Reduction Of Vanadium Research Articles

Vanadium (V) reduction and the performance of electroactive biofilms in microbial fuel cells with Shewanella putrefaciens

The electron transfer ability of biofilms significantly influences the electrochemical activity of microbial fuel cells (MFCs). However, there is limited understanding of pentavalent vanadium (V(V)) bioreduction and microbial response characteristics in MFCs. In this study, the effect of gradient concentrations of V(V) on the performance of EABs with Shewanella putrefaciens in MFCs was investigated. The results showed that as V(V) concentration increased (0–100 mg/L), the voltage output, power densities, polarization, and electrode potential decreased. V(V) was found to act as an electron acceptor and was reduced during MFCs operation, with a yield of 83.16% being observed at 25 mg/L V(V). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated declining electrochemical performance of the MFCs with escalating V(V) concentration. The content of protein and polysaccharide from extracellular polymeric substances (EPS) in anodic biofilms increased to 66.75 and 49.15 mg/L at 75 mg/L V(V), respectively. Three-dimensional fluorescence spectroscopy confirmed increased humic substances in EPS extraction with V(V) exposure. The functional genes narG, nirK, and gor involved in V(V) reduction were upregulated with rising V(V) concentration through quantitative polymerase chain reaction (qPCR) analysis. Additionally, riboflavin, cytochrome c, nicotinamide adenine dinucleotide (NADH), and electron transport system activity (ETSA), key indicators for assessing electron transfer behavior, exhibited a negative correlation with various V(V) concentrations, decreasing by 31.81%, 57.14%, 67.39%, and 51.41%, respectively, at a concentration of 100 mg/L V(V) compared to the blank control. These findings contribute valuable insights into the response of EABs to V(V) exposure, presenting potential strategies for enhancing their effectiveness in the treatment of vanadium-contaminated wastewater.

Process mechanism research on direct vortex melting reduction of vanadium–titanium magnetite

Process mechanism research on direct vortex melting reduction of vanadium–titanium magnetite

Electrode kinetics for the reduction of central hetero VinV and framework addenda VoutV and WVI atoms in the [VinVoutW11O40]4− polyoxometalate: Comparisons with [SVoutW11O40]3− and [VinW12O40]3−

The electrode kinetics associated with the polyoxometalate (POM) [VinVoutW11O40]4-/5-/6−, [VinW12O40]3-/4-/5− and [SVoutW11O40]3-/4-/5− (Vin – central hetero vanadium atom, Vout – framework addenda vanadium atom) reduction processes in CH3CN (0.10 M [Bu4N][PF6]) have been determined by Fourier Transformed large amplitude alternating current voltammetry at a glassy carbon electrode. [VinVoutW11O40]4− provides an interesting situation where both the VinV and VoutV vanadium atoms can be reduced to the VIV state. The heterogeneous charge transfer rate constant kVout0′ value for the framework [VinVVoutVW11O40]4−/[VinVVoutIVW11O40]5− process of 0.15 cm s−1 (reversible formal potential E0ʹ = −223 mV vs Fc0/+) is almost ten times that of 0.020 for the kVin0′ (E0ʹ = −1027 mV vs Fc0/+) one associated with the central [VinVVoutIVW11O40]5−/[VinIVVoutIVW11O40]6− reaction. The significant decrease in the electrode kinetics for the process involving reduction of the central vanadium could in principle be attributed to differences in the Vin and Vout coordination geometry or a longer distance required for electron transfer between the electrode surface and Vout. However, neither of these factors is considered to be dominant as kVin0′ associated with the [VinVW12O40]3−/[VinIVW11O40]4- reaction is 0.19 cm s−1 (E0ʹ is −114 mV vs Fc0/+). With this POM, the more negative second process (E0ʹ = −918 mV vs Fc0/+) is associated with a WVI/WV framework reduction with a k0ʹ value of 0.080 cm s−1. With the second control POM, [SVoutW11O40]3−, the initial very fast framework VoutV/VoutIV reduction step (E0ʹ = 145 mV vs Fc0/+) has a k0ʹ value of 0.19 cm s−1 and is followed at considerably more negative potentials (E0ʹ = −1343 mV vs Fc0/+) by the slightly slower framework WVI/WV process with k0ʹ = 0.13 cm s−1. Thus, the k0ʹ values are most strongly influenced by the negative charge (n value) associated with the POMn-(/n+1)- reaction, being close to reversible when n = 3 as in the [VinW12O40]3−4− and [SVoutW12O40]3−/4− reactions, but much slower when n = 5 as in the case of the [VinVoutW11O40]5-/6- reaction. Accordingly, the initial reduction step is always faster than the second one that occurs at more negative potentials, irrespective of whether Vin, Vout or W are reduced. In the case of thermodynamically relevant E0ʹ values, it has been established that a strong correlation exists with the n value in POMn-/(n+1)− process. It is now shown that a similar correlation of k0ʹ with n applies.

Cobalt-vanadium coating deposition via programmed electrolysis mode

In the current work, the co-deposition of cobalt with vanadium from a complex citrate electrolyte via stationary and pulse electrolysis modes was investigated. The process was carried out at a current density of 1–15 Adm–2 in stationary electrolysis mode and 2–10 Adm–2 in pulse electrolysis mode, with variable ratio of pulse time to pause time at a temperature range of 35–400С and pH 3.0–3.5. According to the results of X-ray fluorescence spectrometry, the maximum content of vanadium in the coating obtained via the programmed electrolysis mode is 1.20–1.45%, which is tens of times higher than in the coating deposited by the stationary electrolysis mode (vanadium content of 0.007–0.017%) under similar conditions. The obtained results may confirm the hypothesis of additional vanadium reduction from oxo-anions by adsorbed hydrogen atoms formed on the cathode surface during the pause period. Based on the results of the analysis of 3D graphs, the optimal parameters of the process for fabricating a cobalt-vanadium coating with the maximum vanadium content in the alloy and a coating current efficiency of 80% have been established.

Parameter Optimization and Reaction Kinetics of the Reduction of Vanadium–Titanium Sinter by CO–CO2–H2–N2 Mixed Gases

Parameter Optimization and Reaction Kinetics of the Reduction of Vanadium–Titanium Sinter by CO–CO2–H2–N2 Mixed Gases

Probing Carbon Materials Towards the Vanadium(IV)/(V) Reaction by Scanning Electrochemical Microscopy

AbstractA method is presented to quantitatively analyze the reduction of vanadium(V) to vanadium(IV) over two flat carbon substrates (glassy carbon and graphite foil) using the feedback mode of scanning electrochemical microscopy. A pulse profile is validated and applied during approach curve experiments of a 10 μm Pt microelectrode. By fitting the approach curve data, electron transfer constants are calculated for various potentials and k0 is extracted from the corresponding Tafel plot. Furthermore, surface functional groups were introduced to the carbon substrates by acid treatment; however, kinetic parameters of the sluggish reduction reaction were only influenced to a minor extent. Finally, the same approach, combined with in situ‐Raman microscopy, is applied to a single graphene layer using a 2.7 μm Pt microelectrode. In this case, increased activity for both, the vanadium(V) reduction and vanadium(IV) oxidation reaction, was found close to the graphene edge sites by means of electrochemical microscopy for the first time.

Transcriptome analysis reveals vanadium reduction mechanisms in a bacterium of Pseudomonas balearica

The continuously elevated concentration of vanadium (V) in the environment is of great concern due to its potential risks to organisms. Microbial reduction is considered a green way to remediate the V-contaminated sites. This study presents the first demonstration of Pseudomonas balearica, a bacterium flourishing in vanadium-titanium magnetite tailings, exhibiting the capacity to reduce pentavalent V [V(V)]. We found that P. balearica exhibited strong tolerance to high V(V) levels, despite lacking known V(V)-reducing genes. After 48 h of incubation, the reduction rates of V(V) by P. balearica under 0.5 mM and 10 mM V(V) stress reached 81.1% and 60.6%, respectively. The phosphorus group and carboxyl group on the bacterial cell surface contributed to V(V) binding and reduction. Both extracellular and intracellular V(V) reduction was significantly facilitated by many critical V-induced differentially expressed genes (DEGs) encoding nitrate/nitrite reductases, ABC transporters, NADH, and c-type cytochromes. In addition, up-regulation of DEGs associated with reactive oxygen species (ROS)-scavenging enzymes, such as glutathione peroxidase, superoxide dismutase, and catalase, was observed as a protective response to oxidative stress triggered by V(V). Moreover, some up-regulated DEGs (ureC, ureE, ureA, and ureG) encoding urease subunit or urease accessory proteins significantly enriched in the nickel cation binding pathway, indicating that P. balearica may be resistant to Ni stress by regulating urease activity. This study will help to more thoroughly elucidate the characteristics and mechanisms of V(V) reduction by microbes and provide a native bacterium flourishing in tailings for potential bioremediation of V pollution and bioleaching of V-sources.

Efficient reduction of vanadium (V) with biochar and experimental parameters optimized by response surface methodology

Water pollution deteriorates ecosystems and has a great threaten to the environment. The environmental benefits of wastewater treatment are extremely important to minimize pollutants. Here, the biochar purchased from the related industry was used to treat the wastewater which contained high concentration of vanadium (V). The concentration of vanadium was measured by the IC-OES and the results showed that 96.1% vanadium (V) was reduced at selected reaction conditions: the mass ratio of biochar to vanadium of 5.4, reaction temperature of 90 °C, reaction time at 60 min and concentration of H2SO4 of 10 g/L, respectively. Response surface methodology confirmed that all the experimental parameters had positive effect on the reduction of vanadium (V), which could improve the reduction efficiency of vanadium (V) as increased. The influence of each parameter on the reduction process followed the order: A (Concentration of H2SO4) > C (mass ratio of biochar to vanadium) > B (mass ratio of biochar to vanadium). Especially, the mass ratio of biochar to vanadium and concentration of H2SO4 had the greatest influence on the reduction process. This paper provides a versatile strategy for the treatment of wastewater containing vanadium (V) and shows a bright tomorrow for wastewater treatment.

V2O5·3H2O/N-doped graphite felt cathode efficiently produced H2O2 and ·OH in the electro-Fenton system for enhanced antibiotics degradation

Enhancing H2O2 production and promoting the conversion of H2O2 to ·OH are two major problems that needed to be solved in electro-Fenton process. Herein, the V2O5·3H2O/N-doped graphite felt (V2O5·3 H2O/N-GF) cathode was developed to construct electro-Fenton system for antibiotics degradation. Benefiting from that the N-GF which possessed a large number of 2e-ORR active sites for H2O2 production, and the V2O5·3H2O particles could efficiently activate H2O2 to produce ·OH, the V2O5·3 H2O/N1-GF cathode exhibited outstanding catalytic activity. Besides, the V2O5·3 H2O/N1-GF cathode exhibited only 30 mV overpotential difference between the optimal oxygen reduction potential (OP ORR) and the optimal vanadium reduction potential (OP VRR), thereby facilitating ·OH generation. The V2O5·3 H2O/N1-GF cathode displayed desired degradation performance in a wide pH range (2.1–7.2), with TC removal of 93.8% within 60 min at pH of 3.3, and total organic carbon (TOC) removal of 62.8%. DFT calculations revealed that V2O5·3H2O were more readily to adsorb H2O2 than V2O5, which was conducive to improving H2O2 utilization and conversion. Four possible degradation pathways for TC were proposed and toxicity analysis of the intermediates were determined. The V2O5·3H2O/N1-GF could also decompose various antibiotics effectively in the system, and it exhibited great stability. This work can provide reference for designing efficient V-based cathode for electro-Fenton system.

Vanadium substituted Fe, Cr co-doped high performance C/Na3V2(PO4)2F3 cathode for sodium-ion batteries

In recent years, Na3V2(PO4)2F3 (NVPF) has been considered as one of the most promising candidates for cathodes in sodium ion batteries (SIBs). However, presence of vanadium makes the material costly. Besides, its electrochemical properties are hampered due to its low electronic conductivity. Herein, carbon coated Fe, Cr co-doped Na3V2(PO4)2F3 has been synthesized using rota-tumbler assisted sol–gel method. The effects of co-doping on structure, morphology and electrochemical performances are systematically studied. It is confirmed that co-doping of Fe and Cr can enhance the electrochemical performances of NVPF. Among all, Na3V1.9Fe0.095Cr0.005(PO4)2F3 shows a high initial capacity of 119.85 mAhg−1 at 0.1C and maintains a capacity retention of 88.58 % after 500 cycles at 1C. Increase in the size of the saddle point, planes of monocapped trigonal prisms and the hexagonal cavities help in decreasing the ion diffusion activation energy, thus improving the diffusivity of the doped material. The improved electrochemical performances can be attributed to the increase in the electronic conductivity of the material. Besides, vanadium reduction in the cathode aids in manufacturing cost reduction. Our work demonstrates that carbon coated Na3V1.9Fe0.095Cr0.005(PO4)2F3 can be considered as a potential cathode candidate for practical applications in SIBs.

Thermodynamic Modeling of the Vanadium Alloy Smelting Process Using a Silicon-aluminum Reducing Agent

The article is devoted to the study of the theoretical aspect of obtaining a vanadium alloy by aluminosilicothermic method. Vanadium pentoxide and converter vanadium slag were studied as charge materials. Silicon-aluminum ferroalloys, such as ferroaluminosilicocalcium, ferrosilicoaluminum and aluminum-silicon-manganese with calcium, will be used as a reducing agent. The chemical composition of the initial vanadium-containing materials and silicon-aluminum reducing agents were studied by the spectral method of analysis. To analyze the aluminosilicothermal reduction of vanadium in the V-Fe-Si-Al-Ca-O system, the method of complete thermodynamic modeling of metallurgical processes was used. Full thermodynamic modeling was implemented in a computer system using the HSC Chemistry software package. As initial data for determining the parameters of thermodynamic equilibrium for the actual composition of the charge for the smelting of vanadium alloys with a stoichiometric consumption of the reducing agent. To analyze the coexistence of phases in a multicomponent system during the aluminosilicothermal reduction of vanadium, a triple phase diagram was constructed for the V2O5-Al-Si system at different isotherms using the «Triangle» program. As a result, the processes of aluminosilicothermal reduction of vanadium in the process of smelting a vanadium alloy using silicon-aluminum reducing agents were studied. The optimal temperature range for vanadium alloy smelting was set. The range is 1650-1850 K. Also, the results of thermodynamic stud

Improvement of Electrochemical Performances of Electrochromic-Zinc Ion Batteries System Utilizing V4+-V2O5 As a Cathode

Recently, many countries are practicing carbon neutrality to lower greenhouse gas emissions to "zero" by 2050. Therefore, zinc ion batteries (ZIBs) have been increasing attention as next-generation batteries due to low cost and high volumetric energy density. In addition, since ZIBs utilize a human-friendly water-based electrolyte, ZIBs has been proposed as an alternative to wearable energy storage systems. Above all, the electrochromic – ZIB system is gaining popularity as the next generation storage technology because it can visualize charging and discharging. Vanadium oxide(V2O5), one of the cathode materials of electrochromic ZIB, exhibits excellent electrochemical characteristics with excellent rate performance through intercalation in the layered structure. However, because of V2O5’s poor electronic and ionic conductivities, it is necessary to improve the structure improvement for increasing energy density.To solve this problem, mixed multiple oxidation states of vanadium are essential to ZIB cathode. This mixed valence states are contributed to increase electrochemical performance and specific capacity.1 V4+-V2O5 exhibit higher electrochemical activity, faster ion transport, better electrical conductivity than Pure V2O5. Also, we can expect that V4+-V2O5 performs outstanding rate capability and long term-cyclic life.In this study, we developed V4+-V2O5 based electrochromic-ZIB cathode to enhance electrochemical performance controlling the temperature for vanadium reduction heat treatment in H2 gas atmosphere. Furthermore, it will be determined whether vanadium oxide is suitable for electrochromic. Between the yellow V2O5 and the black Vanadium-based compounds, an appropriate point with excellent electrochemical and electrochromic properties will be found.

Smartphone-based detection of nitrate in seawater samples with the resorcinol method: Comparison with the vanadium reduction method

The presence of nitrate (NO3−) in the aquatic environment has raised a major concern for scientists and environmental managers. In this study, a smartphone-based resorcinol method was developed for the determination of NO3− in seawater. Simple custom-made devices were used in the method, and the reaction temperature, reaction time, and smartphone camera settings were optimized. Salinity variation did not show any major impact on the determination of NO3− using the proposed method, and hence the incorporation of a correction factor was also not required. The detection limit for this method was observed to be 1.3 µM, and the working range was observed to be 5–60 µM, with a relative standard deviation of 0.7% (5 µM, n = 7), which was adequate for the determination of NO3− in most estuarine and coastal seawater samples. The proposed method was compared with the frequently used vanadium chloride (VCl3) reduction method under the same experimental conditions, and both methods were found to be beneficial. The proposed method procedure was simple and easy to use. It was successfully applied for the determination of NO3− in seawater samples, and the results showed that it was practical and can be used potentially for on-site analysis.

Simultaneous stripping and regeneration of chelate structure of vanadium through vanadium reduction and conversion in vanadium-bearing shale extraction

Chelating extractants have shown excellent selectivity in vanadium extraction. Nevertheless, the resulting extraction complex is stable, making the stripping of chelating extractant a challenge. The H2C2O4-H2SO4 system was proposed to stripping vanadium from the loaded organic phase of chelating extractant Mextral 984 H. The effects of process parameters of H2C2O4-H2SO4 system on the vanadium stripping percentage was investigated. The results show that the single-stage vanadium stripping percentage reached 93.12%, and the vanadium concentration in the single-stage stripping solution reached 13.44 g/L under optimum conditions: the H2SO4 concentration of 1.87 mol/L, the H2C2O4 concentration of 0.16 mol/L, the temperature of 80 °C, the time of 30 min, and phase ratio(O/A) of 4:1. In addition, the high extraction efficiency (>85%) was maintained after 10 cycles, indicating that the developed system can be used in the Mextral 984 H stripping system. The mechanism of stripping was also analysed using FT-IR and 1H NMR combined with thermodynamic and quantum calculations. It was summarized that after H2C2O4 reduces V(V) to V(IV), H+ can replace V(IV), the free V(IV) in organic phase is more prone to coordinated with C2O42- and SO42- and then goes into aqueous phase. Thus the stripping and regeneration of the loaded organic phase of Mextral 984 H can be occurred simultaneously. Meanwhile, the introduction of H+ can speed up the stripping process. The innovative method of the reduction stripping of vanadium is proposed in the black shale extraction field.

Optimal Process Parameters for Direct Carbothermal Reduction of Vanadium–Titanium Magnetite in a Rotary Kiln

Direct reduction in rotary kiln plays a crucial role in the reduction and smelting of vanadium–titanium magnetite. The effect of the process parameters on the metallization rate and reaction mechanism during the reduction process in a rotary kiln is investigated. The results indicate that the optimal process parameters for direct reduction of vanadium–titanium magnetite in a rotary kiln are as follows: a reduction temperature of 1150 °C, reduction time of 4 h, carbon ratio 1.2, particle size of vanadium–titanium magnetite as 8–12 mm, and particle size of pulverized coal of <8 mm. During the direct reduction of vanadium–titanium magnetite, favorable conditions such as absence of smelting phenomenon on the surface of the reduction products, high metallization rate, and high quality of direct reduction iron are achieved. Through direct reduction, the transformation process of iron oxide in vanadium–titanium magnetite is Fe3O4 → iron oxide → Fe, and the transformation process of titanium–iron oxide is Fe9TiO15 → Fe2.75Ti0.25O4 → Fe2.5Ti0.5O4 → iron titanate → Fe. In addition, vanadium and ferrochrome oxides undergo reduction to form oxides or carbides.

Corrosion protection behaviour of electrogalvanised steel sheet by tetravalent vanadium ion

ABSTRACT The corrosion protection behaviour of electrogalvanised steel sheets (EG) by the tetravalent vanadium ion was investigated. Immersion of the bare EG in a NaCl solution revealed that the addition of vanadium(IV) oxide sulphate to the solution led to a transition of the open circuit potential to less noble and the formation of vanadium oxides on the EG surface. The oxide layer included not only vanadium(III) oxides but also a small amount of ZnO, indicating that Zn on the EG surface was oxidised while the vanadium(IV) species was reduced to the vanadium(III) species. The corrosion current density of the EG with the adhering vanadium(III) species was one order of magnitude smaller than that of the bare EG, clearly suggesting that zinc corrosion was reduced by suppressing the reduction reaction of dissolved oxygen. The vanadium(IV) species could be a candidate as a self-healing inhibitor for chromate-free coating technologies by controlling the coupling of Zn oxidation and vanadium(IV) reduction.

Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes.

The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N'-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ε) (acetonitrile, ε = 37.5; N,N-dimethylformamide, ε = 36.7; and dichloromethane, ε = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N'-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field.

Vanadium(V) reduction by using a by-product of the yellow phosphorus industry

Release of vanadium(V) from industry has threatened the environment and human health. In this paper, a removal method of vanadium(V) is proposed using a by-product of the yellow phosphorus industry (phosphorus-iron) as a reducing agent. The thermodynamics analysis shows that the Gibbs free energy is always negative from 0 to 100 °C, indicating a spontaneous process. Effect of the phosphorus-iron slag/sulfuric acid dosage and temperature on the removal efficiency is comprehensively studied, and the kinetics parameters are calculated based on a quasi-first order reaction kinetics model. Results indicate that vanadium(V) can be entirely reduced by using phosphorus-iron slag, the frequency factor and apparent activation energy are 3.23 × 109 min−1 and 64.50 kJ·mol−1 for vanadium(V) reduction. Based on above results, a lab-scale reactor is constructed and achieves a removal efficiency of ∼100% and a treatment capacity of 200 ml vanadium(V) solution (2 g·L–1) within 3 h. This work demonstrates the feasibility of vanadium(V) reduction using phosphorus-iron slag as a reducing agent in applications.

Економічний аналіз технологій акумулювання електричної енергії

The use of cost-effective large-scale electrical energy storage systems is necessary for the reliability of the power system due to the rapid growth of its production by powerful renewable energy sources. The article examines stationary electric energy storage devices, namely: sodium-sulfur; lead-acid; lithium-ion; nickel-cadmium; vanadium reduction, polysulfide-bromine and zinc-bromine flow batteries; supercapacitors; superconducting magnetic energy. Information from open sources on technologies of electric energy storage has been analyzed. As a criterion of optimality in world practice, the weighted average cost of electric energy for the life cycle is used, which ensures the self-sufficiency of the source of its production or accumulation for the entire cycle of its existence. A comparison of modern technical and economic indicators of various electrical energy storage technologies is made. Calculated average cost of electrical energy storage over the life cycle (LCOS) of various storage devices. It was determined that supercapacitors and superconductors of magnetic energy have the lowest cost of storage, and lithium-ion ones have the highest. Therefore, to minimize short-term power fluctuations in power systems, superconducting magnetic and supercapacitor storage devices are preferable. They have a lower cost of electric energy storage, short response time and high specific power.

Shewanella oneidensis MR-1 and oxalic acid mediated vanadium reduction and redistribution in vanadium-containing tailings

The microbially- and chemically-mediated redox process is critical in controlling the fate of vanadium (V) in tailing environment. Although the microbial reduction of V has been widely studied, the coupled biotic reduction mediated by beneficiation reagents and the underlying mechanism remain unclear. Herein, the reduction and redistribution of V in V-containing tailings and Fe/Mn oxide aggregates mediated by Shewanella oneidensis MR-1 and oxalic acid were explored. The dissolution of Fe-(hydr)oxides by oxalic acid promoted the microbe-mediated V release from solid-phase. After 48-day of reaction, the dissolved V concentrations in the bio-oxalic acid treatment reached maximum values of 1.72 ± 0.36 mg L–1 and 0.42 ± 0.15 mg L–1 in the tailing system and the aggregate system, respectively, significantly higher than those in control (0.63 ± 0.14 mg L–1 and 0.08 ± 0.02 mg L–1). As the electron donor, oxalic acid enhanced the electron transfer process of S. oneidensis MR-1 for V(V) reduction. The mineralogical characterization of final products indicates that S. oneidensis MR-1 and oxalic acid promoted solid-state conversion from V2O5 to NaV6O15. Collectively, this study demonstrates that microbe-mediated V release and redistribution in solid-phase were promoted by oxalic acid, suggesting that the role of organic agents for the V biogeochemical cycle in natural systems deserves greater attention.