MIL-100(V) derived porous vanadium oxide/carbon microspheres with oxygen defects and intercalated water molecules as high-performance cathode for aqueous zinc ion battery

The development of aqueous zinc ion battery cathode materials with high capacity and high magnification is still a challenge.Herein,porous vanadium oxide/carbon(p-VO_(x)@C,mainly VO_(2) with a small amount of V_(2)O_(3)) core/shell microspheres with oxygen vacancies are facilely fabricated by using a vanadium-based metal-organic framework(MIL-100(V)) as a sacrificial template.This unique structure can improve the conductivity of the VO_(x),accelerate electrolyte diffusion,and suppress structural collapse during circulation.Subsequently,H_(2)O molecules are introduced into the interlayer of VO_(x) through a highly efficient in-situ electrochemical activation process,facilitating the intercalation and diffusion of zinc ions.After the activation,an optimal sample exhibits a high specific capacity of 464.3 mA h g^(-1) at0.2 A g^(-1) and 395.2 mA h g^(-1) at 10 A g^(-1),indicating excellent rate performance.Moreover,the optimal sample maintains a capacity retention of about 89.3% after 2500 cycles at 10 A g^(-1).Density functional theory calculation demonstrates that the presence of oxygen vacancies and intercalated water molecules can significantly reduce the diffusion barrier for zinc ions.In addition,it is proved that the storage of zinc ions in the cathode is achieved by reversible intercalation/extraction during the charge and discharge process through various ex-situ analysis technologies.This work demonstrates that the p-VO_(x)@C has great potential for applications in aqueous ZIBs after electrochemical activation.

Synergism of preintercalated manganese ions and lattice water in vanadium oxide cathodes for high-capacity and long-life Zn-ion batteries

Aqueous Zn-ion batteries(AZIBs)are recognized as a promising energy storage system with intrinsic safety and low cost,but its applications still rely on the design of high-capacity and stable-cycling cathode materials.In this work,we present an intercalation mechanism-based cathode materials for AZIB,i.e.the vanadium oxide with pre-intercalated manganese ions and lattice water(noted as MVOH).The synergistic effect between Mn^(2+)and lattice H_(2)O not only expands the interlayer spacing,but also significantly enhances the structural stability.Systematic in-situ and ex-situ characterizations clarify the Zn^(2+)/H^(+)co–(de)intercalation mechanism of MVOH in aqueous electrolyte.The demonstrated remarkable structure stability,excellent kinetic behaviors and ion-storage mechanism together enable the MVOH to demonstrate satisfactory specific capacity of 450 mA h g^(−1)at 0.2 A g^(−1),excellent rate performance of 288.8 mA h g^(−1)at 10 A g^(−1)and long cycle life over 20,000 cycles at 5 A g^(−1).This work provides a practical cathode material,and contributes to the understanding of the ion-intercalation mechanism and structural evolution of the vanadium-based cathode for AZIBs.

Mo Doping and Electrochemical Activation Co-Induced Vanadium Composite as High-Rate and Long-Life Anode for Ca-Ion Batteries

Calcium-ion batteries have been considered attractive candidates for large-scale energy storage applications due to their natural abundance and low redox potential of Ca^(2+)/Ca.However,current calcium ion technology is still hampered by the lack of high-capacity and long-life electrode materials to accommodate the large Ca^(2+)(1.00Å).Herein,an amorphous vanadium structure induced by Mo doping and in-situ electrochemical activation is reported as a high-rate anode material for calcium ion batteries.The doping of Mo could destroy the lattice stability of VS4 material,enhancing the flexibility of the structure.The following electrochemical activation further converted the material into sulfide and oxides co-dominated composite(defined as MoVSO),which serves as an active material for the storage of Ca^(2+)during cycling.Consequently,this amorphous vanadium structure exhibits excellent rate capability,achieving discharge capacities of 306.7 and 149.2 mAh g^(-1)at 5 and 50 A g^(-1)and an ultra-long cycle life of 2000 cycles with 91.2%capacity retention.These values represent the highest level to date reported for calcium ion batteries.The mechanism studies show that the material undergoes a partial phase transition process to derive MoVSO.This work unveiled the calcium storage mechanism of vanadium sulfide in aqueous electrolytes and accelerated the development of high-performance aqueous calcium ion batteries.

Bioleaching of vanadium from stone coal vanadium ore by Bacillus mucilaginosus:Influencing factors and mechanism

Vanadium and its derivatives are used in various industries,including steel,metallurgy,pharmaceuticals,and aerospace engineering.Although China has massive reserves of stone coal resources,these resources have low grades.Therefore,the effective extraction and recovery of metallic vanadium from stone coal is an important way to realize the efficient resource utilization of stone coal vanadium ore.Herein,Bacillus mucilaginosus was selected as the leaching strain.The vanadium leaching rate reached 35.5%after 20 d of bioleaching under optimal operating conditions.The cumulative vanadium leaching rate in the contact group reached 35.5%,which was higher than that in the noncontact group(9.3%).The metabolites of B.mucilaginosus,such as oxalic,tartaric,citric,and malic acids,dominated in bioleaching,accounting for 73.8%of the vanadium leaching rate.Interestingly,during leaching,the presence of stone coal stimulated the expression of carbonic anhydrase in bacterial cells,and enzyme activity increased by 1.335-1.905 U.Enzyme activity positively promoted the production of metabolite organic acids,and total organic acid content increased by 39.31 mg·L^(-1),resulting in a reduction of 2.51 in the pH of the leaching system with stone coal.This effect favored the leaching of vanadium from stone coal.Atomic force microscopy illustrated that bacterial leaching exacerbated corrosion on the surface of stone coal beyond 10 nm.Our study provides a clear and promising strategy for exploring the bioleaching mechanism from the perspective of microbial enzyme activity and metabolites.

Multiple-dimensioned defect engineering for graphite felt electrode of vanadium redox flow battery

The scarcity of wettability,insufficient active sites,and low surface area of graphite felt(GF)have long been suppressing the performance of vanadium redox flow batteries(VRFBs).Herein,an ultra-homogeneous multipledimensioned defect,including nano-scale etching and atomic-scale N,O codoping,was used to modify GF by the molten salt system.NH_(4)Cl and KClO_(3) were added simultaneously to the system to obtain porous N/O co-doped electrode(GF/ON),where KClO_(3) was used to ultra-homogeneously etch,and O-functionalize electrode,and NH4Cl was used as N dopant,respectively.GF/ON presents better electrochemical catalysis for VO_(2)+/VO_(2)+ and V3+/V2+ reactions than only O-functionalized electrodes(GF/O)and GF.The enhanced electrochemical properties are attributed to an increase in active sites,surface area,and wettability,as well as the synergistic effect of N and O,which is also supported by the density functional theory calculations.Further,the cell using GF/ON shows higher discharge capacity,energy efficiency,and stability for cycling performance than the pristine cell at 140 mA cm^(−2) for 200 cycles.Moreover,the energy efficiency of the modified cell is increased by 9.7% from 55.2% for the pristine cell at 260 mA cm^(−2).Such an ultra-homogeneous etching with N and O co-doping through“boiling”molten salt medium provides an effective and practical application potential way to prepare superior electrodes for VRFB.

Unraveling high efficiency multi-step sodium storage and bidirectional redox kinetics synergy mechanism of cobalt-doping vanadium disulfide anode

Sodium-based storage devices based on conversion-type metal sulfide anodes have attracted great atten-tion due to their multivalent ion redox reaction ability.However,they also suffer from sodium polysul-fides(NaPSs)shuttling problems during the sluggish Na^(+) redox process,leading to"voltage failure"and rapid capacity decay.Herein,a metal cobalt-doping vanadium disulfide(Co-VS_(2))is proposed to simulta-neously accelerate the electrochemical reaction of VS_(2) and enhance the bidirectional redox of soluble NaPSs.It is found that the strong adsorption of NaPSs by V-Co alloy nanoparticles formed in situ during the conversion reaction of Co-VS_(2) can effectively inhibit the dissolution and shuttle of NaPSs,and ther-modynamically reduce the formation energy barrier of the reaction path to effectively drive the complete conversion reaction,while the metal transition of Co elements enhances reconversion kinetics to achieve high reversibility.Moreover,Co-VS_(2) also produce abundant sulfur vacancies and unsaturated sulfur edge defects,significantly improve ionic/electron diffusion kinetics.Therefore,the Co-VS_(2) anode exhibits ultrahigh rate capability(562 mA h g^(-1) at 5 A g^(-1)),high initial coulombic efficiency(~90%)and 12,000 ultralong cycle life with capacity retention of 90%in sodium-ion batteries(SIBs),as well as impressive energy/power density(118 Wh kg^(-1)/31,250 W kg^(-1))and over 10.000 stable cycles in sodium-ion hybrid capacitors(SIHCs).Moreover,the pouch cell-type SIHC displays a high-energy density of 102 Wh kg^(-1) and exceed 600 stable cycles.This work deepens the understanding of the electrochemical reaction mechanism of conversion-type metal sulfide anodes and provides a valuable solution to the shuttlingofNaPSs inSIBsandSIHCs.

Vanadium oxide nanospheres encapsulated in N-doped carbon nanofibers with morphology and defect dual-engineering toward advanced aqueous zinc-ion batteries

Vanadium-based electrodes are regarded as attractive cathode materials in aqueous zinc ion batteries(ZIBs)caused by their high capacity and unique layered structure.However,it is extremely challenging to acquire high electrochemical performance owing to the limited electronic conductivity,sluggish ion kinetics,and severe volume expansion during the insertion/extraction process of Zn^(2+).Herein,a series of V_(2)O_(3)nanospheres embedded N-doped carbon nanofiber structures with various V_(2)O_(3)spherical morphologies(solid,core-shell,hollow)have been designed for the first time by an electrospinning technique followed thermal treatments.The N-doped carbon nanofibers not only improve the electrical conductivity and the structural stability,but also provides encapsulating shells to prevent the vanadium dissolution and aggregation of V_(2)O_(3)particles.Furthermore,the varied morphological structures of V_(2)O_(3)with abundant oxygen vacancies can alleviate the volume change and increase the Zn^(2+)pathway.Besides,the phase transition between V_(2)O_(3)and Zn_XV_(2)O_(5-m)·n H_(2)O in the cycling was also certified.As a result,the as-obtained composite delivers excellent long-term cycle stability and enhanced rate performance for coin cells,which is also confirmed through density functional theory(DFT)calculations.Even assembled into flexible ZIBs,the sample still exhibits superior electrochemical performance,which may afford new design concept for flexible cathode materials of ZIBs.

Revealing the role of calcium ion intercalation of hydrated vanadium oxides for aqueous zinc-ion batteries

Exploring suitable high-capacity V_(2)O_(5)-based cathode materials is essential for the rapid advancement of aqueous zinc ion batteries(ZIBs).However,the typical problem of slow Zn^(2+)diffusion kinetics has severely limited the feasibility of such materials.In this work,unique hydrated vanadates(CaVO,BaVO)were obtained by intercalation of Ca^(2+)or Ba^(2+)into hydrated vanadium pentoxide.In the CaVO//Zn and BaVO//Zn batteries systems,the former delivered up to a 489.8 mAh g^(-1)discharge specific capacity at 0.1 A g^(-1).Moreover,the remarkable energy density of 370.07 Wh kg^(-1)and favorable cycling stability yard outperform BaVO,pure V_(2)O_(5),and many reported cathodes of similar ionic intercalation compounds.In addition,pseudocapacitance analysis,galvanostatic intermittent titration(GITT)tests,and Trasatti analysis revealed the high capacitance contribution and Zn^(2+)diffusion coefficient of CaVO,while an in-depth investigation based on EIS elucidated the reasons for the better electrochemical performance of CaVO.Notably,ex-situ XRD,XPS,and TEM tests further demonstrated the Zn^(2+)insertion/extraction and Zn-storage mechanism that occurred during the cycle in the CaVO//Zn battery system.This work provides new insights into the intercalation of similar divalent cations in vanadium oxides and offers new solutions for designing cathodes for high-capacity aqueous ZIBs.

Graphene-loaded nickel−vanadium bimetal oxides as hydrogen pumps to boost solid-state hydrogen storage kinetic performance of magnesium hydride

To modify the thermodynamics and kinetic performance of magnesium hydride(MgH_(2))for solid-state hydrogen storage,Ni_(3)V_(2)O_(8)-rGO(rGO represents reduced graphene oxide)and Ni_(3)V_(2)O_(8)nanocomposites were prepared by hydrothermal and subsequent heat treatment.The beginning hydrogen desorption temperature of 7 wt.%Ni_(3)V_(2)O_(8)-rGO modified MgH_(2)was reduced to 208℃,while the additive-free MgH_(2)and 7 wt.%Ni_(3)V_(2)O_(8)doped MgH_(2)appeared to discharge hydrogen at 340 and 226℃,respectively.A charging capacity of about 4.7 wt.%H_(2)for MgH_(2)+7 wt.%Ni_(3)V_(2)O_(8)-rGO was achieved at 125℃ in 10 min,while the dehydrogenated MgH_(2)took 60 min to absorb only 4.6 wt.%H_(2)at 215℃.The microstructure analysis confirmed that the in-situ generated Mg_(2)Ni/Mg_(2)N_(i)H_(4) and metallic V contributed significantly to the enhanced performance of MgH_(2).In addition,the presence of rGO in the MgH_(2)+7 wt.%Ni_(3)V_(2)O_(8)-rGO composite reduced particle aggregation tendency of Mg/MgH_(2),leading to improving the cyclic stability of MgH_(2)during 20 cycles.

Insights into the hydrogen evolution reaction in vanadium redox flow batteries:A synchrotron radiation based X-ray imaging study

The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 m V vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15%–20%in carbon felt electrodes.Contrarily,the bubble fractions stay only around 2%in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30%bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses.The described combination of electrochemical measurements,local X-ray microtomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.

Weakly Polarized Organic Cation-Modified Hydrated Vanadium Oxides for High-Energy Efficiency Aqueous Zinc-Ion Batteries

Vanadium oxides,par-ticularly hydrated forms like V_(2)O_(5)·nH_(2)O(VOH),stand out as promising cathode candidates for aqueous zinc ion batteries due to their adjustable layered structure,unique electronic characteristics,and high theoretical capacities.However,challenges such as vanadium dissolution,sluggish Zn^(2+)diffusion kinetics,and low operating voltage still hinder their direct application.In this study,we present a novel vanadium oxide([C_(6)H_(6)N(CH_(3))_(3)]_(1.08)V_(8)O_(20)·0.06H_(2)O,TMPA-VOH),developed by pre-inserting trimethylphenylammonium(TMPA+)cations into VOH.The incorporation of weakly polarized organic cations capitalizes on both ionic pre-intercalation and molecular pre-intercalation effects,resulting in a phase and morphology transition,an expansion of the interlayer distance,extrusion of weakly bonded interlayer water,and a substantial increase in V^(4+)content.These modifications synergistically reduce the electrostatic interactions between Zn^(2+)and the V-O lattice,enhancing structural stability and reaction kinetics during cycling.As a result,TMPA-VOH achieves an elevated open circuit voltage and operation voltage,exhibits a large specific capacity(451 mAh g^(-1)at 0.1 A g^(-1))coupled with high energy efficiency(89%),the significantly-reduced battery polarization,and outstanding rate capability and cycling stability.The concept introduced in this study holds great promise for the development of high-performance oxide-based energy storage materials.

罗汉果苷V调控高糖状态巨噬细胞M1极化促进骨髓间充质干细胞的成骨分化

背景:糖尿病微环境会造成巨噬细胞过度M1极化,这种高糖炎症状态会抑制骨髓间充质干细胞的成骨分化,从而影响糖尿病骨缺损的愈合。研究表明罗汉果苷Ⅴ具有抗炎、抗氧化、降血糖的作用,但其能否调节高糖炎症状态下巨噬细胞M1极化及骨髓间充质干细胞的成骨分化尚不清楚。目的:探讨罗汉果苷Ⅴ在高糖炎症状态下调节巨噬细胞M1型极化对骨髓间充质干细胞成骨分化的影响。方法:构建糖尿病C57BL/6小鼠模型,从正常和糖尿病小鼠分离骨髓来源巨噬细胞,分别培养于低糖和高糖培养基。使用脂多糖和干扰素γ作为炎症刺激诱导骨髓来源巨噬细胞的M1型极化,同时以160,320,640μmol/L罗汉果苷Ⅴ干预,用流式细胞术检测F4/80^(+)CD86^(+)细胞比例,qRT-PCR检测诱导型一氧化氮合酶、白细胞介素1β、白细胞介素6的mRNA表达水平,ELISA检测骨髓来源巨噬细胞上清液中肿瘤坏死因子α水平。分离C57BL/6小鼠骨髓间充质干细胞,分别使用低糖或高糖成骨诱导液诱导成骨分化,添加M1型巨噬细胞条件培养基作为炎症刺激,以及320μmol/L罗汉果苷Ⅴ干预,成骨诱导14 d后采用qRT-PCR检测碱性磷酸酶、Runt相关因子2、骨钙素、骨桥蛋白的mRNA表达水平,成骨诱导21 d后进行茜素红染色及定量分析。结果与结论:①流式细胞术结果显示320,640μmol/L罗汉果苷Ⅴ组的F4/80^(+)CD86^(+)细胞比例明显低于高糖炎症对照组(P<0.05);②qRT-PCR结果显示160,320,640μmol/L罗汉果苷Ⅴ组的诱导型一氧化氮合酶、白细胞介素6的mRNA相对表达量较高糖炎症对照组显著降低(P<0.05),320,640μmol/L罗汉果苷Ⅴ组白细胞介素1β的mRNA相对表达量较高糖炎症对照组显著降低(P<0.05);③ELISA结果显示160,320,640μmol/L罗汉果苷Ⅴ组的肿瘤坏死因子α分泌水平较高糖炎症对照组显著降低(P<0.05);④320μmol/L罗汉果苷Ⅴ干预后,高糖炎症状态下骨髓间充质干细胞的钙盐沉积增加(P<0.05),且碱性磷酸酶、Runt相关因子2和骨桥蛋白的mRNA相对表达量增加(P<0.05)。结果表明,罗汉果苷Ⅴ可通过抑制高糖炎症状态下骨髓来源巨噬细胞的M1型极化及炎症因子表达,促进骨髓间充质干细胞的成骨分化。

Cohort study on the treatment of BRAF V600E mutant metastatic colorectal cancer with integrated Chinese and western medicine

BACKGROUND Patients with BRAF V600E mutant metastatic colorectal cancer(mCRC)have a low incidence rate,poor biological activity,suboptimal response to conventional treatments,and a poor prognosis.In the previous cohort study on mCRC conducted by our team,it was observed that integrated Chinese and Western medicine treatment could significantly prolong the overall survival(OS)of patients with colorectal cancer.Therefore,we further explored the survival benefits in the population with BRAF V600E mutant mCRC.AIM To evaluate the efficacy of integrated Chinese and Western medicine in the treatment of BRAF V600E mutant metastatic colorectal cancer.METHODS A cohort study was conducted on patients with BRAF V600E mutant metastatic colorectal cancer admitted to Xiyuan Hospital of China Academy of Chinese Medical Sciences and Traditional Chinese Medicine Hospital of Xinjiang Uygur Autonomous Region from January 2016 to December 2022.The patients were divided into two cohorts.RESULTS A total of 34 cases were included,with 23 in Chinese-Western medicine cohort(cohort A)and 11 in Western medicine cohort(cohort B).The median overall survival was 19.9 months in cohort A and 14.2 months in cohort B,with a statistically significant difference(P=0.038,hazard ratio=0.46).The 1-3-year survival rates were 95.65%(22/23),39.13%(9/23),and 26.09%(6/23)in cohort A,and 63.64%(7/11),18.18%(2/11),and 9.09%(1/11)in cohort B,respectively.Subgroup analysis showed statistically significant differences in median OS between the two cohorts in the right colon,liver metastasis,chemotherapy,and first-line treatment subgroups(P<0.05).CONCLUSION Integrated Chinese and Western medicine can prolong the survival and reduce the risk of death in patients with BRAF V600E mutant metastatic colorectal cancer,with more pronounced benefits observed in patients with right colon involvement,liver metastasis,combined chemotherapy,and first-line treatment.

Research and prospect on extraction of vanadium from vanadium slag by liquid oxidation technologies

A series of innovative green metallurgical processes using novel reaction media including the NaOH/KOH sub-molten salt media and the NaOH-NaNO3 binary molten salt medium, for the extraction of vanadium and chromium from the vanadium slag have been developed. In comparison with the traditional sodium salt roasting technology, which operates at 850 ℃, the operation temperatures of these new processes drop to 200-400 ℃. Further, the extraction rates of vanadium and chromium utilizing the new approaches could reach 95% and 90%, respectively, significantly higher than those in the traditional roasting process, which are 75% and approximate zero, respectively. Besides, no hazardous gases and toxic tailings are discharged during the extraction process. Compared with the conventional roasting method, these new technologies show obvious advantages in terms of energy, environments, and the mineral resource utilization efficiency, providing an attractive alternative for the green technology upgrade of the vanadium production industries.

Extraction of vanadium from molten vanadium bearing slag by oxidation with pure oxygen in the presence of CaO

A novel process of vanadium extraction from vanadium slag in its molten state was conducted at the laboratory scale by oxidation with pure oxygen in the presence of CaO. The effect of mass ratio of CaO to V2O5 on the recovery of vanadium was studied. The sintered samples were leached by H2SO4 solution and characterized by XRD, XPS, SEM and EDS techniques. Compared with the roasting process, the energy saving effect of the proposed process was also discussed. The results showed that vanadium-rich phases were formed and vanadium mainly existed in the forms of CaV2O5 and Ca2V2O7. The formation mechanism of calcium vanadates in the molten vanadium bearing slag was explained. The XRD and XPS results implied that there was a limit to the oxidation reaction of V(IV) to V(V) under the high temperatures even though oxygen-supply was sufficient. An increase in the CaO content led to an increase in the formation of Ca2V2O7. About 90%of the vanadium recovery was obtained under optimal experiment conditions (mass ratio of CaO to V2O5 of 0.6, particle size 120 to 150μm, leaching temperature 90 °C, leaching time 2 h, H2SO4 concentration 20%, liquid to solid ratio 5:1 mL/g, stirring speed 500 r/min). The energy of 1.85×106 kJ could be saved in every 1000 kg of vanadium bearing slag using the proposed process from the theoretical calculation results. Recovery of vanadium from the molten vanadium bearing slag and utilisation of its heat energy are important not only for saving metal resources, but also for energy saving and emission reduction.

Flotation recovery of vanadium from low-grade stone coal

Pre-concentration of vanadium from low-grade stone coal by the method of desliming-flotation was investigated. The mineral composition and microstructure of stone coal were studied systematically by means of X-ray fluorescence spectrometry （XRF）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that selective separation of vanadium-bearing minerals can be achieved by flotation in acidic solution using melamine （EA）. The final vanadium concentrate with V2O5 grade of 1.88% and recovery rate of 76.58% is obtained by desliming-flotation process and 72.51% of the raw ore is rejected as tailings. The pre-concentration of vanadium from low-grade stone coal can increase V2O5 grade and decrease the content of acid consuming minerals, which would enable economical utilization of metallurgical vanadium extraction technology.

Vanadium supported on graphitic carbon nitride as a heterogeneous catalyst for the direct oxidation of benzene to phenol

A series of graphitic carbon nitride supported vanadium catalysts（xV/g-C3N4） with different vanadium contents（x/%） were prepared by impregnation.XRD,FT-IR,TEM,TG-DTG,nitrogen adsorption and XPS characterizations were conducted which revealed a strong interaction between the vanadium species and g-C3N4 support.8V/g-C3N4 exhibited the highest activity and showed stable recyclability in the benzene hydroxylation reaction with a benzene conversion of 24.6%and phenol selectivity of 99.2%under the optimized conditions.The excellent catalytic performance of xV/g-C3N4 was due to the integration of vanadium species with high catalytic activity and the g-C3N4support in their interaction with the benzene substrate.

φ-pH diagram of V-Ti-H_2O system during pressure acid leaching of converter slag containing vanadium and titanium

To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.

Thermodynamics and mechanism of vanadium(IV) extraction from sulphate medium with D2EHPA,EHEHPA and CYANEX 272 in kerosene

Extraction of vanadium（IV） from sulphate acid solution was studied using organophosphorous-based extractants D2EHPA, EHEHPA and CYANEX 272 in kerosene. The different parameters affecting the extraction of vanadium（IV） under equilibrium conditions were separately investigated to elucidate the stoichiometry of the extracted species. The distribution ratio of vanadium increased with increasing equilibrium pH of the aqueous phase, concentration of the extractants and temperature. D2EHPA was found to be a stronger extractant, having greater pH functionality than EHEHPA and CYANEX 272. Extraction of vanadium（IV） by these organophosphorous-based extractants involved cation exchange mechanism, and the extracted species appear to be VOR2（HR）2 in the low equilibrium pH and VOR2 in the higher equilibrium pH, where HR refers to the three acidic extractants.

Oxidation process of low-grade vanadium slag in presence of Na_(2)CO_3

The oxidation process of low-grade vanadium slag in the presence of Na2CO3 was investigated by XRD,SEM/EDS and TG-DSC techniques.The results show that the vanadium slag is oxidized in a temperature range from 273 to 700 °C.Olivine phases and spinel phases are completely decomposed at 500 and 600 °C,respectively.Most of water-soluble sodium vanadates are formed between 500 and 600 °C.When roasting temperature reaches above 700 °C,the vanadium-rich phases of sodium vanadates can be obviously observed.However,at temperature above 800 °C,the samples are sintered.Most of the vanadium is enwrapped by glassy phase compounds which lead to the decrease of the leaching rate of vanadium.At the same time,the effect of roasting temperature on extraction of vanadium and characterization of leach residues were discussed.