Kinetics of Vanadium Leaching from a Spent ... - ACS Publications

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Kinetics of Vanadium Leaching from a Spent Industrial V2O5/TiO2 Catalyst by Sulfuric Acid Qichao Li, Zhenyu Liu, and Qingya Liu* State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China ABSTRACT: Recovery of vanadium from various sources is important to the environment and industry. This work investigates vanadium leaching from a spent selective catalytic reduction catalyst by sulfuric acid at atmospheric pressure. It includes the effects of stirring speed, solid to liquid ratio, temperature, and sulfuric acid concentration on the vanadium recovery yield. The results show that the vanadium recovery yield increases with increases in temperature, sulfuric acid concentration, and leaching time and decreases with an increase in solid to liquid ratio. The leaching data can not be described well by kinetic models commonly adopted for similar processes in the literature. The Avrami equation, originally developed for crystallization, is found to be most suitable. The leaching is controlled by diffusion in the solid with an activation energy of 5.90 kJ/mol.

1. INTRODUCTION It has long been recognized that vanadium is a toxic material to man and animals.1 However, vanadium oxides are widely used in industry as important rare additives. Recovery of vanadium from these secondary resources not only avoids wasting of the resources but also prevents environmental pollution. In this sense, various hydrometallurgical processes have been studied and developed to recover vanadium, such as those from fly ash in the oil industry,2 petroleum coke,3 and spent hydrodesulphurization (HDS) catalysts.4 Recently, the recovery of vanadium from spent flue gas De-NOX catalyst has attracted much attention. V2O5 supported TiO2 catalyst has been widely used for flue gas De-NOX via selective catalytic reduction (SCR) with NH3. The catalysts usually contain about 1−2 wt % V2O5. The catalysts have to be used at the upstream of dust precipitators and consequently suffer from attrition, thermal degradation, and alkali and heavy metals poisoning. The life span of the catalysts is about 3 years. Research on regeneration of the deactivated SCR catalyst has been reported in recent years,5−8 including air flushing of the ash accumulated on the surface and water or diluted sulfuric acid washing followed by a supplement of vanadium. However these regeneration methods are not always very effective for a long operation and a large amount of catalyst; it is estimated that 38 000 t/y in China in 20189 will have to be discarded. However, research on recovery of this secondary vanadium resource is rather limited in the literature, except for a few Chinese patents that calcine the spent catalysts with sodium slats and then extract vanadium with hot water.10−12 These methods require a high energy input and suffer from the limited contact between the catalysts and the sodium salts. The above methods were adopted from recovery of vanadium from other resources such as vanadium-bearing minerals, black shale, stone-coal, and petroleum coke. The principle is that vanadium is embedded in the ores’ crystal structure,13−17 which can be destroyed by sodium salts or limestone at high temperatures to generate water-soluble vanadates that are easy to leached out with water or acid.14,15 © 2014 American Chemical Society

With this method, Habib et al. reported a vanadium recovery yield of more than 60% from petroleum coke.3 Direct acid leaching is another method used for extraction of vanadium from various solid sources. Li et al. adopted the method to extract vanadium from black shale, an aluminosilicate matrix embedded with vanadium. The vanadium recovery yield reached 80% under oxygen pressure. The leaching rate was reported to be limited by the interfacial transfer and diffusion of vanadium across the alumino-silicate layer, which can be described by a modified shrinking core model (SCM) with an overall activation energy of 40.14 kJ/ mol.18 Deng et al. adopted the same method to recover vanadium from a raw stone-coal and reported a recovery yield of greater than 90%.19 Szymczycha-Madeja investigated extraction of molybdenum (Mo), nickel (Ni), vanadium (V), and aluminum (Al) from a spent hydrodesulphurization catalyst with a mixed solution of oxalic acid and hydrogen peroxide and reported that the metals were in the form of low valence metal sulfides that can be oxidized by the solution to form soluble oxalates of high valence metal ions.20 This process was described by a chemical reaction controlled model (SCM) with an activation energy of 30 ± 4 kJ/mol for V extraction. Amer used the SCM model to describe vanadium leaching from black shale by sulfuric acid and reported the controlling step as surface chemical reaction at the early stage, with an activation energy of 48 kJ/mol; meanwhile, diffusion of vanadium ions through the solid layer occured in the latter stage, with an activation energy of 32 kJ/mol.21 Clearly the effectiveness of direct leaching of vanadium depends on the forms of vanadium present in the solid materials. Since in most cases the vanadium in the SCR catalysts is dispersed on TiO2 support in the form of V2O5 or VOX, and their interaction with the support is weak,22 the direct acid leaching method may be efficient for vanadium recovery Received: Revised: Accepted: Published: 2956

May 15, 2013 January 2, 2014 January 22, 2014 January 22, 2014 dx.doi.org/10.1021/ie401552v | Ind. Eng. Chem. Res. 2014, 53, 2956−2962

Industrial & Engineering Chemistry Research

Article

metal contents of Ti, V, and W, the active components in the catalyst, are 36.00, 0.29, and 3.00 wt %, respectively, corresponding to TiO2, V2O5, and WO3 contents of 60.07%, 0.52%, and 3.78%, respectively. The minor components in the spent catalyst are K, Ca, As, and P with concentrations of less than 0.3%. It is noted that the uncounted components in the spent catalyst include Si, Al, and Fe oxides, which were from the binders used. Figure 1 shows V 2p XPS spectra of the spent SCR catalyst. The Gaussian−Lorentzian fit to the V 2p3/2 peak shows two

from the spent catalysts. This work investigates the process and develops an intrinsic kinetic model without consideration of reactor configuration and solid−liquid mixing.

2. EXPERIMENTAL SECTION 2.1. Materials and Characterization. The spent SCR catalyst used in this work is a corrugated plate-type which had been used in a thermal power plant in China. The catalyst was peeled off and broken up from the supporting plate and ground to sizes of less than 74 μm for the experiments. This not only avoids the size effect on the leaching but also favors the subsequent utilization of the leaching residue. Chemical composition of the catalyst was analyzed by dissolution of the ground catalyst in an acid solution containing HF, HNO3, and H2SO4 followed by ICP-OES (inductively coupled plasma optical emission spectroscopy, Perkin-Elmer Optima). The concentration of vanadium in the leaching filtrate was routinely analyzed by a titration method, which yielded similar results as that of the ICP-OES with differences of less than 5%. The chemical forms of vanadium in the catalyst were determined by X-ray photoelectron spectroscopy (XPS). The measurement was carried out on an ESCALAB 250 spectrometer (Thermo Fisher Scientific Company) at room temperature with A1-Kα radiation in single anode. The binding energies were corrected by the C1s peak at 284.8 eV. The data analysis was performed with an XPS-Peak 4.0 program, and the spectra were fitted with an optimal Gaussian−Lorentzian ratio after subtraction of a Shirley-type baseline. 2.2. Vanadium Leaching Method. The leaching experiments were performed in a flask equipped with a magnetic stirrer and embedded in a temperature controlled water bath. A certain amount of sulfuric acid solution, from 5 to 20 mL with sulfuric acid concentrations of 0.1−5 M, was added into the flask and heated to a given temperature in a range of 30−80 °C under various stirring conditions. At the steady stage, a certain amount of the catalyst, corresponding to various solid to liquid ratios (S/L in short), was added into the flask to start the leaching process. The process lasted for a certain time, from 5 to 120 min, and then, the slurry was quickly filtered under a vacuum. The filter cake was washed with distilled water until the pH of the used rinsing water reached 7. 2.3. Analysis of Vanadium Content in the Solution. The total amount of vanadium in the filtrate was analyzed by the ferrous ammonium sulfate titration method defined by the national standard of China (GB/T 223.13-2000). The titration was repeated at least 2 times for each sample, and the experimental error was less than 3%. This method was also adopted by Aarabi-Karasgani et al., and the results were found reliable.23 The vanadium recovery yield, termed x, is the percentage of vanadium in the catalyst that dissolved in the filtrate.

Figure 1. XPS spectra of V 2p of the spent SCR catalyst.

peaks at 516.7 and 515.5 eV, with area ratios of 35% and 65%, respectively. The former may be assigned to V5+ in V2O5 as reported by Shang et al.8 while the latter is assinged to V3+ in V2O3 as reported by Odriozola et al.24 Similarly, Andersson et al.25 assigned the peaks in 515.5−517.6 eV to V2O5 and that in 515.4−515.6 eV to V2O3 and V2O4. Figure 2 shows Ti2p XPS

Figure 2. XPS spectra of Ti 2p of the spent SCR catalyst.

3. RESULTS AND DISCUSSION 3.1. Analysis of the Spent SCR Catalyst. Table 1 shows the ICP result of the spent catalyst. It can be seen that the

spectra of the spent SCR catalyst. The Gaussian−Lorentzian fit shows two main peaks of Ti 2p3/2 at 458.6 and 458.1 eV, with area ratios of 37% and 63%, respectively. Since the binding energy of Ti4+ in pure TiO2 was 458.6 eV,26 the spectra suggests that some of the Ti in the catalyst interacts with other components such as V and W. 3.2. Effect of Leaching Parameters on Vanadium Recovery Yield. In order to establish a kinetic equation for the

Table 1. Main Element Composition of the Spent SCR Catalyst component

V

W

Ti

K

As

Ca

P

amount (wt %)

0.29

3.00

36.00

0.11

0.01

1.50

0.30 2957

dx.doi.org/10.1021/ie401552v | Ind. Eng. Chem. Res. 2014, 53, 2956−2962


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vanadium leaching process, effects of various leaching parameters on vanadium recovery yield were investigated. 3.2.1. Effect of Stirring Speed. The effect of stirring speed is complex because it can be attributed to the shape and size of the reactor, the shape and size of the propeller, and the position of the propeller in the solution. The aim of this study is to establish an intrinsic kinetic equation that is not affected by the stirring speed. Therefore, the minimum stirring speed that eliminates the external diffusion barrier needs to be determined. The experiments were carried out at 60 °C with a sulfuric acid concentration of 0.5 M and an S/L ratio of 1/20 g/mL. The result shown in Figure 3 indicates that the recovery yield x

Figure 4. Effect of solid/liquid ratio on vanadium recovery yield (60 °C, 0.5 M H2SO4, and 600 rpm).

Figure 3. Effect of stirring speed on vanadium recovery yield (60 °C, 0.5 M H2SO4, and S/L of 1/20 g/mL).

increases slightly with an increase in stirring speed from 100 to 200 rpm and then becomes constant in the stirring speed range of 200−600 rpm with a yield of 38% in 120 min. This suggests that the reduction of hydrodynamic boundary layer around the catalyst particles becomes minimal when the stirring speed is higher than 200 rpm, which agrees with that reported by Li et al.,18 Bingöl et al.,27 and Souza et al.28 To be conservative, a stirring speed of 600 rpm was chosen in the following experiments to ensure that the external diffusion was completely eliminated. It is noted that Ti and W are also leaded out from the catalyst but the recovery yields are low, 0.56% and 1.99%, respectively, at conditions of 1 M H2SO4, 60 °C, 60 min, 600 rpm, and S/L 1/20 g/mL, for example. Since these data are not very much higher than the experimental errors, detailed analyses on recovery of Ti and W are not performed in the study. 3.2.2. Effect of Solid to Liquid Ratio (S/L). Figure 4 shows the vanadium recovery yields at various S/L ratios while other parameters are kept constant, i.e. 60 °C, 0.5 M H2SO4, and 600 rpm. It can be seen that the yield increases with a decrease in S/ L ratio indicating that a larger amount of acid solution favors the vanadium recovery yield. For a better vanadium recovery, the S/L ratio of 1/20 g/mL is used for the subsequent study. 3.2.3. Effect of Sulfuric Acid Concentration. The effect of sulfuric acid concentration on vanadium recovery yield was studied at 60 °C, S/L of 1/20 g/mL, and 600 rpm. The results in Figure 5 indicate that the yield increases with an increase in sulfuric acid concentration from 0.1 to 5.0 M at the same leaching time, from 35% to 56% in 120 min, for example. This indicates that a high concentration of sulfuric acid is beneficial to vanadium extraction, which agrees with the behavior shown

Figure 5. Effect of sulfuric acid concentration on vanadium recovery yield (60 °C, S/L of 1/20 g/mL, and 600 rpm).

in Figure 4 and that reported by Aarabi-Karasgani et al.,23 Zhou et al.,29 and Chen et al.30 3.2.4. Effect of Temperature. The effect of leaching temperature on vanadium recovery yield was evaluated at 0.5 M sulfuric acid, S/L of 1/20 g/mL, and a stirring speed of 600 rpm. The result shown in Figure 6 indicates that the yield increases with an increase in leaching temperature, from 32% at 30 °C to 42% at 80 °C in 120 min, for example. This suggests that the effect of temperature on the vanadium recovery yield is not large and the process may not be controlled by chemical reaction. 3.3. Kinetics Analysis. To determine the relation between the vanadium recovery yield and the operating parameters, kinetics equation is studied based on the data above. As presented earlier in the introduction, a number of models had been used to describe vanadium leaching from various sources. Therefore, these models are studied first to see their suitability for the data of this work. The models include 1 − (1 − x)1/3 for the surface reaction controlled SCM where the unleached material is not porous, 1 − 2x/3 − (1 − x)2/3 and 1 − 3(1 − x)2/3 + 2(1 − x) for diffusion controlled SCM where the material is porous. The comparisons in Table 2 show that these models do not fit the experimental data well with correlation coefficients (R2) of less than 0.828. 2958



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ln(− ln(1 − x)) = ln k + n ln t

(2)

Figure 6. Effect of temperature on vanadium recovery yield (0.5 M H2SO4, S/L of 1/20 g/mL, and 600 rpm). Figure 7. Plot of Avrami equation using the data in Figure 6

Table 2. Correlation Coefficients (R2) of Various Kinetic Models

It can be seen that the data in Figure 7 show a good linear relationship for all the temperatures with correlation coefficients of greater than 0.945, which are much higher than those listed in Table 2 for other models. The slopes of the lines are very similar, about 0.120 ± 0.03, indicating again a good fitting and suggesting that the leaching is controlled by internal diffusion according to that reported by Li et al.39 The intercepts of the lines are −1.53, −1.43, −1.36, −1.29, −1.25, and −1.19, for temperatures of 30, 40, 50, 60, 70, and 80 °C, respectively, which can be used to determine the rate constant k at these temperatures and activation energy of the leaching process. 3.3.2. Determination of Ea. For a leaching system, it is recognized that the rate constant k can be expressed as eq 3, where k0 is the pre-exponential factor, Ea is the activation energy, M is the reaction order to the acid concentration, and N is the reaction order to the solid/liquid ratio S/L.18,40−42 The natural logarithm of eq 3 yields eq 4, which shows that the plot of ln k vs 1/T is a straight line with a slope −Ea/R if the sulfuric acid concentration and the solid/liquid ratio are kept constant. On the basis of the values of k determined in Figure 7, at a sulfuric acid concentration of 0.5 M and a solid/liquid ratio of 1/20 g/mL, a straight line is obtained in Figure 8 with a

correlation coefficients (R2) of various kinetic models leaching temperature (°C)

1− (1 − x)1/3

1 − 2x/3 − (1 − x)2/3

1 − 3(1 − x)2/3 + 2(1 − x)

30 40 50 60 70 80

0.742 0.759 0.731 0.773 0.747 0.748

0.813 0.828 0.795 0.798 0.810 0.814

0.813 0.828 0.795 0.792 0.810 0.814

Another kinetic equation that had been used to describe leaching of multimetals or metal oxides is the Avrami equation, eq 1,31−33 which has not been used for vanadium leaching from any source to our knowledge. The equation was originally developed and well verified for the kinetics of crystallization in solution.34−36 It assumes that the nucleation occurs randomly and homogeneously over the entire untransformed portion of the material, the growth rate does not depend on the extent of transformation, and the growth occurs at the same rate in all directions.37 In eq 1, x is the volume fraction of the material that is crystallized, k is the crystallization rate constant, t is the crystallization time (min), and n is a parameter that reflected the nature of the crystallization (dimensions). −ln(1 − x) = kt n

(1)

Since the leaching can be considered as the reverse process of crystallization, the Avrami equation may be used, but in this case x is the volume fraction of the material that is leached out, k is the leaching rate constant, t is the leaching time (min), and n is a parameter that reflected the nature of the leaching. Sokić et al.38 and Li et al.39 proposed that, when n in the Avrami equation is less than 0.5, the mechanism is diffusion controlled. To find a better fitting to the data of this work and to understand the leaching mechanism, the Avrami equation is studied below. 3.3.1. Determination of n. The natural logarithm of eq 1 yields eq 2. It shows that the plot of ln(−ln(1 − x)) vs ln t is a straight line with a slope n and an intercept ln k. On the basis of the data in Figure 6, a plot of ln(−ln(1 − x)) vs ln t is shown in Figure 7.

Figure 8. Arrhenius plot of ln k vs 1/T. 2959



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It is interesting to note that the value of n determined in Figure 9 is 0.120 ± 0.004, which is very close to that obtained from Figure 7 at different temperatures, indicating that the Avrami equation is suitable for the leaching process. 3.3.4. Determination of Reaction Order to Solid/Liquid Ratio N. Similar to the determination of M, the reaction order to S/L ratio N can be determined based on the data in Figure 4. The good fit in Figure 11 indicate the suitability of the Avrami

correlation coefficient of 0.988. The slope of the line is 0.71, corresponding to an apparent activation energy of 5.90 kJ/mol, which is close to but smaller than that reported for nickel leaching from a spent hydrogenation catalyst, 12.5 kJ/mol.43 The small activation energy indicates that the leaching is controlled by diffusion.44 k = k 0[H 2SO4 ]M (S /L)N e−Ea / RT ln k = ln k 0 + M ln[H 2SO4 ] + N ln(S /L) −

(3)

Ea RT

(4)

3.3.3. Determination of Reaction Order to Sulfuric Acid Concentration M. According to eq 4, a plot of ln k vs ln[H2SO4] at a given temperature and a given solid/liquid ratio should yield a straight line with a slope M, the reaction order to sulfuric acid concentration. The data in Figure 5, therefore, are first converted to a plot of ln(−ln(1 − x)) vs ln t (Figure 9) to

Figure 11. Plot of Avrami equation using the data in Figure 4.

Figure 9. Plot of Avrami equation using the data in Figure 5.

determine ln k at various sulfuric acid concentrations, and then to Figure 10 to yield a M of 0.21. This value is smaller than that

Figure 12. Relation of ln k and ln[S/L] using data in Figure 11.

equation for the leaching process. The results in Figure 12 indicate that the value of N is about −0.35, which is smaller than that reported for leaching of boron from colemanite in ammonium hydrogen sulfate solutions (−0.54)42 and that for leaching of cadmiumzinc from zinc plant residues in sulfuric acid solution (−0.35).46 3.3.5. Determination of Pre-exponential Factor k0. It can be seen from eq 4 that the pre-exponential factor k0 can easily be determined when Ea, M, and N are known. Using the values of Ea (5.90 kJ/mol), M (0.21), and N (−0.35) determined above, a k0 of 0.96 ± 0.05 is determined. Substituting the above parameters into eqs 1 and 3, the kinetics of vanadium leaching from the spent SCR catalyst by sulfuric acid is expressed as eq 5. The suitability of the equation is demonstrated in Figure 13 as an example.

Figure 10. Relation of ln k and ln[H2SO4] using data in Figure 9.

for the leaching of nickel from a spent Ni−Al2O3 catalyst in HCl, with a reaction order of 0.8 to HCl,45 and that for leaching of vanadium from black shale in sulfuric acid, with a reaction order of 0.61 to H2SO4,18 where a diffusion controlled SCM model was used. This indicates that the vanadium leaching in this work is also diffusion controlled. 2960



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−ln(1 − x) = 0.96 × [H 2SO4 ]0.21 (S /L)−0.35 e−5900/ RT t 0.12

catalysts Part I: Metallurgical processes. Hydrometallurgy 2009, 98, 1−9. (5) Khodayari, R.; Odenbrand, C. U. I. Regeneration of commercial TiO2-V2O5-WO3 SCR catalysts used in bio fuel plants. Appl. Catal. B: Environ. 2001, 30, 87−99. (6) Lee, J. B.; Kim, S. K.; Kim, D. W.; Kim, K. H.; Chun, S. N.; Hur, K. B.; Jeong, S. M. Effect of H2SO4 concentration in washing solution on regeneration of commercial selective catalytic reduction catalyst. Kor. J. Chem. Eng. 2012, 29, 270−276. (7) Khodayari, R.; Ingemar Odenbrand, C. U. Regeneration of commercial SCR catalysts by washing and sulphation: effect of sulphate groups on the activity. Appl. Catal. B: Environ. 2001, 33, 277− 291. (8) Shang, X.; Hu, G.; He, C.; Zhao, J.; Zhang, F.; Xu, Y.; Zhang, Y.; Li, J.; Chen, J. Regeneration of full-scale commercial honeycomb monolith catalyst (V2O5-WO3/TiO2) used in coal-fired power plant. J. Ind. Eng. Chem. 2012, 18, 513−519. (9) Zeng, R. Reclamation and Recycling of SCR Waste Catalyzer. China Environ. Protect. Ind. 2013, 2, 39−42. (10) Zeng, R. Recovery process of honeycomb type selective catalytic reduction (SCR) waste catalyst containing tungsten, vanadium and titanium. CN patent 102936039A, 2013. (11) Zhu, Y.; He, S.; Zhang, Y. Method for recycling metal oxide from waste flue gas denitration catalyst. CN patent 101921916A, 2010. (12) Sun, Y.; Liu, Y.; Cai, M. Method of recovering metallic oxide from SCR denitration spent catalyst. CN patent 103160690A, 2013. (13) Moskalyk, R. R.; Alfantazi, A. M. Processing of vanadium: a review. Miner. Eng. 2003, 16, 793−805. (14) Voglauer, B.; Grausam, A.; Jörgl, H. P. Reaction-kinetics of the vanadium roast process using steel slag as a secondary raw material. Miner. Eng. 2004, 17, 317−321. (15) He, D.; Feng, Q.; Zhang, G.; Ou, L.; Lu, Y. An environmentallyfriendly technology of vanadium extraction from stone coal. Miner. Eng. 2007, 20, 1184−1186. (16) Breit, G. N.; Wanty, R. B. Vanadium accumulation in carbonaceous rocks: A review of geochemical controls during deposition and diagenesis. Chem. Geol. 1991, 91, 83−97. (17) Gehring, A. U.; Fry, I. V.; Luster, J.; Sposito, G. The chemical form of vanadium (IV) in kaolinite. Clays Clay Miner. 1993, 41, 662− 667. (18) Li, M.; Wei, C.; Qiu, S.; Zhou, X.; Li, C.; Deng, Z. Kinetics of vanadium dissolution from black shale in pressure acid leaching. Hydrometallurgy 2010, 104, 193−200. (19) Deng, Z.; Wei, C.; Fan, G.; Li, M.; Li, C.; Li, X. Extracting vanadium from stone-coal by oxygen pressure acid leaching and solvent extraction. T. Nonferr. Metal. Soc. 2010, 20 (Suppl. 1), 118− 122. (20) Szymczycha-Madeja, A. Kinetics of Mo, Ni, V and Al leaching from a spent hydrodesulphurization catalyst in a solution containing oxalic acid and hydrogen peroxide. J. Hazard. Mater. 2011, 186, 2157− 2161. (21) Amer, A. M. Hydrometallurgical processing of Egyptian black shale of the Quseir-Safaga region. Hydrometallurgy 1994, 36, 95−107. (22) García-Bordejé, E.; Lázaro, M. J.; Moliner, R.; Galindo, J. F.; Sotres, J.; Baró, A. M. Structure of vanadium oxide supported on mesoporous carbon-coated monoliths and relationship with its catalytic performance in the SCR of NO at low temperatures. J. Catal. 2004, 223, 395−403. (23) Aarabi-Karasgani, M.; Rashchi, F.; Mostoufi, N.; Vahidi, E. Leaching of vanadium from LD converter slag using sulfuric acid. Hydrometallurgy 2010, 102, 14−21. (24) Odriozola, J. A.; Soria, J.; Somorjai, G. A.; Heinemann, H.; Garcia De La Banda, J. F.; Lopez Granados, M.; Conesa, J. C. Adsorption of nitric oxide and ammonia on vanadia-titania catalysts: ESR and XPS studies of adsorption. J. Phys. Chem. 1991, 95, 240−246. (25) Andersson, S. L. T. ESCA investigation of V2O5 + TiO2 catalysts for the vapour phase oxidation of alkylpyridines. J. Chem. Soc., Faraday Trans. 1 1979, 75, 1356−1370.

(5)

Figure 13. Suitability of Avrami equation to the leaching data.

4. CONCLUSIONS Leaching of vanadium from a spent SCR catalyst by sulfuric acid and its kinetics are investigated. It is found that the vanadium recovery yield increases with increases in temperature and sulfuric acid concentration but decreases with an increase in solid to liquid ratio. The leaching is controlled by diffusion in the solid and can be well described by the Avrami equation, which was originally developed for crystallization. The full form of the leaching kinetics is −ln(1 − x) = 0.96 × [H 2SO4 ]0.21 (S /L)−0.35 e−5900/ RT t 0.12

The suitability of the Avrami equation to the leaching may be attributed to the fact that it can be considered as the reverse process of crystallization.

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AUTHOR INFORMATION

Corresponding Author

*Tel./Fax: +86-10-64421077. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors gratefully acknowledge financial support from the Program for New Century Excellent Talents in University (NCET-11-0558) and the National Natural Science Foundation of China (21121064).

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REFERENCES

(1) Gummow, B. Vanadium: Environmental Pollution and Health Effects. In Encyclopedia of Environmental Health; Nriagu, J. O., Eds.; Elsevier: Burlington, 2011; pp 628−636. (2) Navarro, R.; Guzman, J.; Saucedo, I.; Revilla, J.; Guibal, E. Vanadium recovery from oil fly ash by leaching, precipitation and solvent extraction processes. Waste Manage. 2007, 27, 425−438. (3) Shlewit, H.; Alibrahim, M. Extraction of sulfur and vanadium from petroleum coke by means of salt-roasting treatment. Fuel 2006, 85, 878−880. (4) Zeng, L.; Cheng, C. Y. A literature review of the recovery of molybdenum and vanadium from spent hydrodesulphurisation 2961



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(26) Reddy, B. M.; Rao, K. N.; Reddy, G. K.; Bharali, P. Characterization and catalytic activity of V2O5/Al2O3-TiO2 for selective oxidation of 4-methylanisole. J. Mol. Catal. A: Chem. 2006, 253, 44−51. (27) Bingöl, D.; Canbazoğlu, M.; Aydoğan, S. Dissolution kinetics of malachite in ammonia/ammonium carbonate leaching. Hydrometallurgy 2005, 76, 55−62. (28) Souza, A. D.; Pina, P. S.; Lima, E. V. O.; Da Silva, C. A.; Leão, V. A. Kinetics of sulphuric acid leaching of a zinc silicate calcine. Hydrometallurgy 2007, 89, 337−345. (29) Zhou, X.; Li, C.; Li, J.; Liu, H.; Wu, S. Leaching of vanadium from carbonaceous shale. Hydrometallurgy 2009, 99, 97−99. (30) Chen, X.; Lan, X.; Zhang, Q.; Ma, H.; Zhou, J. Leaching vanadium by high concentration sulfuric acid from stone coal. T. Nonferr. Metal. Soc. 2010, 20 (Suppl. 1), 123−126. (31) Franke, M. D.; Ernst, W. R.; Myerson, A. S. Kinetics of dissolution of alumina in acidic solution. AIChE J. 1987, 33, 267−273. (32) Kurtbaş, A.; Kocakerim, M. M.; Kücu̧ ̈k, Ö .; Yartaşı, A. Dissolution of Colemanite in Aqueous Solutions Saturated with Both Sulfur Dioxide (SO2) Gas and Boric Acid. Ind. Eng. Chem. Res. 2006, 45, 1857−1862. (33) Li, G.; Rao, M.; Jiang, T.; Huang, Q.; Peng, Z. Leaching of limonitic laterite ore by acidic thiosulfate solution. Miner. Eng. 2011, 24, 859−863. (34) Wilkinson, A. P.; Speck, J. S.; Cheetham, A. K.; Natarajan, S.; Thomas, J. M. In situ x-ray diffraction study of crystallization kinetics in PbZr1−xTixO3, (PZT, x = 0.0, 0.55, 1.0). Chem. Mater. 1994, 6, 750−754. (35) Farjas, J.; Roura, P. Modification of the Kolmogorov-JohnsonMehl-Avrami rate equation for non-isothermal experiments and its analytical solution. Acta Mater. 2006, 54, 5573−5579. (36) Millange, F.; Medina, M. I.; Guillou, N.; Férey, G.; Golden, K. M.; Walton, R. I. Time-Resolved In Situ Diffraction Study of the Solvothermal Crystallization of Some Prototypical Metal-Organic Frameworks. Angew. Chem., Int. Ed. 2010, 49, 763−766. (37) Khawam, A.; Flanagan, D. R. Solid-State Kinetic Models: Basics and Mathematical Fundamentals. J. Phys. Chem. B 2006, 110, 17315− 17328. (38) Sokić, M. D.; Marković, B.; Ž ivković, D. Kinetics of chalcopyrite leaching by sodium nitrate in sulphuric acid. Hydrometallurgy 2009, 95, 273−279. (39) Li, X.; Ma, C.; Feng, Y.; Pan, Y.; Yu, L.; Jiang, J.; Wei, Z. Study on Sulfuric Acid Leaching Kinetics of Indium Sulfide at Normal Pressure. Metal Mine 2011, 6, 89−92. (40) Dehghan, R.; Noaparast, M.; Kolahdoozan, M. Leaching and kinetic modelling of low-grade calcareous sphalerite in acidic ferric chloride solution. Hydrometallurgy 2009, 96, 275−282. (41) Okur, H.; Tekin, T.; Ozer, A. K.; Bayramoglu, M. Effect of ultrasound on the dissolution of colemanite in H2SO4. Hydrometallurgy 2002, 67, 79−86. (42) Guliyev, R.; Kuşlu, S.; Ç alban, T.; Ç Olak, S. Leaching kinetics of colemanite in ammonium hydrogen sulphate solutions. J. Ind. Eng. Chem. 2012, 18, 1202−1207. (43) Alex, P.; Mukherjee, T. K.; Sundaresan, M. Leaching behaviour of nickel in aqueous chlorine solutions and its application in the recovery of nickel from a spent catalyst. Hydrometallurgy 1993, 34, 239−253. (44) Tang, A.; Su, L.; Li, C.; Wei, W. Effect of mechanical activation on acid-leaching of kaolin residue. Appl. Clay Sci. 2010, 48, 296−299. (45) Parhi, P. K.; Park, K. H.; Senanayake, G. A kinetic study on hydrochloric acid leaching of nickel from Ni-Al2O3 spent catalyst. J. Ind. Eng. Chem. 2013, 19, 589−594. (46) Safarzadeh, M. S.; Moradkhani, D.; Ojaghi-Ilkhchi, M. Kinetics of sulfuric acid leaching of cadmium from Cd-Ni zinc plant residues. J. Hazard. Mater. 2009, 163, 880−890.

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Kinetics of Vanadium Leaching from a Spent ... - ACS Publications

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