics investigation indicated that the chlorination processes of Fe and Mn were restricted by mass transfer in product layer (Al-Si-O mixture) and the chlorination processes of V and Cr were controlled by surface reaction. The apparent activation energies for Fe, Mn, V, and Cr are 105.28 kJ/mol, 94.26 kJ/mol, 64.64 kJ/mol, and 63.30 kJ/mol, respectively. After chlorination, the separation of metal chlorides was achieved. TiCl₄ is hydrolyzed to obtain TiO₂. Mn can be separated from VCl₃, CrCl₃, FeCl₂, and MnCl₂ by controlling the electrolytic voltages. Fe-V-Cr alloy was obtained by electrolysis at 2.3 V.

Recovery of spent VOSO4 using an organic ligand for vanadium redox flow battery applications

To recover the spent vanadium compound, Rhodamine-B-based Schiff's base ligand (L₁) was synthesized via ultrasonication process and was evaluated with vanadyl sulfate (VOSO₄), which has shown considerable selectivity towards V(IV). The change of the solution color from colorless to pink is attributed to L₁ after the reaction with vanadium ion owing to the successful formation of the vanadium complex and the opening of the spirolactam ring in the L₁ structure. In FT-IR spectra, the vanadyl peaks are co-existed with the L₁ structure, which confirmed the complex formation of the L₁ with vanadium. Similarly, the binding energy of V(IV) was identified at 516.2 eV for V2p_3/2 in XPS spectra. The new strategy for VOSO₄ recovery was established through solvent extraction and acid leaching. After recovery process, the absence of vanadium peak in the XPS confirmed the complete removal of V(IV) from the complex. The recovered VOSO₄ solution used as an electrolyte in vanadium redox flow battery (VRFB) systems, where the unit cell performance is comparable with the conventional electrolyte solution. The advantage of study is reuse of VOSO₄ as a resource for energy storage applications.

Preparation, characterization, and application of magnetic activated carbon for treatment of biologically treated papermaking wastewater

In view of the urgent need for tertiary treatment of papermaking wastewater and the difficulty in separating powdered activated carbon (PAC) from water, the magnetic activated carbon (33%-MPAC, 50%-MPAC and 67%-MPAC) were prepared by chemical coprecipitation method for adsorption of biologically treated papermaking wastewater (BTPW). A series of characterization of MPAC and PAC were carried out and show that the content of iron oxides is negatively related to the proportion of micropores in MPAC. The loaded iron oxides is mainly the mixture of magnetite and maghemite, and the maximum saturation magnetization of MPAC can reach 29.68 emu/g. Batch mode experiments were performed, and found that the adsorption effect of MPAC is slightly worse than that of PAC, the adsorption capacity of COD in MPAC can reach about 65 mg/g, and pH = 2 and 10 °C are more favorable for adsorption. The adsorption isotherms and kinetics were well fitted by the Freundlich model and pseudo-second-order kinetic model, respectively. The selective adsorption was studied by using the excitation emission matrix (EEM) fluorescence spectrum and high-performance size exclusion chromatography (HPSEC). It is concluded that all adsorbents are preferred to adsorb humic acid-like substances (HA). And all adsorbents are preferred to adsorb low apparent molecular weight substances (LAMW, AMW < 1500 Da), with the increase of iron oxides content, the phenomenon of MPAC preferentially adsorbed LAMW became less obvious.

Leaching behavior of metals from iron tailings under varying pH and low-molecular-weight organic acids

The migration of metals (e.g., Fe, Cd, Co, Cr, Cu, Mn, Ni, and Zn) in both of iron tailings under different pH leachates was studied by laboratory static leaching experiments. The results indicated that Fe showed the highest leaching concentration at an initial pH of 2, reaching 16.19 and 51.72 mg L^-1 in the Qian'anling (Q0) and Majuanzi (M0) iron tailings, respectively. Metal ions manifested a strong pH dependence. In addition, the leaching behavior of Cd, Cr, Fe, and Cu for the two tailings was also evaluated under leaching by three low-molecular-weight organic acids (LMWOAs). The results indicated the leaching of Cd and Fe followed the order of citric acid > malic acid > oxalic acid and that the leaching order for Cr and Cu was citric acid > oxalic acid > malic acid. The concentration of Fe was low in 5 mM oxalic acid leaching for 20 days because of the hydrolysis precipitation of iron ions and the complexation with organic ligand. The crystal lattice on the tailings was significantly damaged after leaching. The CO₃^2- peak appeared in M0 with different treatments, and the proportion of COO- fitting peak areas increased markedly after leaching with LMWOAs.

Selective recovery of vanadium as AMV from calcium vanadate sludge by direct AS leaching process: An industrial approach

Generation of calcium vanadate waste sludge their management and treatment.is one of the major problem of metal processing industry. In this paper, we have proposed a simple process for the selective recovery of vanadium as ammonium metavanadate (AMV) from the calcium vanadate sludge using ammonium sulphate (AS) as a leaching agent. Under the optimum leaching condition (pH-7.5, temperature-80 °C, time-1 h, AS reagent-0.5 M) it is possible to leach out 82% of V values from the calcium vanadate sludge. The overall recovery of V is 81% with 98.5% AMV product purity. The AMV product quality from AS leach process has been compared with conventional H₂SO₄ leach process. The proposed process has major advantages such as, better economic benefits, less chemical consumption, minimum effluent recycling and less waste generation.

A critical review on environmental implications, recycling strategies, and ecological remediation for mine tailings

Mine tailings, generated from the extraction, processing, and utilization of mineral resources, have resulted in serious acid mine drainage (AMD) pollution. Recently, scholars are paying more attention to two alternative strategies for resource recovery and ecological reclamation of mine tailings that help to improve the current tailing management, and meanwhile reduce the negative environmental outcomes. This review suggests that the principles of geochemical evolution may provide new perspective for the future in-depth studies regarding the pollution control and risk management. Recent advances in three recycling approaches of tailing resources, termed metal recovery, agricultural fertilizer, and building materials, are further described. These recycling strategies are significantly conducive to decrease the mine tailing stocks for problematic disposal. In this regard, the future recycling approaches should be industrially applicable and technically feasible to achieve the sustainable mining operation. Finally, the current state of tailing phytoremediation technologies is also discussed, while identification and selection of the ideal plants, which is perceived to be the excellent candidates of tailing reclamation, should be the focus of future studies. Based on the findings and perspectives of this review, the present study can act as an important reference for the academic participants involved in this promising field.

An efficient utilization of chromium-containing vanadium tailings: Extraction of chromium by soda roasting-water leaching and preparation of chromium oxide

Chromium-containing vanadium tailings (CCVT), an industrial waste, were utilized to extract chromium efficiently by soda roasting-water leaching process and for the preparation of highly pure chromium oxide. The effect of extraction of chromium under different roasting and leaching conditions were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The maximum chromium extraction rate of 91.51% was obtained when soda (Na₂CO₃) and CCVT were mixed in a molar ratio (n (Na₂CO₃)/n (Cr₂O₃)) of 8, roasted at 900 °C and maintained for 120 min. Then, the roasted product was leached in water at 60 °C for 60 min with a liquid-solid mass ratio (L/S) of 10. During soda roasting, the chromium-containing phase (Fe_0.6Cr_0.4)₂O₃ combines with Na₂CO₃ to form Na₂CrO₄, which was then transferred into the leaching liquid, post water leaching. The by-products such as NaFeTiO₄, Na₂CaSiO₄, and Na_0.68Fe_0.68Si_0.32O₂ were left in the leaching residue which was called chromium tailings (CT). 87.40% chromium oxide was recovered from the unpurified leaching liquid after reduction and precipitation by adding Na₂S, followed by roasting the deposit. This process not only relieved the potential threat of the industrial waste CCVT to the environment but also realized the recovery of the valuable element chromium.