Hydrometallurgy 97 (2009) 194–197

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Hydrometallurgy

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Extraction of vanadium from the leach solution of stone coal using ion exchange resin

Li Zeng ⁎, Qinggang Li, Liansheng XiaoMetallurgical Science and Engineering School, CSU, Changsha, 410083, China

⁎ Corresponding author.E-mail address: li.zeng@csiro.au (L. Zeng).

0304-386X/$ – see front matter © 2009 Elsevier B.V. Adoi:10.1016/j.hydromet.2009.03.005

a b s t r a c t

a r t i c l e i n f o

Article history:Received 18 December 2008Received in revised form 9 March 2009Accepted 10 March 2009Available online 21 March 2009

Keywords:Stone coalVanadiumExtractionIon exchange

The loading of V on weak base resin D314 from sulphuric acid leach solutions of stone coal containing 2.06 g/L V (V2O5) was found to be 260 mg/mL with contact time of 60 min at pH=4, giving a recovery of 99%.Stripping of loaded resin was excellent using 3 mol/L NaOH, with a maximum V concentration of 150 g/L inthe eluate. The resin features stable reusability when regenerated using 1 mol/L H2SO4 or 2 mol/L HCl. Theloading of V on the resin in the industrial trial was found to be as high as 280 mg/mL with a maximum Vconcentration of 200 g/L in the eluate. The final product of V2O5 with high purity (N99%) meeting thestandard specification was produced. Application of this process in industry is expected to make animportant impact on the extraction of vanadium from the leach solution of stone coal and to deliver goodeconomical benefits.

© 2009 Elsevier B.V. All rights reserved.

1. Introduction

There are hundreds of plants producing vanadium from stone coal inChina. Most of them are on small scales and adopt the classic process,which includes chloridizing roasting, water leaching, deposition, alkalimelting and thermal decomposition (Qi,1999). This process is costly andcomplicated with low recovery of vanadium (Luo, 1995). Moreover, itcauses serious environmental pollution by the poisonous gases andwaste water from the process (Dai et al., 2000). Increasing environ-mental concerns and tightening legislation have limited the applicationof this process, and thus, theutilisation of stonecoal (Heet al., 2007). It isurgent to explore an environmentally friendly technology to extractvanadium from stone coal.

A large amount of work has been conducted to improve the classicprocess of recovering vanadium from stone coal. Some new processessuch as hypohaline roasting–acid leaching–solvent extraction, roastingwithout chloride–acid leaching–ion exchange and oxidation roasting–acid leaching–purification–precipitation have been applied in industry(Deng and Liu, 1993; Wang and Li, 1993; Cai, 2001a,b; Bin, 2006). Theformation of third phase and unstable operation limit the industrialapplication of solvent extraction (Cai, 2001a,b; Zeng et al., 2002). Theprocess of oxidation roasting–acid leaching–purification–precipitationis mainly limited by the category of vanadium ores. Ion exchange is costeffective and easy to operate. In addition, it can increase the recovery ofvanadium whilst improving the working environment (Zhang, 2004).However, the resins currently used in the extraction of vanadium inChina are generally the strong base quaternary ammonium anionic onessuch as 201, 201⁎7, D231 and 717 (Commercial name in China). Theseresins are normally used in the extraction of vanadium from wastevanadiferous solution rather than in the main process of extracting

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vanadium. The loading of V on these resins is low, which is normallyless than 40 mg/mL (For D201: 27–41 mg/mL; for 201⁎7 and D231:30 mg/mL; for 717: 80 mg/mL) and the maximum concentration ofvanadium in eluate is less than 50 g/L (Qian, 1984; Che, 1991; Shen andLuo, 1998). In order to explore a novel resin with large loading capacityof V, the present work investigated the adsorption capacity of the weakbase resin D314 for the vanadium from the sulphuric acid leach solutionof stone coal.

2. Experimental

2.1. Anion-exchange resin

The weak base anion exchange resin D314 with function group of[–N(CH3)2] and structure of crosslinking acrylate was obtained fromHangzhou Zhengguang Chemical Company of China. The diameter ofmore than 95% resin beads is in the range of 0.45–1.00 mm. The resinwas first soaked in distilled water for 24 h, and then alternately soakedin 2 mol/L NaOH and 1 mol/L H2SO4 or 2 mol/L HCl for 2 h, repeatedthree times as this way, at last activated with 1 mol/L H2SO4 or 2 mol/LHCl and rinsed with distilled water before use.

2.2. Sample

The sulphuric acid leach solution of stone coal was obtained fromHuaihua Shuangxi Vanadium Plant. The composition of the solution isshown in Table 1. The pH value of the solution was around 4.

2.3. Column experiments

Trials were carried out in a glass column Φ1.8×25 cm whichoperated with the leach solution at the ambient temperature. Forty(40) mL of the resin, previously treated with NaOH and H2SO4 or HCl

Table 1Composition of the leach solution of stone coal.

Element Concentration (g/L)

V 2.059 (V2O5)Mg 0.182Al 0.0029Si 0.083P 0.0726S 1.126Cl 0.761K 0.0655Ca 0.996Na 0.28Mn 0.0093Fe 0.0002Ni 0.0028Cu 0.062Zn 0.106As 0.0093Se 0.0002Rb 0.0005Sr 0.0009Y 0.0003Mo 0.0154

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respectively, were wet-packed into the glass column. The operationwas performed by downstream flow at a certain flow rate. Sampleswere collected periodically from the column eluate and analysed todetermine vanadium content.

2.4. Chemical analyses

Vanadiumwas titratedwithammoniumferrous sulphate (ChemistryDepartment, 1982). The analysis of final product by spectrum was of-fered by Huaihua Shuangxi Vanadium Plant. The pH was determinedwith pH Test Paper.

2.5. Experiment fundamental

The resin was firstly transformed using 2 mol/L hydrochloric or1 mol/L sulphuric acid, followed by contacting with the leach solutionof pH 2–4. Fig. 1 is the forms of vanadium(V) existing in aqueoussolution under different pH and concentration (Zhang and Shen, 1991).It can be seen from Fig. 1 that the vanadium(V) in the sulphuric acidleach solution (lgCv (total)=−1.6, pH=2–4) is mostly in the formsof V10O6−

28, HV10O5−28, and H2V10O4−

28. These vanadium species with otheranionic species such as PO3−

4, AsO3−4 and SiO2−

3 in the feed solution can beadsorbed by resin, whilst cations such as Fe2+, Ni2+, Cu2+, Zn2+, Cd2+,Ca2+and Mg2+ remain in the solution. The separation of vanadium and

Fig. 1. Forms of vanadium (V) existing in aqueous solution.

other cations can thus be achieved. The adsorption of vanadium bythe resin (based on Cl− form) is expressed in the following reactions:

R3N þ HCI ¼ ðR3NHÞCI ð1Þ

4ðR3NHÞCI þ H2V10O4−28 ¼ ðR3NHÞ4:H2V10O28 þ 4CI

− ð2Þ

5ðR3NHÞCI þ HV10O5−28 ¼ ðR3NHÞ5:HV10O28 þ 5CI

− ð3Þ

6ðR3NHÞCI þ V10O6−28 ¼ ðR3NHÞ6:V10O28 þ 6CI

−: ð4Þ

The adsorption is stopped once the concentration of vanadium inthe effluent reaches 0.1 g/L. NaOH solution is then used to strip theloaded resin and the reactions are:

ðR3NHÞ4:H2V10O28 þ 10NaOH ¼ 4R3N þ 10NaVO3 þ 8H2O ð5Þ

ðR3NHÞ5:HV10O28 þ 10NaOH ¼ 5R3N þ 10NaVO3 þ 8H2O ð6Þ

ðR3NHÞ6:V10O28 þ 10NaOH ¼ 6R3N þ 10NaVO3 þ 8H2O: ð7Þ

The eluate with high concentration of vanadium can be used toproduce vanadium products. The resin is then regenerated using2 mol/L HCl or 1 mol/L H2SO4.

3. Results and discussion

3.1. The effect of resin form

The resins with SO2−4 and CI− formwere used to extract vanadium

from the leach solution at pH 4.0 under the contact time of the resinand the feed solution for 40 min at ambient temperature. The volumeof resin in column was 40 mL. The results are shown in Fig. 2.

As can be seen, when effluent/resin volume ratio was 100, theconcentration of vanadium with both two forms of the resin was lessthan 0.02 g/L. If 0.1 g/L V2O5 was set as break through point, theloading of V on the resin with SO2−

4 and CI− forms was more than200 mg/mL wet resin and the recovery of vanadium was as highas 99.9%. The resin with SO2−

4 form was used in the followingexperiments.

3.2. The effect of contact time

Contact time of the resin and feed solution changed from 30, 40to 60 min with the change of flow rate from 80 mL/h, 60 mL/h to40 mL/h was used at pH 4.0 and ambient temperature to investigate

Fig. 2. The effect of resin form on the extraction of vanadium (the V concentration ofeluate versus the bed volume).

Fig. 3. The effect of contact time on the extraction of vanadium (the V concentration ofeluate versus the bed volume). Fig. 5. The stripping of V from loading resin using NaOH or HCl.

196 L. Zeng et al. / Hydrometallurgy 97 (2009) 194–197

the effect on the extraction of vanadium. The results are shown inFig. 3.

It can be seen from Fig. 3, the adsorption of vanadium increasedwith the contact time. When effluent/resin volume ratio was 100,the concentration of vanadium with the contact time of 60 min was0.0139 g/L in comparison to 0.104 g/L and 0.236 g/L for 40 and30 min, respectively. The loading of V on the resin with contact timeof 60 min was thus calculated to be more than 260 mg/mL wet resinand the recovery of vanadiumwas 99.41%. The loading of V on the resinwith contact time of 40 and 30 min decreased to 202 and 171 mg/mLwet resin, respectively.

3.3. The effect of pH

Because the pH of real solution from plant was around 3–4, feedsolutions with pH=3 and 4 were used to investigate the effect of pHon the extraction of vanadium at ambient temperature. The results areshown in Fig. 4.

The loading of V on the resin at pH=4 and 3 were calculated tobe 264 and 195 mg/mL wet resin, respectively, with the recovery ofvanadium being 99.41% and 98.97%, correspondingly. This was probablybecause much more H2V10O4−

28 and HV10O5−28 were formed at pH=4

than at pH=3. Even though, the resin exhibited an excellent perfor-mance in a pH range of 3–4.

3.4. Stripping

After the loaded resin was washed by 120 mL de-ionised water,NaOH solution with three different concentrations or 2 mol/L HClsolution were used to strip vanadium from the loaded resin with a

Fig. 4. The effect of pH on the extraction of vanadium (the V concentration of eluateversus the bed volume).

contact time of 60 min at ambient temperature. The results are shownin Fig. 5.

It can be seen from Fig. 5, the stripping with NaOH solution wasmuch better than that with HCl solution. Themaximum concentrationof vanadium in the eluate increased and span of the curve narrowedwith the increase of NaOH concentration. The stripping was completedwhen eluate/resin volume ratio reached 3 and the maximum con-centration of vanadium in the eluate was 160 g/L. NaOH solution withrelatively high concentration was thus recommended as the strippingreagent for the industrial test.

3.5. Industrial test

The industrial test of recovering vanadium from the real leachsolution of stone coal from the plant of Hunan Province was carriedout using the resinwith volume of 6 m3 and a contact time of the resinand feed solution for 60 min at ambient temperature. The concentra-

Fig. 6. Extraction of V from sulphuric acid leach solution using resin in industrial test.

Fig. 7. Stripping of V from loading resin using NaOH in industrial test.

Table 2Composition of the product by spectrum analysis.

Element Content (wt.%)

V (V2O5) N99Mg 0.078Al 0.018Si 0.012P b0.001Mn b0.001Fe 0.0015Ni b0.001Ca 0.003Sn b0.001Bi b0.0001Cr b0.001Mo 0.028Cu 0.0077Cd b0.001Ti 0.036

197L. Zeng et al. / Hydrometallurgy 97 (2009) 194–197

tion of vanadium in the feed solution was around 2 g/L, and the pHof feed solution was in the range of 3–4. The adsorption was stoppedwhen the concentration of vanadium in the effluent reached 0.05 g/L.After the loaded resinwas washed by water with effluent/resin volumeratio of 2, 3 mol/L NaOH solution was used to strip the vanadiumwitha contact time of 60 min. The results of adsorption and stripping areshown in Figs. 6 and 7, respectively.

It can be seen from Figs. 6 and 7 that the resin exhibited an excellentperformance in the industrial test. The loading of V on the resin was280 mg/mL wet resin. The concentration of vanadium in the effluentwas 0.053 g/L when the effluent/resin volume ratio was 135, with aV recovery of 98.6%. The maximum concentration of vanadium in theeluate was 206 g/L, and the consumption of NaOH solution was 2times of resin volume. A certain amount of MgCl2 solid was thenadded to the solution containing high concentration of V (132.5 g/LV2O5) to remove the impurities such as P, Si and As. Ammoniummetavanadate was crystallised and precipitated with the addition ofNH4Cl at 40 °C and pH 8. After calcination of ammonium metavanadateat 550 °C for 1.5 h, the V2O5 with high purity meeting the standardspecificationwas produced. The spectrum analysis results of the productare shown in Table 2. The purity of V2O5 was more than 99%.

4. Conclusions

Based on the results obtained from the current work, the followingconclusions were made:

(1) There is little difference in loading of V on the resin betweenSO2−

4 and CI− forms.(2) The loading of V on the resin during adsorption decreases with

the increaseof contact time. Even though, a loadingof 171mg/mLwet resin was still achieved for the contact time of 30 min.

(3) There is little difference in loading of V on the resin betweenpH=3 and pH=4 of the feed solution. The loading of V on theresin with SO2−

4 form can be reached 260 mg/mL wet resin atpH=4 with a contact time of 60 min.

(4) NaOH solution exhibits an excellent performance as the strippingreagent. The maximum concentration of vanadium in eluate canbe as high as 160 g/L when using 3 mol/L NaOH solution.

(5) The industrial test indicates that application of the resin processin the extraction of vanadium from stone coal is feasible. Theloading of V on the resin can be reached 280 mg/mL wet resinwith an overall recovery of 98.6% vanadium. Application of theprocess in industry is expected tomake an important impact onthe extraction of vanadium from stone coal with a promisingeconomical outcome.

Acknowledgements

The authors would like to thank Dr Qixiu Zhang and Dr XianwenDai for reviewing this paper and providing valuable comments.

References

Bin, Z.Y., 2006. Progress of the research on extraction of vanadium pentoxide from stonecoal and the market of the V2O5. Hunan Nonferrous Metals 22, 16–20 (In Chinese).

Cai, J.Q., 2001a. Development of vanadium extraction from stone coal in HunanProvince. Rare Metals and Hard Alloy (1), 42–46 (In Chinese).

Cai, J.Q., 2001b. The new process of production of vanadium from stone coal. Inorganicsalt industry (5), 39–40 (In Chinese).

Che, R.R., 1991. The application of ion exchange in treatment of waste vanadiferousliquor. Technology of Water Treatment 17, 333–336 (In Chinese).

Chemistry Department, Hangzhou University, 1982. Chemical Analysis (AnalyticalChemistry Handbook, Part II). Chemical Industry Press, Beijing. (In Chinese).

Dai, W.C., Zhu, Q.J., Chen, Q.B., Liu, R.Y., Sun, S.Y., 2000. The study of comprehensiveutilisation of new processes on the extraction of vanadium from stone coal.Nonferrous Metals (3), 15–17 (In Chinese).

Deng, Q.Y., Liu, S.Y., 1993. The investigation of new process of roasting with NaCl, acidleaching and ion exchange on the extraction of vanadium from stone coal. RareMetals and Hard Alloy (4), 27–30 (In Chinese).

He, D.S., Feng, Q.M., Zhang, G.F., Ou, L.M., Lu, Y.P., 2007. An environmental-friendlytechnology of vanadium extraction from stone coal. Minerals Engineering 20,1184–1186.

Luo, C.Y., 1995. The study of new process on the extraction of vanadium from stone coal.Hunan Nonferrous Metals (4), 5–8 (In Chinese).

Qi, M.J., 1999. The status and prospects of vanadium leaching from stone coal.Hydrometallurgy of China 72, 1–10.

Qian, T.B., 1984. Applied Technology of Ion Exchange Reagent. Tianjin Science andTechnology Press, Tianjin, p. 43 (In Chinese).

Shen, B.W., Luo, Y.J., 1998. Inorganic Chemistry Series: Titanium, Vanadium, Chromium.Science Publisher, Beijing, China, pp. 180–245 (In Chinese).

Wang, Y.S., Li, G.L., 1993. The review on the comprehensive utilisation of the extractionof vanadium from stone coal in China. Vanadium and Titanium (4), 21–26 (InChinese).

Zeng, T.W., Dai, W.C., Zhang, Z., Zhu, Q.J., 2002. Study on exchanging properties of anionexchange resins for vanadium(V). Ion exchange and adsorption 18, 453–458 (InChinese).

Zhang, Q.X., 2004. Metallurgical Separation Science and Engineering. Science Publisher,Beijing, China, p. 118 (In Chinese).

Zhang, Q.L., Shen, P.W., 1991. Titanium, Vanadium and Chromium. Inorganic ChemistrySeries, vol. 8. Science Press, Beijing. 238 pp. (In Chinese).