Initial Vanadium Research Articles

Pilot-scale vanadium adsorption onto in-situ biogenic amorphous ferric hydroxide

In order to reach 4 μg l−1 vanadium in drinking water adsorption onto in-situ biogenic amorphous ferric hydroxide (AFH) is identified as robust new treatment. The evaluation of its technical feasibility and robustness was the aim of this study. As approach at pilot-scale, Fe(II) and oxygen was dosed before pilot waterworks and Fe(II) subsequently biotically oxidized and precipitated in a filter bed. The so in-situ generated biogenic AFH served as adsorbent for vanadium removal. Results show that an initial vanadium concentration of 30 μg l−1 was removed to below 4 μg l−1, if at least 3 mg l−1 Fe(II) were dosed, resulting in a loading of 8.7 mg V per g AFH. A vanadium concentration of 60 μg l−1 with a dosage of 3 mg l−1 Fe(II) was the upper limit for sufficient removal. Vanadium removal increased with increasing pH in the technical setup, due to faster oxidation of Fe(II) in the supernatant, even though adsorption capacity of AFH decreases with increasing pH. A filtration velocity of 20 m h −1 represented the highest velocity to undercut 4 μg l−1 vanadium in the effluent. By mixing Fe(II) containing groundwater with oxygen and vanadium containing water prior to an adsorption filter with AFH sufficient removal was reached, however dependent on the resulting Fe(II) concentration.

The removal of toxic metals from liquid effluents by ion exchange resins. Part XVIII: Vanadium(V)/H+/Amberlite 958

The ion exchange resin Amberlite 958 was used to investigate its behaviour on the removal of hazardous vanadium(V) from aqueous media. This investigation was carried out under various hydrodynamic conditions and chemical conditions, such as variation of the stirring speed, variation of the pH of the aqueous solution, resin dosage, initial vanadium(V) in the aqueous solution, and temperature. Vanadium(V) uptake onto the resin was highly dependent on the pH of the solution, and thus, to the vanadium(V) speciation in this phase; the ion exchange process had an endothermic character. The experimental data, under different experimental conditions, were fitted to various models: kinetics (stirring speed), rate law (vanadium concentration) and model isotherms (resin dosage). Multiwalled carbon nanotubes were also investigated on vanadium(V) removal from the solution. Vanadium(V) loaded onto the resin can be eluted under acidic conditions.

Vanadium (V) Adsorption from Aqueous Solutions Using Xerogel on the Basis of Silica and Iron Oxide Matrix.

Vanadium is considered a strategic metal with wide applications in various industries due to its unique chemical and physical properties. On the basis of these considerations, the recovery of vanadium (V) is mandatory because of the lack of raw materials. Various methods are used to recover vanadium (V) from used aqueous solutions. This study develops a clean and effective process for the recovery of vanadium (V) by using the adsorption method. At the same time, this study synthesizes a material starting from silica matrices and iron oxides, which is used as an adsorbent material. To show the phase composition, the obtained material is characterized by X-ray diffraction showing that the material is present in the amorphous phase, with a crystal size of 20 nm. However, the morphological texture of the material is determined by the N2 adsorption-desorption method, proving that the adsorbent material has a high surface area of 305 m2/g with a total pore volume of 1.55 cm3/g. To determine the efficiency of the SiO2FexOy material for the recovery of vanadium through the adsorption process, the role of specific parameters, such as the L-to-V ratio, pH, contact time, temperature, and initial vanadium concentration, must be evaluated. The adsorption process mechanism was established through kinetic, thermodynamic, and equilibrium studies. In our case, the process is physical, endothermic, spontaneous, and takes place at the interface of SiO2FexOy with V2O5. Following equilibrium studies, the maximum adsorption capacity of the SiO2FexOy material was 58.8 mg (V)/g of material.

The valance state of vanadium-key factor in the flexibility of potassium vanadates structure as cathode materials in Li-ion batteries

Potassium hexavanadate (K2V6O16·nH2O) nanobelts have been synthesized by the LPE-IonEx method, which is dedicated to synthesis of transition metal oxide bronzes with controlled morphology and structure. The electrochemical performance of K2V6O16·nH2O as a cathode material for lithium-ion batteries has been evaluated. The KVO nanobelts demonstrated a high discharge capacity of 260 mAh g−1, and long-term cyclic stability up to 100 cycles at 1 A g−1. The effect of the vanadium valence state and unusual construction of the nanobelts, composed of crystalline and amorphous domains arranged alternately were also discussed in this work. The ex-situ measurements of discharged electrode materials by XRD, MP-AES, XAS and XPS show that during the subsequent charge/discharge cycle the potassium in the K2V6O16·nH2O structure are replacing by lithium. The structural stability of the potassium hexavandate during cycling depends on the initial vanadium valence state on the sample surface and the presence of the “fringe free” domains in the K2V6O16·nH2O nanobelts.

Facile synthesis of self-support vanadium-doped Ni2P nanosheet arrays for highly efficient overall water splitting

It is urgent to explore non-noble metal electrocatalysts with high efficiency and durability for oxygen evolution reaction (OER), which is key to a spectrum of sustainable energy technologies. The electronic regulation via foreign ion/atom doping presents a valid route to improve the intrinsic activity of earth-abundant electrocatalysts. In this research, a facile and cost-effective self-assembly strategy is developed to fabricate the vanadium-doped nickel phosphide electrocatalysts (V-Ni2P) with a three-dimensional nanosheets structure. Then the effect of initial vanadium concentration on the morphology and properties of the target catalyst is investigated. It is found that the V-Ni2P electrocatalyst obtained at the NH4VO3 concentration of 1 mg mL−1 only requires a low overpotential of 228 mV to afford an OER current density of 80 mA cm−2, with a Tafel slope of 76 mV dec–1 and excellent electrocatalytic stability. On the other hand, enhanced hydrogen evolution reaction (HER) performance can also be acquired based on this unique structure under alkaline conditions. Finally, a water electrolysis device is assembled using V-Ni2P as the cathode and anode materials. To afford a current density of 50 mA cm−2, this device only needs a small voltage of 1.65 V, suggesting the potential of V-Ni2P as a bifunctional electrocatalyst for overall water splitting. This study provides a reference for the preparation of a highly active electrocatalyst with controllable composition and microstructure.

Synthesis, Characterization, and Potential Evaluation of Modified Cellulose Immobilized with Hydroxyquinoline as a Sorbent for Vanadium Ions

A considerable increase in the importance of vanadium globally and its common uses in many manufacturable alloys made it a target for much scientific research interested in extraction and recovery. A solid modified cellulose sorbent (GCIHQ) was prepared by simple grafting of cellulose, then immobilized with hydroxyquinoline, and examined as a sorbent for V(V) ions. FT-IR, TGA, BET, and SEM–EDX investigations were used to characterize the GCIHQ. A higher surface area for the synthesized GCIHQ resin has been recorded (65.8 m2/g) more than the used cellulose (21.7m2/g). Several vanadium sorption parameters using the modified GCIHQ from the sulfate medium were optimized namely contact time, pH, initial vanadium ions concentration, sorbent dose, and sorption temperature. The kinetics results revealed that the sorption of vanadium ions upon the synthesized sorbent followed the pseudo-second-order with R2 of > 0.99, which indicated that the sorption mechanism was chemical interaction. The sorption process was studied using Freundlich, Langmuir, Dubinin–Radushkevich, and Temkin isotherm models to describe the adsorbent-adsorbate interaction. The Langmuir model was the most fitting model with the experimental results; the experimental adsorption uptake of 113 mg/g was matched with that of the calculated results. The activation energy (Ea) for adsorption was 12.91 kJ.mol−1, indicating the process is to be chemisorption. Thermodynamic characteristics with ΔH of 13.46 kJ/mol and a ΔS 115.15 J/mol.K revealed the endothermic and spontaneous nature.

Separation and adsorption of V(V) from canadium-containing solution by TOMAC-impregnated resins

Trioctyl methyl ammonium chloride-impregnated resins (TOMAC-IRs) were synthesized and utilized to efficiently separate and recover vanadium from acidic vanadium-containing solution, and the main factors affecting the adsorption properties of V(V) were studied. Under the optimal conditions, that is, initial pH of 1.8, liquid–solid ratio (L/S) of 200:1 mL/g, impregnation ratio of 18.4%, initial vanadium concentration of 1500 mg/L, and adsorption time of 4 h, the adsorption capacity towards V(V) can reach 78.65 mg/g, and impurity ions (Al and Fe) can be hardly adsorbed. The adsorption of V(V) onto TOMAC-IRs conforms to the Langmuir isotherm adsorption model, indicating that V(V) is adsorbed as a monolayer on TOMAC-IRs. The pseudo-second order kinetic model fits better towards the adsorption processes of V(V), which shows that the adsorption process is dominated by chemical adsorption. The desorption and regeneration of the TOMAC-IRs can be accomplished in just one step using 6 mol/L NaOH; in the meanwhile, the adsorption capacity is 98.01% of the original value after six cycles, demonstrating that the TOMAC-IRs have good stability during the cyclic adsorption of V(V).

Vanadium removal by cationized sawdust produced through iodomethane quaternization of triethanolamine grafted raw material

In this study, two-step surface modification of sawdust using triethanolamine (at 180 °C) and iodomethane (at 42 °C) was performed to produce a novel quaternized biosorbent, TEA-I-SD. The characterization studies revealed significant morphological changes in the sawdust and successful quaternization with a nitrogen content of 5.75%. The highest vanadium removal (96.2%) was achieved at pH 4 (dosage 1 g/L, initial vanadium concentration 19.1 mg/L). Equilibrium was achieved within 8 h of contact time and the adsorption kinetics were well fitted with the pseudo-second-order model. Both film diffusion and intra-particle diffusion contributed to the adsorption process, while the latter was the rate-limiting step. The maximum vanadium adsorption capacity of TEA-I-SD (35.0 mg/g, pH 4) was close to the theoretical value obtained from the Langmuir model. The best fit was achieved with the Redlich-Peterson model, exhibiting a monolayer adsorption phenomenon. Tests with real mine water containing 11 mg/L of vanadium also confirmed its high removal (91.3%, dosage 1 g/L) using TEA-I-SD at pH 4. The TEA-I-SD could be reused three times without significant capacity loss after regeneration, although the desorption efficiency was rather low (synthetic solution: 38.5–40.5% and mine water: 26.2–43.1%).

Preparation of nano-micron vanadium adsorbent for VO3− adsorption

With Miyi diatomite as the carrier and ferric nitrate as the modification agent, nano-micron vanadium adsorbent was prepared in the study. Then the adsorption properties of the prepared adsorbent were characterized by XRD, XRF, SEM, and ICP-OES analysis. The effects of adsorption time, initial pH value and initial vanadium concentration on VO3− adsorption performance were studied and the adsorption mechanism was discussed. The adsorption of VO3− on Miyi diatomite was significantly improved by the modification with ferric nitrate. The adsorption process of VO3− on nano-micron vanadium adsorbent was in accordance with Langmuir isothermal equation and quasi-second-order kinetic model. The saturated adsorption capacity was 43.38 mg/g. The adsorption capacity was higher in the weak acid environment and peaked at pH = 4.

Mechanism of vanadium(IV) resistance of the strains isolated from a vanadium titanomagnetite mining region.

Microbial treatment for vanadium contamination of soils is a favorable and environment-friendly method. However, information of the resistant mechanism of the strains in soils to vanadium, especially to tetravalent vanadium [vanadium(IV)], is still limited. Herein, potential of the vanadium(IV) biosorption and biotransformation of the strains (4K1, 4K2, 4K3 and 4K4) which were capable of tolerating vanadium(IV) was determined. For biosorption, the bioadsorption and the bioabsorption of vanadium(IV) occur on the bacterial cell wall and within the cell, respectively, were taken into consideration. Comparison of the vanadium(IV) adsorbed on the bacterial cell walls and remained in the cells after sorption indicated the major bacterial vanadium(IV) sorption role of the bioadsorption which was at least one order of magnitude higher than the bioabsorption amount. Isotherm study using various isotherm models revealed a monolayer and a multilayer vanadium(IV) biosorption by 4K2 and the others (4K1, 4K3 and 4K4), respectively. Higher biosorption was observed in acidic conditions than in alkaline conditions, and the maximum biosorption was 2.41, 9.35, 7.76 and 8.44mgg-1 observed at pH 6 for 4K1, at pH 3 for 4K2, and at pH 4 for 4K3 and 4K4, respectively. At the present experimental range of the initial vanadium(IV) concentration, optimal biosorption capacity of the bacteria was observed at the vanadium(IV) level of 100-250mgL-1. Different biotransformation level of vanadium(IV) in soils by the stains was observed during a 28-d pot incubation of the soils mixed with the strains, which can be attributed to the discrepancy of both soil properties and bacterial species. Present study can help to fill up the gaps of the insufficient knowledge of the vanadium(IV) resistant mechanism of the strains in soils.

A numerical study of electrode thickness and porosity effects in all vanadium redox flow batteries

Vanadium redox flow battery (VRFB) is one of the promising technologies suitable for large-scale energy storage in power grids due to high design flexibility, low maintenance cost and long-life cycle. Vanadium redox flow cell consists of two porous electrodes with serpentine flow channels and electrolyte solutions which is separated by an ion-exchange membrane. The temperature has been set to 298 K for the electrolytes which is composed of 1500 mol/m³ initial vanadium concentration with 4000 mol/m³ initial H2SO4 concentration. We developed a three-dimensional model to scrutinize the complexities of fluid dynamics and electrochemical reactions when considering different electrode thickness sizes, electrode porosity and electrolyte flow rates. In this study, a three-dimensional numerical simulation have been performed in order to investigate the effect of electrode thickness and electrode porosity on the performance of VRFB. The impact of electrolyte solution flow rate on the VRFB electrical characteristics and efficiencies are also numerically investigated. The results show that the cell voltage increases with increasing the electrolyte flow rate and electrode porosity during discharging process of VRFB. Increasing the initial vanadium concentration, the VRFB cell voltage is significantly increased due to reduced overpotential in the porous electrodes. The maximum power-based efficiency of 96.8% is calculated with the electrode thickness of 1 mm at 10 ml/min, while the power-based efficiency of 96.4% is calculated with the electrode thickness of 4 mm at 50 ml/min. This work gives comprehensive insights on electrode configurations for VRFBs.

Trypsin-Immobilized Silica: A Novel Adsorbent for V(IV) and V(V) Removal from Water.

In the present study, trypsin-immobilized silica was employed for the removal of V(IV) and V(V) ions from water. The synthesized sorbent was first characterized and then investigated for the removal of V(IV) and V(V) under various experimental conditions. The adsorption performance of the sorbent was tested as a function of pH, sorbent amount, initial vanadium concentration, contact time, and temperature. The sorption process was then investigated, both from a kinetic perspective and also in terms of isotherm models. The Langmuir adsorption isotherm was the best model to describe the sorption process. Sorption thermodynamics were spontaneous and exothermic. The proposed method was successfully applied to real samples for the removal of V(IV)and V(V) with sufficient accuracy and precision.

Oxidation behaviour of composite CrN/(Cr,V)N coatings with different contents of vanadium induced by UV nanosecond laser pulses

The oxidation behaviour and morphological modification of CrN/(Cr,V)N coatings on Si wafers were studied after UV nanosecond laser (wavelength 248 nm, pulse duration 25 ns) processing in ambient air. The evolution of the surface composition and microstructure with the number of accumulated/subsequent pulses was systematically analysed depending on the initial content of vanadium in the as-deposited coatings. Irradiation of CrN/(Cr,V)N coatings with different content of vanadium was carried out at a fluence of 0.17 J cm−2 with different number of pulses. The concentration of metallic components was fairly homogeneous distributed throughout the sample. However, on surface and in sub-surface regions the contents of Cr and V are diminished due to laser-induced oxidation. The composition and thickness of forming oxides mixture, Cr2O3 and V2O5, are depending on the number of applied laser pulses and the initial vanadium content. The asymmetric progress of surface morphology is characterized by the formation of grainy structures at peripheries and the appearance of cracks and irregular closed shapes in the centre of the irradiation area.

Characteristics of vanadium adsorption on and desorption from humic acid

ABSTRACTInformation about geochemical behaviour of vanadium in soil to date is very limited. This study explored the characteristics and factors that affect vanadium adsorption-desorption by humic acid (HA) which was extracted from red soil. Fourier-transform infrared analysis illustrated that various functional groups on HA participated in vanadium adsorption. Monolayer vanadium adsorption at certain range of HA concentrations was detected, and main adsorption-desorption controlling step was chemical reactions. The adsorption-desorption was strongly dependent on HA concentration, solution pH and coexisting anion species. The main existing form and valence of vanadium at different solution pH, HA and vanadium concentration predominantly contributed to the variable vanadium adsorption ability. The presence of , Cl−, and had insignificant effect (p > 0.05) on adsorption, whereas , , , and significantly promoted (p < 0.05) the adsorption. Similarly, and significantly increased (p < 0.05) the desorption. The maximum adsorption amount was 19.2 mg g–1 by 0.727 g L–1 HA at the initial vanadium(V) concentration of 182 mg L–1, and the corresponding desorption rate was 9.44%, indicating that HA can fix vanadium in soil to a certain degree and may thus reduce bioavailability and toxicity of vanadium, which is important to keep the ecological dynamic balance.

Unit Cell Modelling and Simulation of All Vanadium Redox Flow Battery

AbstractVanadium redox flow battery (VRFB) is one of the promising technologies for large scale renewable energy storage due to its long life time and flexible design. Electrolyte flow rate, electrolyte concentration, electrode porosity, temperature and applied magnitude of current have significant effect on the efficiency of VRFB. In the present work, a simplified dynamic lumped parameter model is developed in MATLAB to provide accurate results at unit cell level which can be used to control and optimize the parameters. The proposed model is based on the mass balance and charge conservation of various vanadium species and hydrogen ion concentration in the electrolyte. Major losses such as ohmic losses and activation losses are included in the cell potential. Recirculation of the electrolyte through external reservoirs is also considered. Numerical simulation demonstrates the effect of change in initial vanadium concentration and operating temperature on unit cell performance. It is shown that variations in electrolyte flow rate, magnitude of applied current substantially alter the charge/discharge characteristics and efficiency.

BOF steel slag as a low-cost sorbent for vanadium (V) removal from soil washing effluent

Soil washing is an effective remediation method to remove heavy metals from contaminated soil. However, it produces wastewater that contains large amounts of heavy metals, which lead to serious pollution. This study investigated the removal of vanadium (V) from synthetic soil washing effluent using BOF steel slag. The effects of particle size, slag dosage, initial pH, and initial vanadium concentration on removal behavior were studied. Adsorption kinetics and isotherms were also analyzed. The results showed that the vanadium removal efficiency increased as the steel slag particle size decreased and as the amount of slag increased. The initial pH and vanadium concentration did not play key roles. At the optimum particle size (<0.15 mm) and dosage (50 g/L), the removal rate reached 97.1% when treating 100 mg/L of vanadium. The influence of the washing reagent residue was studied to simulate real conditions. Citric acid, tartaric acid, and Na2EDTA all decreased the removal rate. While oxalic acid did not have negative effects on vanadium removal at concentrations of 0.05–0.2 mol/L, which was proved by experiments using real washing effluents. Considering both soil washing effect and effluent treatment, oxalic acid of 0.2 mol/L is recommended as soil washing reagent.

Solvent extraction and selective separation of vanadium (V) from an acidic sulfate solution using 2-Ethyl-1-Hexanol

Abstract In this work, 2-ethyl-1-hexanol, a long chain alcohol, is used to extract pentavalent vanadium V(V) from both sodium metavanadate solution and a synthetic leach liquor. At first, effects of process parameters on the extraction of V(V) from a solution free from the other metals are examined and discussed. The maximum extraction yield has been achieved at initial pH (pH0) about 2.0. Moreover, the influences of the concentration of extracting reagent, initial vanadium concentration, and organic/aqueous (O/A) phase ratio on the extraction are investigated. Subsequently, recovery of V(V) from a synthetic leach solution in the presence of Fe(III), U(VI), Si(IV), and Al(III) was explored. Under the extraction conditions of initial pH of 1.9, 2-ethyl-1-hexanol concentration of 70 v/v%, extraction temperature of 60 °C, and phase ratio (O/A) of 2/1; about 93% of V(V) was extracted while the extraction of the other coexisting metals was lower than 8%. The present results showed that 2-ethyl-1-hexanol is a suitable solvent for the selective separation of V(V) from the acidic sulfate solutions. Moreover, a method for the stripping and precipitation of the V(V) compound was proposed to achieve the complete recovery of vanadium. The presented method led to the selective stripping of V(V) from the organic phase and its complete precipitation in the form of ammonium metavanadate.

Removal of vanadium from wastewater by multi-walled carbon nanotubes

ABSTRACTNitric acid heating reflux modified multi-walled carbon nanotubes (HMWCNTs) were used for the removal of vanadium(V) in aqueous solution. The removal rate of vanadium(V) decreased with the increase of the initial vanadium(V) concentration and the solution pH, and increased with the increase of reaction time, HMWCNTs amount and solution temperature. The adsorption equilibrium and dynamic kinetics fitted the Langmuir adsorption isotherm and pseudo-second order models. The results obtained by scanning electron micrography and Fourier transform infrared spectroscopy analysis revealed that the hydroxyl and carboxyl functional groups are mainly responsible for the vanadium adsorption. This study showed that the HMWCNTs proved to be a considerable adsorbent for the removal of vanadium from wastewater.

Removal of vanadium from industrial wastewater using iron sorbents in batch and continuous flow pilot systems

This study investigated the removal of vanadium from real industrial wastewater by using six iron materials: commercial iron sorbent (CFH-12), commercial mineral sorbent (AQM), blast furnace sludge (BFS), steel converter sludge (SCS), ferrochrome slag (FeCr) and slag from a steel foundry (OKTO). Batch tests revealed that CFH-12 (ferric oxyhydroxide) removed vanadium most efficiently, which was explained by its high iron content and the amorphous form of the iron, and that the sorption followed the Langmuir isotherm. With a dosage of 10 g/l and an initial vanadium concentration of 58.2 mg/l, 91–94% removal rates for vanadium were achieved in the studied pH range (3–9). Other sorbents showed significantly lower efficiency than CFH-12, with the exception of BFS at acidic pH (93%). Based on the batch test results, CFH-12 was selected for a pilot study made on site. The pilot study demonstrated the feasibility of CFH-12 to remove vanadium at high temperature (80 °C) from concentrated industrial wastewater with fluctuating water quality (vanadium concentration varied from 51 to 83 mg/l, pH about 9 (at 25 °C)). Leaching of impurities (mainly S, Ca, Mg and K) into the effluent occurred during the first day, but subsequently good quality effluent was produced (e.g. <0.1 mg/l V). During the pilot study, the amorphous iron material of CFH-12 was crystallized into a hematite-like phase (Fe1.67 H0.99 O3), and goethite (FeO(OH)) with a higher average pore diameter, probably due to the hot process conditions to which CFH-12 was exposed for over five days.

Performance Modeling of a Vanadium Redox Flow Battery during Discharging

A two-dimensional quasi-steady-state model is presented to simulate coupled mass-species-charge transfer and electrochemical reactions in all vanadium redox flow battery. Emphasis is located on examining the influences of applied current density, initial vanadium concentration, initial acid concentration and electrolyte flow rate on overpotentials in both electrodes, ohmic loss in electrolyte phase as well as battery discharging voltage. It is indicated that overpotential in negative electrode is the dominant factor causing the loss of battery discharging voltage at relatively lower or higher state of charge, while ohmic loss in electrolyte phase is dominant when discharging at moderate state of charge. Increasing initial vanadium concentration, the battery discharging voltage is significantly increased due to the reduced overpotentials in both electrodes. With the increase in initial acid concentration, the battery discharging voltage is also obviously increased because of increased open circuit voltage and decreased ohmic loss in electrolyte phase. As the electrolyte flow rate increases, the total discharging time is extended due to the retarded concentration polarization and the battery discharging voltage is obviously increased at lower state of charge.