Phase Behavior of Aqueous Biphasic Systems Composed of Ionic

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Phase Behavior of Aqueous Biphasic Systems Composed of Ionic Liquids and Organic Salts Jing Gao,†,‡ Li Chen,† and Zongcheng Yan*,† †

Department of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China College of Food Science and Technology, Guangdong Ocean University, Zhanjiang 524008, China

‡

S Supporting Information *

ABSTRACT: This study evaluated the effects of ionic liquids (ILs) on the formation of aqueous biphasic systems (ABS) with organic salts. Phase diagrams, tie lines, and respective tie line lengths were determined at 298 K and atmospheric pressure. Using imidazoliumbased ILs, the effects of the IL anions and salt anions, as well as the addition of dipolar aprotic solvents (DAS) on ABS formation were investigated. In general, the IL with hydrogen bond basicity ranging between 0.38 and 0.60 formed ABS with organic salts. However, those below this range were insoluble, and those above this range did not undergo phase separation. The salt anion capacity to induce ABS increased with increased valence and decreased Gibbs free energy of hydration. Moreover, the biphasic area for the IL-based ABS reduced with increased DAS concentration.

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out before. In 2013, Gao et al.21 were the first to show that dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC), can be used to tune the phase behavior of the ABS composed of 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) and K3PO4. The trends in the density of the two phases, the surface tension, the conductivity, and the dipolarity of the mixtures are dependent on the changes in hydrophobicity of ILs caused by the addition of DAS.22 Moreover, DMSO preferentially partitions for the ILrich phase,6 because the hydrogen of the IL cation can form a weak bond with the DMSO oxygen atom. Compared with [C4mim]Cl, the ILs used to form ABS with organic salts, such as 1-butyl-3-methylimidazolium terafluoroborate ([C4mim][BF4]), show more hydrophobic properties. Therefore, to evaluate the effect of DAS on the formation of IL-based ABS is highly relevant. In this study, a large array of organic salts and ILs were explored, and their abilities to form ABS were presented and discussed. The phase diagrams, tie lines, and respective tie line lengths (TLLs) were obtained at 298 K and under atmospheric pressure. The effects of the IL anion and salt anion, and the addition of DAS on the phase behavior were also investigated.

INTRODUCTION The aqueous biphasic system (ABS) is an efficient and green approach to the separation and purification of biomolecules. In recent years, ionic liquid (IL)-based ABS have been significantly explored for the liquid−liquid extraction of a large array of enzymes,1 biomolecules,2,3 and polar solutes.4−6 In IL processing of biomass, ABS is used as an alternative separation method for the recovery and purification of IL from aqueous effluents, and a recovery of over 95 wt % of the IL could be obtained.7−9 IL-based ABSs are formed when a salt, saccharide, or polymer is dissolved in IL aqueous solutions above critical concentrations.10−12 A large set of literature data has focused on the ABS composed of IL and inorganic salts, and the effects of the IL nature, salt, pH, and temperature have been evaluated.10,13−17 However, common inorganic salts lead to environmental problems when discharged at high concentrations into effluent streams.18 Apart from phosphates, sulfates, and carbonates, organic salts have also been used as possible alternatives for the preparation of IL-based ABS. Given that citrate-based salts are biodegradable and nontoxic, C6H5K3O7 and C6H5Na3O7 are extensively explored.18 Moreover, Han et al.19,20 showed that the salting-out ability of the anions of organic salts follows the order C6H5O73+ > C4H4O42+ > C4H4O62+. Nevertheless, a wide variety of organic salts and ILs are absent in most of these systems. The addition of dipolar aprotic solvents (DASs) is a crucial subject regarding the separation and recovery of hydrophilic ILs by forming ABS. However, a systematic study involving these particular systems and addressing the effect of the addition of DAS on the formation of IL-based ABS had not been carried © XXXX American Chemical Society

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EXPERIMENTAL SECTION Materials. The ILs used in this study included the following: [C4mim]Cl; [C4mim][BF4]; 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6]; 1-butyl-3-methylReceived: May 12, 2014 Accepted: January 27, 2015

A

DOI: 10.1021/je500419b J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Figure 1. Ionic structures of the studied ionic liquids: (a) [C4mim][BF4]; (b) [C4mim][PF6]; (c) [C4mim][CF3SO3]; (d) [C4mim][Tf2N]; (e) [C4mim][N(CN)2].

Figure 2. Ionic structures of the studied salts: (a) CHNaO2; (b) C2H3NaO2; (c) C3H5NaO2; (d) C4H7NaO2; (e) C8H15NaO2; (f) C4H4Na2O4; (g) C4H4Na2O6; (h) C6H5Na3O7; (i) C6H11NaO7.

composition of each phase diagram. To evaluate the effect of dipolar aprotic solvent, DMSO, DMF, or DMAC was added into the IL solutions with concentrations between 0 % and 20 % (wDAS/wIL). Salt solutions were repetitively added dropwise to each IL solution until a cloudy solution formed. Then, water was added dropwise until a clear and limpid solution formed. All solutions were added under constant stirring. This process was continued until sufficient points were available to create a binodal curve. The system composition was determined through weight quantification of all components within ± 10−4 g. The experimental binodal curves were fitted by least-squares regression according to eq 1:23

imidazolium trifluoromethanesulfonate, [C4mim][CF3SO3] 1butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [C4mim][Tf2N]; and 1-butyl-3-methylimidazolium dicyanamide, [C4mim][N(CN)2]. All ILs have purities of ≥ 99 wt % and were supplied by the Center of Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics. After drying the ILs under vacuum, the purity of the ILs was further confirmed using 1H, 13C, and 19F NMR analyses at 323 K for 48 h. The organic salts used were CHNaO2 ≥ 99.5 wt %, C2H3NaO2 ≥ 99 wt %, C3H5NaO2 ≥ 99 wt %, C4H7NaO2 ≥ 98 wt %, C6H11NaO2 ≥ 98 wt %, C4H4Na2O4·6H2O ≥ 99 wt %, C4H4Na2O6·2H2O ≥ 99 wt %, C6H5Na3O7·2H2O ≥ 99 wt %, and C6H11NaO7 ≥ 98.5 wt % from Aladdin. Samples (∼20 g) of all salts were air-dried in an oven at 378 K and for 48 h before preparing their aqueous solutions for the determination of the phase diagrams. The dipolar aprotic solvents used were DMSO (≥ 99.7 wt %), DMF (≥ 99.7 wt %), and DMAC (≥ 99.5 wt %) from Sigma-Aldrich. Ultrapure water was doubledistilled, passed through a reverse osmosis system, and further treated with a Milli-Q plus 185 water purification apparatus. The investigated structures of the ILs and organic salts are displayed in Figures 1 and 2, respectively. Phase Diagrams and Tie Lines. The binodal curves of the systems composed of hydrophobic IL, water, and organic salts were determined using cloud point titration method at 298 K. The experimental procedure adopted in this study follows a previously validated method for ABS consisting of hydrophilic ILs and inorganic salts.6,21 Aqueous solutions of each salt with variable concentrations (50 mg/mL for CHNaO 2 , C 3 H 5 NaO 2 , C 4 H 7 NaO 2 , C8H15NaO2, and C4H4Na2O4, 35 mg/mL for C2H3NaO2 and C4H4Na2O6·2H2O, and 40 mg/mL for C6H5Na3O7·2H2O and C6H11NaO7), and aqueous solutions of each IL ranging with concentrations between (0 and 70) wt % were prepared. It should be stressed that the amount of water complexed to the commercial salts was removed in the calculations of the molality or the mass fraction of salts and added to the water

Y = a exp(bX 0.5 − cX 0.3)

(1)

where X and Y are the mass fractions of IL and organic salt, respectively, and the constants a, b, and c are fitted constants obtained by the regression of the experimental data. To determine each tie-line, a ternary mixture composed of [C4mim][BF4] + salt + H2O at the biphasic region was gravimetrically prepared within ± 10−4 g, vigorously stirred, and left to equilibrate at 298 K for at least 12 h. The top and bottom phases were further separated and separately weighed within ± 10−4 g. The IL and salt concentrations in the upper and lower phases were determined using ion chromatography (Basic IC 792, Methohm, Switzerland).24 Throughout the study, a flow rate of 1 mL·min−1 and a sample size of 10 μL were applied. For the eluent solution, 1.8 mM Na2CO3 and 1.7 mM NaHCO3 were used as a mixture. Karl−Fisher titration was used to measure the water content of all samples. The TLL and tie-line slope S at different compositions were calculated by the using eqs 2 and 3, respectively.

B

TLL = [(YT − YB)2 + (X T − XB)2 ]1/2

(2)

S = (Y T − Y B)/(XT − X B)

(3) DOI: 10.1021/je500419b J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 1. Liquid−Liquid Equilibria of Aqueous Biphasic Systems Containing Different Ionic Liquids and Organic Saltsa

a

IL

CHNaO2

C2H3NaO2

C3H5NaO2

C4H7NaO2

C6H11NaO2

C4H4Na2O4

C4H4Na2O6·2H2O

C6H5Na3O7·2H2O

C6H11Na3O7

[C4mim]Cl [C4mim][BF4] [C4mim][PF6] [C4mim][CF3SO3] [C4mim][NTf2] [C4mim][N(CN)2]

× √ × √ × √

× √ × √ × √

× √ × √ × ×

× × × × × ×

× × × × × ×

× √ × √ × √

× √ × √ × √

× √ × √ × √

× √ × √ × ×

√, ABS was formed; ×, ABS could not be formed.

where Y and X are the mass fractions (w/w) of IL and salt, respectively, and the subscripts T and B are the points representing the top and the bottom phases, respectively.

could form ABS with CHNaO2, C2H3NaO2, C4H4Na2O4, C4H4Na2O6·2H2O, and C6H5Na3O7·2H2O. Moreover, those below this range are not water-soluble, and those above this range cannot undergo liquid−liquid demixing in organic salt aqueous solutions. To compare the ability of [C4mim][BF4], [C4mim][CF3SO3], and [C4mim][N(CN)2] in generating ABS with organic salts, the experimental phase diagrams obtained at 298 K and under atmospheric pressure for the ternary systems composed of IL + water + C4H4Na2O6 or IL + water + CHNaO2 are presented in Figure 3. All phase diagrams are presented in molality units. The experimental mole fraction data are reported in the Supporting Information. A large biphasic region suggests a high aptitude for each IL to produce ABS. From the gathered data, the overall tendency of the IL in forming ABS with organic salts follows the order: [C4mim][CF3SO3] > [C4mim][BF4] ≫ [C4mim][N(CN)2].

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RESULTS AND DISCUSSION Phase Diagrams. Six ILs were studied to identify the IL structural features responsible for the formation of ABS in aqueous solutions of organic salts. The ILs investigated were [C 4 mim]Cl, [C 4 mim][BF 4 ], [C 4 mim][PF 6 ], [C 4 mim][CF3SO3], [C4mim][Tf2N], and [C4mim][N(CN)2]. The salt solutions used for the evaluation of the formation of liquid− liquid biphasic systems were saturated. Table 1 shows that the ILs which formed ABS with CHNaO2, C2H3NaO2, C3H5NaO2, C 4 H 4 Na 2 O 4 , C 4 H 4 Na 2 O 6 ·2H 2 O, C 6 H 5 Na 3 O 7 ·2H 2 O, or C6H11NaO7, are [C4mim][BF4] and [C4mim][CF3SO3]. In addition, [C4mim][N(CN)2] formed the ABS with CHNaO2, C2H3NaO2, C4H4Na2O4, C4H4Na2O6·2H2O, or C6H5Na3O7· 2H2O. The ILs that were unable to produce ABS with any organic salt were [C4mim]Cl, [C4mim][PF6], and [C4mim][Tf2N]. In general, [C4mim][BF4], [C4mim][CF3SO3], and [C4mim][N(CN)2] could be salted out using organic salts. In ABS, ILs are hydrogen bond acceptors and depend on the hydrogen bond basicity (β). Most discussions on the IL capacity for producing ABS are based on the hydrogen bond basicity. ILs with low β values are apt to produce ABS.6,15 Table 2 lists the β values for the distinct ILs investigated in this study. Table 2. Hydrogen Bond Basicity Values (β) for Individual Ionic Liquids and Dipolar Aprotic Solvents solvent

β

[C4mim]Cl [C4mim][BF4] [C4mim][PF6] [C4mim][CF3SO3] [C4mim][NTf2] [C4mim][N(CN)2] DMSO DMF DMAC

0.876 0.3822 0.2122 0.4625 0.2422 0.6025 0.82 0.74 0.69

The β values for [C4mim][BF4] (0.38), [C4mim][CF3SO3] (0.46), and [C4mim][N(CN)2] (0.60) are significantly lower than that of [C4mim]Cl (0.87). The data agree well with the results for the ILs to produce ABS, as shown in Table 1. However, the β values for [C4mim][PF6] (0.21) and [C4mim][Tf2N] (0.24) unsuitable to form ABS are lower than that of [C4mim][BF4]. The [PF6]− and [Tf2N]−-based ILs have severely low hydrogen bond basicities and high hydrophobic properties to be miscible with water and, thus, are unable to create ABS. The results listed in Tables 1 and 2 indicate that ILs with β values ranging between 0.38 and 0.60

Figure 3. Ternary phase diagrams of IL + water + C4H4Na2O6 and IL + water + CHNaO2 systems at 298 K and under atmospheric pressure: ■, [C4mim][BF4]; ●, [C4mim][CF3SO3]; ▲, [C4mim][N(CN)2]. C

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To compare the effects of the DAS addition on the phase formation of hydrophobic IL-based ABS with the results of our previous study on ABS composed of hydrophilic IL + inorganic salt + water,6,21,22 the phase diagrams of the various systems composed of [C4mim][CF3SO3] + water + C6H5Na3O7, or [C4mim][BF4] + water + C6H5Na3O7 in the presence of DMSO, DMF, or DMAC are presented in Figure 5. Each IL

To investigate the effects of anion salts on the formation of ABS, the experimental phase diagrams for the ternary systems composed of [C4mim][CF3SO3] + water + salt or [C4mim][BF4] + water + salt are presented in Figure 4. The trend

Figure 4. Ternary phase diagrams of [C4mim][CF3SO3] + water + salt and [C4mim][BF4] + water + salt systems at 298 K and under atmospheric pressure: ●, CHNaO2; ■, C2H3NaO2; ▲, C3H5NaO2; ▽, C4H4Na2O4; ⧫, C4H4Na2O6; ★, C6H5Na3O7; ☆, C6H11NaO7.

Figure 5. Phase diagrams of [C4mim][CF3SO3] + water + C6H5Na3O7 and [C4mim][BF4] + water + C6H5Na3O7 systems in the presence of dipolar aprotic solvents at 298 K and under atmospheric pressure: ■, none; ○, DMSO; △, DMF; ▽, DMAC.

displayed by the salts in forming ABS with [C4mim][BF4] is similar to the ABS composed of [C4mim][CF3SO3]. The binodal curves for the [C4mim]BF4 (1) + C2H3NaO2/ C4H4Na2O6/C6H5Na3O7 (2) + H2O (3) ABS was consistent with the literature reported by Han et al.19 Figure 4 shows that the anion salts follow the order C6H5O73− > C4H4O42− ≈ C4H4O62− > C6H11O7− ≫ CHO2− > C2H3O2− > C3H5O2−. The trend displayed by the anion salts in forming ABS implies that the organic salts with a higher valence anions are better salting-out agents than those with a lower valence because the higher valence anion hydrates better than the lower valence anions.20 Moreover, the Gibbs free energy of hydration (ΔhydG) for CHO2−, C2H3O2−, and C4H4O62− are −395 kJ· mol−1, −365 kJ·mol−1, and −1090 kJ·mol−1, respectively.10,26,27 Therefore, the salting-out ability of organic salts increases with the ΔhydG value, which is in accordance with the results on the phase behavior of ABS composed of inorganic salts.10 The results suggest that the salting-out ability of organic salts to form ABS can be related to the valence and ΔhydG value of the anions.

solution was prepared by adding 20 wt % DAS (wDAS/wIL). Based on the gathered data, adding DAS decreases the ability of ILs to form ABS. Table 2 shows that the β values for DMSO (0.82), DMF (0.74), and DMAC (0.69) are significantly higher than those of [C4mim][CF3SO3] and [C4mim][BF4]. Thus, the DASs investigated in this study are more hydrophilic than the ILs. In addition, the hydrogen from the [C4mim][CF3SO3] and cations forms a weak bond with the oxygen atom of the DAS. Therefore, DAS addition increases the hydrogen bond basicity and the hydrophilic properties of the ILs. Figure 6 shows that the DMSO concentration affects ABS. A higher DMSO concentration for IL solution reduces the ability of ILs to produce ABS. However, the β values for DMSO, DMF, DMAC, and [C4mim][BF4] have a trend of DMSO > DMF > DMAC ≫ [C4mim][BF4]. Thus, no remarkable difference among the phase diagrams for DMSO, DMF, and DMAC was observed in Figure 5. Table 3 presents the parameters obtained by the leastsquares regression of the experimental binodal curves (in mole fraction) using eq 1. Excellent correlation coefficients were D

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the bottom phase relates to the salt-rich phase. When the initial concentrations of [C4mim][BF4] and C6H5Na3O7 in the mixture were 30 and 24 wt %, respectively, the highest recovery efficiency of [C4mim][BF4] could reach 95 wt %. The following correlating equations proposed by Othmer− Tobias (eq 4) and Bancroft (eq 5) were used to correlate the tie-line compositions: ⎛ 1 − w b ⎞n ⎛ 1 − w1t ⎞ 2 ⎜⎜ ⎟⎟ K = ⎟ ⎜ t b ⎝ w1 ⎠ w ⎝ ⎠ 2

(4)

⎛w b⎞ ⎛ w t ⎞r ⎜⎜ 3 b ⎟⎟ = K1⎜ 3t ⎟ ⎝ w1 ⎠ ⎝ w2 ⎠

(5)

w1t

in the top phase; w2b is phase; w3b and w3t are

where is the mass fraction of ILs the mass fraction of salt in the bottom the mass fractions of water in the bottom and top phases, respectively; and K, n, K1, and r are the fit parameters. Equations 4 and 5 are linearized by obtaining the logarithm of both sides of the equations to determine the fit parameters. Table 5 presents the values of the parameters. The corresponding correlation coefficient values (R2) and standard deviations (σa) shown in Table 5 indicate that the tie-line data of the investigated systems can be satisfactorily correlated by the Othmer−Tobias and Bancroft equations.

Figure 6. Phase diagrams of [C4mim][BF4] + water + C6H5Na3O7 systems in the presence of DMSO at 298 K and under atmospheric pressure: ■, none; ●, 10 wt %; ▲, 20 wt %; ▼, 30 wt %.

generally obtained for all systems, indicating that the fitting can be used to predict the data in a given region of the phase diagram where no experimental results are available. Tie Lines. The tie lines and TLLs for the ternary systems composed of salt + [C4mim][BF4] + H2O, were determined through the application of eq 2. The weight fraction compositions for the coexisting phases of each system and the respective TLLs, as well as the recovery efficiencies of the ILs (RIL), are reported in Table 4. The tie lines for [C4mim]BF4 + C6H5Na3O7 + H2O ABS show consistence with the literature reported by Han et al.,19 while the tie lines for [C4mim]BF4 + C2H3NaO2/C4H4Na2O6 + H2O ABS show crossings with the literature. The difference between the two data sources may resulted from the tie line measurement. However, a general trend in TLL and RIL values was verified in which increasing IL and salt concentrations increase the TLL and RIL values. The top phase corresponds to the [C4mim][BF4]-rich phase, and

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CONCLUSIONS In this study, the ability of a broad range of organic salts to induce the formation of IL-based ABS was evaluated. The effect of salt and IL anions and addition of DAS on the phase diagrams, tie lines, and TLLs were determined at 298 K and under atmospheric pressure. The data obtained in this study show that the organic salt aptitude for forming ABS with IL follows the order: C6H5Na3O7 > C4H4Na2O4 ≈ C4H4Na2O6 > C6H11NaO7 ≫ CHNaO2 > C2H3NaO2 > C3H5NaO2. The phase separation is facilitated by the salts with a higher valence and ΔhydG value for anions. The overall tendency of the IL in creating ABS with organic salts follows the order: [C4mim][CF3SO3] > [C4mim][BF4] ≫ [C4mim][N(CN)2]. Any IL with β values approximately ranging between 0.38 and 0.60

Table 3. Parameters (a, b, and c) Obtained by the Regression of the Experimental Binodal Data through the Application of eq 1 for the IL + Salt + Water Systems at the Temperature T = 298.2 K and Pressure p = 0.1 MPaa IL [C4mim][BF4]

[C4mim][CF3SO3]

[C4mim][N(CN)2]

a

a

salt CHNaO2 C2H3NaO2 C3H5NaO2 C4H4Na2O4 C4H4Na2O6 C6H5Na3O7 C6H11NaO7 CHNaO2 C2H3NaO2 C3H5NaO2 C4H4Na2O4 C4H4Na2O6 C6H5Na3O7 C6H11NaO7 CHNaO2 C4H4Na2O6

6.938 6.711 8.384 6.057 5.706 6.555 6.027 5.182 5.984 6.515 4.216 4.228 4.555 4.226 7.033 5.950

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

b 0.152 0.119 0.295 0.125 0.061 0.090 0.141 0.175 0.102 0.146 0.061 0.071 0.134 0.081 0.187 0.097

−1.880 −1.936 −1.912 −3.087 −2.958 −4.107 −2.677 −1.584 −2.005 −1.659 −2.753 −2.747 −3.521 −2.220 −0.803 −1.819

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.037 0.033 0.060 0.059 0.027 0.040 0.063 0.060 0.031 0.036 0.053 0.057 0.102 0.057 0.027 0.040

c

R2

σ

−0.006 ± 0.001 −0.015 ± 0.002 −0.004 ± 0.032 −0.173 ± 0.060 −0.027 ± 0.030 −0.739 ± 0.100 0.007 ± 0.064 0.038 ± 0.014 0.003 ± 0.005 0.053 ± 0.012 0.300 ± 0.122 0.807 ± 0.201 0.654 ± 0.466 0.510 ± 0.108 0.012 ± 0.001 0.543 ± 0.033

0.9942 0.9966 0.9939 0.9949 0.9983 0.9973 0.9942 0.9811 0.9964 0.9970 0.9941 0.9941 0.9891 0.9915 0.9965 0.9974

0.0060 0.0031 0.0030 0.0039 0.0010 0.0012 0.0051 0.0161 0.0026 0.0015 0.0049 0.0042 0.0053 0.0065 0.0048 0.0030

Standard uncertainties u are u(T) = 0.1 K and u(p) = 10 kPa. E

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Table 4. Mass Fraction Compositions for the Mixture (M), Top Phases (T), and Bottom Phases (B) of Salt (X) + [C4mim][BF4] (Y) + H2O Systems, Respective Values of TLL, Two-Phase Volume Ratio (VT/VB), Slope of Tie Line (S), and RIL at the Temperature T = 298.2 K and Pressure p = 0.1 MPaa mass fraction/(w/w) salt CHNaO2

C2H3NaO2

C3H5NaO2

C4H4Na2O4

C4H4Na2O6

C6H5Na3O7

C6H11NaO7

a

XM

YM

XT

YT

XB

YB

TLL

RIL

VT/VB

S

0.1695 0.1797 0.2028 0.1496 0.1985 0.2321 0.1957 0.2231 0.2605 0.1537 0.1937 0.2366 0.1986 0.2325 0.2312 0.1597 0.2071 0.2432 0.1454 0.1773 0.1917

0.1967 0.2175 0.2493 0.1967 0.2498 0.2879 0.2493 0.2807 0.2961 0.1914 0.2513 0.2874 0.2174 0.2470 0.2608 0.1970 0.2474 0.3002 0.1949 0.2203 0.2567

0.0378 0.0254 0.0115 0.0512 0.0363 0.0266 0.0456 0.0399 0.0261 0.0335 0.0208 0.0185 0.0105 0.0084 0.0075 0.0338 0.0145 0.0130 0.0394 0.0318 0.0257

0.3243 0.4967 0.6691 0.3156 0.4412 0.5351 0.5353 0.5682 0.6629 0.5145 0.5997 0.6764 0.6809 0.7274 0.7454 0.4155 0.5867 0.7294 0.4456 0.5309 0.6127

0.2224 0.2532 0.3033 0.2513 0.3138 0.3492 0.2598 0.3112 0.3399 0.1873 0.2631 0.3471 0.3155 0.3253 0.3301 0.2864 0.3200 0.3618 0.1904 0.2597 0.3228

0.1142 0.0942 0.0765 0.1037 0.0869 0.0850 0.1517 0.1296 0.1192 0.1174 0.0913 0.0807 0.0489 0.0491 0.0429 0.0451 0.0416 0.0384 0.1258 0.0966 0.0654

0.2797 0.4625 0.6605 0.2914 0.4500 0.5538 0.4394 0.5157 0.6278 0.4258 0.5632 0.6803 0.7017 0.7523 0.7730 0.4483 0.6249 0.7740 0.3537 0.4905 0.6227

63.84 77.21 89.69 61.32 74.95 88.46 60.66 76.40 82.52 64.44 75.72 90.77 74.17 87.46 92.75 75.53 88.32 94.62 65.74 77.21 80.28

7.64 5.46 0.21 7.65 4.56 0.35 6.91 5.96 1.85 7.45 3.88 2.51 0.36 0.34 0.26 4.93 0.49 0.32 9.11 4.50 0.32

−1.138 −1.766 −2.031 −1.058 −1.276 −1.395 −1.791 −1.616 −1.732 −2.582 −2.098 −1.813 −2.072 −2.140 −2.177 −1.466 −1.784 −1.981 −2.117 −1.905 −1.842

Standard uncertainties u are u(X) = 0.005, u(Y) = 0.005, u(T) = 0.1 K, and u(p) = 10 kPa.

Table 5. Values of the Parameters of Equations 4 and 5 for the Coexisting Phases of Salt + [C4mim][BF4] + H2O Systems salt

K

n

R2

σa

K1

r

R2

σa

CHNaO2 C2H3NaO2 C3H5NaO2 C4H4Na2O4 C4H4Na2O6 C6H5Na3O7 C6H11NaO7

0.0286 0.2701 0.2003 0.2873 0.0116 0.0408 0.3167

3.382 1.921 1.408 1.012 4.770 3.847 1.053

0.9878 0.9935 0.9986 0.9997 0.9987 0.9955 0.9510

0.024 0.012 0.008 0.003 0.010 0.017 0.064

2.527 1.779 2.697 4.325 2.336 2.181 8.941

0.2664 0.5067 0.6952 0.9175 0.1869 0.2586 0.4885

0.9817 0.9984 0.9992 0.9996 0.9991 0.9972 0.9923

0.025 0.008 0.005 0.005 0.008 0.011 0.020

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could form ABS with CHNaO2, C2H3NaO2, C4H4Na2O4, C4H4Na2O6·2H2O, and C6H5Na3O7·2H2O at 298 K. Those below this range are not water-soluble, and those above cannot undergo liquid−liquid demixing in organic salt aqueous solutions. In contrast with our previous studies in which the addition of DAS increased the biphasic area for the hydrophilic IL-based ABS, the biphasic area decreased in the hydrophobic IL-based ABS. In general, the β values of DMSO, DMF, or DMAC range between [C4mim][BF4] and [C4mim]Cl. This close relationship agreed with the results in which the addition of DAS increases the capability of hydrophobic IL to form a hydrogen bond with water, and decrease hydrophilic property of IL.

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AUTHOR INFORMATION

Corresponding Author

*Tel: + 86 20 87111109; fax: + 86 20 87111109. E-mail address: [email protected] (Z.Y.). Funding

This research was supported by the National Natural Science Foundation of China (21376088), the Project of Production, Education and Research, Guangdong Province and Ministry of Education (2012B09100063, 2012A090300015), and the Key Social Development Program of Guangdong Province (2011A030600011). The authors would also gratefully acknowledge the support from the Guangdong Provincial Laboratory of Green Chemical Technology. Notes

The authors declare no competing financial interest.

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ASSOCIATED CONTENT

S Supporting Information *

REFERENCES

(1) Khupse, N. D.; Kumar, A. Delineating Solute-Solvent Interactions in Binary Mixtures of Ionic Liquids in Molecular Solvents and Preferential Solvation Approach. J. Phys. Chem. B 2011, 115, 711−718. (2) Louros, C. L. S.; Claudio, A. F. M.; Neves, C. M. S. S.; Freire, M. G.; Marrucho, I. M.; Pauly, J.; Coutinho, J. A. P. Extraction of

Experimental binodal mass fraction data for the ABSs composed by each system. This material is available free of charge via the Internet at http://pubs.acs.org. F

DOI: 10.1021/je500419b J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

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. (21) Gao, J.; Chen, L.; Yan, Z.; Yu, S. Influence of Aprotic Solvents on the Phase Behavior of Ionic Liquid Based Aqueous Biphasic Systems. J. Chem. Eng. Data 2013, 58, 1535−1541. (22) Gao, J.; Chen, L.; Xin, Y.; Yan, Z. C. Ionic liquid-based aqueous biphasic systems with controlled hydrophobicity: The polar solvent effect. J. Chem. Eng. Data 2014, 59, 2150−2158. (23) Merchuk, J. C.; Andrews, B. A.; Asenjo, J. A. Aqueous two-phase systems for protein separation Studies on phase inversion. J. Chromatogr. B 1998, 711, 285−293. (24) Gao, J.; Chen, L.; He, Y. Y.; Yan, Z. C.; Zheng, X. J. Degradation of imidazolium-based ionic liquids in aqueous solution using plasma electrolsis. J. Hazard. Mater. 2014, 265, 261−270. (25) Khupse, N. D.; Kumar, A. Contrasting Thermosolvatochromic Trends in Pyridinium-, Pyrrolidinium-, and Phosphonium-Based Ionic Liquids. J. Phys. Chem. B 2010, 114, 376−381. (26) Marcus, Y. Thermodynamics of Solvation of Ions. Part 5. Gibbs Free Energy of Hydration at 298.15 K. J. Chem. Soc., Faraday Trans. 1991, 87, 2995−2999. (27) Lungwitz, R.; Strehmel, V.; Spange, S. The Dipolarity/ polarisability of 1-Alkyl-3-methylimidazolium Ionic Liquids as Function of Anion Structure and the Alkyl Chain Length. New J. Chem. 2010, 34, 1135−1140.

Biomolecules Using Phosphonium-Based Ionic Liquids + K3PO4 Aqueous Biphasic Systems. Int. J. Mol. Sci. 2010, 11, 1777−1791. (3) Ventura, S. P. M.; Neves, C. M. S. S.; Freire, M. G.; Marrucho, I. M.; Oliveira, J.; Coutinho, J. A. P. Evaluation of Anion Influence on the Formation and Extraction Capacity of Ionic-Liquid-Based Aqueous Biphasic Systems. J. Phys. Chem. B 2009, 113, 9304−9310. (4) Cláudio, A. F. M.; Freire, M. G.; Freire, C. S. R.; Silvestre, A. J. D.; Coutinho, J. A. P. Extraction of Vanillin Using Ionic-Liquid-Based Aqueous Two-Phase Systems. Sep. Purif. Technol. 2010, 75, 39−47. (5) Chen, Y.; Meng, Y.; Yang, J.; Li, H.; Liu, X. Phenol Distribution Behavior in Aqueous Biphasic Systems Composed of Ionic LiquidsCarbohydrate-Water. J. Che. Eng. Data 2012, 57, 1910−1914. (6) Gao, J.; Chen, L.; Yan, Z. C. Extraction of Dimethyl Sulfoxide Using Ionic-Liquid-Based Aqueous Biphasic Systems. Sep. Purif. Technol. 2014, 124, 107−116. (7) Shill, K.; Padmanabhan, S.; Xin, Q.; Prausnitz, J. M.; Clark, D. S.; Blanch, H. W. Ionic Liquid Pretreatment of Cellulosic Biomass: Enzymatic Hydrolysis and Ionic Liquid Recycle. Biotechnol. Bioeng. 2011, 108, 511−520. (8) Gao, J.; Chen, L.; Yan, Z.; Wang, L. Effect of Ionic Liquid Pretreatment on the Composition, Structure and Biogas Production of Water Hyacinth (Eichhornia crassipes). Bioresour. Technol. 2013, 132, 361−364. (9) Gao, J.; Chen, L.; Yuan, K.; Huang, H.; Yan, Z. Ionic Liquid Pretreatment to Enhance the Anaerobic Digestion of Lignocellulosic Biomass. Bioresour. Technol. 2013, 150, 352−358. (10) Shahriari, S.; Neves, C. M. S. S.; Freire, M. G.; Coutinho, J. A. P. Role of the Hofmeister Series in the Formation of Ionic-Liquid-Based Aqueous Biphasic Systems. J. Phys. Chem. B 2012, 116, 7252−7258. (11) Wu, B.; Zhang, Y.; Wang, H.; Yang, L. Temperature Dependence of Phase Behavior for Ternary Systems Composed of Ionic Liquid plus Sucrose plus Water. J. Phys. Chem. B 2008, 112, 13163−13165. (12) Freire, M. G.; Pereira, J. F. B.; Francisco, M.; Rodriguez, H.; Rebelo, L. P. N.; Rogers, R. D.; Coutinho, J. A. P. Insight into the Interactions That Control the Phase Behaviour of New Aqueous Biphasic Systems Composed of Polyethylene Glycol Polymers and Ionic Liquids. Chem.Eur. J. 2012, 18, 1831−1839. (13) Ventura, S. P. M.; Sousa, S. G.; Serafim, L. S.; Lima, A. S.; Freire, M. G.; Coutinho, J. A. P. Ionic-Liquid-Based Aqueous Biphasic Systems with Controlled pH: The Ionic Liquid Anion Effect. J. Chem. Eng. Data 2012, 57, 507−512. (14) Ventura, S. P. M.; Sousa, S. G.; Serafim, L. S.; Lima, A. S.; Freire, M. G.; Coutinho, J. A. P. Ionic Liquid Based Aqueous Biphasic Systems with Controlled pH: The Ionic Liquid Cation Effect. J. Chem. Eng. Data 2011, 56, 4253−4260. (15) Claudio, A. F. M.; Ferreira, A. M.; Shahriari, S.; Freire, M. G.; Coutinho, J. A. P. Critical Assessment of the Formation of IonicLiquid-Based Aqueous Two-Phase Systems in Acidic Media. J. Phys. Chem.B 2011, 115, 11145−11153. (16) Freire, M. G.; Neves, C. M. S. S.; Canongia Lopes, J. N.; Marrucho, I. M.; Coutinho, J. A. P.; Rebelo, L. P. N. Impact of SelfAggregation on the Formation of Ionic-Liquid-Based Aqueous Biphasic Systems. J. Phys. Chem. B 2012, 116, 7660−7668. (17) Freire, M. G.; Cláudio, A. F. M.; Araújo, J. M. M.; Coutinho, J. A. P.; Marrucho, I. M.; Canongia Lopes, J. N.; Rebelo, L. P. N. Aqueous biphasis systems: a boost brought about by using ionic liquids. Chem. Soc. Rev. 2012, 41, 4966−4995. (18) Passos, H.; Ferreira, A. R.; Cláudio, A. F. M.; Coutinho, J. A. P.; Freire, M. G. Characterization of Aqueous Biphasic Systems Composed of Ionic Liquids and a Citrate-based Biodegradable Salt. Biochem. Eng. J. 2012, 67, 68−76. (19) Han, J.; Yu, C.; Wang, Y.; Xie, X.; Yan, Y.; Yin, G.; Guan, W. Liquid-Liquid Equilibria of Ionic Liquid 1-Butyl-3-methylimidazolium Tetrafluoroborate and Sodium Citrate/tartrate/acetate Aqueous TwoPhase Systems at 298.15 K: Experiment and Correlation. Fluid Phase Equilib. 2010, 295, 98−103. (20) Han, J.; Wang, Y.; Yu, C.; Li, Y.; Kang, W.; Yan, Y. (Liquid + Liquid) Equilibrium of (Imidazolium Ionic Liquids + Organic Salts) G

DOI: 10.1021/je500419b J. Chem. Eng. Data XXXX, XXX, XXX−XXX