Equilibrium Data for Aqueous Two-Phase Systems Formed by Ionic

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Equilibrium Data for Aqueous Two-Phase Systems Formed by Ionic Liquid (1-Butyl-3-methylimidazolium Methanesulfonate, 1‑Butyl-3-methylimidazolium Chloride, and 1‑Ethyl-3-methylimidazolium Chloride) and Inorganic Salts (Dibasic Potassium Phosphate and Tripotassium Phosphate) at 298.15 K Downloaded via NOTTINGHAM TRENT UNIV on August 30, 2019 at 22:57:29 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Pedro Henrique Silva Calhau,† Rita de Cássia Superbi de Sousa,† Igor José Boggione Santos,§ Simone Monteiro Silva,∥ and Jane Sélia dos Reis Coimbra*,‡ †

Department of Chemistry and ‡Department of Food Technology, Universidade Federal de Viçosa, Avenida PH Rolfs, s/n, Viçosa 36570-000, Minas Gerais, Brazil § Department of Chemistry, Biotechnology, and Bioprocess Engineering, Universidade Federal de São João del-Rei, Campus Alto Paraopeba, Rodovia MG 443, km 7, Ouro Branco, São João del Rei 36420-000, Minas Gerais, Brazil ∥ Institute of Chemistry, Universidade de Brasília, Brasília 70910-000, Distrito Federal, Brazil ABSTRACT: Equilibrium data were obtained for aqueous two-phase systems composed of ionic liquid (IL) and two inorganic salts (dibasic potassium phosphate, K2HPO4, and tripotassium phosphate, K3PO4) at 298.15 K. The evaluated ionic liquids were 1-butyl-3-methylimidazolium methanesulfonate ([C4mim][CH3SO3]), 1-butyl-3-methylimidazolium chloride ([C4mim][Cl]), and 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]). Equilibrium curves of salt and ionic liquid were determined. Additionally, each curve was fitted into three mathematical models. The aqueous two-phase system composed of the IL [C2mim][Cl] required a lower mass fraction of IL and salt to form the systems than the other two systems studied in this work containing [C4mim][Cl] and [C4mim][CH3SO3]. Furthermore, the type of inorganic salts studied did not affect the equilibrium curves for the same ionic liquid.

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INTRODUCTION

provide a mild environment for the extraction of molecules like proteins, peptides, nucleic acids, and other types of sensitive components but also have a low superficial tension, allowing an easier migration of the solutes among the phases.5−15 The ATPS components are chemical species that form two phases of different compositions when combined in specific concentration and conditions. Generally, these species are two polymers or a combination of a polymer and a salt. Ionic liquids (ILs) are a group of salts that have low melting points due to their disordered crystal lattice. This group of salts has desirable physiochemical properties, like volatility, great capacity of solubilizing several types of molecules, high physical and chemical stabilities, nonflammability, and great recovery potential.1−12 Accordingly, the ATPS formed with ILs have been widely studied lately, since they have the potential to replace the traditional LLE methods.13−22 The compositions of the phases are generally represented in a rectangular diagram, denominated equilibrium phase diagram. In this diagram, the two axes represent the concentration of the

Liquid−liquid extraction (LLE) consists of a unit operation that has been frequently used for more than sixty years to separate several compounds, such as antibiotics and organic acids, in chemical, pharmaceutical, metallurgical, and food industries. LLE has also been used in the treatment of several types of wastes. This method consists of the extraction of one or more compounds from a liquid solution by another liquid solution, which acts as an extractor solvent. The two solutions must be immiscible or partially immiscible with each other to create a two-phase system and allow extraction. The partition of the solute between these two phases is not equal due to its different solubilities in phases.1−4 Despite all applications, the traditional LLE has as a disadvantage the use of an organic solvent as the extractor solution, which is generally toxic, carcinogenic, and flammable, harmful to the human health and the environment. Moreover, the phases that are formed from organic solvents are an aggressive environment for handling biomolecules and other kinds of sensitive solutes. The aqueous two-phase systems (ATPS) are a viable alternative to the traditional LLE once their phases are composed mostly of water in the presence of other components that are neither toxic nor flammable. These systems not only © XXXX American Chemical Society

Received: January 16, 2019 Accepted: August 20, 2019

A

DOI: 10.1021/acs.jced.9b00055 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Adjustment of the Equilibrium Curve to Mathematical Models. Han et al.8 gave three models for the equilibrium curve that were fitted to the experimental data. In these models, the concentration (in mass fraction) of the ionic liquid is w1 and that of the salt is w2. A, B, C, and D are the fitting parameters of the models. These models are described by eqs 1−3

system components, frequently expressed in mass fraction. This type of graphic allows to distinguish the compositions in which the system is heterogeneous or homogeneous. The curve that limits these two regions is the denominated equilibrium curve, so the area above the curve is the biphasic region and the area below the curve is the monophasic region. This curve can be determined experimentally through turbidimetric titration and is affected by environmental conditions, like pH, temperature, and pressure.11 The purpose of this work was to provide the phase equilibrium data at 25 °C for the ATPS formed by the combination of three ILs (1-butyl-3-methylimidazolium methanesulfonate ([C4mim] [CH3SO3]), 1-butyl-3-methylimidazolium chloride ([C4mim][Cl]), and 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl])) and two inorganic salts (dibasic potassium phosphate, K2HPO4, and tripotassium phosphate, K3PO4).

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EXPERIMENTAL SECTION Materials. The ILs ([C2mim][Cl], [C4mim][Cl], and [C4mim][CH3SO3]) and the inorganic salts (K3PO4 and K2HPO4) utilized in this work were purchased from SigmaAldrich. The ILs and the potassium phosphates have mass purity higher than 95% and were used without further purification (Table 1). Deionized water (Milli-Q, Millipore) was used in the

source

[C4mim] [CH3SO3]a [C4mim][Cl]b

Sigma-Aldrich

≥95.0%

Sigma-Aldrich

≥98.0%

[C2mim][Cl]c potassium hydrogen phosphate potassium phosphate

Sigma-Aldrich Sigma-Aldrich

≥98.0% ≥98.0%

65039-09-0 7758-11-4

Sigma-Aldrich

≥98.0%

7778-53-2

analysis method HPLC Area HPLC Area

w1 = A + Bw20.5 + Cw2 + Dw22

(2)

w1 = exp(A + Bw20.5 + Cw2 + Dw22)

(3)

Table 2. Binodal Data for the {[C4mim][Cl] (1) + K3PO4/ K2HPO4 (2) + H2O (3)} ATPS at Temperature T = 298.15 K and Pressure p = 1015 hPaa K3PO4 100 w1 60.39 57.22 52.86 49.59 44.69 41.34 38.52 36.69 34.36 32.14 29.58 27.39 25.33 23.54 21.62 19.90 18.65 17.30 16.01 14.84 12.44 10.65 9.89 9.85 9.16 8.49 7.74 7.29 6.75 6.23 5.41

Table 1. Sample Table chemical name

(1)

RESULTS AND DISCUSSION Tables 2−4 provide with the binodal data of IL ([C4mim][CH3SO3], [C4mim][Cl], [C2mim][Cl]) + salt (K3PO4, K2HPO4) + H2O ATPS.

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final mass fraction purity

w1 = A exp(Bw20.5 − Cw23)

CAS number 342789-81-5 79917-90-1

a

[C4mim][CH3SO3] = 1-butyl-3-methylimidazolium methanesulfonate. b[C 4mim][Cl] = 1-butyl-3-methylimidazolium chloride. c [C2mim][Cl] = 1-ethyl-3-methylimidazolium chloride.

formation of ATPS and the preparation of other solutions. All other reagents were of analytical grade. Equilibrium Phase Diagram Construction. The diagrams were determined using the turbidimetric titration (cloud point method). This method consists of the addition of an aqueous solution of an inorganic salt dropwise in an aqueous solution of an ionic liquid until the mix become turbid. For the construction of the diagrams, stock solutions of the ionic liquid (70% mass fraction) and inorganic salt (40% mass fraction) were prepared with deionized water (Milli-Q, Millipore). Approximately 1 g of the IL solution was transferred to a test tube, which was put in a thermostatic bath (170M020, Matoli) at the desired temperature (298.15 K) until the thermal equilibrium was achieved. Then, the salt solution was added dropwise into the tube until the final solution became turbid (cloud point). After that, the solution in the tube was weighed on an analytical balance (BEL Engineering, M214A) to determine the concentrations of the salt and the ionic liquid. The solution was then diluted with deionized water until it was clear and homogeneous again. The procedure was repeated until there were enough points to make the equilibrium curve.

K2HPO4 100 w2 1.10 1.39 1.93 2.42 2.72 3.53 4.22 4.58 5.34 5.97 6.85 7.59 8.18 9.04 9.95 10.97 11.70 12.44 13.22 13.61 14.74 15.90 16.33 16.38 16.92 17.54 18.17 18.43 18.63 18.93 19.77

100 w1 64.19 55.73 52.04 48.57 44.45 40.97 37.86 34.97 31.50 28.58 25.70 23.25 20.07 17.36 14.94 12.69 11.18 9.38 8.30

100 w2 1.01 1.32 1.64 1.92 2.46 3.23 3.89 4.69 5.97 6.77 7.91 8.81 11.09 13.02 14.63 16.23 17.56 19.26 22.75

a

Standard uncertainties are u(100 wi) = 0.05, u(T) = 0.1 K, and u(p) = 20 hPa.

The equilibrium curves experimentally obtained for all combinations of ILs and salts are exhibited in Figure 1 in which the concentrations of both components are expressed in mass fractions. This plot reveals that the systems formed with [C2mim][Cl] separated into two phases with a lower content B



Article

Table 3. Binodal Data for the {[C4mim][CH3SO3] (1) + K3PO4/K2HPO4 (2) + H2O (3)} ATPS at Temperature T = 298.15 K and Pressure p = 1015 hPaa K3PO4 100 w1 69.43 60.48 55.24 50.59 45.97 41.67 37.61 33.71 29.98 26.10 22.75 19.94 17.45 15.58 13.87 12.48 11.31 10.17 8.99 8.08 7.15 6.42 5.74 5.02

Table 4. Binodal Data for the {[C2mim][Cl] (1) + K3PO4/ K2HPO4 (2) + H2O (3)} ATPS at Temperature T = 298.15 K and Pressure p = 1015 hPaa

K2HPO4 100 w2 1.09 1.43 1.74 2.39 3.25 4.26 5.62 6.89 8.02 10.06 11.81 13.33 14.69 15.82 16.80 17.58 18.15 18.96 19.88 20.66 21.44 22.06 22.57 23.19

100 w1 65.63 62.21 57.32 53.06 49.37 45.29 41.20 37.55 33.52 30.22 26.32 22.66 19.07 16.06 13.62 11.59 9.21 7.67 5.31 4.02

K3PO4 100 w2 1.07 1.52 1.86 2.16 2.41 2.94 3.68 4.58 5.45 6.75 8.56 10.13 12.40 14.36 16.05 17.42 19.10 20.25 20.94 22.42

100 w1 42.53 40.11 37.45 34.79 32.15 29.87 27.10 25.28 23.18 21.18 17.60 16.24 15.08 13.74 12.78 11.85 11.09 10.42 9.68 8.43 7.56 6.83 6.23 5.67

a

K2HPO4 100 w2 2.10 2.31 2.78 3.44 4.24 4.93 6.03 6.67 7.64 8.56 10.30 10.98 11.56 12.35 12.96 13.58 14.09 14.52 15.00 15.86 16.40 17.06 17.62 18.14

100 w1 43.91 40.54 37.61 35.04 33.05 30.18 27.51 25.02 22.90 20.70 18.31 16.42 14.71 13.10 11.64 10.29 9.22 8.49 6.82 5.48

100 w2 1.51 2.09 2.59 3.01 3.41 4.15 4.97 5.81 6.89 8.01 9.05 10.24 11.38 12.39 13.51 14.59 15.46 16.05 17.31 18.84

a

Standard uncertainties are u(100 wi) = 0.04, u(T) = 0.1 K, and u(p) = 20 hPa.

Standard uncertainties are u(100 wi) = 0.05, u(T) = 0.1 K, and e u(p) = 20 hPa.

of ionic liquid than those formed with [C4mim][Cl] and [C4mim][CH3SO3], giving a higher two-phase area. Similar results were described by Ventura et al.3 for the ATPS composed of [C4mim][Cl] and [C2mim][Cl] with K3PO4. The equilibrium curves constructed with [C4mim][Cl] and [C4mim][CH3SO3] are below the [C2mim][Cl] curve. It is also remarkable that there is no significant difference between the curves made with K3PO4 and K2HPO4, considering that the equilibrium curves for the same ionic liquid and both salts almost overlapped. It is important to note that the ATPS formed by ILs and inorganic salts are more complex because the phase equilibrium can occur through different mechanisms, such as ion exchange.16 Thus, small deviations in the concentration of the ions in the different TLs may not be considered as an error2. Ventura et al.3 evaluated the ATPS formed by K3PO4 and imidazolium ILs with different anions of ILs ([C4mim]X, X = CF3SO3, N(CN)2, CF3CO2, Br, CH3SO3, Cl, or CH3CO2) and concluded that the ability of the anion to form ATPS is of the order of [CF3SO3] > [N(CN)2] > [CF3CO2] > Br > [CH3SO3] > Cl > [CH3CO2]. Mourão et al.4 studied the ATPS formed by K2HPO4 and imidazolium ILs with different anions ([C4mim]X, X = CF3SO3, TOS N(CN)2, C2H5SO5, CF3CO2, CH3SO4, CH3SO3, DMP, Br, Cl, or CH3CO2) and found that the anions’ ability to form ATPS is of the order of [CF3SO3] > [TOS] > [N(CN)2] > [C2H5SO4] > [CF3CO2] ≈ [CH3SO4] ≈ [DMP] > Br > [CH3CO2] ≈ [CH3SO3] > Cl. Our results pointed out to a larger biphasic region for ILs-Cl with K3PO4 and a similar ability for ILs-Cl and ILs-CH3SO3 with K2HPO4. Ventura et al.16 studied the effect of the type of the anions in the systems formed with [C4mim]X (X = CF3SO3,

Figure 1. Equilibrium phase diagrams for systems formed with ionic liquid (1) and inorganic salt (2), at 298.15 K: [C4mim][Cl] + K3PO4 (◆); [C4mim][Cl] + K2HPO4 (◇); [C4mim][CH3SO3] + K3PO4 (■); [C4mim][CH3SO3] + K2HPO4 (□); [C2mim][Cl] + K3PO4 (●) and [C2mim][Cl] + K2HPO4 (○).

N(CN)2, Cl, or CH3SO3) and K2HPO4/KH2PO4 buffer. The sequence found regarding the ability of the anions to form ATPS was: [CF3SO3] > [N(CN)2] > Cl > [CH3SO3]. This result is close to our findings. According to Ventura et al.,16 this change in the order of the anions’ ability, Cl and CH3SO3, is probably due to the difference in the concentration of the solutions of the inorganic salts. Bridges et al.2 reported for the ATPS formed by [C4mim][Cl] with K3PO4 a greater ability to form ATPS than K2HPO4, notwithstanding the curves almost overlapped. The curves were fitted to the mathematical models given by eqs 1−3. The fitting parameters, along with the correlation C



Article

Table 5. Values of Parameters of Equation 1 for the {[C4mim][Cl]/[C4mim][CH3SO3]/[C2mim][Cl] (1) + K3PO4/K2HPO4 (2)} ATPS at Temperature T = 298.15 K and Pressure p = 1015 hPaa salt

A

K3PO4 K2HPO4 K3PO4 K2HPO4 K3PO4 K2HPO4

105 C

B

R2

[C4mim][Cl] + Inorganic Salt + H2O 95.4296 −0.4353 10.0000 0.9989 97.8996 −0.4779 2.1697 0,9948 [C4mim][CH3SO3] + Inorganic Salt + H2O 99.1203 −0.4074 7.0347 0.9950 108.4675 −0.4849 5.4585 0.9957 [C2mim][Cl] + Inorganic Salt + H2O 74.6667 −0.4028 10.0000 0.9995 77.1307 −0.4527 9.6120 0.9995

100 sdb 0.6392 1.1949 1.3346 1.2836 1.1437 0.2496

Standard uncertainties are u(T) = 0.1 K and u(p) = 20 hPa. bsd = exp 2 exp 0.5 is the experimental mass (∑ni=1(wcal 1 − w1 ) /n) , where w1 fraction of IL in Tables 1−3 and w1cal is the corresponding data calculated using eq 1. n represent the number of binodal data.

Figure 2. Experimental LLE data, at 298.15 K, for the system [C2mim][Cl] + K2HPO4 + H2O ATPS (this work: ■) and the system [C4mim][Cl] + K2HPO4 + H2O ATPS (this work: ▲; Mourão et al., 2012: Δ).

coefficients (R2) and the corresponding standard deviations (sd), are given in Tables 5−7. Although the p-value for some coefficients is higher than 5%, the p-value for all analysis of variances is less than 0.01%, which indicates that the models are valid. Moreover, the residues for all models are randomly distributed and all coefficients of determination (R2) are close to 1, which indicates a good fitting of the models. Nevertheless, eq 3 describes better the binodal curve based on the R2 and sd values. Hence, eq 3 was used for the estimations of the tie-lines and the plait point. It is possible to verify the difference in the binodal data of this work and the diagram reported in the literature (Figures 2

and 3). This difference among the data probably occurs due to the reagents and whether the additional methods of purification are used or not.17 The difference is mainly in the systems formed by K2HPO4 and seems to be connected to the presence of water. The results presented in this study showed less water amount than those described in the literature, which demonstrates the need for further purification of the reagents or the quantification of the water content by using a sensitive technique.

a

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CONCLUSIONS In this work, equilibrium data are presented for ATPS formed with combinations between ionic liquids ([C2mim][Cl],

Table 6. Values of Parameters of Equation 2 for the {[C4mim][Cl]/[C4mim][CH3SO3]/[C2mim][Cl] (1) + K3PO4/K2HPO4 (2)} ATPS at Temperature T = 298.15 K and Pressure p = 1015 hPaa salt

A

K3PO4 K2HPO4

92.6190 95.2755

K3PO4 K2HPO4

101.5587 112.7973

K3PO4 K2HPO4

69.0145 73.7318

B

C

D

[C4mim][Cl] + Inorganic Salt + H2O −35.4551 4.6906 −0.0583 −40.4651 6.0105 −0.0620 [C4mim][CH3SO3] + Inorganic Salt + H2O −40.8293 6.0697 −0.0774 −53.9889 9.3148 −0.1247 [C2mim][Cl] + Inorganic Salt + H2O −21.8049 2.0184 −0.0225 −28.6024 3.7883 −0.0443

R2

100 sdb

0.9991 0.9941

0.4965 1.2648

0.9957 0.9982

1.2469 0.8285

0.9993 0.9996

0.3112 0.2298

a exp 2 exp 0.5 Standard uncertainties are u(T) = 0.1 K and u(p) = 20 hPa. bsd = (∑ni=1(wcal is the experimental mass fraction of IL in 1 − w1 ) /n) , where w1 Tables 1−3 and w1cal is the corresponding data calculated using eq 2. n represents the number of binodal data.

Table 7. Values of Parameters of Equation 3 for the {[C4mim][Cl]/[C4mim][CH3SO3]/[C2mim][Cl] (1) + K3PO4/K2HPO4 (2)} at Temperature T = 298.15 K and Pressure p = 1015 hPaa salt

A

K3PO4 K2HPO4

4.7564 4.8853

K3PO4 K2HPO4

5.1194 5.0462

K3PO4 K2HPO4

4.7336 4.5004

B

C

D

[C4mim][Cl] + Inorganic Salt + H2O −0.7240 0.1116 −0.0050 −0.8847 0.1368 −0.0036 [C4mim][CH3SO3] + Inorganic Salt + H2O −1.1013 0.2308 −0.0066 −0.9664 0.1644 −0.0049 [C2mim][Cl] + Inorganic Salt + H2O −0.9325 0.1839 −0.0072 −0.6706 0.0840 −0.0040

R2

100 sdb

0.9988 0.9969

0.5598 0.9200

0.9985 0.9970

0.7349 1.0608

0.9997 0.9994

0.2013 0.2844

exp 2 exp 0.5 Standard uncertainties are u(T) = 0.1 K and u(p) = 20 hPa. bsd = (∑ni=1(wcal is the experimental mass fraction of IL in 1 − w1 ) /n) , where w1 cal Tables 1−3 and w1 is the corresponding data calculated using eq 3. n represent the number of binodal data. a

D



Article

(7) Gharehbaghi, M.; Shemirani, F. A novel method for dye removal: ionic liquid-based dispersive liquid-liquid extraction (ILDLLE). Clean: Soil, Air, Water 2012, 40, 290−297. (8) Han, J.; Wang, Y.; Yu, C.; Li, Y.; Kang, W.; Yan, Y. (Liquid + liquid) equilibrium of (imidazolium ionic liquids + organic salts) aqueous two-phase systems at T = 298.15 K and the influence of salts and ionic liquids on the phase separation. J. Chem. Thermodyn. 2012, 45, 59−67. (9) Li, Y.; Huang, R.; Zhu, Q.; Yu, Y.; Hu, J. Phase behavior at different temperatures of an aqueous two-phase ionic liquid containing ([BPy] NO3 + ammonium sulfate and sodium sulfate + water). J. Chem. Eng. Data 2017, 62, 796−803. (10) Xu, S.; Zhu, Q.; Luo, Q.; Li, Y. Influence of Ions and Temperature on Aqueous Biphasic Systems Containing Ionic Liquid and Ammonium Sulfate. J. Chem. Eng. Data 2019, 64, 3139−3147. (11) Pei, Y.; Wang, J.; Liu, L.; Wu, K.; Zhao, Y. Liquid-liquid equilibria of aqueous biphasic systems containing selected imidazolium ionic liquids and salts. J. Chem. Eng. Data 2007, 52, 2026−203. (12) Pereira, M. M.; Pedro, S. N.; Quental, M. V.; Lima, A. S.; Coutinho, J. A. P.; Freire, M. G. Enhanced extraction of bovine serum albumin with aqueous biphasic systems of phosphonium- and ammonium-based ionic liquids. J. Biotechnol. 2015, 206, 17−25. (13) da Silva, R. M. M.; Coimbra, J. S. D. R.; da Silva, C. A.; da Costa, A. R.; da Rocha, R. A.; Giménez, A. R. M.; Santos, I. J. B. Green extraction by aqueous two-phase systems of porcine pancreatic and snake venom phospholipase A2. Sep. Purif. Technol. 2015, 141, 25−30. (14) Treybal, R. E. Mass Transfer Operations, 3rd ed.; McGraw Hill India, 2012. (15) Xanthopoulos, V. A. Aqueous Two-phase Systems: Properties, Functions and Advantages; Nova Science Pub Inc.: NY, 2018. (16) Ventura, S. P.; Sousa, S. G.; Freire, M. G.; Serafim, L. S.; Lima, Á S.; Coutinho, J. A. Design of ionic liquids for lipase purification. J. Chromatogr. B 2011, 879, 2679−2687. (17) Dimitrijevic′, A.; Trtic′-Petrovic′, T.; Vraneš, M.; Papovic′, S.; Tot, A.; Dožic′, S.; Gadžuric′, S. Liquid−liquid equilibria in aqueous 1-alkyl-3-methylimidazolium-and 1-butyl-3-ethylimidazolium-based ionic liquids. J. Chem. Eng. Data 2015, 61, 549−555. (18) Wu, X.; Liu, Y.; Zhao, Y.; Cheong, K. Effect of salt type and alkyl chain length on the binodal curve of an aqueous two-phase system composed of imidazolium ionic liquids. J. Chem. Eng. Data 2018, 63, 3297−3304. (19) Deng, Y.; Chen, J.; Zhang, D. Phase diagram data for several salt + salt aqueous biphasic systems at 298.15 K. J. Chem. Eng. Data 2007, 52, 1332−1335. (20) Sosa, F. H. B.; Farias, F. O.; Igarashi-Mafra, L.; Mafra, M. R. Measurement and correlation of aqueous two-phase systems of polyvinylpyrrolidone (PVP) and manganese sulfate: Effects of molecular weight and temperature. Fluid Phase Equilib. 2018, 472, 204−211. (21) Haghtalab, A.; Mokhtarani, B. On extension of UNIQUACNRF model to study the phase behavior of aqueous two phase polymer−salt systems. Fluid Phase Equilib. 2001, 180, 139−149. (22) Belchior, D. C. V.; Sintra, T. E.; Carvalho, P. J.; Soromenho, M. R. C.; Esperança, J. M. S. S.; Ventura, S. P. M.; Rogers, R. D.; Coutinho, J. A. P.; Freire, M. G. Odd-even effect on the formation of aqueous biphasic systems formed by 1-alkyl-3-methylimidazolium chloride ionic liquids and salts. J. Chem. Phys. 2018, 148, No. 193842.

Figure 3. Experimental LLE data, at 298.15 K, for the system [C2mim][Cl] + K3PO4 + H2O ATPS (this work: ■; Belchior et al., 2018: □) and the system [C4mim][Cl] (1) + K3PO4 + H2O ATPS (this work: ▲; Belchior et al., 2018: Δ).

[C4mim][Cl], and [C4mim][CH3SO3]) and the inorganic salts (K3PO4 and K2HPO4). The determined equilibrium curves show good fitting in the three equations used to describe them. The equilibrium curves formed with the same IL were not considerably affected by the type of the inorganic salt studied; however, the systems composed by [C2mim][Cl] form two phases with lower concentrations of ionic liquid and salt.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: 55 31 38991618. ORCID

Jane Sélia dos Reis Coimbra: 0000-0002-5998-189X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge the Conselho Nacional de ́ Desenvolvimento Cientifico e Tecnológico (CNPq) and the Fundaçaõ de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) for the financial support.

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REFERENCES

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Equilibrium Data for Aqueous Two-Phase Systems Formed by Ionic

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