Cleaning method of vanadium precipitation from stripped vanadium solution using oxalic acid

Powder Technology 355 (2019) 667–674

Contents lists available at ScienceDirect

Powder Technology journal homepage: www.elsevier.com/locate/powtec

Cleaning method of vanadium precipitation from stripped vanadium solution using oxalic acid Qian Kang a, Yimin Zhang a,b,c,d,⁎, Shenxu Bao a,b a

School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China Hubei Key Laboratory of Mineral Resources Processing and Environment, Wuhan University of Technology, Wuhan 430070, China State Environmental Protection Key Laboratory of Mineral Metallurgical Resources Utilization and Pollution Control, Wuhan University of Science and Technology, Wuhan 430081, Hubei Province, China d Hubei Collaborative Innovation Center for High Efficient Utilization of Vanadium Resources, Wuhan University of Science and Technology, Wuhan 430081, Hubei Province, China b c

a r t i c l e

i n f o

Article history: Received 30 April 2019 Received in revised form 3 June 2019 Accepted 13 July 2019 Available online 15 July 2019 Keywords: Vanadium precipitation NaV2O5 Hydrothermal process Stripped vanadium solution Oxalic acid

a b s t r a c t Adding ammonium salt to the stripped vanadium solution followed by calcination is the most commonly used vanadium precipitation method in the vanadium industry. However, the problem of ammonia waste water and waste gas emission in this process urgently needs to be solved. To avoid the ammonia emissions and utilize the sodium ion, a hydrothermal method was used to precipitate NaV2O5 by stripped vanadium solution. Under optimal conditions of a pH of 4.0, a time of 10 h, a temperature of 220 °C, and a molar ratio of oxalic acid to vanadium of 0.50, a NaV2O5 product with 99.83% of purity and 98.79% of vanadium precipitation rate was obtained. In view of crystal form, microscopy and granularity changes of products, a rational reaction and growth mechanism is put forward and that is condensation (oxolation and olation)-intercalation-reduction and self-assembly. The sodium in the stripped vanadium solution also can be utilized in this study. In short, one-step vanadium precipitation of NaV2O5 via hydrothermal process is an innovative, cleaning and efficient method, and it will also play a great role in NaV2O5 synthesis. © 2019 Elsevier B.V. All rights reserved.

1. Introduction Vanadium is a significant transition metal [1] and commonly applied in modern industries, such as catalysts [2,3], alloy steels [4,5], vanadium redox flow batteries [6,7], electrode material for lithium battery [8,9]. In China, vanadium reserves in vanadium-bearing shale are much higher than these in vanadium-titanium magnetite. Therefore, the production of vanadium from vanadium-bearing shale has caused widespread concern [10,11]. However, the grade and appearance of vanadium in vanadium-bearing shale is not conducive to its extraction. Vanadium extraction from vanadium-bearing shale needs complex process that is roasting - leaching - purification - vanadium precipitation – calcinations [12–15]. In the commonly adopted vanadium precipitation process, excessive ammonium salt is used to convert the sodium salt of vanadium into ammonium vanadate which can be pyrolyzed into V2O5 in calcination [16,17]. Therefore, the ammonium salt precipitation process produces a series of pollutants. First, the ammonium salt that has not reacted with vanadium remains in the vanadium residual liquid producing high-ammonium wastewater [18–20]. Moreover, the numerous sodium ⁎ Corresponding author at: School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China. E-mail addresses: [email protected] (Q. Kang), [email protected] (Y. Zhang).

https://doi.org/10.1016/j.powtec.2019.07.056 0032-5910/© 2019 Elsevier B.V. All rights reserved.

ions exchanged by ammonium ions in the vanadium residual liquid make it also a high-salt wastewater. In addition, ammonium vanadate releases ammonia gas during subsequent pyrolysis causing gas pollution. The generation of these pollutants seriously restricts the development of vanadium industry. To achieve environmental protection while developing, it is imperative to propose an eco-friendly vanadium precipitation method. Among the vanadium compound, NaV2O5 is a typical kind of alkali vanadium oxide bronze. Recently, NaV2O5 has been used as cathode materials both in Li-ion and Na-batteries due to its layered orthorhombic structure and showed good performance at the cost, discharge rate, and cycle life [21–23]. In the synthesis of NaV2O5, it is often necessary to introduce a vanadium source and a sodium source. Hydrothermal method is popular in NaV2O5 synthesis [24–27] because it has great advantages in morphology control and material structure stability and it is also eco-friendly, economic, and easy to be implemented. In the hydrothermal process, NaVO3 and V2O5 are reported as the most common vanadium source, and Na2CO3 and Na2C2O4 are generally selected as sodium source. The stripped vanadium solution contains a large amount of vanadium ions and sodium ions, which has the potential to prepare NaV2O5. Oxalic acid is selected as a reducing agent because it is environmentally friendly, inexpensive, and easy to handle. In this work, NaV2O5 was generated by hydrothermal method with oxalic acid reduction in vanadium precipitation process. To study the

668

Q. Kang et al. / Powder Technology 355 (2019) 667–674

effects of reaction condition on vanadium precipitation, some factors including initial pH, temperature, time and n(H2C2O4)/n(V(V)) (i.e. the molar ratio of oxalic acid to vanadium) were explored. To characterize the structural, morphology, and chemical composition of the NaV2O5, systematic tests including inductively coupled plasma-optical emission spectroscopy, X-ray diffractometer, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive spectroscopy and Transmission electron microscopy were performed. Furthermore, the reaction mechanism and crystal growth mechanism of NaV2O5 were also expounded.

Table 1 Main chemical elements in stripped vanadium solution.

2. Experimental

In vanadium precipitation test, a quantity of oxalic acid was added in stripped vanadium solution under stirring forming feed solution. After that, the pH of the feed solution was adjusted to a set value by adding sulfuric acid solution or sodium hydroxide solution drop by drop. Then, feed solution was diverted into Teflon-lined stainless-steel autoclave and placed in an oven for a certain time at different temperatures. When the autoclave was cooled, filtration was used to collect the solid. After washed with deionized water and absolute ethanol, the product was dried in vacuum drying oven. The vanadium precipitation rate is calculated as Eq. (1).

2.1. Materials Based on the previous achievements of our group [1,28], the preparation process of stripped vanadium solution is as follows (Fig. 1). The main chemical elements in stripped vanadium solution are shown in Table 1. It can be seen that there are a large amount of

Content

V

Na

Al

Fe

P

Si

Mg

Concentration (mg/L)

24,861

23,052

41

36

31

17

24

vanadium ion and sodium ion, and a bit of impurity ions such as Al, Fe, Mg, P, Si in the solution. 2.2. Vanadium precipitation tests

R ¼ ð1−CR VR =C F V F Þ  100%

ð1Þ

where R represents vanadium precipitation rate, CR and VR represent the vanadium concentration and volume of residue liquid, respectively. CF and VF represent the vanadium concentration and volume of feed solution, respectively. 2.3. Analytical methods The concentrations of chemical elements in stripped vanadium solution and the synthesized NaV2O5 were obtained with ICP–OES carried on an Optima 4300DV instrument (Perkin–Elmer, America). The crystal phase of synthesized NaV2O5 was tested with XRD by a D/MAX-RB (Rigaku, Japan), with Cu Kα radiation. The bonds of synthesized NaV2O5 were studied by a RENISHAW Raman microscope (InVia, Britain) using argonion laser (at 633 nm) as excitation light source. The combination of sodium, vanadium and oxygen in synthesized NaV2O5 were reflected by an X-ray photoelectron spectroscopy on VG ESCALAB 210 electron spectrometer (Britain). A JSM-IT300 scanning electron microscope (JEOL, Japan) equipped with a X-Act energy dispersive spectrometer (OXFORD, Britain) was used to study the microstructure. A JEM-2100F Transmission electron microscopy with high resolution microscopy and selected area electron diffraction was employed for lattice research (JEOL, Japan). 3. Results and discussion 3.1. Vanadium precipitation tests

Fig. 1. Flow sheet for stripped vanadium solution preparation.

To investigate effect of initial pH on vanadium precipitation rate, tests were conducted as pH value changed from 2.0 to 8.0 under the condition of a n(H2C2O4)/n(V) of 0.5, a temperature of 220 °C and a time of 10 h (Fig. 2). It can be seen that pH plays a significant effect on rate. The rate first increased from 85.22 to 98.79% at a pH value of 4.0 and then leveled off. However, the rate decreased quickly to 61.96% with pH value continuously increasing to 8.0. The forms of vanadium and oxalic acid vary at difference pH value, leading to the diversification of vanadium oxidation and oxalic acid reduction [29]. The initial pH values also affect the precipitates (Fig. S1). When initial pH values were 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0, the corresponding precipitates are both NaV2O5. While it presents many diffuse peaks and not a NaV2O5when the pH is 2.0. Considering the product phase and the vanadium precipitation rate, pH = 4.0 is the optimum.

Q. Kang et al. / Powder Technology 355 (2019) 667–674

669

Fig. 2. Effect of pH value on vanadium precipitation rate.

Fig. 4. Effect of time on vanadium precipitation rate.

To study effect of temperature on vanadium precipitation rate, tests were conducted as temperature differed from 180 °C to 260 °C under the condition of an initial pH value of 0.8, a time of 8 h and a n (H2C2O4)/n(V) of 0.5 (Fig. 3). When temperature raised from 180 °C to 220 °C, vanadium precipitation rate went up from 72.0% to 98.8% quickly. However, as temperature continued to rise to 260 °C, the increasing of vanadium precipitation rate became negligible. The higher temperature, the greater growth rate of the crystal, so a proper high temperature benefits the hydrothermal process [30]. Considering the energy consumption and the vanadium precipitation rate, 220 °C is chosen as the optimal temperature. The time effect on vanadium precipitation rate was explored with time ranging from 2 h to 12 h under the condition of an initial pH value of 4.0, a temperature of 220 °C and a n(H2C2O4)/n(V) of 0.5 (Fig. 4). As time was extended to 10 h, vanadium precipitation rate quickly reached 99%. However, over time, the increase in vanadium precipitation rate can be ignored. The results indicated that almost all vanadium was converts into the precipitate as the time was extended to 10 h. Vanadium precipitation is a step-by-step process that includes hydrolysis, condensation, intercalation, reduction and the growth of

crystal. Extension of reaction time facilitates sufficient reaction and crystal growth. The effect of n(H2C2O4)/n(V) on vanadium precipitation rate was investigated with n(H2C2O4)/n(V(V)) ranged from 0.10 to 1.00 under the condition of an initial reaction pH value of 0.8, a temperature of 220 °C and a time of 10 h (Fig. 5). The vanadium precipitation rate increased from 61% to 99% with the n(H2C2O4)/n(V(V)) increasing from 0.1 to 0.5, illustrating that at this point there are enough V(V) reduced to V (IV). However, vanadium precipitation rate increased a little with n (H2C2O4)/n(V(V)) increasing. Moreover, excess oxalic acid would continue to reduce the V(V) to V(IV), resulting in a product of VO2·(H2O) 0.5 appeared when the n(H2C2O4)/n(V(V)) is 0.75 or 1.00 and the peak intensity of VO2·(H2O)0.5 is more stronger when the n(H2C2O4)/n(V (V)) is 1.00 (Fig. S2). Hence, it is obvious that the n(H2C2O4)/n(V(V)) of 0.50 is the optimum. After batch tests, an optimal condition is obtained. The details are as follows: an initial pH of 4.0, a time of 10 h, a temperature of 220 °C, and a n(H2C2O4)/n(V(V)) of 0.50. Under optimal condition, vanadium precipitation rate can reach 98.79%. When the solution pH value is 4.0, exist − forms of vanadium and oxalic acid are V2O4− 7 and HC2O4 , respectively

Fig. 3. Effect of temperature on vanadium precipitation rate.

Fig. 5. Effect of n(H2C2O4)/n(V) on vanadium precipitation rate.

670

Q. Kang et al. / Powder Technology 355 (2019) 667–674

[31]. Based on the exist forms of vanadium and oxalic acid and their molar ratio under optimal vanadium precipitation conditions, the probable reaction was inferred and shown in Eq. (2). 2V2 O7 4− þ 2Naþ þ 7Hþ þ HC2 O4 – →2 NaV2 O5 þ 2CO2 þ 4H2 O

ð2Þ

3.2. Crystal structure, morphology and composition Fig. 6a shows the XRD pattern of the NaV2O5. Diffraction peaks in the product at 18.42, 20.03, 24.25, 25.86, 30.06, 30.92, 31.58, 34.34, 37.38, 38.25, 44.66 and 48.18 are in accord with those of (001), (101), (201), (110), (301), (011), (111), (211), (002), (102), (411) and (600) crystal planes in NaV2O5 (JCPDS card No. 70-0870). No other peaks appear, illustrating that there is only one crystal of NaV2O5. The strong and sharp peaks indicate that NaV2O5 crystallizes well and (001) crystal plane has priority of orientation. XRD results indicate that the vanadium precipitation conditions are fit for precipitating NaV2O5 product. Fig. 6b displays XPS spectra of NaV2O5. The binding energy peaks at 533.5 eV and 530.3 eV agree with NaKL2 and O1s states, respectively. The peaks between 514 eV and 527 eV are classified to V2p state. Due to spin-orbit coupling, the binding energy of V2p centers at 517 eV and 524 eV, respectively [32]. A fitness of V2p3/2 peaks contain two binding energies of 516 eV and 517 eV, which are equal to binding energies of V4+ in VO2 [33] and V5+ in V2O5 [34]. The ratio of peak area from V4+ peak to it from V5+ peak close to 1. This conforms that the chemical formula of the tested substance is NaV2O5.

Fig. 6c demonstrates the Raman spectrum of the NaV2O5. There are three types of oxygen atoms in NaV2O5, namely, vanadyl oxygen atoms (O1), chain oxygen atoms (O2) and bridge (O3) oxygen atoms. Peaks in Raman spectrum situs at 176, 229, 300, 420, 528, 673 and 968 cm−1 belong to the Raman signature of NaV2O5. Band at 968 cm−1 is ascribed to stretching vibration of V\\O1, and it is the highest wave. This shows that V\\O1 bond is the strongest one. Peaks at 673 cm−1 and 528 cm−1 are derived from V\\O2 stretching vibration. Raman band at 229 cm−1 and 420 cm−1 are ascribed to O3\\V\\O3 bending vibrations. Finally, peak at 170 cm−1 ascribed to displacement of Na atom [24–26,35,36]. Fig. 7 displays SEM images of the NaV2O5. As shown in Fig. 7, the NaV2O5 exists in the form of rods whose diameter is about 10 μm and the length are between tens to hundreds micrometers. The layer structure is seen from the fracture section which can be inferred the formation and growth of crystals. Considering the impurities contained in the simulated stripped vanadium solution, point sweep and face sweep were conducted to characterize the element in the NaV2O5 and it can be seen that only V, Na and O appeared in the element point sweep and they have a good relevance. It reflects that the impurity ions do not enter the crystal lattice of the product, which is consistent with the results of XRD. The possible presence of impurities is inclusion or adsorption. The chemical composition of the NaV2O5 produced is shown in Table 2. It can be seen from the table that the purity of the NaV2O5 prepared can reach as high as 99.83% despite the presence of a small amount of impurities.

Fig. 6. Crystal structure of NaV2O5 produced at optimal condition. a: XRD pattern, b: XPS fine spectrums of V, c: Raman spectrum.

Q. Kang et al. / Powder Technology 355 (2019) 667–674

671

Fig. 7. SEM-EDS images of NaV2O5 produced in the optimal condition.

TEM of NaV2O5 rods were conducted to investigate the details about the microstructure. A micron rod was shown after the sample is evenly dispersed in absolute ethanol (Fig. 8(a, b)), which is corresponding to the SEM image. From the SAED image, clear and tidy diffraction point indicating the single crystal structure of the product, Many continuous and clear lattice fringes appear in HRTEM image (Fig. 8d). The lattice fringes of 0.34 nm and 0.57 nm corresponding to the (110) and (200) planes, respectively, are observed. Based on the TEM observation and the XRD measurement, it is reasonably inferred that NaV2O5 is preferably grown along [010] to form rod.

3.3. Reaction mechanism The vanadium precipitation of NaV2O5 from simulated stripped vanadium solution is a complicated process. It consists hydrolysis, condensation, intercalation and reduction processes. The pH value of stripped vanadium solution changed to 4.0 by adding sulfuric acid and oxalic acid. In this condition, two condensation reactions (i.e. oxolation and

Table 2 Chemical elements of NaV2O5 produced in optimal conditions. Item

NaV2O5

Fe

Al

Content (wt%)

99.833

0.081

0.016

0.025

Si

S

0.025

0.021

olation) happened in the hydrothermal process [37–39]. Oxolation : V–OH þ HO–V→V–O–V þ H2 O

ð3Þ

Olation : V–OH þ V–OH2 →V–OH–V þ H2 O

ð4Þ

Through the above reactions, VO5 layers is forming. The oxalic acid species in the solution tend to react with the binding site of oxygen in the bridge oxygen bond, resulting in the expansion of VO5 layer spacing. The formation of NaV2O5 involves a redox reaction that pentavalent vanadium ions is reduced to tetravalent vanadium ions, meanwhile oxalate spices is oxidized to CO2 and H2O. Every oxalate provides one electron for V2O5 unit and reduces a V(+5) to V(+4). The decomposition of oxalates results from the homolytic C\\C bond cleavage [40,41]. The potentiometric titration of pentavalent vanadium ions and tetravalent vanadium ions in the NaV2O5 samples shows their ratio is approximately equal to 1, which in agree with the result of XPS test. The VO5 layer is negatively charged after reduction, so that Na+ in the solution inserted into the interlayer of VO5 to keep the charge balanced, so NaV2O5 formed [38,39,42]. Unlike other NaV2O5 synthesis experiments, where Na2CO3 and V2O5 were added as sodium source and vanadium source respectively, the Na-ion and V-ion in the stripped vanadium solution were completely dissociated, so NaV2O5 formation from simulated stripped vanadium solution is not affected by hydrolysis of sodium salt and V2O5. Oxolation and olation and oxalic acid reduction are both time-consuming processes, when time is

672

Q. Kang et al. / Powder Technology 355 (2019) 667–674

Fig. 8. TEM observation of NaV2O5 produced at optimal condition (a, b) TEM images, (c) SAED image, (d) HRTEM image and the FFT selected-area electron diffraction spot pattern inset.

insufficient, the content of VO5 layers is very low. With time prolonging, the reduction reaction continuously decreased the content of V5+ and more NaV2O5 generated. The reducibility of oxalic acid is increases with pH decreases, so VO2 generates when the pH ≤ 1.0 [43,44]. Based on the above research, a mechanism of vanadium precipitation of NaV2O5 from stripped vanadium solution by hydrothermal process using oxalic acid reduction is put forward in Fig. 9. 3.4. Crystal growth mechanism To investigate the crystal growth mechanism, granularity and morphology evolution of NaV2O5 obtained in different time were explored

by particle size and SEM tests and the results are shown in Fig. S3 and Fig. 10. The granularity of the product presents a process of decreasing first and then increasing (Fig. S3), which conforms to the theory of dissolution-recrystallization. The SEM images show that the product exists in a rod-like structure. As the reaction time increases, the diameter and length of the product gradually increase and the layered structure of the product becomes more and more obvious. However, when the time is 12 h, the particle size of the product becomes significantly larger and the some of the rod structure were destroyed, even a plate structure appears. The preferential stacking of NaV2O5 layered implies that the growth of NaV2O5 crystals in hydrothermal method conforms a selfassembly mechanism [26]. By analyzing the particle size result and

Fig. 9. Schematic of vanadium precipitation of NaV2O5 from stripped vanadium solution.

Q. Kang et al. / Powder Technology 355 (2019) 667–674

673

Fig. 10. SEM images of NaV2O5 treated for (a) 2 h, (b) 4 h, (c) 8 h, (d) 10 h, (e) 12 h.

SEM images of the products synthesized at different time, a reasonably conclusion is that the formation of NaV2O5 is consistent with the typical dissolution and recrystallization theory. 4. Conclusions (1) A hydrothermal process with oxalic acid reduction is used in vanadium precipitation. The vanadium precipitation rate can reach 98.79% and the purity of NaV2O5 is 99.83% in the optimal condition: an initial pH of 4.0, a temperature of 220 °C, a time of 10 h and a n(H2C2O4)/n(V(V)) of 0.5. (2) XRD, Raman spectroscopy, XPS, SEM-EDS and ICP-OES tests of NaV2O5 precipitated in optimal condition show the product is pure NaV2O5. SEM images illustrate that NaV2O5 presents as microrods with a diameter of about 10 μm and a length ranging from tens to hundreds micrometers. TEM results reveal that the NaV2O5 rod is a single crystal structure and preferably grown along [010]. (3) The reaction mechanism of vanadium precipitation from stripped vanadium solution is proposed, which is condensation (oxolation and olation)-intercalation-reduction and self-assembly. The formation of NaV2O5 microrods is in accordance with the typical dissolution and recrystallization theory according to the results of particle size and SEM images. (4) The vanadium precipitation with oxalic acid hydrothermal process is a novel and eco-friendly process. This method will have a big impact on NaV2O5 synthesis. Acknowledgements This research is financially supported by the National Natural Science Foundation of China (No. 51874222). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.powtec.2019.07.056.

References [1] Y.M. Zhang, S.X. Bao, T. Liu, T.J. Chen, J. Huang, The technology of extracting vanadium from stone coal in China: history, current status and future prospects, Hydrometallurgy 109 (2011) 116–124. [2] G.Q. Lv, S.W. Chen, H.F. Zhu, M. Li, Y.X. Yang, Determination of the crucial functional groups in graphene oxide for vanadium oxide nanosheet fabrication and its catalytic application in 5-hydroxymethylfurfural and furfural oxidation, J. Clean. Prod. 196 (2018) 32–41. [3] N. Saadatkhah, M.G. Rigamonti, D.C. Boffito, H. Li, G.S. Patience, Spray dried SiO2 WO3/TiO2 and SiO2 vanadium pyrophosphate core-shell catalysts, Powder Technol. 316 (2017) 434–440. [4] S. Camero, E.S. Puchi, G. Gonzalez, Effect of 0.1% vanadium addition on precipitation behavior and mechanical properties of Al-6063 commercial alloy, J. Mater. Sci. 41 (2006) 7361–7373. [5] S. Nafisi, B.S. Amirkhiz, F. Fazeli, M. Arafin, R. Glodowski, L. Collins, Effect of vanadium addition on the strength of API X100 Linepipe steel, ISIJ Int. 56 (2016) 154–160. [6] C.Y. Choi, S. Kim, R. Kim, Y. Choi, S. Kim, H.Y. Jung, J.H. Yang, H.T. Kim, A review of vanadium electrolytes for vanadium redox flow batteries, Renew. Sust. Energ. Rev. 69 (2017) 263–274. [7] L.H. Yu, F. Lin, W.D. Xiao, L. Xu, J.Y. Xi, Achieving efficient and inexpensive vanadium flow battery by combining CexZr1−xO2 electrocatalyst and hydrocarbon membrane, Chem. Eng. J. 356 (2018) 622–632. [8] Q.Y. Li, L. Zhang, J.L. Dai, H. Tang, Q. Li, H.G. Xue, H. Pang, Polyoxometalate-based materials for advanced electrochemical energy conversion and storage, Chem. Eng. J. 351 (2018) 441–461. [9] S.C. Li, B.Q. Wen, J. Zhai, X. Guo, Effect of rare earth elements substitution for vanadium on microstructures and electrochemical properties of Ti0.26Zr0.07V0.24Mn0.1Ni0.33 alloy, Powder Technol. 303 (2016) 1–6. [10] L.Y. Ren, H. Qiu, Y.M. Zhang, A.V. Nguyen, M. Zhang, P.G. Wei, Q.R. Long, Effects of Alkyl Ether Amine and Calcium Ions on Fine Quartz Flotation and its Guidance for Upgrading Vanadium from Stone Coal, vol. 338, 2018 180–189. [11] X.B. Li, Z.G. Deng, C. Wei, C.X. Li, M.T. Li, G. Fan, H. Huang, Solvent extraction of vanadium from a stone coal acidic leach solution using D2EHPA/TBP: continuous testing, Hydrometallurgy 154 (2015) 40–56. [12] G.Z. Zhang, D.S. Chen, W. Zhao, H.X. Zhao, L.N. Wang, D. Li, T. Qi, A novel synergistic extraction method for recovering vanadium (V) from high-acidity chloride leaching liquor, Sep. Purif. Technol. 165 (2016) 166–172. [13] S.X. Bao, J.H. Duan, Y.M. Zhang, Recovery of V(V) from complex vanadium solution using capacitive deionization (CDI) with resin/carbon composite electrode, Chemosphere 208 (2018) 14–20. [14] P. Xiong, Y.M. Zhang, J. Huang, S.X. Bao, X. Yang, C. Shen, High-efficient and selective extraction of vanadium (V) with N235-P507 synergistic extraction system, Chem. Eng. Res. Des. 120 (2017) 284–290. [15] N.N. Xue, Y.M. Zhang, T. Liu, J. Huang, Q.S. Zheng, Effects of hydration and hardening of calcium sulfate on muscovite dissolution during pressure acid leaching of black shale, J. Clean. Prod. 149 (2017) 989–998.

674

Q. Kang et al. / Powder Technology 355 (2019) 667–674

[16] D.S. Chen, H.X. Zhao, G.P. Hu, T. Qi, H.D. Yu, G. Zhang, L. Wang, W. Wang, An extraction process to recover vanadium from low-grade vanadium-bearing titanomagnetite, J. Hazard. Mater. 294 (2015) 35–40. [17] Y.H. Liu, C. Yang, P.Y. Li, S.Q. Li, A new process of extracting vanadium from stone coal, Int. J. Miner. Metall. Mater. 17 (2010) 381–388. [18] Q.H. Shi, Y.M. Zhang, T. Liu, J. Huang, Recycling of Ammonia wastewater during vanadium extraction from shale, JOM (2018) 1–6. [19] X. Yang, Y.M. Zhang, S.X. Bao, C. Shen, Separation and recovery of vanadium from a sulfuric-acid leaching solution of stone coal by solvent extraction using trialkylamine, Sep. Purif. Technol. 164 (2016) 49–55. [20] D.A. Fang, X.F. Zhang, M.G. Dong, X.X. Xue, A novel method to remove chromium, vanadium and ammonium from vanadium industrial wastewater using a byproduct of magnesium-based wet flue gas desulfurization, J. Hazard. Mater. 336 (2017) 8–20. [21] E. Andrukaitis, Lithium intercalation in electrodeposited vanadium oxide bronzes, J. Power Sources 119 (2003) 205–210. [22] G. Nagaraju, G.T. Chandrappa, Solution phase synthesis of Na0.28V2O5 nanobelts into nanorings and the electrochemical performance in Li battery, Mater. Res. Bull. 47 (2012) 3216–3223. [23] G. Nagaraju, S. Sarkar, J. Dupont, S. Sampath, Na0.33V2O5·1.5H2O nanorings/nanorods and Na0.33V2O5·1.5H2O/RGO composite fabricated by a facile one pot synthesis and its lithium storage behavior, Solid State Ionics 227 (2012) 30–38. [24] I. Mjejri, N. Etteyeb, F. Sediri, NaV2O5 nanoplates: hydrothermal synthesis, characterization and study of their optical and electrochemical properties, Ceram. Int. 40 (2014) 5379–5386. [25] F. Hu, X. Ming, G. Chen, C.Z. Wang, A. Li, J.X. Li, Y.J. Wei, Synthesis and characterizations of highly crystallized α`-NaV2O5 needles prepared by a hydrothermal process, J. Alloys Compd. 479 (2009) 888–892. [26] P.C. Liu, D.H. Zhou, K.J. Zhu, Q.L. Wu, Y.F. Wang, G.A. Tai, W. Zhang, Q.L. Gu, Bundlelike α`-NaV2O5 mesocrystals: from synthesis, growth mechanism to analysis of Naion intercalation/deintercalation abilities, Nanoscale 8 (2016) 1975–1985. [27] P.C. Liu, K.J. Zhu, K. Bian, Y. Xu, F. Zhang, W. Zhang, W.Q. Huang, J.H. Zhang, One-step and short-time synthesis of 3D NaV2O5 mesocrystal as anode materials of Na-ion batteries, J. Power Sources 395 (2018) 158–162. [28] X. Yang, Y.M. Zhang, S.X. Bao, Preparation of high purity V2O5 from a typical lowgrade refractory stone coal using a pyro-hydrometallurgical process, Minerals 6 (2016) 69. [29] Y. Mu, X. Jiang, Z.H. Ai, F.L. Jia, L.Z. Zhang, Mn2+ promoted Cr(VI) reduction with oxalic acid: the indispensable role of in-situ generated Mn3+, J. Hazard. Mater. 343 (2018) 356–363.

[30] S.L. Skjaervo, K.H. Wells, W.V. Beek, T. Grande, M.A. Einarsrud, Kinetics during hydrothermal synthesis of nanosized KxNa1-xNbO3, Cryst. Eng. Comm. 20 (2018) 6795–6802. [31] X.J. Zhou, C. Wei, M.T. Li, S. Qiu, X.B. Li, Thermodynamics of vanadium-sulfur-water systems at 298 K, Hydrometallurgy 106 (2011) 104–112. [32] M.J. Konstantinović, S.V. Berghe, M. Isobe, Y. Ueda, X-ray photoelectron spectroscopy study of mixed-valence effects and charge fluctuation in NaxV2O5, Phys. Rev. B 72 (2005), 125124. [33] J. Mendialdua, R. Casanova, Y. Barbaux, XPS studies of V2O5, V6O13, VO2 and V2O3, J. Electron Spectrosc. 71 (1995) 249–261. [34] N. Ibris, A.M. Salvi, M. Liberatore, F. Decker, A. Surca, XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification, Surf. Interface Anal. 37 (2005) 1092–1104. [35] Z.V. Popovic, M.J. Konstantinovic, R. Gajic, V. Popov, Y.S. Raptis, A.N. Vasil'ev, M. Isobe, Y. Ueda, Lattice vibrations in spin-Peierls compound NaV2O5, Solid State Commun. 110 (1999) 381–386. [36] X.J. Wang, H.D. Li, Y.J. Fei, X. Wang, Y.Y. Xiong, Y.X. Nie, K.A. Feng, XRD and Raman study of vanadium oxide thin films deposited on fused silica substrates by RF magnetron sputtering, Appl. Surf. Sci. 177 (2001) 8–14. [37] T. Chirayil, P.Y. Zavalij, M.S. Whittingham, Hydrothermal synthesis of vanadium oxides, Chem. Mater. 10 (1998) 2629–2640. [38] J. Livage, Synthesis of polyoxovanadates via “chimie douce”. Coordin, Chem. Rev. 178 (1998) 999–1018. [39] O. Durupthy, N. Steunou, T. Coradin, J. Maquet, C. Bonhomme, J. Livage, Influence of pH and ionic strength on vanadium(V) oxides formation. From V2O5·nH2O gels to crystalline NaV3O8·1.5H2O, J. Mater. Chem. 15 (2005) 1090–1098. [40] W.F. Wu, C.Y. Wang, W.J. Bao, H.Q. Li, Selective reduction leaching of vanadium and iron by oxalic acid from spent V2O5-WO3/TiO2 catalyst, Hydrometallurgy 179 (2018) 52–59. [41] D. Ballivet-Tkatchenko, J. Galy, J.L. Parize, J.M. Savariault, Thermal decomposition of sodium oxalate in the presence of V2O5, Thermochim. Acta 232 (1994) 215–223. [42] M. Dubarry, J. Gaubicher, D. Guyomard, O. Durupthy, N. Steunou, J. Livage, N. Dupre, C.P. Grey, Sol gel synthesis of Li1+rV3O8. 1. From precursors to Xerogel, Chem. Mater. 17 (2005) 2276–2283. [43] G. Gannon, C. O'Dwyer, J.A. Larsson, D. Thompson, Interdigitating organic bilayers direct the short interlayer spacing in hybrid organic-inorganic layered vanadium oxide nanostructures, J. Phys. Chem. B 115 (2011) 14518–14525. [44] C.J. Patridge, T.L. Wu, C. Jaye, B. Ravel, E.S. Takeuchi, D.A. Fischer, G. Sambandamurthy, S. Banerjee, Synthesis, spectroscopic characterization, and observation of massive metal-insulator transitions in nanowires of a nonstoichiometric vanadium oxide bronze, Nano Lett. 10 (2010) 2448–2453.