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Solvent extraction of indium(III) from HCl solutions by the ionic liquid (A324H+)(Cl−) dissolved in Solvesso 100
Hydrometallurgy 189 (2019) 105104
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Solvent extraction of indium(III) from HCl solutions by the ionic liquid (A324H+)(Cl−) dissolved in Solvesso 100
T
⁎
Francisco Jose Alguacil , Esther Escudero Centro Nacional de Investigaciones Metalurgicas (CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain
A R T I C LE I N FO
A B S T R A C T
Keywords: Indium(III) Ionic liquids Hydrochloric acid Extraction Stripping
Indium(III) is extracted from HCl solutions (0.1–6 M HCl) by the ionic liquid (A324H+)(Cl−). The ionic liquid was generated in a previous reaction of the tertiary amine Hostarex A324 (triisooctyl amine) dissolved in Solvesso 100 with 1 M HCl solution. The metal extraction was investigated under various experimentalconditions: equilibration time, temperature, metal and HClconcentrations in the aqueous solution and ionic liquid concentration in the organic solution. Experimental results suggested that the indium extraction is due to an anionic exchange reaction between the chloride ion of the ionic liquid and the InCl4− of the aqueous solution. The performance of the system was compared against the extraction of other metals in binary solution (indium and accompanying metal) and against other ionic liquids. Indium(III) was stripped from metal-loaded organic solutions by the use of diluted hydrochloric acid solutions, and the precipitation of zero valent indium is possible by a further addition of sodium borohydride to the In-bearing strip solution.
1. Introduction The ionic liquids are a type of chemical compounds which special properties make of them useful in many fields of interest (Amde et al., 2015), though their environmental greenness status still is under debate (Bystrzanowska et al., 2019). One of these fields is the removal of metals, either toxic or valuables, from different aqueous environments. Also the versatility of the ionic liquids makes possible that they can be used in a series of separations technologies, i.e.: solvent extraction, liquid membranes, ion exchange (impregnating resins) or impregnating advanced metal-adsorbents such as carbon nanotubes. Included in the post-transition element series, indium is a metal that nowadays has a great interest due to its price, scarcity and usefulness in a number of modern technologies. Basically, indium is obtained as a sub-product of zinc production, whereas tungsten and tin raw materials contained the highest concentration of this element (Tolcin, 2016). Due to its properties, indium is used in modern technologies such as the manufacture of LCD lighting, flat-panels screens, solar panels, etc. Thus, the life of these devices and their consequent recycle make of them an important raw material for indium. The logical approach for the treatment of these systems is their leaching in an acidic medium, the separation of indium from other undesirable elements, yielding aqueous solutions from which indium can be recovered in a purified form (Regel-Rosocka, 2018); also, bioleaching had been considered as an
⁎
alternative to the recovery of this metal (Wilner et al., 2018). Thus, several investigations were published on the recovery of indium using some of the separations technologies mentioned above, with and without the use of ionic liquids, and also from different wastes (Alguacil et al., 2016; Chou et al., 2016; De la Torre et al., 2018; Garcia-Diaz et al., 2017; Li et al., 2015a; Li et al., 2015b; Lopez Diaz-Pavon et al., 2014; Martin et al., 2015; Pereira et al., 2018; Yang et al., 2016; Zhang et al., 2017). In the case of solvent extraction, a summary of solvent extraction previous work (Nusen et al., 2016) indicated that no references appeared on the use of ionic liquids to recover indium from aqueous solutions, and just only recently, these extractants are being used to recover the element (Alguacil et al., 2019; Deferm et al., 2017; Tereshatov et al., 2015) In order to gain knowledge about the use of these ionic liquids in the recovery of indium, the present investigation presented results about the liquid-liquid extraction of indium(III) from HCl solutions using the ionic liquid (A324H+)(Cl−), which is derived from the reaction of the tertiary amine Hostarex A324 (tri-isooctyl amine) with HCl solution. Several variables affecting the extraction process were investigated as well as the performance of the present system against the presence of other metals in the aqueous solutions (binary In(III)-metal solutions), and against the use of others ionic liquids. Furthermore, the stripping of indium(III) was also investigated by the use of diluted HCl solutions.
Corresponding author. E-mail address: [email protected] (F.J. Alguacil).
https://doi.org/10.1016/j.hydromet.2019.105104 Received 20 March 2019; Received in revised form 9 July 2019; Accepted 10 July 2019 Available online 13 July 2019 0304-386X/ © 2019 Published by Elsevier B.V.
Hydrometallurgy 189 (2019) 105104
F.J. Alguacil and E. Escudero
2. Experimental The precursor of the ionic liquid used in the present work was the tertiary amine Hostarex A324 (Hoechst), which active group being triisooctyl amine. It was used without further purification. As diluent for the amine-ionic liquid, Solvesso 100 (Exxon Chem. Iberia), 99% aromatics, was used. Several authors had claimed that diluents were not necessary when ionic liquids were used to extract metals, however, the experience of the authors of the present investigation indicated that the use of a suitable diluent is also necessary in these ionic liquid systems, because: i) the ionic liquids has a high viscosity, which makes doubtful a quick and easy phases separation, together with a probable flowing problem, caused by the high viscosity of a given ionic liquid, when scaling up to mixer-settler devices, ii) the diluent allows to work with a suitable ionic liquid concentration for a given system. Being the ionic liquid (extractant) the most expensive item of the inventory, it is without sense to maintain a quantity of unused reagent in the system, i.e. in the solvent extraction circuit. Fig. 1. Plot of log DHCl versus log [R3N]org, e. Aqueous phase: 1 M HCl. Organic phase: amine solutions (0.023–0.23 M) in Solvesso 100. Temperature: 20 °C. Time: 15 min. Vorg/Vaq relationship: 1. Dotted line shown 95% confidence interval of the regression line.
All the other chemicals used in the present work were of AR grade, except Cyphos IL101 (Cytec), Aliquat 336 (Fluka), Amberlite LA2 (Fluka) and Primene JMT (Rohm and Haas), all of these were also used without further purification. The compositions of the above reagents were shown in Table 1. Extraction experiments were carried out in jacketed separatory funnels provided of mechanical shaking (four blades impeller). In extraction experiments, 25 mL of each phase were used. After extraction and phases disengagement (no > 5 min), indium (and metals) were analyzed in the aqueous phase by AAS, except tin which was analyzed by ICP-OES. The metal concentration in the organic phases was estimated by the mass balance. Stripping experiments were performed in the same manner that above, but using various Vorg/Vaq relationships.
where aq and org represented the aqueous and organic solutions, respectively. In order to verify the assumption showed in Eq. (2), the experimental results were treated by a tailored computer program which compared the experimental distribution coefficient (Dexp) results with the calculated distribution coefficients (Dcal) results, minimizing the expression:
U = Σ(log Dcal − logDexp )2
The results from this calculation concluded that Eq. (2) occurs with log K = 8.94 ± 0.0001 and U = 0.44 × 10−5, being K the extraction constant of Eq. (2).
3. Results and discussion 3.1. Generation of the ionic liquid
3.2. Indium extraction
The ionic liquid used in this work was generated by reaction of the amine with 1 M HCl solution. The results of these series of tests were shown in Fig. 1, plotting log DHCl versus log [R3N]org, where DHCl was the HCl distribution coefficient and [R3N]org was the amine concentration in the organic phase at equilibrium. The distribution coefficient was calculated as:
DHCl =
(3)
The influence of the equilibration time on indium extraction was studied in order to obtain data about the time that the system needs to achieve equilibrium with the aqueous and organic solutions being maintained as follows: In(III) 0.1 g/L (8.7 × 10−4 M) in 0.75 M HCl and 0.12 M ionic liquid in Solvesso 100, respectively. The results showed that the system attained equilibrium within 10 min of contact (47% indium extraction); thus, an equilibration time of 15 min was kept constant throughout the experiments conducted along this work. The variation of the temperature (20–60 °C) on indium extraction was investigated using the same aqueous and organic solutions as above. These series of experiments showed that there is an increase of indium extraction with the increase of the temperature (47% at 20 °C against 59% at 60 °C), therefore, the metal extraction seemed to have and endothermic character.
[HCl]org,e [HCl]aq,e
(1)
being [HClorg,e and [HCl]aq,e the acid concentration in the organic and aqueous phases at equilibrium, respectively. The slope of the regression line, derived from the representation of Fig. 1, was 1.08. Thus, it can be ascertain, that the ionic liquid was formed accordingly to the next equilibrium:
R3Norg + H+aq + Cl−aq ⇔ R3NH+Cl−org
(2)
Table 1 Ionic liquids used in the extraction of indium(III). Trade name of precursor Cyphos IL101 Aliquat 336 Amberlite LA2 Primene JMT
Type
Active substance used in the experimentation +
−
R4P Cl R4N+Cl− R2NH2+Cl− b RNH3+Cl−
quaternary phosphonium salt quaternary ammonium salt secondary amine primary amine
a
R: different alkyl chains. a and b generated by reaction of the amine with 1 M HCl solution. 2
Acronysm C101 A336 ALA2 PJMT
Hydrometallurgy 189 (2019) 105104
F.J. Alguacil and E. Escudero
K 0 = Km
γA324H+InCl−4 γCl− γInCl−4 γA324H+Cl−
(5)
in the above expression, Km is the extraction constant in the molality scale. Assuming ideal behaviour in the organic solution, the next expression can be derived:
log K0 = log Km + log γCl− − log γInCl−4
(6)
In a given solution of ionic strength Im, the activity coeffcicient γi of an ion of charge Zi can be defined as:
log γi = −Z2i DI + ΣεIm
(7)
in this expression, DI is the Debye-Hückel term, ε is the interaction coefficient between the charged species of the system, and Im is the ionic strength. Both DI and Im are expressed in the molality scale. From Eq. (7) for each of the charged species of this system, InCl4− and Cl− and substituting them in Eq. (6), the following expression was obtained:
log Km = log K0 + (εInCl−4 ,H+ − εCl−,H+)Im
thus, a plot of log Km against Im should give a line of intercept log K0 and slope εInCl4-,H+ -εCl-,H+. For the present system, such plot gives log K0 = 0.84 and slope 0.38 (r2 = 0.961), since εCl-,H+ is 0.12 (Martinez et al., 1997), εInCl4-,H+ is estimated as 0.50. The effect of varying the initial indium concentration in the aqueous solution on the metal extraction was investigated using an organic phase containing 0.12 M extractant in Solvesso 100, and aqueous solutions of 0.05–0.25 g/L (4.4 × 10−4-2.2 × 10−3 M) In(III) at various HCl concentrations (0.1–6 M). Other variables were 20 °C and 15 min of equilibration time. The experimental data suggest that for all of the HCl concentrations (0.1–6 M) experimented in this work, the variation of the initial indium concentration in the aqueous solution has no effect on the percentage of indium extracted into the organic phase, i.e., at 1 M HCl averaging 60% (distribution coefficient value of 1.5) of extraction and at 6 M HCl averaging 99% (distribution coefficient value of 99) of extraction, for the range of initial indium concentrations examined in this work. The no variation of the percentage of indium extraction (or the distribution coefficient) on the initial indium concentration in the aqueous phase, suggests about the no presence of metal-polynuclear complexes in the equilibrated organic solutions, this assert is, as shown in Eq. (4), in accordance with the stoichiometry of the metal-ionic liquid species in the organic phase. In these extraction systems and in order to gain knowledge about the extraction performance of a given extractant, it is of interest to compare the results of the system against the results obtained in the extraction of indium(III) in presence of other metals in the aqueous solutions. Table 3 shows the results obtained from these series of experiments using binary solutions of indium with the accompanying metal and using equimolar concentrations of each. These results are expressed as the separation factor β, defined as:
Fig. 2. Variation of the percentage of indium(III) extraction at various HCl concentrations in the aqueous phase and ionic liquid in the organic phase. Aqueous phase: 0.1 g/L In(III) at various HCl concentrations. Organic phase: various ionic liquid solutions in Solvesso 100. Temperature: 20 °C. Time: 15 min. Vorg/Vaq relationship: 1.
To investigate the influence of the HCl concentration in the aqueous solution and the ionic liquid concentration in the organic solution on indium extraction, various series of experiments were conducted at different HCl (0.1–6 M) and ionic liquid (0.06–0.48 M) concentrations. Fig. 2 shows that the indium extraction increases as the HCl concentration in the aqueous phase becomes higher, being this behaviour more evident as the ionic liquid concentration in the organic solution decreases, since with the solution of 0.48 M of the ionic liquid in Solvesso 100 the variation in indium extraction is less evident from HCl concentrations above 2 M. At these HCl concentrations range, i.e. above 2 M, indium forms an anionic complex with InCl4− stoichiometry (Deferm et al., 2017; Tereshatov et al., 2015), thus, it is logical to attribute that the extraction of indium is due to an anionic exchange reaction with the chloride ion of the ionic liquid:
(A324H+Cl−)org + InCl−4aq ⇔ (A324H+InCl−4 )org + Cl−aq
(4)
where subscripts org and aq refereeing to the organic and aqueous phases, respectively. Using the same approach than above, Eq. (3), it was found that indium extraction at various HCl concentrations responded well to the equilibrium showed in Eq. (4); though the extraction constant value varies with the HCl concentration, and thus, with the ionic strength (I) of the aqueous solution (Table 2). It is possible to correlate the extraction constant K0, for the equilibrium showed in Eq. (4), with the ionic strength in the molality scale Im. Then:
β=
Im
log K
U
1 2 4 6
1.022 2.080 4.357 6.851
1.04 1.78 2.49 3.04
1.6 2.2 1.3 0.63
DIn DMetal
(9)
where DIn and DMetal are the distribution coefficients for indium and the accompanying metal, respectively. It can be seen that, practically in all the experimental conditions, indium is extracted preferably to the other metal (β values > 1, however, these values are no indicative about the ease of the separation process, and/or the number of stages needed to accomplished it). Fe(III) is extracted in preference to indium due to the affinity of the FeCl4− complex to be exchanged with the chloride ions from the ionic liquid, this situation can be overcome by a pH-controlled iron precipitation, or co-extracting both metals and then carry out a selective stripping. Also, and depending of the metal concentrations in the feed solution, an ion exchange or even a liquid membrane operation can be considered. In any case, these, or other options, i.e. masking Fe (III) with a suitable complexing agent or reducing to the Fe(II) state (though its extractability may be probed), must to be thought more
Table 2 Values of log K for Eq. (4) at various ionic strengths of the aqueous solution. HCl, M
(8)
Values of log Km are identical to those showed for log K. 3
Hydrometallurgy 189 (2019) 105104
F.J. Alguacil and E. Escudero
IneCl complex), though from 4 M the difference in indium extraction with respect to that of the ionic liquids Aliquat 336 and A324H+Cl− became less important, and at 6 M HCl the performance of the three ionic liquids with respect to indium extraction is the same. In all of the HCl concentrations experimented in this work, these two ionic liquids, Aliquat 336 and A324H+Cl−, have practically the same behaviour with respect to indium extraction. Under the present experimental conditions, the performances of ALA2H+Cl− and PJMTH+Cl− ionic liquids are marginal with respect to those of the other three ionic liquids investigated in this work, however, in all the cases, indium extraction tends to increase with the increase of the HCl concentration in the aqueous solution, supporting the idea that in all these systems an anion exchange reaction is responsible for indium extraction, and that the extraction constant is dependent of the ionic strength of the aqueous solution.
Table 3 Values of the percentages of extraction and of the separation factor βIn/M from the extraction of binary mixtures. System
In-metal concentrations, g/L
In-Ni
In-Co
0.1–0.05
In-Cu
0.1–0.05
In-Zn
0.1–0.05
In-Fe(III)
0.1–0.05
In-Sn(IV)
0.1–0.1
HCl, M
% extraction inmetal
βIn/Metal
0.1 1 6 0.1 1 6 0.1 1 6 0.1 1 6 0.1 1 6 0.1 1 6
8-0 57-0.9 99-3 16.0-2 61-2 99-31 3-31 48-30 99-80 8-10 51-53 99-61 9-8 54–82 > 99- > 99 37-10 69-55 > 99-99
quant. 134 > 3000 12 86 199 0.1 2 27 0.8 1 50 1 0.3 0.1 5 2 2
3.3. Indium stripping The stripping of indium(III) from metal-loaded organic solutions had been investigated using 0.1 M HCl solution as strippant due to the poor extraction percentages presented for the system at these low HCl concentrations (see Fig. 2) and that with this strippant, the ionic liquid is regenerated (shifting the equilibrium represented in Eq. (4) to the left). Fig. 4 represented the percentage of indium(III) stripped at various organic/aqueous volume phases relationships. It can be observed that the efficiency of the strip operation decreased as the Vorg/Vst ratio increases, however, at the lower Vorg/Vst ratios the strippant solution seemed to be highly effective with respect to the indium recovery from metal-loaded organic phases.
Aqueous solution: 8.7 × 10−4 M each metal at various HCl concentrations. Organic phase: 0.12 M A324H+Cl− in Solvesso 100. Temperature: 20° C. Time: 15 min. Vorg/Vaq relationship: 1.
deeply. It is also of interest to compare the performance of the present system with the extraction of indium by different ionic liquids. In this case, the experiments were carried out with aqueous solutions containing 0.1 g/L In(III) in HCl (0.1–6 M) and organic solutions of the respective ionic liquid (0.12 M in Solvesso 100). The results obtained are represented in Fig. 3, plotting the percentage of indium extraction against the HCl concentration in the aqueous solution. It can be seen, that for HCl concentration up to 3 M, the best extraction yields are regularly obtained with Cyphos IL101 (probably this result can be attributable to the different reactivity, kinetic and/or chemical, of the phosphonium and the ammonium cations toward the extraction of the
3.4. An approach to the treatment of the in-bearing strip solutions Aimed to the final treatment of the metal-bearing solutions obtained in the previous subsection, the use of sodium borohydride was investigated. After adding the salt to the solution, a greenish precipitate is yielded which is apparently composed of indium and oxygen (Fig. 5), though the diffractogram of the solid also indicated the presence of zero valent indium (Fig. 6). In Fig. 5 the peaks characteristics for indium at
Fig. 3. Indium(III) extraction using different ionic liquids dissolved in Solvesso 100. Aqueous phase: 0.1 g/L In(III) at various HCl concentrations. Organic phase: 0.12 M ionic liquid in the diluent. Temperature: 20 °C. Time: 15 min. Vorg/Vaq relationship: 1.
Fig. 4. Influence of the Vorg/Vst relationship on indium(III) stripping. Strippant solution: 0.1 M HCl. Organic phase: 0.12 M ionic liquid in Solvesso 100 loaded with 0.098 g/L In(III). Temperature: 20 °C. Time: 15 min. 4
Hydrometallurgy 189 (2019) 105104
F.J. Alguacil and E. Escudero
Fig. 5. Energy dispersive X-ray spectroscopy spectrum of the solid precipitated after adding sodium borohydride to the In-bearing strip solution.
hydrochloric acid solution, the extraction constant value for such reaction was estimated as log K = 8.94. This ionic liquid can be used for the recovery of indium(III) from hydrochloric acid solutions, being the extraction equilibrium of an apparent endothermic character. The extraction of indium(III) was enhanced as the HCl concentration in the aqueous solution was increased, from 0.1 to 6 M, and also with the increase of the ionic liquid concentration in the organic phase. The extraction of the metal was attributable to the InCl4− extraction in the organic phase via its exchange with the chloride ions of the ionic liquid,
3.28 KeV (Lα1), 3.48 KeV (Lβ1) and even at 3.71 KeV (Lβ2) are observed, whereas the precipitation of the solid could be attributed to the next reaction:
4In3 + + 7H2 O + BH4− → 2In0 + In2 O3 + 12H+ + B (OH )−4 + H2
(10)
4. Conclusions The ionic liquid was generated by reaction of the amine with
In-1 500
Lin (Counts)
400
300
200
100
0 5
10
20
30
40
50
60
70
80
90
100
2-Theta - Scale In-1 - File: In-1.raw - Type: 2Th/Th locked - Start: 5.000 ° - End: 100.010 ° - Step: 0.030 ° - Step time: 3. s - Temp.: 25 °C (Room) - Time Started: 48 s - 2-Theta: 5.000 ° - Theta: 2.500 ° - Chi: 0.00 ° - Phi: 0.00 ° - X: 0.0 Operations: Background 0.120,1.000 | Import 00-005-0642 (*) - Indium, syn - In - Y: 116.65 % - d x by: 1. - WL: 1.5406 - Tetragonal - a 3.25170 - b 3.25170 - c 4.94590 - alpha 90.000 - beta 90.000 - gamma 90.000 - Body-centered - I4/mmm (139) - 2 - 52.2957 - I
Fig. 6. X-ray diffractogram of the solid obtained in the precipitation with sodium borohydride of the In-bearing strip solution. The peaks corresponded to zero valent indium. 5
Hydrometallurgy 189 (2019) 105104
F.J. Alguacil and E. Escudero
that is, an extraction equilibrium typical of an anion-exchange reaction. The extracted species have extraction constant values which were dependent on the ionic strength of the aqueous solution. By the use of such values, the interaction coefficient ε, between InCl4− and H+ species was calculated as 0.50. Indium(III) can be stripped from Inloaded organic phase by the use of diluted (i.e. 0.1 M) HCl solutions. Finally the metal can be precipitated, from the above strip solutions, by the use of sodium borohydride, though this step needed to be investigated more deeply.
Garcia-Diaz, I., Lopez, F.A., Alguacil, F.J., 2017. Transport of indium(III) using pseudoemulsion based hollow fiber strip dispersion with ionic liquid RNH3+HSO4. Chem. Eng. Res. Des. 126, 134–141. https://doi.org/10.1016/j.cherd.2017.08.012. Li, X.B., Deng, Z.G., Li, C.X., Wei, C., Li, M.T., Fan, G., Rong, H., 2015a. Direct solvent extraction of indium from a zinc residue reductive leach solution by D2EHPA. Hydrometallurgy 156, 1–5. https://doi.org/10.1016/j.hydromet.2015.05.003. Li, X.B., Wei, C.W., Deng, Z.G., Li, C.X., Fan, G., Rong, H., Zhang, F., 2015b. Extraction and separation of indium and copper from zinc residue leach liquor by solvent extraction. Sep. Purif. Technol. 156, 348–355. https://doi.org/10.1016/j.seppur.2015. 10.021. Lopez Diaz-Pavon, A., Cerpa, A., Alguacil, F.J., 2014. Processing of indium(III) solutions via ion exchange with Lewatit K-2621 resin. Rev. Metal. 50, e010. https://doi.org/10. 3989/revmetalm.010. Martin, M., Janneck, E., Kermer, R., Patzig, A., Reichel, S.M., 2015. Recovery of indium from sphalerite ore and flotation tailings by bioleaching and subsequent precipitation processes. Miner. Eng. 75, 94–99. https://doi.org/10.1016/j.mineng.2014.11.015. Martinez, S., Sastre, A., Alguacil, F.J., 1997. Gold extraction equilibrium in the system Cyanex 921-HCl-Au(III). Hydrometallurgy 46, 205–214. https://doi.org/10.1016/ S0304-386X(97)00014-5. Nusen, S., Chairuangsri, T., Zhu, Z., Cheng, C.Y., 2016. Recovery of indium and gallium from synthetic leach solution of zinc refinery residues using synergistic solvent extraction with LIX 63 and Versatic 10 acid. Hydrometallurgy 160, 137–146. https:// doi.org/10.1016/j.hydromet.2016.01.007. Pereira, E.B., Suliman, A.L., Tanabe, E.H., Bertuol, D.A., 2018. Recovery of indium from liquid crystal displays of discarded mobile phones using solvent extraction. Min. Eng. 119, 67–72. https://doi.org/10.1016/j.mineng.2018.01.022. Regel-Rosocka, M., 2018. Electronic wastes. Phys. Sci. Rev. 20180020. https://doi.org/ 10.1515/psr-2018-0020. Tereshatov, E.E., Boltoeva, M.Y., Folden III, C.M., 2015. Resin ion exchange and liquidliquid extraction of indium and thallium from chloride media. Solvent Extr. Ion Exch. 33, 607–624. https://doi.org/10.1080/07366299.2015.1080529. Tolcin, A.C., 2016. Mineral Commodities Summary 2016: Indium. US Geol. Surv. 703. pp. 80–81. Wilner, J., Fernalczyk, A., Gadja, B., Saternus, M., 2018. Bioleaching of indium and tin from used LCD panels. Phys. Probl. Mine. Proc. 54, 639–645. https://doi.org/10. 5277/ppmp1878. Yang, J., Retegan, T., Steenari, B., Ekberg, C., 2016. Recovery of indium and yttrium from Flat Panel Display waste using solvent extraction. Sep. Purif. Technol. 166, 117–124. Zhang, Y.H., Jin, B.J., Ma, B.Z., Feng, X.Y., 2017. Separation of indium from lead smelting hazardous dust via leaching and solvent extraction. J. Environ. Chem. Eng. 5, 2182–2188. https://doi.org/10.1016/j.jece.2017.04.034.
Acknowledgement To the CSIC Agency (Spain) for support. References Alguacil, F.J., Lopez, F.A., Rodríguez, O., Martinez-Ramirez, S., Garcia-Diaz, I., 2016. Sorption of indium(III) onto carbon nanotubes. Ecotox. Environ. Safety 120, 81–86. https://doi.org/10.106/j.ecoenv.2016.04.008. Alguacil, F.J., Garcia-Diaz, I., Escudero, E., 2019. Extraction of indium(III) from sulphuric acid medium by the ionic liquid (PJMTH+HSO4−). Sep. Purif. Technol. 211, 764–767. https://doi.org/10.1016/j.seppur.2018.10.051. Amde, M., Liu, J.-F., Pang, L., 2015. Environmental application, fate, effects, and concerns of ionic liquids: a review. Environ. Sci. Technol. 49, 12611–12627. https://doi. org/10.1021/acs.est.5b03123. Bystrzanowska, M., Pena-Pereira, F., Marcinkowski, L., Tobiszewski, L., 2019. How green are ionic liquids? – a multicriteria decision analysis approach. Ecotoxicol. Environ. Saf. 174, 455–458. https://doi.org/10.1016/j.ecoenv.2019.03.014. Chou, W.S., Shen, Y.H., Yang, S.J., Hsiao, T.C., Huang, L.F., 2016. Recovery of indium from the etching solution of indium tin oxide by solvent extraction. Environ. Prog. Sustain. Energy 35, 758–763. https://doi.org/10.1002/ep.12304. De la Torre, E., Vargas, E., Ron, C., Gámez, S., 2018. Europium, yttrium, and indium recovery from electronic wastes. Metals 8, 777. https://doi.org/10.3390/ met8100777. Deferm, C., Onghena, B., Vander Hoogerstraete, T., Banerjee, D., Luyten, J., Oosterhof, H., Fransaerc, J., Binnemans, K., 2017. Speciation of indium(III) chloro complexes in the solvent extraction process from chloride aqueous solutions to ionic liquids. Dalton Trans. 46, 4412–4421. https://doi.org/10.1039/c7dt00618g.
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Solvent extraction of indium(III) from HCl solutions by the ionic liquid (A324H+)(Cl−) dissolved in Solvesso 100
T
⁎
Francisco Jose Alguacil , Esther Escudero Centro Nacional de Investigaciones Metalurgicas (CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain
A R T I C LE I N FO
A B S T R A C T
Keywords: Indium(III) Ionic liquids Hydrochloric acid Extraction Stripping
Indium(III) is extracted from HCl solutions (0.1–6 M HCl) by the ionic liquid (A324H+)(Cl−). The ionic liquid was generated in a previous reaction of the tertiary amine Hostarex A324 (triisooctyl amine) dissolved in Solvesso 100 with 1 M HCl solution. The metal extraction was investigated under various experimentalconditions: equilibration time, temperature, metal and HClconcentrations in the aqueous solution and ionic liquid concentration in the organic solution. Experimental results suggested that the indium extraction is due to an anionic exchange reaction between the chloride ion of the ionic liquid and the InCl4− of the aqueous solution. The performance of the system was compared against the extraction of other metals in binary solution (indium and accompanying metal) and against other ionic liquids. Indium(III) was stripped from metal-loaded organic solutions by the use of diluted hydrochloric acid solutions, and the precipitation of zero valent indium is possible by a further addition of sodium borohydride to the In-bearing strip solution.
1. Introduction The ionic liquids are a type of chemical compounds which special properties make of them useful in many fields of interest (Amde et al., 2015), though their environmental greenness status still is under debate (Bystrzanowska et al., 2019). One of these fields is the removal of metals, either toxic or valuables, from different aqueous environments. Also the versatility of the ionic liquids makes possible that they can be used in a series of separations technologies, i.e.: solvent extraction, liquid membranes, ion exchange (impregnating resins) or impregnating advanced metal-adsorbents such as carbon nanotubes. Included in the post-transition element series, indium is a metal that nowadays has a great interest due to its price, scarcity and usefulness in a number of modern technologies. Basically, indium is obtained as a sub-product of zinc production, whereas tungsten and tin raw materials contained the highest concentration of this element (Tolcin, 2016). Due to its properties, indium is used in modern technologies such as the manufacture of LCD lighting, flat-panels screens, solar panels, etc. Thus, the life of these devices and their consequent recycle make of them an important raw material for indium. The logical approach for the treatment of these systems is their leaching in an acidic medium, the separation of indium from other undesirable elements, yielding aqueous solutions from which indium can be recovered in a purified form (Regel-Rosocka, 2018); also, bioleaching had been considered as an
⁎
alternative to the recovery of this metal (Wilner et al., 2018). Thus, several investigations were published on the recovery of indium using some of the separations technologies mentioned above, with and without the use of ionic liquids, and also from different wastes (Alguacil et al., 2016; Chou et al., 2016; De la Torre et al., 2018; Garcia-Diaz et al., 2017; Li et al., 2015a; Li et al., 2015b; Lopez Diaz-Pavon et al., 2014; Martin et al., 2015; Pereira et al., 2018; Yang et al., 2016; Zhang et al., 2017). In the case of solvent extraction, a summary of solvent extraction previous work (Nusen et al., 2016) indicated that no references appeared on the use of ionic liquids to recover indium from aqueous solutions, and just only recently, these extractants are being used to recover the element (Alguacil et al., 2019; Deferm et al., 2017; Tereshatov et al., 2015) In order to gain knowledge about the use of these ionic liquids in the recovery of indium, the present investigation presented results about the liquid-liquid extraction of indium(III) from HCl solutions using the ionic liquid (A324H+)(Cl−), which is derived from the reaction of the tertiary amine Hostarex A324 (tri-isooctyl amine) with HCl solution. Several variables affecting the extraction process were investigated as well as the performance of the present system against the presence of other metals in the aqueous solutions (binary In(III)-metal solutions), and against the use of others ionic liquids. Furthermore, the stripping of indium(III) was also investigated by the use of diluted HCl solutions.
Corresponding author. E-mail address: [email protected] (F.J. Alguacil).
https://doi.org/10.1016/j.hydromet.2019.105104 Received 20 March 2019; Received in revised form 9 July 2019; Accepted 10 July 2019 Available online 13 July 2019 0304-386X/ © 2019 Published by Elsevier B.V.
Hydrometallurgy 189 (2019) 105104
F.J. Alguacil and E. Escudero
2. Experimental The precursor of the ionic liquid used in the present work was the tertiary amine Hostarex A324 (Hoechst), which active group being triisooctyl amine. It was used without further purification. As diluent for the amine-ionic liquid, Solvesso 100 (Exxon Chem. Iberia), 99% aromatics, was used. Several authors had claimed that diluents were not necessary when ionic liquids were used to extract metals, however, the experience of the authors of the present investigation indicated that the use of a suitable diluent is also necessary in these ionic liquid systems, because: i) the ionic liquids has a high viscosity, which makes doubtful a quick and easy phases separation, together with a probable flowing problem, caused by the high viscosity of a given ionic liquid, when scaling up to mixer-settler devices, ii) the diluent allows to work with a suitable ionic liquid concentration for a given system. Being the ionic liquid (extractant) the most expensive item of the inventory, it is without sense to maintain a quantity of unused reagent in the system, i.e. in the solvent extraction circuit. Fig. 1. Plot of log DHCl versus log [R3N]org, e. Aqueous phase: 1 M HCl. Organic phase: amine solutions (0.023–0.23 M) in Solvesso 100. Temperature: 20 °C. Time: 15 min. Vorg/Vaq relationship: 1. Dotted line shown 95% confidence interval of the regression line.
All the other chemicals used in the present work were of AR grade, except Cyphos IL101 (Cytec), Aliquat 336 (Fluka), Amberlite LA2 (Fluka) and Primene JMT (Rohm and Haas), all of these were also used without further purification. The compositions of the above reagents were shown in Table 1. Extraction experiments were carried out in jacketed separatory funnels provided of mechanical shaking (four blades impeller). In extraction experiments, 25 mL of each phase were used. After extraction and phases disengagement (no > 5 min), indium (and metals) were analyzed in the aqueous phase by AAS, except tin which was analyzed by ICP-OES. The metal concentration in the organic phases was estimated by the mass balance. Stripping experiments were performed in the same manner that above, but using various Vorg/Vaq relationships.
where aq and org represented the aqueous and organic solutions, respectively. In order to verify the assumption showed in Eq. (2), the experimental results were treated by a tailored computer program which compared the experimental distribution coefficient (Dexp) results with the calculated distribution coefficients (Dcal) results, minimizing the expression:
U = Σ(log Dcal − logDexp )2
The results from this calculation concluded that Eq. (2) occurs with log K = 8.94 ± 0.0001 and U = 0.44 × 10−5, being K the extraction constant of Eq. (2).
3. Results and discussion 3.1. Generation of the ionic liquid
3.2. Indium extraction
The ionic liquid used in this work was generated by reaction of the amine with 1 M HCl solution. The results of these series of tests were shown in Fig. 1, plotting log DHCl versus log [R3N]org, where DHCl was the HCl distribution coefficient and [R3N]org was the amine concentration in the organic phase at equilibrium. The distribution coefficient was calculated as:
DHCl =
(3)
The influence of the equilibration time on indium extraction was studied in order to obtain data about the time that the system needs to achieve equilibrium with the aqueous and organic solutions being maintained as follows: In(III) 0.1 g/L (8.7 × 10−4 M) in 0.75 M HCl and 0.12 M ionic liquid in Solvesso 100, respectively. The results showed that the system attained equilibrium within 10 min of contact (47% indium extraction); thus, an equilibration time of 15 min was kept constant throughout the experiments conducted along this work. The variation of the temperature (20–60 °C) on indium extraction was investigated using the same aqueous and organic solutions as above. These series of experiments showed that there is an increase of indium extraction with the increase of the temperature (47% at 20 °C against 59% at 60 °C), therefore, the metal extraction seemed to have and endothermic character.
[HCl]org,e [HCl]aq,e
(1)
being [HClorg,e and [HCl]aq,e the acid concentration in the organic and aqueous phases at equilibrium, respectively. The slope of the regression line, derived from the representation of Fig. 1, was 1.08. Thus, it can be ascertain, that the ionic liquid was formed accordingly to the next equilibrium:
R3Norg + H+aq + Cl−aq ⇔ R3NH+Cl−org
(2)
Table 1 Ionic liquids used in the extraction of indium(III). Trade name of precursor Cyphos IL101 Aliquat 336 Amberlite LA2 Primene JMT
Type
Active substance used in the experimentation +
−
R4P Cl R4N+Cl− R2NH2+Cl− b RNH3+Cl−
quaternary phosphonium salt quaternary ammonium salt secondary amine primary amine
a
R: different alkyl chains. a and b generated by reaction of the amine with 1 M HCl solution. 2
Acronysm C101 A336 ALA2 PJMT
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F.J. Alguacil and E. Escudero
K 0 = Km
γA324H+InCl−4 γCl− γInCl−4 γA324H+Cl−
(5)
in the above expression, Km is the extraction constant in the molality scale. Assuming ideal behaviour in the organic solution, the next expression can be derived:
log K0 = log Km + log γCl− − log γInCl−4
(6)
In a given solution of ionic strength Im, the activity coeffcicient γi of an ion of charge Zi can be defined as:
log γi = −Z2i DI + ΣεIm
(7)
in this expression, DI is the Debye-Hückel term, ε is the interaction coefficient between the charged species of the system, and Im is the ionic strength. Both DI and Im are expressed in the molality scale. From Eq. (7) for each of the charged species of this system, InCl4− and Cl− and substituting them in Eq. (6), the following expression was obtained:
log Km = log K0 + (εInCl−4 ,H+ − εCl−,H+)Im
thus, a plot of log Km against Im should give a line of intercept log K0 and slope εInCl4-,H+ -εCl-,H+. For the present system, such plot gives log K0 = 0.84 and slope 0.38 (r2 = 0.961), since εCl-,H+ is 0.12 (Martinez et al., 1997), εInCl4-,H+ is estimated as 0.50. The effect of varying the initial indium concentration in the aqueous solution on the metal extraction was investigated using an organic phase containing 0.12 M extractant in Solvesso 100, and aqueous solutions of 0.05–0.25 g/L (4.4 × 10−4-2.2 × 10−3 M) In(III) at various HCl concentrations (0.1–6 M). Other variables were 20 °C and 15 min of equilibration time. The experimental data suggest that for all of the HCl concentrations (0.1–6 M) experimented in this work, the variation of the initial indium concentration in the aqueous solution has no effect on the percentage of indium extracted into the organic phase, i.e., at 1 M HCl averaging 60% (distribution coefficient value of 1.5) of extraction and at 6 M HCl averaging 99% (distribution coefficient value of 99) of extraction, for the range of initial indium concentrations examined in this work. The no variation of the percentage of indium extraction (or the distribution coefficient) on the initial indium concentration in the aqueous phase, suggests about the no presence of metal-polynuclear complexes in the equilibrated organic solutions, this assert is, as shown in Eq. (4), in accordance with the stoichiometry of the metal-ionic liquid species in the organic phase. In these extraction systems and in order to gain knowledge about the extraction performance of a given extractant, it is of interest to compare the results of the system against the results obtained in the extraction of indium(III) in presence of other metals in the aqueous solutions. Table 3 shows the results obtained from these series of experiments using binary solutions of indium with the accompanying metal and using equimolar concentrations of each. These results are expressed as the separation factor β, defined as:
Fig. 2. Variation of the percentage of indium(III) extraction at various HCl concentrations in the aqueous phase and ionic liquid in the organic phase. Aqueous phase: 0.1 g/L In(III) at various HCl concentrations. Organic phase: various ionic liquid solutions in Solvesso 100. Temperature: 20 °C. Time: 15 min. Vorg/Vaq relationship: 1.
To investigate the influence of the HCl concentration in the aqueous solution and the ionic liquid concentration in the organic solution on indium extraction, various series of experiments were conducted at different HCl (0.1–6 M) and ionic liquid (0.06–0.48 M) concentrations. Fig. 2 shows that the indium extraction increases as the HCl concentration in the aqueous phase becomes higher, being this behaviour more evident as the ionic liquid concentration in the organic solution decreases, since with the solution of 0.48 M of the ionic liquid in Solvesso 100 the variation in indium extraction is less evident from HCl concentrations above 2 M. At these HCl concentrations range, i.e. above 2 M, indium forms an anionic complex with InCl4− stoichiometry (Deferm et al., 2017; Tereshatov et al., 2015), thus, it is logical to attribute that the extraction of indium is due to an anionic exchange reaction with the chloride ion of the ionic liquid:
(A324H+Cl−)org + InCl−4aq ⇔ (A324H+InCl−4 )org + Cl−aq
(4)
where subscripts org and aq refereeing to the organic and aqueous phases, respectively. Using the same approach than above, Eq. (3), it was found that indium extraction at various HCl concentrations responded well to the equilibrium showed in Eq. (4); though the extraction constant value varies with the HCl concentration, and thus, with the ionic strength (I) of the aqueous solution (Table 2). It is possible to correlate the extraction constant K0, for the equilibrium showed in Eq. (4), with the ionic strength in the molality scale Im. Then:
β=
Im
log K
U
1 2 4 6
1.022 2.080 4.357 6.851
1.04 1.78 2.49 3.04
1.6 2.2 1.3 0.63
DIn DMetal
(9)
where DIn and DMetal are the distribution coefficients for indium and the accompanying metal, respectively. It can be seen that, practically in all the experimental conditions, indium is extracted preferably to the other metal (β values > 1, however, these values are no indicative about the ease of the separation process, and/or the number of stages needed to accomplished it). Fe(III) is extracted in preference to indium due to the affinity of the FeCl4− complex to be exchanged with the chloride ions from the ionic liquid, this situation can be overcome by a pH-controlled iron precipitation, or co-extracting both metals and then carry out a selective stripping. Also, and depending of the metal concentrations in the feed solution, an ion exchange or even a liquid membrane operation can be considered. In any case, these, or other options, i.e. masking Fe (III) with a suitable complexing agent or reducing to the Fe(II) state (though its extractability may be probed), must to be thought more
Table 2 Values of log K for Eq. (4) at various ionic strengths of the aqueous solution. HCl, M
(8)
Values of log Km are identical to those showed for log K. 3
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IneCl complex), though from 4 M the difference in indium extraction with respect to that of the ionic liquids Aliquat 336 and A324H+Cl− became less important, and at 6 M HCl the performance of the three ionic liquids with respect to indium extraction is the same. In all of the HCl concentrations experimented in this work, these two ionic liquids, Aliquat 336 and A324H+Cl−, have practically the same behaviour with respect to indium extraction. Under the present experimental conditions, the performances of ALA2H+Cl− and PJMTH+Cl− ionic liquids are marginal with respect to those of the other three ionic liquids investigated in this work, however, in all the cases, indium extraction tends to increase with the increase of the HCl concentration in the aqueous solution, supporting the idea that in all these systems an anion exchange reaction is responsible for indium extraction, and that the extraction constant is dependent of the ionic strength of the aqueous solution.
Table 3 Values of the percentages of extraction and of the separation factor βIn/M from the extraction of binary mixtures. System
In-metal concentrations, g/L
In-Ni
In-Co
0.1–0.05
In-Cu
0.1–0.05
In-Zn
0.1–0.05
In-Fe(III)
0.1–0.05
In-Sn(IV)
0.1–0.1
HCl, M
% extraction inmetal
βIn/Metal
0.1 1 6 0.1 1 6 0.1 1 6 0.1 1 6 0.1 1 6 0.1 1 6
8-0 57-0.9 99-3 16.0-2 61-2 99-31 3-31 48-30 99-80 8-10 51-53 99-61 9-8 54–82 > 99- > 99 37-10 69-55 > 99-99
quant. 134 > 3000 12 86 199 0.1 2 27 0.8 1 50 1 0.3 0.1 5 2 2
3.3. Indium stripping The stripping of indium(III) from metal-loaded organic solutions had been investigated using 0.1 M HCl solution as strippant due to the poor extraction percentages presented for the system at these low HCl concentrations (see Fig. 2) and that with this strippant, the ionic liquid is regenerated (shifting the equilibrium represented in Eq. (4) to the left). Fig. 4 represented the percentage of indium(III) stripped at various organic/aqueous volume phases relationships. It can be observed that the efficiency of the strip operation decreased as the Vorg/Vst ratio increases, however, at the lower Vorg/Vst ratios the strippant solution seemed to be highly effective with respect to the indium recovery from metal-loaded organic phases.
Aqueous solution: 8.7 × 10−4 M each metal at various HCl concentrations. Organic phase: 0.12 M A324H+Cl− in Solvesso 100. Temperature: 20° C. Time: 15 min. Vorg/Vaq relationship: 1.
deeply. It is also of interest to compare the performance of the present system with the extraction of indium by different ionic liquids. In this case, the experiments were carried out with aqueous solutions containing 0.1 g/L In(III) in HCl (0.1–6 M) and organic solutions of the respective ionic liquid (0.12 M in Solvesso 100). The results obtained are represented in Fig. 3, plotting the percentage of indium extraction against the HCl concentration in the aqueous solution. It can be seen, that for HCl concentration up to 3 M, the best extraction yields are regularly obtained with Cyphos IL101 (probably this result can be attributable to the different reactivity, kinetic and/or chemical, of the phosphonium and the ammonium cations toward the extraction of the
3.4. An approach to the treatment of the in-bearing strip solutions Aimed to the final treatment of the metal-bearing solutions obtained in the previous subsection, the use of sodium borohydride was investigated. After adding the salt to the solution, a greenish precipitate is yielded which is apparently composed of indium and oxygen (Fig. 5), though the diffractogram of the solid also indicated the presence of zero valent indium (Fig. 6). In Fig. 5 the peaks characteristics for indium at
Fig. 3. Indium(III) extraction using different ionic liquids dissolved in Solvesso 100. Aqueous phase: 0.1 g/L In(III) at various HCl concentrations. Organic phase: 0.12 M ionic liquid in the diluent. Temperature: 20 °C. Time: 15 min. Vorg/Vaq relationship: 1.
Fig. 4. Influence of the Vorg/Vst relationship on indium(III) stripping. Strippant solution: 0.1 M HCl. Organic phase: 0.12 M ionic liquid in Solvesso 100 loaded with 0.098 g/L In(III). Temperature: 20 °C. Time: 15 min. 4
Hydrometallurgy 189 (2019) 105104
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Fig. 5. Energy dispersive X-ray spectroscopy spectrum of the solid precipitated after adding sodium borohydride to the In-bearing strip solution.
hydrochloric acid solution, the extraction constant value for such reaction was estimated as log K = 8.94. This ionic liquid can be used for the recovery of indium(III) from hydrochloric acid solutions, being the extraction equilibrium of an apparent endothermic character. The extraction of indium(III) was enhanced as the HCl concentration in the aqueous solution was increased, from 0.1 to 6 M, and also with the increase of the ionic liquid concentration in the organic phase. The extraction of the metal was attributable to the InCl4− extraction in the organic phase via its exchange with the chloride ions of the ionic liquid,
3.28 KeV (Lα1), 3.48 KeV (Lβ1) and even at 3.71 KeV (Lβ2) are observed, whereas the precipitation of the solid could be attributed to the next reaction:
4In3 + + 7H2 O + BH4− → 2In0 + In2 O3 + 12H+ + B (OH )−4 + H2
(10)
4. Conclusions The ionic liquid was generated by reaction of the amine with
In-1 500
Lin (Counts)
400
300
200
100
0 5
10
20
30
40
50
60
70
80
90
100
2-Theta - Scale In-1 - File: In-1.raw - Type: 2Th/Th locked - Start: 5.000 ° - End: 100.010 ° - Step: 0.030 ° - Step time: 3. s - Temp.: 25 °C (Room) - Time Started: 48 s - 2-Theta: 5.000 ° - Theta: 2.500 ° - Chi: 0.00 ° - Phi: 0.00 ° - X: 0.0 Operations: Background 0.120,1.000 | Import 00-005-0642 (*) - Indium, syn - In - Y: 116.65 % - d x by: 1. - WL: 1.5406 - Tetragonal - a 3.25170 - b 3.25170 - c 4.94590 - alpha 90.000 - beta 90.000 - gamma 90.000 - Body-centered - I4/mmm (139) - 2 - 52.2957 - I
Fig. 6. X-ray diffractogram of the solid obtained in the precipitation with sodium borohydride of the In-bearing strip solution. The peaks corresponded to zero valent indium. 5
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that is, an extraction equilibrium typical of an anion-exchange reaction. The extracted species have extraction constant values which were dependent on the ionic strength of the aqueous solution. By the use of such values, the interaction coefficient ε, between InCl4− and H+ species was calculated as 0.50. Indium(III) can be stripped from Inloaded organic phase by the use of diluted (i.e. 0.1 M) HCl solutions. Finally the metal can be precipitated, from the above strip solutions, by the use of sodium borohydride, though this step needed to be investigated more deeply.
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