Issue 03, 2026
Research Status and Progress of High-Purity Manganese Preparation Technology
JIANG Dongsheng;ZHAO Zhuan;TANG Huimin;ZHANG Huan;CHE Yusi;HE Jilin;High-purity manganese(generally defined as metallic manganese with purity ≥ 3N) serves as a critical foundational material in advanced technological fields, including semiconductor manufacturing, magnetic materials, and high-performance alloys. Its purity level plays a decisive role in determining the performance, reliability, and service life of the final products. The production of high-purity manganese involves a complex and multi-stage refining process, the core of which lay in the deep removal of diverse impurity elements— both metallic and nonmetallic. The industrial production of high-purity manganese primarily relies on three key techniques: electrolysis, vacuum distillation, and zone melting. These methods are often employed not in isolation, but in integrated process routes that combined their respective strengths to achieve progressively higher purity levels. Electrolysis remains the most widely adopted and mature technique. In this process, commercial-grade manganese is used as the starting material. It was first dissolved to form an electrolyte, which then underwent deep purification through hydrometallurgical methods such as solvent extraction, precipitation, adsorption, or ion exchange to remove the majority of metallic impurities. During the electrolysis stage, process improvements— including the use of novel selenium-free additives, dimensionally stable anodes(DSA), anion exchange membranes(AEM), pulse electrolysis, and chromium-free passivation agents— were implemented. By precisely controlling key parameters such as current density, temperature, and pH value, high-purity manganese( ≥ 3N) was preferentially deposited at the cathode. While this method is well-suited for large-scale production due to its maturity, it struggles to consistently achieve purity levels above 4N and imposes extremely stringent requirements on electrolyte purity. For impurities with vapor pressures significantly different from that of manganese, vacuum distillation offers distinct advantages. This method effectively removes both low-boiling-point and high-boiling-point impurities, enabling the refinement of manganese to purity levels between 4N and 5N. A major benefit of this approach is the absence of chemical additives, making it an environmentally friendly option. However, its efficiency drops considerably for impurities with boiling points close to that of manganese. To attain ultra-high-purity manganese exceeding 5N, zone melting becomes an indispensable final refining step. This technique leverages the segregation effect— the differential solubility of impurities in the solid and liquid phases of manganese. By repeatedly passing a molten zone along the solid ingot, difficult-to-remove impurities such as phosphorus, sulfur, and various interstitial elements are effectively swept toward the end of the bar. Despite its effectiveness in achieving the highest purity grades, this process proves energy-intensive and timeconsuming, leading to lower production efficiency. In modern practice, a sequential purification chain— "Electrolysis → Vacuum distillation → Zone melting" — was commonly employed. This integrated approach systematically leverages the complementary strengths of each technique, forming a comprehensive purification pathway that progressively elevates product purity.This study provides a detailed analysis of the technical characteristics, operational principles, and research progress in these high-purity manganese production routes. It also highlights the inherent challenges, particularly the steep increases in energy consumption and declines in production efficiency associated with higher purity targets. Future development directions are suggested to focus on emerging technologies such as multi-physical field-coupled purification, intelligent full-process control, and advanced methods like vapor deposition or plasma decomposition. These innovations aim to achieve greater refinement, stability, and sustainability in manganese purification, thereby providing valuable insights for the development of next-generation high-purity manganese production processes.
Current Situation and Prospects of Hydrometallurgical Recovery Technology for Cathode Materials of Spent Lithium-ion Batteries
BAO Shenxu;LI Kehui;DING Wei;WANG Zhanhao;ZHANG Hongwei;ZHAO Zhiwei;With the rapid popularization of new energy vehicles and the increasing deployment of energy storage systems, the demand for lithium-ion batteries(LIBs) soars in recent years. This surge leads to a dramatic rise in the number of spent LIBs, presenting significant environmental challenges and resource sustainability concerns. Spent LIBs, particularly their cathode materials, are rich in substantial amounts of valuable metals such as lithium(Li), nickel(Ni), cobalt(Co), and manganese(Mn). These metals are not only strategic resources but also essential raw materials for the continued growth of the battery and energy storage industries. Consequently, the efficient recovery and recycling of these valuable metals become critical for addressing resource depletion, mitigating environmental pollution, and promoting a circular economy. Among the various recycling approaches, hydrometallurgical processes emerge as the mainstream technology for recovering valuable metals from spent LIBs cathode materials. Compared to pyrometallurgical and direct regeneration methods, hydrometallurgical techniques offer higher recovery efficiencies, more controllable operational parameters, and lower energy consumption. This review systematically examines recent advances and key trends in hydrometallurgical recovery processes for spent LIBs cathode materials. It focuses on three major stages of the recycling process: pretreatment of spent LIBs, leaching, and purification of the leachate, each of which plays a pivotal role in overall recovery performance and environmental sustainability.Leaching is identified as the core step in hydrometallurgical recovery, where valuable metals are selectively dissolved into solution. Conventional inorganic acid leaching processes, employing sulfuric or hydrochloric acid, demonstrates excellent metal recovery rates. However, these processes often involve harsh reaction conditions and generate large volumes of acidic wastewater, raising environmental concerns. In recent years, organic acid leaching and bioleaching gain significant attention due to their environmentally friendly nature and capacity to selectively leach metals. Organic acids, such as citric and oxalic acid, exhibit effective complexation and chelation with metal ions, provide potential advantages in leaching efficiency and selectivity. Furthermore, bioleaching using microbial consortia offers a promising green alternative for metal recovery, although its industrial application still face challenges related to reaction kinetics and scalability. The purification and separation of metal ions from the leachate are critical for producing high-purity products and ensuring the economic viability of the recycling process. Solvent extraction is widely adopted in industry due to its superior selectivity and scalability. However, challenges such as the high cost of organic extractants and the potential for solvent loss and environmental pollution limit its wide application. Chemical precipitation provides a simple and cost-effective approach but often suffered from coprecipitation of impurities, which compromise product purity. Ion exchange technology shows promise for selective removal of impurities, yet issues such as resin fouling and regeneration require further investigation. Electrochemical methods, particularly electrochemical deposition, recently attract attention for their potential in green and energyefficient metal recovery, though additional research is needed to optimize operational parameters and improve deposition efficiency. This paper also evaluates these hydrometallurgical processes from multiple perspectives, including process energy consumption, metal recovery rates, environmental impacts, and economic feasibility. It highlights the advantages and limitations of different methods, providing a comprehensive understanding of the current state of the field. Furthermore, the critical knowledge gaps and technical challenges that must be addressed to promote the industrial application of hydrometallurgical recycling processes are identified. Finally, considering evolving industrial needs and technological advancements, the research directions and potential applications in the future are discussed. The integration of green chemistry principles, such as the development of low-cost, biodegradable leaching agents and environmentally benign separation techniques, is seen as essential for achieving sustainable recycling practices.
Progress of Highly Efficient and Clean Vanadium Extraction Technology
WANG Jin;YU Wenhao;XIANG Junyi;ZHONG Dapeng;HOU Yong;HE Wenyi;XIN Yuntao;L?? Xuewei;Vanadium, renowned as "modern industry's monosodium glutamate", is a critical strategic metal indispensable in fields such as steel strengthening, aerospace, chemical catalysis, and particularly vanadium flow batteries for large-scale energy storage. Despite China's significant advantages in vanadium resource reserves and industrial scale, its vanadium metallurgy sector faces pressing challenges related to high energy consumption, environmental pollution, and the need for product diversification and valorization. The complex and diverse nature of vanadium-bearing resources necessitates the development of efficient and clean extraction technologies, which has attracted widespread attention from both academia and industry. This paper provides a comprehensive review of the recent advances in vanadium extraction technologies, aiming to outline a path towards sustainable vanadium production. The review begins with an overview of the global vanadium landscape, including resource distribution(highlighting the dominance of vanadium-titanium magnetite and China's unique vanadium-bearing stone coal), market supply and demand trends, and the extensive application sectors of vanadium products. It systematically elaborates on the entire vanadium extraction process, which typically involves pre-treatment, roasting, leaching, purification, and precipitation, focusing on the technological progress for major resources like vanadium slag, vanadium-bearing stone coal, and secondary resources. The core of this technical review lies in a detailed and critical analysis of the key unit operations. For roasting, the workhorse for liberating vanadium from refractory phases, various techniques are compared. While traditional sodium roasting offers high conversion efficiency, it generates harmful gases. Calcium roasting is more environmentally friendly but suffers from lower vanadium recovery and requires subsequent acid leaching. Composite roasting demonstrates synergistic effects for improved efficiency, whereas additive-free roasting avoids pollution but demands extreme conditions. Emerging technologies like sub-molten salt roasting are highlighted for their high extraction rates at lower temperatures and potential for synchronous extraction of valuable elements like chromium, though challenges related to severe equipment corrosion and high reagent consumption remain. In the leaching stage, beyond conventional water, acid, and alkali leaching, the potential of environmentally benign organic acids is discussed. Process intensification methods such as pressure leaching(which omits the roasting step), electric field enhancement, and multi-stage leaching schemes are analyzed for their benefits in improving kinetics and reducing consumption, albeit often at the cost of higher operational complexity or capital investment. Bioleaching, though green, is hampered by extremely slow kinetics. The purification of pregnant leach solutions is critical for obtaining high-purity products. Established methods like chemical precipitation(simple but less selective), solvent extraction(high selectivity but costly organic phases), and ion exchange(suited for dilute solutions) are reviewed. Emerging techniques such as solvent-impregnated resins and selective capacitive adsorption are introduced as promising avenues for high-precision separation. For the final precipitation step, the review contrasts the industrially dominant ammonium salt precipitation(which produces high-purity products but causes ammonia-nitrogen pollution) with emerging ammonia-free methods using reagents like alcohols or organic acids, noting the need for cost reduction. The direct precipitation of high-value lowervalent vanadium oxides is also highlighted as a valuable strategy. Finally, the paper concludes with perspectives on future directions, emphasizing the need for integrated innovation. This includes the development of novel roasting systems and additive formulations, the creation of organic acid compound leaching systems coupled with reagent regeneration technologies, and the optimization of purification sequences. Furthermore, the review stresses the importance of establishing resource circulation models for by-products and waste streams, mitigating the carbon footprint through low-carbon processes and green energy integration, and diversifying vanadium products to meet the demands of high-end applications. It is envisioned that through interdisciplinary collaboration and a focus on fundamental research addressing engineering challenges, efficient and clean vanadium extraction technologies will advance significantly, fostering the green and sustainable development of the global vanadium industry.
Research Status and Development Trend of Electrolyte Technology for Vanadium Redox Flow Battery
WEN Hanwei;YE Guohua;WANG Junshu;HONG Jiaxing;YANG Xirui;AO Hongpeng;As a key technology to meet the needs of large-scale energy storage, all-vanadium redox flow battery(VRFB) has the core advantages of high safety, excellent stability, long service life, flexible design and environmental friendliness. It has broad application prospects in the fields of power grid peak shaving, new energy grid connection and emergency power supply. As the core energy storage medium of VRFB, the cost of electrolyte accounts for about 52% of the total cost of the battery. Its performance directly determines the energy density, cycle stability, temperature adaptability and overall economy of the battery. Therefore, it is of great significance to carry out systematic research on the preparation, performance optimization, impurity control and recycling of vanadium electrolyte, which is of great significance to promote the large-scale application of VRFB technology. Focusing on the vanadium electrolyte technology system, this paper reviews the research progress of its preparation process, performance optimization, impurity effect and recycling. In terms of preparation methods, the technical characteristics of three mainstream processes of chemical reduction, electrolysis and solvent extraction are compared and analyzed. The chemical reduction process is simple and suitable for large-scale production, but there are problems such as low reduction rate and easy introduction of impurities. The electrolysis process is short and the product purity is high, but it faces challenges such as high energy consumption and complex equipment. Solvent extraction method shows good development potential due to its wide adaptability of raw materials, high purity of products and low energy consumption. It is especially suitable for the preparation of high purity electrolyte from complex vanadiumcontaining feed solution by short process. In terms of electrolyte performance optimization, the mechanism of supporting electrolyte systems(such as sulfur-phosphorus mixed acid, HCl solution, proton ionic liquid, etc.) to improve the solubility of vanadium ions, inhibit the formation of precipitates, and broaden the working temperature range was systematically summarized. The effects of additives such as NaCl, Zn2+, and sodium dihydrogen phosphate on enhancing the electrochemical activity, ion conductivity, and thermal stability of the electrolyte were discussed. In terms of impurity influence and control, the effects of typical impurities such as Al and K+ on electrolyte viscosity, conductivity, electrode reaction reversibility and battery efficiency were reviewed. The applicability and limitations of impurity removal technologies such as chemical precipitation, solvent extraction, ion exchange and capacitive deionization were introduced. In addition, this paper also summarizes the methods of resource recovery and regeneration of spent electrolyte, including two technical routes of vanadium resource extraction and valence state rebalancing, which provides a reference for the whole life cycle management of electrolyte. Finally, combined with the current technical bottlenecks, the future development trend is prospected from the aspects of low-cost green preparation process development, wide temperature range high concentration electrolyte system construction, impurity synergy mechanism research and multi-process joint innovation, which provides a certain reference for the performance breakthrough and industrial application of vanadium electrolyte technology.
Aluminum Thermal Reduction Technology and Its Application in Tantalum and Niobium Metallurgy
QI Qi;LI Xianfeng;YANG Bin;CHEN Hubing;WAN Jun;LAN Weifeng;Aluminum thermal reduction technology, an efficient metallurgical method based on high-temperature redox reactions between aluminum and metal oxides, holds a crucial role in modern industry due to its advantages of self-heating, fast reaction rate, high product purity, and flexible processes. Its core principle relies on aluminum's strong reducibility to reduce metal oxides via spontaneously generated high temperatures; the heat released sustains the reaction without external heat sources, combining environmental friendliness and efficiency. The general chemical reaction is 3M_xO_y+2y Al=y Al_2O_3+3x M(M=target metal)+ΔH(reaction enthalpy). This reaction produces stable Al_2O3 and substantial heat, keeping the resulting metal molten to facilitate slag-metal separation. Precise control of the process requires regulating key factors: reaction heat effect, smelting slag properties, reactor performance, and reaction rate. For heat effect control, strategies include adjusting reactant ratios(e.g., increasing metal oxide proportion), adding diluents(inert Al_2O3 powder) to absorb excess heat, or using exothermic agents(NaClO3, KClO3) to supplement heat for insufficient reactions. Slag regulation uses formers like CaO, MgO, and CaF2 to modify slag acidity-alkalinity and melting point, improving fluidity and impurity adsorption— vital for efficient separation. Reactors, as core equipment, use refractory materials(high-magnesium bricks, corundum bricks) or water-cooled metal crucibles to withstand temperatures over 2 500 ℃ and resist slag erosion. Reaction rate is controlled by adjusting reactant particle size(ultrafine Al powder accelerates reactions without excess violence), staged feeding, or catalysts(CaF2, chlorides) to lower activation energy. Additionally, vacuum aluminum thermal technology expands applications: vacuum reduces gas partial pressure, promoting reduction, reducing metal oxidation and impurities, and enhancing purity. Industrially, the technology is widely used in metal smelting, special alloy preparation, welding, and weapon manufacturing. In smelting, it produces ferroalloys, master alloys, and refractory metals(chromium, manganese). For example, Dalian Rongde Special Materials makes 1.5-ton master alloys for titanium; Chengde Tianda Vanadium Industry produces high-purity V-Al-Fe alloys via vacuum methods for aerospace. Germany's GfE uses ceramic crucibles to make high-purity alloys like VAl and NiNb. Beyond mainstream uses, it manufactures corrosive ammunition(high-temperature reactions), aluminum thermal welding(rails, oil pipelines), and special materials(ceramic-lined steel pipes). Its application in tantalum-niobium(Ta-Nb) metallurgy is prominent, covering direct reduction of low-grade ores, high-purity oxide reduction, and alloy preparation. For ore reduction, it outperforms traditional carbothermal/sodium thermal methods with lower energy, shorter processes, and less equipment investment. Pyrochlore(major niobium ore) undergoes aluminum thermal reduction plus arc furnace smelting to get niobium oxides/metal; tantalite and manganese tantalate need pretreatment, acid leaching for Ta_2O5, then reduction. Scholars have conducted in-depth studies: R.I. Gulyaev explored natural manganese tantalate's lowtemperature interaction with Al powder and Ca-Al alloys, revealing Ta-Nb intermetallic phases; Wang Xiaorong separated Ta-Nb from U-Th in pyrochlore(over 90% U-Th in slag). Global Ta-Nb resources are concentrated—Brazil dominates niobium, the DRC and Rwanda major dominates tantalum sources. Key enterprises include Brazil's CBMM(FeNb with 65%–67% Nb, low impurities), UK/Australia's Materion(high-purity FeNb with Nb>70%), and China's CNMC Eastern, CITIC Metal, Ximei Resources(FeNb with 60%–70% Nb, FeTa with 30%–70% Ta). For oxide reduction, the process includes raw material preparation(crushing Ta_2O5/Nb_2O5 to pass 40–100 mesh, high-purity Al powder>99.5%), batching(1.1–1.3 times of theoretical Al), ignition, separation, and refining. Ta_2O5 reduction(ΔH=–1398.12 kJ/kg charge) and Nb_2O5 reduction(ΔH=–2503.23 kJ/kg charge) release massive heat, requiring precise particle size and ratio control. In production, Ta-Nb recovery exceeds 95% and purity over 99.5%. The US's Materion makes industrial-grade(99.5%–99.9%) and ultra-high-purity( ≥ 99.995%) Ta-Nb; China's Ximei Resources stably produces 3N5-grade niobium(over 1 000 t/a), and CNMC Eastern makes 5N9-grade tantalum target blanks. For Ta-Nb alloy preparation, the technology produces FeTa, Nb-Al, FeNb, and Nb-Ni alloys. FeTa(used in electronics/superalloys) needs process optimization to avoid brittleness; Wang Xiaorong makes low-impurity Ta-Al-Fe alloys under inert gas. Nb-Al alloys(aerospace-critical) show phase changes with Al excess(e.g., Nbss+Nb3 Al at 10% excess, Nb3 Al+Nb2 Al+NbAl3 at 30% excess). FeNb(FeNb20-70, key steel additive) achieves over 97% Nb recovery via one-step reduction, costing 30% less than traditional methods. Nb-Ni alloys(high-temperature components) are made by China's Chengde Tianda Vanadium and Jiangsu Metlink, meeting standards like Brazil's VG221 with low O-N(O<0.05%, N<0.01%). Additionally, the technology prepares Nb-Cr, Ta-Cr, and Nb-Si alloys, expanding applications. Currently, aluminum thermal reduction in Ta-Nb metallurgy evolves toward ultra-high purity, customization, green low-carbon processes, and intelligent manufacturing. This will enhance its strategic value in rare metal metallurgy and new material preparation, supporting high-end equipment manufacturing upgrades and capacity expansion.
Study on the Occurrence State of Vanadium and Minor Elements in Mica-type Vanadium Shale
HU Fangyao;ZHANG Yimin;XUE Nannan;ZHENG Qiushi;This study focuses on mica-type vanadium shale and aims to elucidate the microscopic mechanisms governing vanadium occurrence and its interaction with impurity elements within mica lattices. By integrating multiscale mineralogical characterization with first-principles calculations, this study systematically investigates the site occupancy of vanadium and impurity elements, as well as the electronic-level regulation of vanadium stability induced by these impurities. Comprehensive mineralogical analyses, including X-ray diffraction(XRD), scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS), TESCAN Integrated Mineral Analyzer(TIMA), and polarizing microscopy, collectively confirm that vanadium is mainly hosted in mica minerals and spatially coexists with Fe, Mg, and Al within the octahedral layers. These results indicate that vanadium is structurally bound rather than present in easily leachable forms, explaining its generally low recovery efficiency in hydrometallurgical extraction. Density functional theory(DFT) simulations were performed to further clarify the atomic-scale substitution behavior and energetic preference of vanadium and impurity elements. The calculations demonstrate that vanadium preferentially occupies octahedral coordination sites within the mica structure, substituting for Al3+. However, the mechanisms of impurity accommodation vary among different mica types. In dioctahedral muscovite, Fe and Mg are incorporated through single coordination substitution at the octahedral centers, slightly stabilizing the lattice. In contrast, in trioctahedral phlogopite, Fe and Al atoms enter through tri-coordination, resulting in a significant reduction in total system energy and a stronger lattice stabilization effect. For biotite, however, the replacement of cations by impurities is energetically unfavorable, implying that structural rigidity may restrict element migration and substitution. Further electronic structure analysis based on density of states(DOS) reveals that impurity incorporation exerts a pronounced influence on the local electronic configuration of vanadium. The presence of Fe, Mg, and Al alters the charge distribution around the V— O bonds, enhances orbital hybridization between vanadium 3d and oxygen 2p states, and ultimately increases both the V— O bond strength and the overall binding energy of the system. These modifications contribute to the enhanced structural stability of vanadiumbearing mica but simultaneously reduce the reactivity of vanadium during leaching, providing a fundamental explanation for its refractory behavior. In summary, this work establishes a clear structure-property relationship between impurity element substitution, vanadium site occupancy, and lattice stability in mica-type vanadium shale. The findings highlight that the coexistence and coordinated substitution of Fe, Mg, and Al with vanadium are key factors controlling the extractability and leaching kinetics of vanadium. This study provides not only a theoretical framework for understanding the mineralogical constraints of vanadium occurrence but also valuable guidance for optimizing chemical leaching processes and improving vanadium recovery from shale-type deposits.
Construction of Nitrogen-Doped Graphite Felt Electrodes and the Application in Vanadium Batteries
HEI Fuqian;ZHANG Yimin;XUE Nannan;LIU Hong;2-methylimidazole was selected as the nitrogen source, nitrogen atoms were introduced onto the GF surface via an ultrasonic impregnation method, which was favored for its operational simplicity, mild reaction conditions, and avoidance of the high complexity and safety risks associated with traditional nitrogen-doping techniques(such as ammonia gas treatment) or the high equipment requirements of hydrothermal methods. Subsequent to impregnation, the modified GF was subjected to heat treatment at 500 ℃ under nitrogen atmosphere to fabricate nitrogen-doped graphite felt(N-GF) electrodes. Energy-dispersive X-ray spectroscopy(EDS) confirms the uniform distribution of nitrogen on the GF surface, with a measured nitrogen content of 2.3%. X-ray photoelectron spectroscopy(XPS) identifies the chemical states of nitrogen, revealing the presence of pyridinic N, pyrrolic N, and graphitic N, which are critical for providing active sites for vanadium ion reactions. Raman spectroscopy analysis shows that the ID/IG ratio(a key indicator of material defect level) of N-GF is 1.258, significantly higher than that of pristine GF(1.224), indicating that nitrogen doping effectively increases the surface defect level of GF, thereby creating more channels and sites for vanadium ion adsorption and reaction. Electrochemical tests were performed of N-GF. N-GF exhibits higher redox peak currents(177.93 mA/cm2 for oxidation and –170.43 mA/cm2 for reduction in the positive electrolyte, compared to 162.33 mA/cm2 and-155 mA/cm2 for pristine GF) and a more balanced Ipa/Ipc ratio(closer to 1), along with smaller peak potential differences(ΔEp). These results confirm that nitrogen doping significantly enhance the catalytic activity and reversibility of GF for both V2+/V3+ and VO2+/VO2~+ redox couples. Additionally, electrochemical impedance spectroscopy(EIS) tests reveal that N-GF has lower charge transfer resistance compared to pristine GF, which effectively reduce the reaction barrier for vanadium ions at the electrode-electrolyte interface, thereby improving the reaction kinetics. At 220 mA/cm2, the N-GF-based battery achieves a voltage efficiency(VE) of 79.5% and an energy efficiency(EE) of 76.8%, both outperforming the pristine GF-based battery(which has a VE of 76% and an EE of 74%). Long-term stability tests involving 200 consecutive charge-discharge cycles show that N-GF maintain an energy efficiency retention rate of 95.6%, which is higher than the 95.2% retention rate of pristine GF, demonstrating the excellent durability of N-GF for prolonged use in VRFB. This study employed 2-methylimidazole as a nitrogen source to fabricate high-performance N-GF electrodes. The incorporation of nitrogen elements restructure the GF surface, increasing defect sites and active sites, thereby enhancing catalytic activity and reaction kinetics. Ultimately, this improves the efficiency and stability of the VRFB.
In-situ Preparation of VOSO4 from the Leachate of Sodium-Roasted Vanadium Slag
LIU Ziyang;XIAFUHATI Airikenjiang;XIE Yifan;DAI Jiayu;YANG Wentao;WEN Jing;JIANG Tao;Vanadyl sulfate(VOSO4) is a key active material for all-vanadium redox flow batteries(VRFBs), but traditional preparation processes rely on high-purity V_2O5 as raw material, featuring long flow, high energy consumption and high production cost. To achieve efficient and low-cost utilization of vanadium resources, a shortprocess technology for in-situ preparation of VOSO4 was proposed using sodium roasting-water leaching solution of vanadium slag(vanadium concentration: 16.5 g/L, Cr concentration: 0.66 g/L) as the vanadium source and sodium sulfite(Na2 SO3) as the reducing agent. The process includes four steps: reduction, precipitation, acid dissolution and crystallization. The effects of reduction parameters(pH value, temperature, time, mass ratio of S to V(m(S)/m(V)) and precipitation parameters(pH value, temperature, time) on vanadium recovery rate were systematically investigated. A variety of material characterization techniques were employed to analyze the phase composition, chemical structure, and micro-morphology of the intermediate product VO(OH)2 and the final VOSO4 product, while electrochemical testing methods were used to evaluate the electrochemical performance of the VOSO4 electrolyte. The results show that the maximum vanadium recovery rate of 97.08% is obtained under the optimal process conditions including reduction pH value of 2.5, reduction temperature of 70 ℃, reduction time of 60 min, m(S)/m(V)=0.5, precipitation pH value of 6.0, precipitation temperature of 20 ℃, and precipitation time of 10 min. X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR) analyses confirm that the intermediate product VO(OH)2 is amorphous, and washing with ethanol and deionized water effectively reduces the Na+ content from 0.66 g/L to 0.03 g/L without significant loss of V4+(maintained at about 16.3 g/L). Scanning electron microscopy(SEM) observations reveal that the synthesized VOSO4 consist of blocky crystals with a diameter of 1–3 μm, and XRD results indicate it is a mixture of VOSO4· 3H_2O and VOSO4· 2H_2O. Energy dispersive spectroscopy(EDS) and impurity detection show that trace Cr impurities exist in the product, with a Cr content of 2 836 mg/L, which affect the product purity. Electrochemical test results demonstrate that after 10 cyclic voltammetry(CV) cycles(scan rate: 10 mV/s, potential range from –0.2 V to 1.5 V), the VOSO4 electrolyte exhibites a reduction peak potential of 0.49 V and an oxidation peak potential of 1.17 V, with a peak potential difference(ΔEp) of 0.68 V and an oxidation-reduction peak current ratio of 11. The peak current has a good linear relationship with the square root of the scan rate, indicating the electrochemical reaction is controlled by vanadium ion diffusion. The limiting diffusion current density fitted from the steady-state polarization curve is 0.516 mA/cm2. Electrochemical Impedance Spectroscopy(EIS) tests show that the electrolyte impedance is 26.9 Ω after the first cycle and increases to 55.7 Ω after 10 cycles due to the formation of a stable solid electrolyte interphase(SEI) film, while the charge transfer resistance in the high-frequency region decreases, leading to improved conductivity. This study provides a feasible technical route for the efficient utilization of vanadium slag resources and the development of VRFB electrolytes. Future work should focus on reducing Cr impurity content to further enhance the electrochemical performance and industrial application value of VOSO4 products.
Analysis of the Network Characteristic and Competitiveness of the Global Trade Supply of New Energy Metal Resources
LI Baihua;WANG Gang;LIU Xiaoxue;Hebei Province Collaborative Innovation Center for Strategic Critical Mineral Research;The global shift towards a green and low-carbon energy infrastructure has catalyzed the rapid expansion of the new energy sector, resulting in a sustained increase in demand for critical metal resources, notably lithium, cobalt, and nickel. These metals are indispensable components in electric vehicles, energy storage systems, and renewable power generation, among other applications. Consequently, the security of their supply and the architecture of their global trade networks have emerged as significant factors influencing national energy strategies and economic stability. However, the geopolitical landscape of these resources is complex; their distribution is highly uneven, and a pronounced geographical disconnect exists between sites of production and consumption. This disparity, compounded by volatile prices and intricate trade dynamics, exposes the supply chain to multifaceted risks, including geopolitical tensions and structural dependencies. This context underscores the critical need for a comprehensive analysis of key supplying nations, the structure of trade relationships, and national competitiveness within the global flow of these essential commodities. To address these questions, this study constructes a series of global trade supply networks for lithium, cobalt, and nickel, utilizing detailed product-level trade data sourced from the UN Comtrade database for the decade spanning 2013 to 2022. Within these complex network models, individual countries were represented as nodes, bilateral trade relationships as edges, and the total trade volume was assigned as the weight for each edge. The analysis employs a multifaceted suite of metrics to evaluate the system from several angles: network density and modularity were used to assess overall connectivity and community formation; node strength(weighted degree) identifies major importers and exporters; betweenness centrality quantified a country's role as an intermediary; and the Herfindahl-Hirschman Index(HHI) measures the concentration of a country's trade partnerships, indicating potential vulnerability. The following conclusions are drawn: From 2013 to 2022, the trade relations between countries in lithium and nickel resources have become denser, while cobalt resource trade is the most active and has the highest degree of trade grouping. The trade relations between countries are relatively stable and close, and trade cooperation is more mature. Japan and South Korea are identified as typical lithiumimporting countries, while Chile and Argentina are recognized as typical lithium-exporting countries. China and New Caledonia are found to be prominent in nickel trade, serving as major importers and exporters, respectively. However, the characteristics of typical lithium-trading countries are not as distinct. Significant trade relationships are observed in lithium exports, particularly between Ireland and Indonesia, as well as between Zimbabwe and the Czech Republic. In the cobalt trade, the most notable export relationships exist between the Democratic Republic of the Democratic Republic of the Congo and China, and between Sweden and Denmark. China also emerges as the largest export partner for nickel-exporting countries. Meanwhile, the most significant import relationships for nickel are identified between China and Indonesia, and between India and Indonesia. Import-oriented countries for nickel generally demonstrate stronger trade competitiveness. In contrast, lithium-importing countries exhibite relatively weaker competitiveness, primarily due to limitations in intermediary control capacity and trade structure. In conclusion, by integrating complex network theory with a multi-dimensional indicator framework, this research delineates the structural evolution and key characteristics of the global trade system for new energy metals. It successfully identifies critical nations and pinpoints specific competitiveness shortcomings. These insights offer valuable empirical support for policymakers seeking to optimize resource import structures, enhance supply chain resilience, and formulate strategic industrial policies. The study recommends that importing countries actively pursue diversification of their supply channels to mitigate single-source dependency, while simultaneously engaging in deeper international collaboration to improve their intermediary control and informational capacity within the global trade network.
Effects of Thermal Activation Atmosphere on the Properties of Geopolymers Based on Vanadium Shale Tailings
FU Xiuqiong;FAN Yong;WAN Qian;ZHANG Yimin;GUO Zhijie;Thermal activation has been demonstrated to markedly enhance the reactivity of vanadium shale tailings(VST), enabling the synthesis of geopolymers with superior mechanical performance. However, the VST employed in most existing studies are primarily derived from the roasting-leaching process, in which the roasting stage leads to extensive volatilization of carbon and sulfur species. In contrast, tailings produced via the widely adopted direct acid leaching process retain substantial amounts of carbon and sulfide phases in their native states. When conventional thermal activation is applied to such tailings, significant changes in their physicochemical characteristics are inevitable, potentially affecting the properties of the resulting geopolymers. Nevertheless, the influence of these transformations on geopolymers performance has yet to be systematically elucidated. This study investigates how, in the presence or absence of O2, carbonaceous constituents influence the physicochemical properties of VST and on the compressive strength and microstructure of the geopolymers produced therefrom. The thermal activation reaction processes were analyzed using thermodynamic analysis methods. Phase transformations during activation were detected by X-ray diffraction(XRD). The pore size distribution of the tailings was characterized by mercury intrusion porosimetry(MIP), and their water absorption capacity was tested. To elucidate the differences in geopolymers compressive strength, microstructure and chemical features were further characterized using Raman microscope, field emission scanning electron microscopy(FESEM), and solid-state nuclear magnetic resonance(SSNMR). The results indicate that under an O2 atmosphere, the oxidation and volatilization of carbon components generate capillary pores, which significantly enhance the water absorption of the activated vanadium shale tailings(AVST). This process impedes the efficiency of mass transfer during geopolymerization, leading to insufficient formation of the silico-aluminate network structure within the geopolymers. The resulting product contains numerous cracks and pores, yielding a comparatively low 7-day compressive strength of only 18.73 MPa. In contrast, under an atmosphere devoid of O2, the carbon components act as reductant, decomposing calcium sulfate to form loose and porous calcium sulfide particles. This process increases the porosity of the tailings. The resulting calcium sulfide undergoes slow hydrolysis upon contact with water, which has a minor impact on the water absorption of the AVST. This condition promotes a higher degree of cross-linking between SiO4 and AlO4 tetrahedra in the silico-aluminate network, thereby enhancing the mechanical properties of the geopolymer. The 7-day compressive strength reaches 37.6 MPa. Overall, this work elucidates the mechanisms underlying the contrasting performances of geopolymers synthesized from thermally activated VST under different atmospheric conditions. The findings provide a theoretical basis and technical guidance for optimizing the utilization of direct acid leaching vanadium shale tailings in geopolymer production.