Investigation of the Thermodynamic Properties in Aqueous Solutions

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

pubs.acs.org/jced

Investigation of the Thermodynamic Properties in Aqueous Solutions Containing D‑Fructose and Some Imidazolium-Based Ionic Liquids at Different Temperatures Mohammed Taghi Zafarani-Moattar, Hemayat Shekaari, and Elnaz Mazaher Haji Agha* Department of Physical Chemistry, University of Tabriz, Tabriz 51664, Iran

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S Supporting Information *

ABSTRACT: To investigate the interactions present in aqueous {D-fructose + ionic liquids 1-butyl-3-methylimidazolium bromide or 1-octyl-3-methylimidazolium bromide or 1octyl-3-methylimidazolium chloride} solutions, volumetric compressibility and viscometric properties of these systems have been studied at temperatures T = 288.15−318.15 K and atmospheric pressure. The positive and increasing values of transfer volume and transfer partial molar isentropic compression with increasing ionic liquid concentration indicated predominance of ionic−hydrophilic interactions in these systems. The calculated hydration number showed dehydration of fructose in the presence of studied ionic liquids. Further, the interaction and cavity volumes were computed using the scaled particle theory.

1. INTRODUCTION Saccharides as inexpensive and easily accessible compounds have gained much interest in food, biological, and biorefinery processes.1−3 Aqueous solutions of saccharides in the presence of some additives such as ethanol, salts, and glycerol can provide an immersion medium for freezing fruits.4,5 Saccharides are able to protect biological molecules such as proteins and phospholipid biolayers against freezing and drying processes during extreme dehydration.6 In recent years, special attention has been paid on utilizing saccharides as feedstock in the synthesis of valuable chemicals and fuels by biorefinery process.3 However, due to rigidity and low solubility of saccharides in traditional solvents, their applications face some challenges.7 A potential key to this problem is the utilization of ionic liquids. They are able to dissolve biomass components and covert them to many useful new chemicals such as 5hydroxymethylfurfural.8−10 Studying the thermodynamic and transport properties of these systems, including volumetric, compressibility, and viscometric properties, can yield valuable information about the interactions occurring in the {saccharide + ionic liquid} mixtures in aqueous media and can promote the performances of processes related to these systems. In recent years, aqueous solutions containing saccharides and ionic liquids have been studied in the literature.11−23 Singh and co-workers studied the solvation behavior of some saccharides in aqueous ionic liquid solutions.19,20 Jin et al. measured densities of aqueous {sucrose + ionic liquid 1-allyl-3-methylimidazolium chloride} solutions.21 Zafarani-Moattar et al. studied volumetry, compressibility, viscometry, and vapor−liquid equilibrium of {sucrose or fructose + ionic liquid + water} systems.11−18 The scope of this paper is to investigate the effect of ionic liquids on aqueous fructose solutions. To reach this purpose, volumetric, © XXXX American Chemical Society

compressibility, and viscometric properties of ternary {Dfructose + ionic liquids 1-butyl-3-methylimidazolium bromide [BMIm]Br or 1-octyl-3-methylimidazolium bromide [OMIm] Br or 1-octyl-3-methylimidazolium chloride [OMIm]Cl + water} solutions have been studied at various ionic liquid molalities mIL = 0.1, 0.2, and 0.3 mol·kg−1 and T = 288.15− 318.15 K. From the measured density, speed of sound, and viscosity data, some properties, including standard partial molar volume (V0Φ), transfer volume (ΔtrV0Φ), standard partial molar isentropic compression (K0Φ), and viscosity B-coefficient, have been computed. The interaction (Vint) and cavity volumes (Vcav) were computed using the scaled particle theory (SPT). To investigate the hydration behavior of fructose in these solutions, the hydration number (nH) is computed. In this study, the effects of temperature, chain length, anion type, and concentration of ionic liquids on fructose−ionic liquid interactions have been discussed.

2. EXPERIMENTAL SECTION 2.1. Materials. The chemicals utilized in this study, namely, 1-bromobutane, 1-bromooctane, 1-chlorooctane, ethyl acetate, D-fructose, and N-methylimidazole, were purchased from Merck. D-Fructose was dried in vacuum over P2O5 at room temperature for at least 72 h. Double-distilled water was utilized. The mass fractions of water in D-fructose, ionic liquids 1-butyl-3-methylimidazolium bromide, 1-octyl-3methylimidazolium bromide, and 1-octyl-3-methylimidazolium chloride measured by Karl−Fischer titration were 0.0009, Received: October 23, 2018 Accepted: March 22, 2019

A

DOI: 10.1021/acs.jced.8b00958 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Description of the Chemicals Used CAS number

purity (mass fraction)

616-47-7 109-65-9 111-83-1 111-85-3 141-78-6 57-48-7

>0.99 >0.99 >0.99 >0.99 >0.99 >0.995 ∼0.98

material

provenance

N-methylimidazole 1-bromobutane 1-bromooctane 1-chlorooctane ethyl acetate D-fructose [BMIm]Br

Merck Merck Merck Merck Merck Merck synthesis

[OMIm]Br

synthesis

∼0.98

[OMIm]Cl

synthesis

∼0.98

purification method none none none none none dried in vacuum over P2O5 rotary evaporator and dried under vacuum rotary evaporator and dried under vacuum rotary evaporator and dried under vacuum

analysis method

Karl−Fischer and 1 H NMR Karl−Fischer and 1 H NMR Karl−Fischer and 1 H NMR

water content (mass fraction)

0.0009 0.0034 0.0042 0.0037

polynomial function (y = a + bx + cx2), the root-mean-square deviation (RMSD) % values of 0.005, 0.013, 0.006, and 0.025 are obtained at T = 288.15, 298.15, 308.15, and 318.15 K, respectively. Plots of deviations of measured and literature values from the d(mfructose) fits of measured data to the corresponding polynomial function at each temperature are shown in Figures S8−S11. The VΦ values of fructose in binary and ternary solutions are listed in Table 2. By least-squares fitting of VΦ values, standard partial molar volume V0Φ can be obtained30

0.0034, 0.0042, and 0.0037, respectively. The water content in the ionic liquids and D-fructose was considered in the calculations. The detailed specifications of these materials are reported in Table 1. In the ternary solutions, {water + ionic liquid} solutions have been used as solvents. 2.2. Synthesis of Ionic Liquids. The ionic liquids 1-butyl3-methylimidazolium bromide, [BMIm]Br, 1-octyl-3-methylimidazolium bromide, [OMIm]Br, and 1-octyl-3-methylimidazolium chloride [OMIm]Cl were synthesized as described in the literature.24,25 1H NMR spectra of these ionic liquids are given in Figures S1−S3 in the Supporting Information. 2.3. Apparatus and Procedure. To prepare the solutions on molality concentration, an analytical balance (Shimadzu, 321-34553, Shimadzu Co., Japan) with a precision of ±1 × 10−7 kg was utilized. Measurements of density and speed of sound were carried out using a vibrating tube densimeter and speed of sound analyzer (DSA5000, Anton Paar Co.). For speed of sound experiment, the frequency of the instrument is about 3 MHz. To control the temperature within ±10−3 K in densimeter, a built-in Peltier thermostat was utilized. The experimental uncertainties for density and speed of sound measurements were 0.3 kg m−3 and 0.5 m s−1, respectively. Viscosities of the solutions were determined using an Anton Paar rolling-ball viscometer, Lovis 2000 M/ME. To control the temperature to ±0.005 K, a Peltier technique built-in thermostat was utilized. In each measurement, the uncertainty of the viscosity is about 0.015 mPa s.

VΦ = V Φ0 + Svm

(2)

In eq 2, V0Φ and Sv are indicative of solute−solvent and solute− solute interactions, respectively. The V0Φ and Sv values are given in Table 3. The obtained standard partial molar volumes of fructose in water in this work show a good agreement with the literature.31−35 In ternary solutions, Sv values are negative, indicative of weak fructose−fructose interactions. Our results show that in ternary solutions, the V0Φ values of fructose are affected by temperature, nature of ionic liquid, and its concentrations. In Figures 1 and 2, the effects of ionic liquid molality and temperature on VΦ0 values are illustrated. According to Figure 1, the V0Φ values of fructose increase with enhancement in ionic liquid molality, indicating strengthening of attractive interactions between fructose and studied ionic liquids. Figure 1 also shows that the computed V0Φ values of fructose in ternary solutions have this trend: V0Φ[OMIm]Br > V0Φ[BMIm]Br and V0Φ[OMIm]Br > V0Φ[OMIm]Cl. This means that in ternary solution, the attractive interactions between [OMIm]Br and fructose are stronger compared to [BMIm]Br−fructose and [OMIm]Cl−fructose interactions. This can be interpreted based on the hydration behavior of ionic liquids. According to our previous studies, ionic liquids with shorter chain length show higher affinity for water.11,15 The reason for this behavior is increase in the hydrophobicity of ionic liquids with increasing chain length from butyl to octyl, which reduces their interactions with water molecules. Therefore, [BMIm]Br−water interactions are stronger compared to [OMIm]Br−water interactions. Furthermore, the comparison of hydration behaviors of ionic liquids [OMIm]Br and [OMIm]Cl, which have common chain length and different anions, indicates that the ionic liquid containing Cl− anion shows higher interaction with water rather than Br− anion.15 In ternary solutions, there is a relationship between ionic liquid−water and ionic liquid−fructose interactions. In fact, as the affinity of ionic liquids for interaction with water increases, their tendency to interact with fructose decreases.

3. RESULTS AND DISCUSSION 3.1. Volumetric Properties. To investigate the interactions present in binary {fructose + water} and aqueous {fructose + ionic liquid} solutions, density data for these mixtures at different temperatures have been measured. Using the density of the solvent d0 and solutions d, the apparent molar volumes (VΦ) for fructose were computed as follows26 ÄÅ É ÅÅ (d − d0) ÑÑÑ M Å ÑÑ VΦ = − ÅÅÅ Ñ ÅÅÇ mdd0 ÑÑÑÖ d (1) where M is the molar mass of fructose and m is the molality of solution. The obtained density data for {fructose + water} and {fructose + ionic liquid + water} solutions are reported in Tables S1−S3 in the Supporting Information. The density data for binary {D-fructose + water} solutions together with literature data are illustrated in Figures S4−S7.27−29 By fitting the experimental density data measured in this work to a B



Article

Table 2. Apparent Molar Volume (VΦ) and Apparent Molar Isentropic Compression (KΦ) of Fructose in Water and Aqueous Ionic Liquids [BMIm]Br, [OMIm]Br, and [OMIm]Cl Solutions at T = 288.15−318.15 K T = 288.15 K

T = 298.15 K

mf (mol·kg−1)

VΦ × 106 (m3·mol−1)

KΦ × 1014 (m3·mol−1·Pa−1)

VΦ × 106 (m3·mol−1)

0.0498 0.1521 0.2488 0.3494 0.4476 0.5483 0.6491

109.34 109.39 109.41 109.47 109.55 109.65 109.72

−2.67 −2.67 −2.66 −2.63 −2.58 −2.53 −2.47

110.82 110.89 110.95 110.97 110.99 111.06 111.08

0.0499 0.1499 0.2493 0.3495 0.4496 0.5494 0.6492

109.81 109.80 109.79 109.78 109.78 109.76 109.74

−2.55 −2.47 −2.45 −2.43 −2.37 −2.34 −2.30

111.08 111.07 111.06 111.06 111.06 111.05 111.05

0.0476 0.1491 0.2498 0.3499 0.4471 0.5167 0.6480

110.12 110.10 109.99 109.89 109.86 109.83 109.81

−2.25 −2.25 −2.19 −2.16 −2.13 −2.12 −2.12

111.36 111.33 111.26 111.25 111.24 111.23 111.21

0.0497 0.1496 0.2486 0.3495 0.4490 0.5501 0.6486

110.34 110.29 110.10 110.06 109.94 109.88 109.86

−2.05 −2.01 −2.00 −1.99 −1.98 −1.96 −1.94

111.49 111.42 111.41 111.38 111.36 111.34 111.33

0.0501 0.1498 0.2481 0.3486 0.4491 0.5499 0.6476

110.12 109.91 109.83 109.81 109.80 109.78 109.73

−2.47 −2.45 −2.37 −2.34 −2.29 −2.27 −2.22

111.29 111.14 111.07 111.06 111.04 110.97 110.96

0.0508 0.1503 0.2491 0.3507 0.4500 0.5459 0.6480

110.41 110.20 110.04 109.92 109.88 109.86 109.82

−2.19 −2.15 −2.11 −2.06 −2.04 −1.99 −1.94

111.59 111.40 111.33 111.25 111.19 111.17 111.12

0.0507 0.1492 0.2482 0.3497 0.4531 0.5522 0.6497

110.78 110.46 110.29 110.23 110.19 110.12 110.05

−1.97 −1.89 −1.87 −1.80 −1.79 −1.76 −1.74

111.86 111.70 111.59 111.52 111.51 111.51 111.42

T = 308.15 K

KΦ × 1014 (m3·mol−1·Pa−1)

mIL

mIL

mIL

mIL

mIL

mIL

VΦ × 106 (m3·mol−1)

In Water −2.09 112.06 −2.05 112.09 −2.04 112.16 −1.95 112.17 −1.89 112.21 −1.86 112.21 −1.82 112.23 [BMIm]Br = 0.1005 mol·kg−1 −1.95 112.64 −1.90 112.63 −1.83 112.55 −1.80 112.45 −1.79 112.44 −1.78 112.39 −1.68 112.33 = 0.2004 mol·kg−1 −1.66 112.73 −1.65 112.66 −1.63 112.59 −1.62 112.56 −1.55 112.49 −1.55 112.47 −1.43 112.41 = 0.3001 mol·kg−1 −1.49 112.84 −1.48 112.73 −1.47 112.66 −1.46 112.62 −1.44 112.55 −1.44 112.49 −1.38 112.47 [OMIm]Br = 0.1009 mol·kg−1 −1.86 112.85 −1.79 112.59 −1.74 112.52 −1.72 112.40 −1.69 112.38 −1.68 112.36 −1.68 112.36 = 0.2009 mol·kg−1 −1.60 112.96 −1.58 112.78 −1.55 112.60 −1.51 112.44 −1.49 112.43 −1.45 112.41 −1.41 112.36 = 0.2975 mol·kg−1 −1.47 113.12 −1.44 112.87 −1.44 112.70 −1.40 112.63 −1.37 112.58 −1.36 112.56 −1.34 112.49 C

T = 318.15 K

KΦ × 1014 (m3·mol−1·Pa−1)

VΦ × 106 (m3·mol−1)

KΦ × 1014 (m3·mol−1·Pa−1)

−1.58 −1.51 −1.47 −1.43 −1.39 −1.32 −1.27

113.23 113.31 113.36 113.39 113.40 113.45 113.50

−1.19 −1.11 −1.09 −1.03 −0.96 −0.95 −0.90

−1.51 −1.47 −1.42 −1.35 −1.28 −1.24 −1.24

113.59 113.56 113.55 113.54 113.51 113.51 113.51

−1.01 −1.00 −0.97 −0.89 −0.87 −0.84 −0.83

−1.38 −1.30 −1.21 −1.18 −1.14 −1.12 −1.08

113.72 113.69 113.62 113.59 113.57 113.55 113.52

−0.87 −0.82 −0.81 −0.78 −0.76 −0.74 −0.71

−1.08 −1.07 −1.04 −1.01 −1.00 −0.99 −0.96

113.84 113.72 113.67 113.63 113.60 113.57 113.55

−0.67 −0.66 −0.65 −0.64 −0.64 −0.63 −0.63

−1.29 −1.28 −1.28 −1.23 −1.21 −1.18 −1.13

113.89 113.81 113.69 113.68 113.67 113.65 113.47

−0.93 −0.91 −0.89 −0.88 −0.80 −0.78 −0.76

−1.19 −1.13 −1.11 −1.07 −1.02 −0.98 −0.97

114.16 113.99 113.87 113.73 113.71 113.65 113.61

−0.68 −0.65 −0.64 −0.64 −0.63 −0.62 −0.60

−1.03 −1.02 −1.01 −1.01 −0.96 −0.92 −0.91

114.29 114.09 113.95 113.81 113.75 113.74 113.68

−0.63 −0.63 −0.62 −0.59 −0.61 −0.60 −0.56



Article

Table 2. continued T = 288.15 K mf (mol·kg−1)

VΦ × (m3·mol ) 106 −1

KΦ × 1014 3 −1 −1

(m ·mol ·Pa )

T = 298.15 K VΦ × (m3·mol ) 106 −1

0.0507 0.1495 0.2499 0.3479 0.4486 0.5432 0.6484

109.76 109.74 109.71 109.69 109.68 109.65 109.63

−2.57 −2.50 −2.46 −2.36 −2.32 −2.27 −2.27

111.13 111.12 111.11 111.11 111.09 111.09 111.06

0.0507 0.1508 0.2489 0.3494 0.4491 0.5465 0.6450

109.91 109.86 109.84 109.83 109.82 109.80 109.77

−2.33 −2.30 −2.28 −2.18 −2.08 −2.03 −1.99

111.34 111.27 111.24 111.21 111.19 111.16 111.13

0.0505 0.1492 0.2448 0.3496 0.4488 0.5497 0.6491

110.46 110.38 110.28 110.27 110.22 110.15 110.15

−2.11 −2.01 −1.90 −1.83 −1.77 −1.76 −1.73

111.69 1 11.67 111.64 111.60 111.60 111.58 111.56

T = 308.15 K

KΦ × 1014 3 −1 −1

(m ·mol ·Pa )

VΦ × (m3·mol ) 106 −1

[OMIm]Cl mIL = 0.1008 mol·kg−1 −2.03 112.48 −1.98 112.47 −1.82 112.45 −1.77 112.37 −1.71 112.30 −1.67 112.29 −1.66 112.29 mIL = 0.2001 mol·kg−1 −1.72 112.60 −1.64 112.55 −1.64 112.50 −1.49 112.44 −1.49 112.40 −1.43 112.36 −1.42 112.33 mIL = 0.3004 mol·kg−1 −1.60 112.88 −1.49 112.83 −1.45 112.75 −1.35 112.73 −1.30 112.59 −1.27 112.53 −1.22 112.52

KΦ × 1014 3 −1 −1

T = 318.15 K

(m ·mol ·Pa )

VΦ × 106 (m3·mol−1)

KΦ × 1014 (m3·mol−1·Pa−1)

−1.54 −1.46 −1.39 −1.35 −1.29 −1.19 −1.17

113.44 113.33 113.33 113.27 113.25 113.22 113.20

−1.15 −1.13 −0.97 −0.91 −0.86 −0.85 −0.80

−1.39 −1.35 −1.30 −1.23 −1.16 −1.12 −1.06

113.91 113.72 113.62 113.39 113.32 113.29 113.28

−0.93 −0.92 −0.91 −0.91 −0.85 −0.81 −0.79

−1.22 −1.16 −1.08 −1.01 −0.95 −0.91 −0.90

113.95 113.87 113.78 113.77 113.62 113.59 113.60

−0.83 −0.76 −0.71 −0.69 −0.63 −0.61 −0.59

to releasing of some electrostricted water molecules to the bulk by increasing temperature. Partial molar volumes of fructose (V̅ 2) in binary and ternary solutions can be calculated using apparent molar volumes as follows37

Among the studied ionic liquids, [OMIm]Br due to weaker interaction with water is expected to have stronger interaction with fructose. The higher V0Φ values obtained for fructose in aqueous [OMIm]Br solution fulfill this expectation. Our results in regard to the effect of chain length of ionic liquid on saccharide−ionic liquid interactions are consistent with the volumetric and viscometric results obtained by Shekaari and co-workers.22,23 They studied the density and viscosity of ternary {D-xylose + ionic liquids 1-hexyl-3-methylimidazolium bromide or 1-octyl-3-methylimidazolium bromide or 1-decyl3-methylimidazoliume bromide + water} systems.22 Their results showed that the standard partial molar volumes (V0Φ) and the viscosity B-coefficient values increase as the alkyl chain length increases, which indicate that when the chain length of ionic liquid increases, D-xylose ionic liquid interactions become stronger.22 In other study, they showed that the standard partial molar volumes of glucose in the presence of ionic liquid 1-hexyl-3-methylimidazolium bromide have higher values in comparison to ionic liquid 1-pentyl-3-methylimidazolium bromide. 23 Our results are also consistent with the Kazempour36 results in regard to the volumetric and viscometric properties of D-glucose in ternary aqueous solutions containing ionic liquids [HMIm]Br and [HMIm]Cl. They showed that standard partial molar volumes and viscosity B-coefficient values of D-glucose in the presence of ionic liquid [HMIm]Br are higher than the corresponding values in the presence of ionic liquid [HMIm]Cl, which mean that [HMIm]Br−glucose interactions are stronger than [HMIm]Cl−glucose interactions.36 A close examination of Figure 2 shows that increasing temperature leads to increase in V0Φ values. This may be related

i ∂V y V2 = VΦ + mjjj Φ zzz k ∂m {

(3)

Table 4 enlists the computed V̅ 2 values at different molalities of ionic liquids. It shows that the V̅ 2 values have a similar trend to VΦ values. To have a clear picture regarding fructose−ionic liquid interactions, the transfer volume, ΔtrV0Φ, for fructose from water to aqueous ionic liquid solutions is computed as follows Δtr V Φ0 = V Φ0 (in aqueous ionic liquid solution) − V Φ0 (in water)

(4)

According to Table 3, a positive value for ΔtrV0Φ is observed at all ionic liquid molalities. Based on the cosphere overlap model,38 in ternary solutions, different interactions between fructose and ionic liquids can occur: (i) hydrophobic−ionic; (ii) hydrophobic−hydrophobic; (iii) hydrophilic−ionic; and (iv) hydrophilic−hydrophobic interactions. Following this model, interactions of types (i), (ii), and (iv) result a negative ΔtrV0Φ, whereas the interaction of type (iii) would result a positive ΔtrV0Φ. The positive values obtained for ΔtrV0Φ indicate that hydrophilic−ionic interactions are stronger than other interactions. Further, increasing ΔtrV0Φ values with the ionic liquid concentration shows that increasing the ionic liquid molality leads to strengthening of hydrophilic−ionic interactions. Furthermore, the same trend is observed for ΔtrV0Φ D



Article

Table 3. Standard Partial Molar Volume (V0Φ), Experimental Slope (Sv), Transfer Volumes (ΔtrV0Φ), and Partial Molar Expansion (E0Φ) of Fructose in Water and Aqueous Ionic Liquids [BMIm]Br, [OMIm]Br, and [OMIm]Cl Solutions at T = 288.15−318.15 Ka,b,c,d,e,f T (K)

V0Φ × 106 (m3·mol−1)f

288.15

109.25 ± 0.04 110.18a ± 0.01 109.54b 110.82 ± 0.01 111.09a ± 0.02 110.99b 111.06c ± 0.06 110.88d 110.7e 112.06 ± 0.01 112.12c ± 0.02 113.32 ± 0.03 112.94a ± 0.004 112.96c ± 0.08

298.15

308.15 318.15

Sv × 106 (m3·mol−2·kg)f

σ(VΦ) × 106 (m3·mol−1)f

Δtr(V0Φ) × 106 (m3·mol−1)

E0Φ × 106 (m3·mol−1·K−1)

0.80 ± 0.10g

Water 0.06

0.16

0.41 ± 0.04g

0.02

0.14

0.29 ± 0.03g

0.02

0.13

1.06 ± 0.08g

0.04

0.11

288.15 298.15 308.15 318.15

109.82 111.08 112.68 113.58

± ± ± ±

0.01 0.01 0.02 0.01

−0.11 −0.05 −0.54 −0.13

± ± ± ±

0.01 0.01 0.05 0.02

288.15 298.15 308.15 318.15

110.15 111.35 112.74 113.72

± ± ± ±

0.03 0.02 0.01 0.01

−0.59 −0.25 −0.53 −0.34

± ± ± ±

0.07 0.04 0.03 0.03

288.15 298.15 308.15 318.15

110.37 111.47 112.84 113.80

± ± ± ±

0.03 0.01 0.02 0.03

−0.86 −0.24 −0.61 −0.43

± ± ± ±

0.09 0.03 0.05 0.07

288.15 298.15 308.15 318.15

110.04 111.25 112.77 113.89

± ± ± ±

0.05 0.03 0.06 0.04

−0.53 −0.49 −0.79 −0.58

± ± ± ±

0.13 0.08 0.16 0.10

288.15 298.15 308.15 318.15

110.35 111.55 112.91 114.13

± ± ± ±

0.06 0.04 0.07 0.05

−0.94 −0.72 −0.97 −0.89

± ± ± ±

0.16 0.10 0.17 0.12

288.15 298.15 308.15 318.15

110.67 111.81 113.04 114.24

± ± ± ±

0.08 0.05 0.06 0.07

−1.06 −0.64 −0.94 −0.98

± ± ± ±

0.19 0.12 0.17 0.15

288.15 298.15 308.15 318.15

109.77 111.14 112.51 113.42

± ± ± ±

0.01 0.01 0.02 0.02

−0.23 −0.11 −0.39 −0.37

± ± ± ±

0.01 0.01 0.05 0.05

288.15 298.15 308.15 318.15

109.91 111.33 112.62 113.89

± ± ± ±

0.01 0.01 0.01 0.06

−0.21 −0.33 −0.47 −1.11

± ± ± ±

0.02 0.03 0.02 0.16

[BMIm]Br mIL = 0.1005 mol·kg−1 0.01 0.01 0.03 0.01 mIL = 0.2004 mol·kg−1 0.04 0.02 0.01 0.02 mIL = 0.3001 mol·kg−1 0.05 0.02 0.03 0.03 [OMIm]Br mIL = 0.1009 mol·kg−1 0.07 0.04 0.08 0.05 mIL = 0.2009 mol·kg−1 0.08 0.05 0.09 0.06 mIL = 0.2975 mol·kg−1 0.10 0.06 0.09 0.08 [OMIm]Cl mIL = 0.1008 mol·kg−1 0.01 0.01 0.03 0.03 mIL = 0.2001 mol·kg−1 0.01 0.02 0.01 0.08

E

0.57 0.26 0.62 0.26

0.15 0.14 0.12 0.10

0.91 0.53 0.68 0.42

0.14 0.13 0.12 0.10

1.10 0.81 0.72 0.45

0.13 0.12 0.11 0.11

0.79 0.43 0.71 0.57

0.14 0.13 0.13 0.12

1.10 0.73 0.85 0.81

0.13 0.13 0.13 0.13

1.42 0.99 0.98 0.92

0.11 0.12 0.12 0.12

0.52 0.32 0.45 0.10

0.16 0.13 0.11 0.09

0.66 0.51 0.56 0.57

0.14 0.14 0.13 0.12



Article

Table 3. continued T (K)

V0Φ × 106 (m3·mol−1)f

Sv × 106 (m3·mol−2·kg)f

σ(VΦ) × 106 (m3·mol−1)f

Δtr(V0Φ) × 106 (m3·mol−1)

E0Φ × 106 (m3·mol−1·K−1)

1.20 0.87 0.86 0.64

0.13 0.12 0.11 0.10

−1

288.15 298.15 308.15 318.15

110.45 111.69 112.92 113.96

± ± ± ±

−0.51 −0.21 −0.66 −0.63

0.02 0.01 0.02 0.03

± ± ± ±

0.06 0.02 0.06 0.08

mIL = 0.3004 mol·kg 0.03 0.01 0.03 0.04

i ∑in=Dat1 (Q exp − Q cal)2 yz zz Ref 31. bRef 32. cRef 33. dRef 34. eRef 35. fThe standard deviation (σ) issuing from the fits: σ = jjjj z nDat k {

1/2

a

errors for V0Φ: std err(m , VΦ).

1 nDat

+

, errors for Sv:

std err(m , VΦ) ∑(m − m̅ )2

,

2

m̅ ∑(m − m̅ )2

, in which nDat is the number of experimental points.

Figure 1. (a) Standard partial molar volumes of fructose (V0Φ) vs ionic liquid molality (m) in aqueous ionic liquid [BMIm]Br and [OMIm]Br solutions at T = 298.15 K: ⧫, [BMIm]Br; ▲, [OMIm]Br. (b) Standard partial molar volumes of fructose (V0Φ) vs ionic liquid molality (m) in aqueous ionic liquid [OMIm]Br and [OMIm]Cl solutions at T = 298.15 K: ×, [OMIm]Cl; ▲, [OMIm]Br.

Vintrinsic = VVW + Vvoid

where Vvw is the van der Waals volume, Vvoid is the volume associated with voids, and Vshrinkage is the volume of shrinkage caused by interaction of hydrogen-bonding groups of fructose with water. If it is assumed that Vintrinsic is approximately same in water and aqueous ionic liquid solutions, ΔtrV0Φ can be found as: ΔtrV0Φ = −ΔVshrinkage. In fact, the increase in the ΔtrV0Φ values may be attributed to decrease in Vshrinkage. This indicates that fructose−water interactions become weak in the presence of studied ionic liquids. To have a clear picture in regard to the volume contributions involved in V0Φ, the scaled particle theory (SPT) was used.40 In this theory, the solvation process of solute in a solvent occurs in two steps: (i) formation of a cavity in the solvent for the solute and (ii) interaction of solute with the solvent. The following equation is used to express the standard partial molar volume of solute, V0Φ40

Figure 2. Variation of standard partial molar volumes of fructose, V0Φ, in aqueous ionic liquid solutions at different temperatures and at mIL = 0.2 mol·kg−1 of ionic liquids: ▲, [BMIm]Br; ⧫, [OMIm]Br; ×, [OMIm]Cl. 0 0 values and VΦ0 as: ΔtrVΦ[OMIm]Br > ΔtrVΦ[BMIm]Br and ΔtrV0Φ[OMIm]Br > ΔtrV0Φ[OMIm]Cl. This trend shows that hydrophilic−ionic interactions between fructose and [OMIm]Br are stronger than the corresponding interactions between fructose and ionic liquids [BMIm]Br or [OMIm]Cl. In fact, due to attractive interactions between fructose and ionic liquids, water molecules are released from the hydration layer to the bulk. The released water molecules contribute a higher volume compared to those in the hydration layer, so ΔtrV0Φ values increase. According to the equation proposed by Shahidi, the V0Φ values can be expressed as39

V φ0 = Vintrinsic − Vshrinkage

(6)

V Φ0 = Vcav + Vint + κT·R ·T

(7)

where Vcav and Vint are the volume contributions due to cavity formation and the solute−solvent interactions, respectively, and κT and R represent the isothermal compressibility of a solvent and the gas constant, respectively. The cavity volume (Vcav) is calculated using eq 8.41 In this equation, y represents the ratio of the volume occupied by 1 mol of hard sphere solvent particles to the molar volume of solvent shown in eq 9, z is the ratio of the hard sphere diameters of solute (σ2) and solvent (σ1), NA is Avogadro’s constant, and V01 denotes the molar volume of solvent.

(5) F



Article

Table 4. Partial Molar Volumes (V̅ 2) of Fructose in Water and Aqueous Ionic Liquids [BMIm]Br, [OMIm]Br, and [OMIm]Cl Solutions at T = 288.15−318.15 K V̅ 2 × 106 (m3·mol−1) mf (mol·kg−1)

T = 288.15 K

0.0498 0.1521 0.2488 0.3494 0.4476 0.5483 0.6491

109.37 109.49 109.57 109.70 109.84 110.00 110.14

0.0476 0.1491 0.2498 0.3499 0.4471 0.5167 0.6480

109.80 109.78 109.76 109.74 109.73 109.70 109.67

0.0476 0.1491 0.2498 0.3499 0.4471 0.5167 0.6480

110.09 110.01 109.84 109.69 109.60 109.53 109.43

0.0497 0.1496 0.2486 0.3495 0.4490 0.5501 0.6486

110.30 110.16 109.89 109.76 109.55 109.40 109.30

0.0501 0.1498 0.2481 0.3486 0.4491 0.5499 0.6476

110.09 109.83 109.70 109.63 109.57 109.49 109.39

T = 298.15 K

mIL

mIL

mIL

mIL

Vcav

T = 308.15 K

In Water 110.84 112.07 110.95 112.13 111.05 112.23 111.12 112.27 111.18 112.34 111.29 112.37 111.35 112.42 [BMIm]Br = 0.1005 mol·kg−1 111.08 112.61 111.06 112.55 111.05 112.41 111.04 112.26 111.04 112.20 111.02 112.09 111.02 111.98 = 0.2004 mol·kg−1 111.35 112.70 111.29 112.58 111.20 112.46 111.16 112.38 111.13 112.25 111.10 112.20 111.05 112.07 = 0.3001 mol·kg−1 111.48 112.81 111.38 112.64 111.35 112.51 111.29 112.41 111.25 112.28 111.20 112.16 111.17 112.08 [OMIm]Br = 0.1009 mol·kg−1 111.27 112.81 111.07 112.47 110.95 112.33 110.89 112.13 110.82 112.03 110.70 111.93 110.64 111.81

V̅ 2 × 106 (m3·mol−1) mf (mol·kg−1)

T = 318.15 K

0.0508 0.1503 0.2491 0.3507 0.4500 0.5459 0.6480

110.36 110.06 109.81 109.59 109.46 109.35 109.21

0.0507 0.1492 0.2482 0.3497 0.4531 0.5522 0.6497

110.73 110.30 110.03 109.86 109.71 109.54 109.36

113.70 113.64 113.53 113.47 113.42 113.37 113.30

0.0501 0.1498 0.2481 0.3486 0.4491 0.5499 0.6476

109.75 109.71 109.66 109.62 109.58 109.53 109.49

113.82 113.65 113.56 113.48 113.40 113.33 113.26

0.0507 0.1508 0.2489 0.3494 0.4491 0.5465 0.6450

109.90 109.83 109.79 109.76 109.73 109.69 109.64

0.0505 0.1492 0.2448 0.3496 0.4488 0.5497 0.6491

110.43 110.30 110.15 110.09 109.99 109.87 109.81

113.25 113.37 113.46 113.53 113.58 113.67 113.76

113.58 113.54 113.52 113.49 113.45 113.44 113.42

113.86 113.72 113.55 113.48 113.41 113.34 113.10

z=

κT =

πσ13NA

σ2 σ1

(9)

(10)

V10(1 − y)4 RT (1 + 2y)2

T = 308.15 K

T = 318.15 K

mIL = 0.2009 mol·kg 111.55 112.91 111.29 112.63 111.15 112.36 111.00 112.10 110.86 111.99 110.78 111.88 110.65 111.73 mIL = 0.2975 mol·kg−1 111.83 113.07 111.61 112.73 111.43 112.47 111.30 112.30 111.22 112.16 111.16 112.04 111.01 111.88 [OMIm]Cl mIL = 0.1008 mol·kg−1 111.12 112.46 111.10 112.41 111.08 112.35 111.07 112.24 111.04 112.13 111.03 112.08 110.99 112.04 mIL = 0.2001 mol·kg−1 111.32 112.58 111.22 112.48 111.16 112.38 111.1 112.28 111.04 112.19 110.98 112.11 110.92 112.03 mIL = 0.3004 mol·kg−1 111.68 112.85 111.64 112.73 111.59 112.59 111.52 112.50 111.50 112.30 111.46 112.17 111.42 112.09

114.11 113.86 113.65 113.42 113.31 113.16 113.03 114.24 113.94 113.71 113.47 113.31 113.20 113.05

113.42 113.28 113.24 113.14 113.09 113.02 112.96 113.85 113.55 113.35 113.01 112.83 112.69 112.57 113.92 113.78 113.63 113.55 113.34 113.24 113.19

The hard sphere diameter of studied ionic liquids and fructose is computed using the group contribution method.42 The hard sphere diameter of water is taken from the literature.43 The values of κT have been calculated using eq 11.44 The mixing rule proposed by Ali and Bidhuria was used to calculate y.45 In Table 5, the computed Vcav and Vint values at different ionic liquid concentrations at T = 298.15 K are reported. The results show that compared to pure water, in the presence of all studied ionic liquids, the Vint values become less negative. This confirms that fructose−water interactions become weaker in the presence of ionic liquids. In the case of ionic liquid [OMIm]Br, the Vint values are less negative than the corresponding values of other studied ionic liquids. This indicates that in the presence of ionic liquid [OMIm]Br,

(8)

6V10

T = 298.15 K

−1

ÉÑ ÄÅ ÅÅ y 3yz(1 + z) 9y 2 z 2 ÑÑÑ πσ23NA Å ÑÑ + Å = κTRT ÅÅ + + ÅÅ 1 − y 6 (1 − y)2 (1 − y)3 ÑÑÑÑÖ ÅÇ

y=

T = 288.15 K

(11) G



Article

Table 5. Cavity Volumes, Vcav × 106 (m3·mol−1), and Interaction Volumes, Vint × 106 (m3·mol−1), of Fructose in Water and Aqueous Ionic Liquid [BMIm]Br, [OMIm]Br, and [OMIm]Cl Solutions at T = 298.15 K mIL (mol·kg−1)

Vcav × 106 (m3·mol−1) Water 141.033 [BMIm]Br 141.666 141.582 141.496 [OMIm]Br 141.570 141.392 141.242 [OMIm]Cl 141.576 141.405 141.245

0.0 0.1 0.2 0.3 0.1 0.2 0.3 0.1 0.2 0.3

Table 6. Paired Volumetric Interaction Parameter VAI and Triplet Volumetric Interaction Parameter VAII of Fructose in Aqueous Ionic Liquids [BMIm]Br, [OMIm]Br, and [OMIm]Cl Solutions at T = 288.15−318.15 K

Vint × 106 (m3·mol−1)

T (K)

VAI × 106 (m3·mol−2·kg)

−31.187

288.15 298.15 308.15 318.15

3.254 1.244 1.246 1.246

288.15 298.15 308.15 318.15

2.348 1.489 1.614 1.474

288.15 298.15 308.15 318.15

1.608 1.608 1.213 1.213

[BMIM]Br

−30.586 −30.232 −30.026

ij ∂V 0 yz EΦ0 = jjj Φ zzz j ∂T z k {P

−30.320 −29.842 −29.432

1 i ∂V y 1 κs = − jjj zzz = 2 V k ∂P {S du

κM (κsd − κs0d) + s mdd0 d

0.853 0.853 0.675 0.675

(16)

The speed of sound values for {fructose + water} and {fructose + ionic liquid + water} solutions are given in Tables S1−S3. The speed of sound data for binary {D-fructose + water} solutions together with literature data are illustrated in Figure S12.27 By fitting the experimental speed of sound data measured in this work to a polynomial function (y = a + bx + cx2), the RMSD % values of 0.022, 0.016, 0.022, and 0.020 are obtained at T = 288.15, 298.15, 308.15, and 318.15 K, respectively. Plots of deviations of measured and literature speed of sound values from the u(mfructose) fits of measured data to the corresponding polynomial function are shown in Figures S13−S16. The KΦ values for fructose in binary and ternary solutions at studied temperatures are given in Table 2. The results reported in this table show that both temperature and molality of ionic liquid increase KΦ values. From extrapolation of KΦ values to zero concentration, the standard partial molar isentropic compression K0Φ is obtained by the following equation30

(12)

(13)

(14)

where A denotes fructose, I represents ionic liquid, mB is the molality of ionic liquid, and VAI and VAII are the paired and triplet volumetric interaction parameters, respectively. By fitting the ΔtrV0Φ values to ionic liquid molality, volumetric interaction parameters were obtained. These parameters are reported in Table 6. The large positive VAI values suggest that the interactions between fructose and studied ionic liquids are mainly pairwise. 3.2. Acoustic Properties. Acoustic properties can also provide some information in regard to fructose−water interactions in binary and fructose−ionic liquid interactions in ternary solutions. Based on the speed of sound u and densities of solvent and solution, the apparent molar isentropic compression, KΦ, values of fructose can be calculated as47 KΦ =

0.628 0.647 0.759 0.758 [OMIM]Cl

−30.436 −30.075 −29.555

In eq 12, A, B, and C are empirical parameters. The calculated E0Φ values are reported in Table 3. It shows that the E0Φ values in binary and ternary solutions are positive. Positive E0Φ means that at higher temperatures, some water molecules from the hydration layers of fructose are released into the bulk. The McMillan−Mayer theory46 of solutions can be used to express transfer volumes of fructose by the following equation Δtr V φ0 = 2VAI + 3VAIImB

−3.173 0.243 0.238 0.238 [OMIM]Br

fructose−water interactions become weaker than the corresponding interactions in the case of other ionic liquids. By differentiating eq 12 with respect to temperature at constant pressure, the partial molar expansion E0Φ can be obtained V Φ0 = A + BT + CT 2

VAII × 106 (m3·mol−3·kg2)

K Φ = K Φ0 + S km

(17)

where Sk is the experimental slope. The values of K0Φ and Sk at different temperatures and ionic liquid molalities are reported in Table 7. The values of K0Φ for fructose in water show a fairly good compatibility with the literature.48−50 The results show that the K0Φ values in pure water are negative. The reason for this behavior is the attractive interactions between fructose and water that reduce the compressibility and lead to negative K0Φ values. In ternary solution, the stronger attractive interactions between ionic liquids and fructose cause release of water molecules from the solvation layer of the fructose and thereby increase the compressibility of the medium, so K0Φ values become less negative. For ionic liquids [OMIm]Br and [OMIm]Cl, the K0Φ values of fructose increase by changing the anion type from Cl− to Br−. For ionic liquids [OMIm]Br and [BMIm]Br, by increasing the chain length of ionic liquid from butyl to octyl, the K0Φ values increase. These results are consistent with the volumetric properties studied in the above section. The concentration and temperature dependences of

(15)

κ0s

where and κs stand for isentropic compressibility of the solvent and solution, respectively. The values of κs can be computed according to the Laplace−Newton equation H



Article

Table 7. Values of Standard Partial Molar Isentropic Compression (K0Φ), Experimental Slope (Sk) Standard Deviations σ(KΦ), Hydration Number (nH), and Partial Molar Isentropic Compression of Transfer ΔtrK0Φ of Fructose in Water and Aqueous Ionic Liquids [BMIm]Br, [OMIm]Br, and [OMIm]Cl Solutions at T = 288.15−318.15 Ka,b,c,d T (K)

K0Φ × 1014 (m3·mol−1·Pa−1)d

Sk × 1014 (m3·mol−2·Pa−1·kg)d

σ(KΦ) × 1014 (m3·mol−1·Pa−1)d

288.15

−2.72 ± 0.02 −3.05a ± 0.01 −2.94b −2.12 ± 0.01 −2.20a ± 0.01 −2.2c ± 0.1 −2.14b −1.60 ± 0.01 −1.67a ± 0.01 −1.19 ± 0.01 −1.20a ± 0.01

0.36 ± 0.06

0.03

3.24

0.48 ± 0.03

0.02

2.62

0.49 ± 0.02

0.01

2.03

0.52 ± 0.03

0.02

1.53

0.01 0.03 0.03 0.02

3.06 2.42 1.95 1.32

0.17 0.17 0.06 0.16

0.02 0.03 0.03 0.01

2.72 2.12 1.74 1.11

0.46 0.41 0.23 0.32

0.01 0.01 0.01 0.01

2.48 1.87 1.39 0.85

0.67 0.62 0.51 0.52

0.01 0.03 0.01 0.02

2.99 2.28 1.67 1.21

0.23 0.28 0.28 0.24

0.01 0.01 0.01 0.01

2.67 2.01 1.51 0.86

0.51 0.50 0.40 0.51

0.02 0.01 0.02 0.01

2.35 1.81 1.32 0.80

0.76 0.64 0.54 0.55

0.03 0.05 0.02 0.04

3.10 2.53 1.98 1.50

0.14 0.08 0.04 0.02

0.03 0.03 0.01 0.02

2.89 2.15 1.81 1.22

0.33 0.39 0.17 0.23

0.04 0.03 0.03

2.54 1.98 1.54

0.63 0.52 0.37

nH

ΔtrK0Φ × 1014 (m3·mol−1·Pa−1)

Water

298.15

308.15 318.15

[BMIm]Br mIL = 0.1005 mol·kg−1 −2.55 −1.95 −1.54 −1.03

± ± ± ±

0.01 0.02 0.02 0.02

288.15 298.15 308.15 318.15

−2.26 −1.71 −1.37 −0.87

± ± ± ±

0.01 0.03 0.02 0.01

288.15 298.15 308.15 318.15

−2.05 −1.50 −1.09 −0.67

± ± ± ±

0.01 0.01 0.01 0.01

288.15 298.15 308.15 318.15

± ± ± ±

0.03 0.05 0.05 0.04

0.25 0.36 0.48 0.25

± ± ± ±

0.03 0.06 0.05 0.02

0.17 0.15 0.21 0.07

± ± ± ±

0.02 0.03 0.02 0.01

0.39 0.39 0.51 0.33

mIL = 0.2004 mol·kg−1

mIL = 0.3001 mol·kg−1

[OMIm]Br mIL = 0.1009 mol·kg−1 288.15 298.15 308.15 318.15

−2.49 −1.84 −1.32 −0.95

± ± ± ±

0.01 0.02 0.01 0.01

0.42 0.29 0.26 0.3

± ± ± ±

0.03 0.05 0.03 0.03

288.15 298.15 308.15 318.15

−2.21 −1.62 −1.20 −0.68

± ± ± ±

0.01 0.01 0.01 0.01

0.41 0.32 0.38 0.11

± ± ± ±

0.01 0.01 0.02 0.01

288.15 298.15 308.15 318.15

−1.96 −1.48 −1.06 −0.64

± ± ± ±

0.02 0.01 0.01 0.01

0.36 0.22 0.22 0.10

±0.04 ± 0.02 ± 0.03 ± 0.03

mIL = 0.2009 mol·kg−1

mIL = 0.2975 mol·kg−1

[OMIm]Cl mIL = 0.1008 mol·kg−1 288.15 298.15 308.15 318.15

−2.58 −2.04 −1.56 −1.17

± ± ± ±

0.02 0.03 0.01 0.03

0.54 0.66 0.63 0.61

± ± ± ±

0.05 0.09 0.03 0.08

288.15 298.15 308.15 318.15

−2.39 −1.73 −1.43 −0.96

± ± ± ±

0.02 0.03 0.01 0.01

0.62 0.53 0.58 0.26

± ± ± ±

0.06 0.07 0.02 0.04

288.15 298.15 308.15

−2.09 ± 0.03 −1.60 ± 0.02 −1.23 ± 0.02

mIL = 0.2001 mol·kg−1

mIL = 0.3004 mol·kg−1

0.63 ± 0.08 0.63 ± 0.05 0.56 ± 0.05 I



Article

Table 7. continued T (K)

K0Φ × 1014 (m3·mol−1·Pa−1)d

Sk × 1014 (m3·mol−2·Pa−1·kg)d

σ(KΦ) × 1014 (m3·mol−1·Pa−1)d

nH

ΔtrK0Φ × 1014 (m3·mol−1·Pa−1)

1.04

0.36

−1

mIL = 0.3004 mol·kg −0.83 ± 0.01

0.39 ± 0.04

i Ref 48. bRef 49. cRef 50. dThe standard deviation (σ) issuing from the fits: σ = jjjj k 318.15

a

std err(m , K )Φ .

1 nDat

+

0.02 2 ∑in=Dat 1 (Q exp − Q cal)

nDat

yz zz z {

1/2

, errors for Sk:

std err(m , K Φ) ∑(m − m̅ )2

, errors for K0Φ:

2

m̅ ∑(m − m̅ )2

, where nDat is the number of experimental points.

Figure 3. (a) Standard partial molar isentropic compression of fructose (K0Φ) vs ionic liquid molality (m) at T = 298.15 K: ▲, [BMIm]Br; ⧫, [OMIm]Br. (b) Standard partial molar isentropic compression of fructose (K0Φ) vs ionic liquid molality (m) at T = 298.15 K: ×, [OMIm]Cl; ⧫, [OMIm]Br.

K0Φ for these systems are illustrated in Figures 3 and 4, respectively. These figures show that the K0Φ values increase with increasing ionic liquid molality and temperature.

that the ionic−hydrophilic interactions are dominant in these systems. In addition, enhancement of ionic liquid molality leads to increase in ΔtrK0Φ values. Furthermore, a larger value for ΔtrK0Φ is observed in aqueous ionic liquid [OMIm]Br solutions. In fact, due to strong attractive interaction between fructose and ionic liquid [OMIm]Br, more water molecules from the solvation layer of the fructose are released to the bulk, which makes it difficult to compress the solution. These results are in agreement with the ones obtained from the volumetric properties discussed above. To evaluate the hydration behavior of fructose in these systems, the number of water molecules around fructose in both binary and ternary solutions nH is calculated. There are different procedures for the determination of hydration number,51−54 although different values for nH can be obtained depending on the used technique. In this study, hydration number values were computed according to the method proposed by Millero52 from the following equation

Figure 4. Variation of standard partial molar isentropic compression of fructose, K0Φ, in aqueous ionic liquid solutions with different temperatures and at mIL = 0.1 mol·kg −1: ▲, [BMIm]Br; ⧫, [OMIm]Br; ×, [OMIm]Cl.

nH =

−K Φ0 (elect. ) κs0V10

(19)

where κ0s is the isentropic compressibility of solvent, K0Φ(elect.) is the electrostriction standard partial molar compression, and V01 is the molar volume of the solvent. The obtained nH values for fructose in binary and ternary solutions at different temperatures are listed in Table 7. It is observed that the nH values in ternary solutions are less than those in binary solutions, which indicates that all studied ionic liquids show a dehydration effect on the studied systems. This indicates the predominance of attractive interactions between fructose and studied ionic liquids over weak fructose−water interactions. The nH values of fructose in the case of ionic liquid [OMIm]Br

Transfer of partial molar isentropic compression from water to the aqueous ionic liquid solutions has been computed as follows Δtr K Φ0 = K Φ0 (in aqueous ionic liquid) − K Φ0 (in water) (18)

The values of ΔtrK0Φ for studied solutions are presented in Table 7. Positive values were observed for ΔtrK0Φ at all temperatures and ionic liquid concentrations. According to the cosphere overlap model,38 the positive values of ΔtrK0Φ indicate J



Article

experimental viscosity data measured in this work. This may be due to differences in purity, source of fructose, experimental error, and differences in the viscometer used in this work. However, the data reported in ref 55 are more scattered. The R2 values for our viscosity data are 0.995, 0.994, 0.996, and 0.994 at T = 288.15, 298.15, 308.15, and 318.15 K, respectively. The R2 values for the data reported in ref 55 are 0.986, 0.980, 0.925 and 0.979 at T = 288.15, 298.15, 308.15, and 318.15 K, respectively. Plots of deviations of measured and literature values from the η(mfructose) fits of measured data to the polynomial function are shown in Figures S18−S21. The relative viscosity, ηr, is computed by using the Jones− Dole equation56 η = 1 + Ac1/2 + Bc ηr = η0 (20)

are less than the corresponding values in presence of ionic liquids [BMIm]Br and [OMIm]Cl, which confirm stronger fructose−[OMIm]Br interactions. The values of nH decrease by increasing temperatures and ionic liquid molalities. This demonstrates that the dehydration effect of the investigated ionic liquids on the aqueous fructose solutions increases by heating and ionic liquid concentrations. The effects of ionic liquid concentration and temperature on the nH values for fructose are illustrated in Figures 5 and 6, respectively. These results are in agreement with those obtained by volumetric and compressibility properties discussed above.

where η and η0 represent the viscosities of the solution and solvent, respectively, and c stands for the molarity of the solution. The A-coefficient and B-coefficients are attributed to solute−solute and solute−cosolute interactions, respectively.57,58 The A-coefficients are negligible for nonelectrolytes, so eq 20 is simplified to the following equation η = 1 + Bc ηr = η0 (21) The values of viscosity B-coefficients together with the literature data59,60 are reported in Table 8, which shows that in ternary solutions, the viscosity B-coefficients have larger values compared to their corresponding values in binary solutions, so it was concluded that fructose−ionic liquid interactions are stronger compared to fructose−water interactions. Among the studied ionic liquids, the greater viscosity B-coefficients are observed in aqueous ionic liquid [OMIm]Br solutions indicating stronger fructose−[OMIm]Br interactions. These results are in agreement with the volumetric and compressibility results discussed above. The viscosity Bcoefficients for these solutions at different ionic liquid concentrations at T = 298.15 K are illustrated in Figure 7. According to the theory proposed by Feakins and coworkers, the viscosity B-coefficient is represented by the equation61

Figure 5. Hydration number of fructose vs ionic liquid molality, in aqueous ionic liquid solutions at T = 298.15 K: ▲, [BMIm]Br; ⧫, [OMIm]Br; ×, [OMIm]Cl.

ij Δμ 0 ≠ − Δμ 0 ≠ yz 1 z zz B = (V1̅ 0 − V2̅ 0) + V1̅ 0jjjj 2 zz j RT k {

Figure 6. Hydration number of fructose in aqueous ionic liquid solutions with different temperatures and at mIL = 0.2 mol·kg −1: ▲, [BMIm]Br; ⧫, [OMIm]Br; ×, [OMIm]Cl.

(22)

V̅ 01

where is the molar volume of solvent (=∑(xiMi/d)), V̅ 02 0 (=VΦ) is the standard partial molar volume of the solute, xi and Mi are the mole fractions and molar masses of water and ionic liquids, and d is the density of the solvent mixture (ionic liquid + water). The free energies of activation per mole of the 0≠ solvent (Δμ0≠ 1 ) and the solute (Δμ2 ) are calculated from the 61 following equations

3.3. Viscometric Properties. Viscometric properties can be used to confirm volumetric and acoustic results by providing valuable information about interactions occurring in these systems. The obtained viscosity data (η) for {fructose + water} and {fructose + water + ionic liquid} solutions are reported in Tables S4−S6. The viscosity data for binary {fructose + water} solutions together with literature data are illustrated in Figure S17.55 By fitting the experimental viscosity data measured in this work to a polynomial function (y = a + bx + cx2), the RMSD % values of 0.185, 0.397, 0.156, and 0.250 are obtained at T = 288.15, 298.15, 308.15, and 318.15 K, respectively. Figure S17 indicates that viscosity values reported in ref 55 are systematically lower than the

Δμ10 ≠ = ΔG10 ≠ = RT ln Δμ20 ≠ = Δμ10 ≠ +

η0V1̅ 0 hNA

(23)

RT [B − (V1̅ 0 − V2̅ 0)] V1̅ 0

(24)

where h, NA, and η0 are Planck’s constant, Avogadro number, and the viscosity of the solvent, respectively. The calculated 0≠ values of Δμ0≠ 1 and Δμ2 are reported in Table 8. It is observed K



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0≠ Table 8. Viscosity B-Coefficients, Free Energy of Activation Per Mole of Solvent (Δμ0≠ 1 ), and the Solute (Δμ2 ) for Fructose in a,b,c Water and the Aqueous Solutions of [BMIm]Br, [OMIm]Br, and [OMIm]Cl at T = 288.15−318.15 K

T (K) 288.15 298.15

308.15

318.15

B (dm3·mol−1)c 0.547 ± 0.02 0.482a ± 0.001 0.519 ± 0.01 0.451a ± 0.001 0.603b 0.506 ± 0.01 0.420a ± 0.001 0.494b 0.496 ± 0.01 0.381a ± 0.001

288.15 298.15 308.15 318.15

0.641 0.579 0.549 0.532

± ± ± ±

288.15 298.15 308.15 318.15

0.646 0.582 0.553 0.533

± ± ± ±

288.15 298.15 308.15 318.15

0.661 0.617 0.579 0.557

± ± ± ±

288.15 298.15 308.15 318.15

0.643 0.606 0.564 0.527

± ± ± ±

σ(B) (dm3·mol−1)c

Δμ0≠ 1 (kJ·mol−1)


T (K)

Water 0.010 0.006

0.003

0.006

[BMIm]Br mIL = 0.1005 mol·kg−1 0.016 0.015 0.010 0.009 0.019 0.008 0.013 0.005 mIL = 0.2004 mol·kg−1 0.013 0.014 0.011 0.012 0.011 0.008 0.009 0.004 mIL = 0.3001 mol·kg−1 0.021 0.020 0.020 0.010 0.016 0.010 0.013 0.006 [OMIm]Br mIL = 0.1009 mol·kg−1 0.012 0.013 0.011 0.009 0.008 0.006 0.009 0.005

9.57 9.31 9.09 8.89

105.46 100.10 98.67 98.69

9.71 9.45 9.21 9.02

104.86 99.31 97.99 97.62

9.85 9.57 9.34 9.14

105.56 102.73 100.34 99.78

9.68 9.39 9.17 8.99

105.25 103.24 100.24 97.52

B (dm3·mol−1)c

288.15 298.15 308.15 318.15

0.647 0.610 0.571 0.537

± ± ± ±

288.15 298.15 308.15 318.15

0.662 0.647 0.582 0.574

± ± ± ±

288.15 298.15 308.15 318.15

0.637 0.605 0.557 0.523

± ± ± ±

288.15 298.15 308.15 318.15

0.645 0.607 0.568 0.535

± ± ± ±

288.15 298.15 308.15 318.15

0.652 0.622 0.570 0.556

± ± ± ±

σ(B) (dm3·mol−1)c

mIL = 0.2009 mol·kg−1 0.017 0.015 0.012 0.012 0.015 0.010 0.016 0.007 mIL =0.2975 mol·kg−1 0.03 0.020 0.02 0.009 0.02 0.012 0.02 0.013 [OMIm]Cl mIL = 0.1008 mol·kg−1 0.012 0.014 0.012 0.010 0.012 0.009 0.013 0.009 mIL = 0.2001 mol·kg−1 0.007 0.009 0.007 0.007 0.016 0.012 0.008 0.004 mIL = 0.3004 mol·kg−1 0.006 0.011 0.018 0.013 0.016 0.012 0.015 0.007



9.90 9.62 9.39 9.21

104.05 102.07 99.50 97.28

10.12 9.82 9.63 9.43

104.32 105.23 99.41 100.79

9.68 9.39 9.18 9.00

104.50 103.16 99.32 96.96

9.89 9.60 9.36 9.18

103.87 101.77 99.17 97.09

10.11 9.81 9.59 9.37

103.19 102.13 97.89 98.36

Ref 59. bRef 60. cThe standard deviation issuing from the fits: (σ), ÄÅ ÉÑ1/2 Å Ñ n σ = ÅÅÅ ∑i =Dat1 (Q exp − Q cal)2 /nDat ÑÑÑ ; errors for viscosity B-coefÅÇ ÑÖ ficients, std err(m , η)2 , where nDat is the number of experimental points. a

(

)

∑(m − m̅ )

4. CONCLUSIONS In this study, to investigate the salt effect of ionic liquids 1butyl-3-methylimidazolum bromide, 1-octyl-3-methylimidazolum bromide, and 1-octyl-3-methylimidazolum chloride on aqueous fructose solutions, volumetric, compressibility, and viscometric properties have been obtained for {fructose + water} and {fructose + ionic liquid + water} solutions at various molalities of ionic liquids and temperatures. From the measured density, speed of sound, and viscosity data, various thermodynamic properties such as standard partial molar volumes, V0Φ, and standard partial molar isentropic compression, K0Φ, viscosity B-coefficient, and hydration number have been computed. It was found that all studied ionic liquids have favorable interactions with fructose (salting-in effect) in aqueous solutions and the calculated ΔtrV0Φ and ΔtrK0Φ values suggested that hydrophilic−ionic interactions are dominant in these mixtures. Also, the results show that increase in ionic liquid molality and temperature intensifies fructose−ionic liquid interactions. Viscosity B-coefficient values in ternary solutions are higher than the corresponding values in binary solutions. This indicates strong interactions between fructose and ionic liquids in comparison to fructose and water. In addition, it was concluded that with increasing chain length of ionic liquids from butyl to octyl, and changing anion from Cl− to Br−, the interactions between ionic liquid and fructose

Figure 7. Viscosity B-coefficients of fructose in aqueous ionic liquid solutions at different ionic liquid molalities at T = 298.15 K: ▲, [BMIm]Br; ⧫, [OMIm]Br; ×, [OMIm]Cl.

that the values of Δμ0≠ 2 are positive and have larger values compared to Δμ0≠ 1 . This means that fructose−ionic liquid interactions are stronger in the ground state than in the transition state. L



Article

(10) Sievers, C.; Musin, I.; Marzialetti, T.; Olarte, M. B. V.; Agrawal, P. K.; Jones, C. W. Acid-catalyzed conversion of sugars and furfurals in an ionic-liquid phase. ChemSusChem 2009, 2, 665−671. (11) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Vapor−Liquid equilibrium study of the ternary systems containing sucrose in aqueous solutions of ionic liquids, 1-butyl-3-methyl imidazolium bromide and 1-hexyl-3-methyl imidazolium bromide at 298.15 K and atmospheric pressure. Fluid Phase Equilib. 2016, 429, 45−54. (12) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Effect of ionic liquids, 1-butyl-3-methyl imidazolium bromide and 1hexyl-3- methyl imidazolium bromide on the vapor−Liquid equilibria of the aqueous D-fructose solutions at 298.15 K and atmospheric pressure using isopiestic method. J. Chem. Thermodyn. 2017, 105, 142−150. (13) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Thermodynamic studies on the phase equilibria of ternary {ionic liquid, 1-hexyl-3-methyl imidazolium chloride + D-fructose or sucrose + water} systems at 298.15 K. Fluid Phase Equilib. 2017, 436, 38−46. (14) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Isopiestic determination of water activity and vapor pressure for ternary (ionic liquid, 1-hexyl-4-methyl pyridinium bromide + Dfructose or sucrose + water) systems and corresponding binary ionic liquid solutions at 298.15 K. J. Chem. Thermodyn. 2018, 116, 42−49. (15) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Investigation of the solute-solute and solute-solvent interactions in ternary {saccharide + ionic liquid + water} systems. J. Mol. Liq. 2018, 256, 191−202. (16) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Effect of ionic liquid, 1-hexyl-3-methylimidazolium bromide on the volumetric, acoustic and viscometric behaviour of aqueous sucrose solutions at different temperatures. J. Chem. Thermodyn. 2016, 93, 60−69. (17) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. The study of solute−solute and solute−solvent interactions in aqueous solutions containing sucrose and ionic liquid, 1-butyl-3methylimidazolium bromide at different temperatures. J. Mol. Liq. 2015, 212, 930−940. (18) Zafarani-Moattar, M. T.; Shekaari, H.; Mazaher Haji Agha, E. Salting-out Effect of Ionic Liquid, 1-Butyl-3-methyl Imidazolium Chloride on Aqueous D-Fructose or Sucrose Solutions at T = 298.15 K: Vapor−Liquid Equilibrium Study. J. Chem. Eng. Data 2018, 63, 3196−3205. (19) Singh, V.; Chhotaray, P. K.; Gardas, R. L. Effect of protic ionic liquid on the volumetric properties of ribose in aqueous solutions. Thermochim. Acta 2015, 610, 69−77. (20) Singh, V.; Chhotaray, P. K.; Gardas, R. L. Volumetric and ultrasonic properties of ternary (sucrose + water + protic ionic liquid) solutions. J. Chem. Thermodyn. 2015, 89, 60−68. (21) Jin, H. X.; Chen, H. Y. Volumetric properties for ionic liquid− sucrose−water systems. J. Chem. Eng. Data 2011, 56, 4392−4395. (22) Shekaari, H.; Kazempour, A. Density and viscosity in Ternary D-Xylose +Ionic liquid (1-Alkyl-3-methylimidazolium Bromide) + Water Solutions at 298.15 K. J. Chem. Eng. Data 2012, 57, 3315− 3320. (23) Shekaari, H.; Kazempour, A.; Ghasedi-Khajeh, Z. Structuremaking tendency of ionic liquids in the aqueous d-glucose solutions. Fluid Phase Equilib. 2012, 316, 102−108. (24) 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, 2026−2031. (25) Yang, J. Z.; Tong, J.; Li, J. B. Study of the volumetric properties of the aqueous ionic liquid 1-methyl-3-pentylimidazolium tetrafluoroborate. J. Solution Chem. 2007, 36, 573−582. (26) Zamyatnin, A. A. Amino acid, peptide, and protein volume in solution. Annu. Rev. Biophys. Bioeng. 1984, 13, 145−165. (27) Kumar, H.; Sharma, S. K. Volumetric and Acoustic Behaviour of D(+)-glucose and D(−)-fructose in Aqueous Trisodium Citrate

strengthen. This may be due to the hydration behavior of ionic liquids. In ternary solutions, there is a competition between ionic liquid−water and ionic liquid−fructose interactions. In fact, as the affinity of ionic liquids for interaction with water increases, their tendency to interact with fructose decreases. Among the studied ionic liquids, [OMIm]Br, due to weaker interaction with water, has stronger interaction with fructose.

■

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.8b00958. 1 H NMR spectra of the ionic liquids; density of aqueous fructose solutions; plots of deviations of measured and literature values of density, speed of sound, and viscosity; speed of sound values for fructose in water; and viscosity of binary solution of fructose versus mass fraction (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Mohammed Taghi Zafarani-Moattar: 0000-0002-2174-1639 Hemayat Shekaari: 0000-0002-5134-6330 Elnaz Mazaher Haji Agha: 0000-0001-6742-4594 Funding

The authors acknowledge the graduate council of the University of Tabriz for financial support. Notes

The authors declare no competing financial interest.

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Investigation of the Thermodynamic Properties in Aqueous Solutions

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