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Study of Apparent Molar Volumes for Ionic Liquid, 1‑Ethyl-3-methyl Imidazolium Chloride in Aqueous Lithium Nitrate, Lithium Bromide, and Lithium Chloride Solutions at Temperatures (298.15 to 318.15) K Hamid Reza Rafiee* and Farshid Frouzesh Department of Physical Chemistry, Faculty of Chemistry, Razi University, Kermanshah 67149, Iran

Downloaded by UNIV OF NEBRASKA-LINCOLN on September 12, 2015 | http://pubs.acs.org Publication Date (Web): September 11, 2015 | doi: 10.1021/acs.jced.5b00329

S Supporting Information *

ABSTRACT: The densities of ternary systems ([Emim][Cl]+ LiCl + H2O), ([Emim][Cl] + LiBr + H2O), and ([Emim][Cl]+ LiNO3 + H2O) and also binary system ([Emim][Cl] + H2O) were measured at T = (298.15 to 318.15) K using a vibrating U-tube densimeter. On the basis of experimental density data, the apparent molar volumes, Vφ, were computed. The values of apparent molar volumes for binary system were correlated to Redlich−Meyer and Pitzer equations and for ternary systems were correlated to Redlich−Meyer equation and apparent molar volumes at infinite dilution, Vφ0, are also calculated. Our results showed a negative transfer volume of [EmimCl] from water to the aqueous LiCl, LiBr, and LiNO3 solutions, which decrease by enhancing the salt mass fraction. The solute−solvent interactions and structure making or breaking ability of [Emim][Cl] have been discussed in details. The results of second derivative of limiting apparent molar volumes showed that the studied ionic liquid in this work acts as a structure maker. the working pair. In previous work,13 we studied volumetric, acoustic, and transport properties of ionic liquid, 1-butyl-3methyl imidazolium chloride [Bmim][Cl] in aqueous lithium bromide solutions at T = (298.15 to 318.15) K. In continuation of that work, we evaluated apparent molar volumes of ionic liquid (IL), 1-ethyl-3-methyl imidazolium chloride [Emim][Cl] in aqueous lithium nitrate, lithium bromide, and lithium chloride solutions at temperature range of (298.15 to 318.15) K. The effects of temperature and electrolyte concentration on the volumetric properties of [Emim][Cl] in these aqueous solutions have been studied.

1. INTRODUCTION The absorption heat pumps are widely used in industry processes. So far, in these pumps especially, the working pairs such as ammonia + water solution (NH3 + H2O) or aqueous solutions of lithium bromide, lithium chloride, or lithium nitrate (H2O + LiBr, LiCl, or LiNO3) were used.1,2 The principle is based on the latent heat involved in the transfer of water between the vapor and the liquid phase. The solution can be recycled almost indefinitely because the lithium bromide, lithium chloride, and lithium nitrate are stable. This technology is gaining in importance because it is a possible substitute for chlorofluorocarbons, which are known to be damaging to the ozone layer. However, the crystallization, corrosion, and toxicity are their chief drawbacks in industrial applications.1 To overcome the crystallization problem in these systems, some anticrystallization additives such as sodium formate, potassium formate,3 and 1,3-propanediol4 have been tested. Recently, it was found that aqueous solutions of some ionic liquids (ILs) are very suitable to be used as absorbent species in the absorption cooling cycle for air conditioning due to their characteristics such as high hygroscopic ability, large solubility, corrosion-resistance, and so on.5,6 Thermophysical data are useful industrially for optimization of the design of various industrial processes.7−10 For this purpose, Kim et al.11 reported thermodynamic analysis of an absorption refrigeration system with ionic liquid, [Emim][BF4]/refrigerant mixture as a working fluid, Zhao et al.12 measured thermodynamic properties of a new working pair: 1-ethyl-3-methylimidazolium ethyl sulfate and water and Zhang et al.1 evaluated performance simulation of the absorption chiller using water and ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate as © XXXX American Chemical Society

2. EXPERIMENTAL SECTION 2.1. Materials. All chemical were purchased from Merck Company. Table 1 includes our material properties. Lithium chloride (LiCl), lithium bromide (LiBr), and lithium nitrate (LiNO3) with minimum mass fraction purities of > 0.99 were dried in the electrical oven at about 110 °C for 24 h prior to use. The [Emim][Cl] with mass fraction purity > 0.98 were used without further purification. The ionic liquid was further dried under high vacuum at T = 353.15 K for 24 h to remove trace amount of moisture prior to use. 2.2. Apparatus and Procedures. All solutions were prepared fresh by mass using an analytical balance (Sartorius, CP224S, Germany) with a standard uncertainty of 10−4 g. Received: April 8, 2015 Accepted: September 4, 2015

A

DOI: 10.1021/acs.jced.5b00329 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Provenance and Mass Fraction Purity of the Studied Compoundsa compound

CAS RN

supplier

mass fraction purity

purification method

molar mass (g mol−1)

[Emim][Cl] LiCl LiBr LiNO3


a

65039-09-0 7447-41-8 7550-35-8 7790-69-4

Merck Merck Merck Merck

≥ ≥ ≥ ≥

0.98 0.99 0.99 0.99

HPLC argenometric titration argenometric titration perchloric acid titration

146.62 42.39 86.85 68.95

All materials are used without further purification.

All the solutions were kept tightly sealed to minimize absorption of atmospheric moisture. The water content in the IL was determined using a microprocessor-based automatic Karl− Fischer titrator. The mass fraction of water [Emim][Cl] was w = 0.0032. This water content in the ionic liquid was taken into account during preparation of the aqueous solutions. All samples before injection were degassed by using ultrasound instrument (Hielscher UP100H, Germany). Measurements were performed immediately after preparation of solutions. Double distilled water was used for preparation of solutions. The density of mixtures was measured using a U-tube densimeter (Anton Paar DMA 4500 densimeter). The density is extremely sensitive to temperature, so it was automatically kept constant within ± 0.01 K. All measurements were performed three times and the reported results are the relevant averages. The expanded uncertainty Uc for density was Uc(ρ) = 5 × 10−5 g·cm−3 with 0.95 level of confidence. The apparatus was calibrated with double distilled deionized, degassed water, and dry air at ambient pressure, which was 0.087 MPa.

3. RESULTS AND DISCUSSION The measured values of density for binary ([Emim][Cl] + H2O) system and ternary ([Emim][Cl] + LiCl + H2O), ([Emim][Cl] + LiBr + H2O), and ([Emim][Cl] + LiNO3 + H2O) mixtures at different concentrations of [Emim][Cl] and (LiCl, LiBr and LiNO3), and at different temperatures are given in Suppporting Information Tables S1 to S4. Figure 1 shows the comparison of

Figure 2. Variation tendency of apparent molar volumes, Vφ, of [Emim][Cl] in aqueous LiCl, LiBr and LiNO3 solutions. (a) wsalt = 0.05 at T = 298.15 K: blue ◇, LiCl; red □, LiBr; green ○; LiNO3. At T = 318.15 K: blue ◆, LiCl; red ■, LiBr; green ●; LiNO3. (b) wsalt = 0.1 at T = 298.15 K: blue ◇, LiCl; red □, LiBr; green ○; LiNO3. At T = 318.15 K: blue ◆, LiCl; red ■, LiBr; green ●; LiNO3. (c) wsalt = 0.15 at T = 298.15 K: blue ◇, LiCl; red □, LiBr; green ○; LiNO3. At T = 318.15 K: blue ◆, LiCl; red ■, LiBr; green ●; LiNO3. Figure 1. Comparison of measured densities for ([Emim][Cl] + H2O) binary system with literature at T = 298.15 K: ◇, this work; ◆, ref 14.

differences are probably small. The apparent molar volumes Vφ were determined from the solution densities using the following equation:

measured densities for ([Emim][Cl] + H2O) binary system in this work and literature14 at T = 298.15 K. Both data show linear dependence to molality of ionic liquid with same intercepts but different slopes. This discrepancy in slopes may come from differences in purities of used ionic liquid and also little differences in densities due to pressure. Our density values belong to 0.087 MPa, which is different than atmospheric pressure, but because we are concerned with liquid phase, the

Vφ =

1000(ρ − ρ0 ) M − ρ mρρ0

(1)

where M is the molar mass of the IL, m is the molality of the IL, and ρ0 and ρ are the densities of the pure solvent and solution, respectively. The values of apparent molar volume for binary ([Emim][Cl] + H2O) and ternary ([Emim][Cl] + LiCl + H2O), B



Article

Table 2. Adjustable Parameters of Redlich−Meyer and Pitzer Equations from Correlated the Apparent Molar Volumes for Binary [Emim][Cl]+H2O System with Standard Deviations at Different Temperatures in P = 0.087 MPaa T

106·Vϕ

K

m ·mol

298.15 303.15 308.15 313.15 318.15 298.15 303.15 308.15 313.15 318.15

3

−1

135.82 135.98 136.30 136.84 137.57 135.41 135.61 135.95 136.37 137.00

106·Sv

106·bv −2

m ·kg·mol 3

−1.13 −0.75 −0.35 −1.11 −1.75

m ·kg ·mol 3

1/2

106·βχ(0) −3/2

−1

106·βχ(1) −1

kg·mol ·Pa

−1

106·Cχ −1

kg·mol ·Pa

−2

kg ·mol ·Pa 2

106·σ(Vϕ) −1

0.13 0.01 −0.35 0.09 0.33 −0.00158 −0.00134 −0.00102 −0.00143 −0.00183

0.000159 0.000116 −0.000005 0.000081 0.000153

−0.000058 −0.000046 −0.000024 −0.000033 −0.000050

m3·mol−1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

a


Standard uncertainties u are u(P) = 5 kPa, u(T) = 0.01 K, (0.68 level of confidence), and combined expanded uncertainties Uc are Uc (V0ϕ) = 0.02 cm3·mol−1, (0.95 level of confidence).

([Emim][Cl] + LiBr + H2O), and ([Emim][Cl] + LiNO3 + H2O) systems are also reported in Supporting Information Tables S1 to S4. For the systems containing both solutes (LiCl, LiBr, or LiNO3) and IL, the (lithium salt + water) is considered as the pure solvent and the IL is considered as solute. Supporting Information Tables S2 to S4 and Figure 2a,b,c show the apparent molar volumes for IL in aqueous solutions of studied salts (wsalt = 0.05, 0.1, and 0.15) at T = 298.15 K and T = 318.15 K. The results show that apparent molar volume of IL decreases with increasing concentration of salt and increase with enhancing temperature. This indicates that [Emim][Cl] components are smaller in size in solutions with higher salt concentration. This effect can be attributed to the strong interaction between [Emim][Cl] and lithium salts components. Also, a comparison between the apparent molar volumes of IL in studied aqueous solutions of LiCl, LiBr, and LiNO3 shows that the order is aqueous LiNO3 > aqueous LiBr > aqueous LiCl, which is compatible with the order of the size of the salts, that is, LiNO3 > LiBr > LiCl. In electrolyte solutions, the values of apparent molar volumes at infinite dilutions are very important because give us the useful information for solute−solvent interactions. For this purpose, the apparent molar volume values were fitted to the Redlich− Meyer and Pitzer equations.15,16 In order to obtain apparent molar volumes at infinite dilution for ternary ([Emim][Cl]+ salt + H2O) and binary ([Emim][Cl]+H2O) systems, the Redlich−Meyer equation was used as follows:15 Vφ = Vφ 0 + Svm1/2 + bvm

Vϕ = V ϕ0 + vzcza

Av ln(1 + bI 0.5) + 2vcvaRT 2b

× m(Bχ + mvczcCχ ) Bχ = βχ(0) + βχ(1)

(3)

2 [1 − (1 + αm0.5)exp( −αm0.5)] α 2m (4)

where the Vφ0 is the apparent molar volume at infinite dilution and βχ(0), βχ(1),Cχ are the Pitzer adjustable parameters that

obtained by correlating the apparent molar volume values to the Pitzer equation using least-squares method. In eq 3, the symbols za and zc are the charges of the cation and anion in the electrolyte, νa and νc are the stoichiometric coefficients of the ions in the salt, with the notation ν = νa + νc, Av is the Debye− Huckel slope for apparent molar volume that was obtained from literature,16 m is the molality of electrolyte solution, R is the gas constant, and I is the stoichiometric ionic strength of the solution I=

1 2

∑ miZ2i

(5)

The internal parameters used in this work, b = 1.2 (kg· mol−1)1/2, α = 2.0 (kg·mol−1)1/2, are the standard values proposed by Pitzer.16 The values of Vφ0 that obtained from Pitzer equation are available in Tables 2 and 3. The estimated uncertainties in Vφ0 are equal to standard deviation σ, the root mean square of the deviations between the experimental and calculated Vφ0 for each data point. The values of apparent molar volumes at infinite dilution against temperature, which were obtained from Redlich−Meyer and Pitzer equations, are drawn in Figure 3. Figure 3 shows that the values of apparent molar volumes at infinite dilution obtained from two equations reveal good agreement with each other. Table 3 and Figure 4 show that Vφ0 values for ternary (IL + salt + H2O) systems are generally positive, decrease with a rise in weight fraction of salts in the mixtures, and increase with increasing temperature. This reveals the presence of solute−solvent interactions, which are more intense at higher weight fraction of salts in the solutions due to the presence of larger amounts of ions in solution. Also, the same trend for the apparent molar volumes values at infinite dilution has been observed. That is, these values for IL in LiNO3 aqueous solutions are greater than LiBr and LiCl aqueous solutions.

(2)

in which Vφ0 is the apparent molar volume at infinite dilution, Sv is the Debye−Huckel limiting slope, and bv is the empirical parameter. The values of Vφ0, Sv, and bv for this equation are evaluated by fitting apparent molar volumes, Vφ, to molalities, m, using the least-squares method with the MathCAD 11 (2001i) software using conjugate gradient algorithm. The values of Vφ0, bv, and Sv at each temperature are reported in Tables 2 and 3. Pitzer equation16 can be used with good precision to fit the apparent molar volume of binary aqueous and nonaqueous electrolyte solutions C



Article

Table 3. Apparent Molar Volume at Infinite Dilution V0ϕ, Adjustable Parameters bν and Sν, for [Emim][Cl] in Aqueous LiCl, LiBr, and LiNO3 Solutions with Standard Deviations at Different Temperatures in P = 0.087 MPaa T

106·V0ϕ

K

m ·mol

298.15 303.15 308.15 313.15 318.15


298.15 303.15 308.15 313.15 318.15 298.15 303.15 308.15 313.15 318.15 298.15 303.15 308.15 313.15 318.15 298.15 303.15 308.15

3

−1

106·Sv

106·bv −2

m ·kg·mol 3

106·σ(Vϕ) −3/2

m ·kg ·mol 3

1/2

[Emim][Cl] + H2O + LiCl (wLiCl = 0. 05) 127.58 −3.69 0.83 127.94 −3.06 0.41 128.72 −3.56 0.62 129.38 −3.95 0.83 129.69 −3.53 0.52 [Emim][Cl] + H2O + LiBr (wLiBr = 0.05) 133.58 −3.71 1.28 133.67 −3.39 1.17 134.05 −3.02 0.86 134.41 −2.81 0.78 135.16 −3.26 0.90 [Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.05) 134.96 135.13 135.22 135.94 135.98 [Emim][Cl] 123.47 123.89 124.26 124.43 124.85 [Emim][Cl] 130.46 130.91 131.29

−3.74 1.57 −3.19 1.16 −5.98 2.06 −3.76 1.30 −2.84 0.56 + H2O + LiCl (wLiCl = 0.1) −1.67 −0.37 −1.71 −0.37 −1.57 −0.52 −1.25 −0.62 −1.45 −0.48 + H2O + LiBr (wLiBr = 0.1) −3.68 1.06 −4.02 1.32 −4.28 1.50

−1

m ·mol 3

0.01 0.01 0.01 0.01 0.01

T

106·V0ϕ

K

m ·mol

313.15 318.15 298.15 303.15 308.15 313.15 318.15

0.01 0.01 0.01 0.01 0.01

298.15 303.15 308.15 313.15 318.15

0.02 0.02 0.02 0.02 0.02

298.15 303.15 308.15 313.15 318.15

0.01 0.01 0.01 0.01 0.01

298.15 303.15 308.15 313.15 318.15

0.01 0.01 0.01

3

−1

106·Sv m ·kg·mol 3

106·bv −2

106·σ(Vϕ) −3/2

m ·kg ·mol 3

1/2

[Emim][Cl] 131.45 131.79 [Emim][Cl] +

+ H2O + LiBr (wLiBr = 0.1) −3.81 1.25 −3.83 1.20 H2O + LiNO3 (wLiNO3 = 0. 1)

133.59 134.18 134.42 134.84 135.08 [Emim][Cl] 121.93 122.39 122.82 123.32 123.66 [Emim][Cl] 129.36 130.02 130.69 131.13 131.60 [Emim][Cl] +

−3.81 0.93 −4.90 1.68 −4.29 1.19 −4.50 1.29 −4.15 0.92 + H2O + LiCl (wLiCl = 0.15) −3.52 0.93 −3.48 0.78 −3.60 0.84 −3.91 0.95 −3.83 0.87 + H2O + LiBr (wLiBr = 0.15) −4.83 1.02 −4.66 0.64 −4.84 0.62 −4.30 0.09 −4.17 −0.08 H2O + LiNO3 (wLiNO3 = 0. 15)

131.37 131.56 131.95 132.19 132.39

−4.31 −4.20 −4.40 −4.34 −3.48

1.45 1.44 1.55 1.56 0.99

m3·mol−1 0.01 0.01 0.02 0.02 0.02 0.01 0.02 0.01 0.01 0.01 0.01 0.01 0.03 0.02 0.02 0.03 0.02 0.01 0.01 0.01 0.02 0.01

a

Standard uncertainties u are u(P) = 5 kPa, u(T) = 0.01 K, (0.68 level of confidence), and combined expanded uncertainties Uc are Uc (V0ϕ) = 0.02 cm3 mol−1, (0.95 level of confidence).

Figure 3. Variation tendency of apparent molar volumes at infinite dilution for binary ([Emim][Cl]) system at different temperature obtained from: blue ◇, Redlich−Meyer equation; red ○, Pitzer equation.

Figure 4. Variation tendency of apparent molar volumes at infinite dilution, Vφ0, of [Emim][Cl] in aqueous LiCl LiBr and LiNO3 solutions: At T = 298.15 K: blue ◇, LiCl; green ○, LiBr; red □, LiNO3. At T = 318.15 K: blue ◆, LiCl; green ●, LiBr; red ■, LiNO3.

Transfer volumes of IL from pure water to aqueous salt solutions ΔVφ0 were calculated using the following relation:

agreement. The ΔVφ0 values, by definition, are free from solute−solute interactions and, therefore, provide information about solute−solvent interactions.17,18 According to Table 4 and Figure 5, the values of ΔVφ0 are negative at all experimental temperatures and decrease monotonically with the weight fraction of salt in ternary systems. These results can be explained by the cosphere overlap model developed by Friedman and Krishnan.19 Properties of the water molecules in the hydration cosphere depend on the nature of the solute species. The various possible and important

ΔVφ 0(water → aqueous Li salt) = Vφ 0(in aqueous Li salt) − Vφ 0(in pure water) (6)

The results are illustrated in Table 4 and Figure 5. The ΔVφ0 values, in which, Vφ0 values for binary (IL+H2O) system obtained from Redlich−Meyer and Pitzer equations, are in good D



Article

Table 4. Limiting Partial Molar Volume of Transfer ΔVφ0 for the [Emim][Cl] from Water to Aqueous LiCl, LiBr, and LiNO3 Solutions at Different Temperatures at P = 0.087 MPaa T [Emim][Cl] + water + LiCl (wLiCl = 0.05) [Emim][Cl] + H2O + LiBr (wLiBr = 0.05) [Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.05) [Emim][Cl] + water + LiCl (ws = 0.10) [Emim][Cl] + H2O + LiBr (wLiBr = 0.10)


[Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.10) [Emim][Cl] + water + LiCl (ws = 0.15) [Emim][Cl] + H2O + LiBr (wLiBr = 0.15) [Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.15)

298.15 K

303.15 K

308.15 K

313.15 K

318.15 K

−8.24b −7.83c −2.24b −1.83c −0.86b

−8.04b −7.67c −2.31b −1.94c −0.85b

−7.58b −7.23c −2.25b −1.90c −1.08b

−7.46b −6.99c −2.43b −1.96c −0.90b

−7.88b −7.31c −2.41b −1.84c −1.59b

−0.45c −12.35b −11.94c −5.36b −4.95c −2.23b

−0.48c −12.09b −11.72b −5.07b −4.70c −1.80b

−0.73c −12.04b −11.69c −5.01b −4.66c −1.88b

−0.43c −12.41b −11.94c −5.39b −4.92c −2.00b

−1.02c −12.72b −12.15c −5.78b −5.21c −2.49b

−1.82c −13.89b −13.48c −6.46b −6.05c −4.45b

−1.43c −13.59b −13.22c −5.96b −5.59c −4.42b

−1.53c −13.48b −13.13c −5.61b −5.26c −4.35b

−1.53c −13.52b −13.05c −5.71b −5.24c −4.65b

−1.92c −13.91b −13.34c −5.97b −5.40c −5.18b

−4.04c

−4.05c

−4.00c

−4.18c

−4.61c

a Standard uncertainties u are u(P) = 5 kPa, u(T) = 0.01 K, (0.68 level of confidence), and combined expanded uncertainties Uc are Uc (ΔVφ0) = 0.02 cm3 mol−1, (0.95 level of confidence). bThe Vφ0 values for (IL + H2O) system obtained from Redlich−Meyer equation. cThe Vφ0 values for (IL + H2O) obtained from Pitzer equation.

where a0, a1, and a2 are empirical parameters and values of these parameters for [Emim][Cl] in LiCl, LiBr, and LiNO3 aqueous solutions are listed in Table 5. The limiting apparent molar expansibility can be evaluated by differentiating from eq 7 with respect to temperature as follows: Eφ0 = (∂V φ0 /∂T )p = a1 + 2a 2T

The values for different coefficients of ternary solutions at T = (298.15 to 318.15 K) are given in Table 5. Table 5 reveals that at each temperature Eφ0 for IL in electrolyte solutions have positive values, an aspect that reveals the hydrophobic hydration in aqueous solutions. This behavior is distinguishing for salvation and electrostriction of electrolytes in aqueous solutions. By increasing temperature, some water molecules can be unconfined from the hydration layer, thereby raising the solution volume and so Eφ0 would be positive. According to Hepler22 the sign of (∂E0φ/∂T)p is a better condition to make a distinction the long-range structure making or breaking ability of the solutes in solution. The general thermodynamic term used is as follows:

Figure 5. Variation tendency of standard volumes of transfer for [Emim][Cl] from water to aqueous LiCl LiBr and LiNO3 solutions at T = 298.15 K. Redlich−Meyer equation: blue ◇, LiCl; orange △, LiBr; red □, LiNO3. Pitzer equation: blue ◆, LiCl; orange ▲, LiBr; red ■, LiNO3.

interactions between the [Emim][Cl] and lithium salt ions can be mentioned as20 (a) Interaction of Li+ ion with the N atom in the heterocyclic ring of [Emim][Cl], (b) interaction of Li+ ion with the Cl− ion in the ionic liquid, (c) interaction of Emim+ cation with the anions in the lithium salts, and (d) ionic− hydrophobic interactions between ions of salts and nonpolar part of [Emim][Cl]. According to the cosphere overlap model,19 interactions (a) to (c) could direct to a positive ΔVφ0, whereas (d) may result to a negative ΔVφ0. The observed negative ΔVφ0 in this study implies the predominance of the contributions of type (d) relative to (a) to (c). Noting the large ratio of charge to radius in Li+ could justify its role in the strong interaction with nonpolar part of [Bmim][Cl] molecule, which also is pointed out by Takada et al.21 With the aim of appraising the temperature dependence of the partial molar volumes, Vφ0 are fitted to a polynomial of the following type in terms of absolute temperature T Vφ 0 = a 0 + a1T + a 2T 2

(8)

(∂Eφ0 /∂T )p = (∂ 2V φ0 /∂T 2)p = 2a 2

(9)

If the sign of (∂E0φ/∂T)p is positive or its value would be close to zero, the solute is a structure maker, otherwise is a structure breaker. By referring to Table 5, it can be found that [Emim][Cl] essentially acts as a structure maker. McMillan−Mayer theory23 permits us to express and interconnect the excess thermodynamic function to a series of interaction parameters, such as pair, triplet, and higher order items. For the studied system, volumetric interaction parameters can be obtained by fitting experimental data using the following equation:24,25 ΔV φ0 ,IL = 2υνISms + 3υ2νIISmIL ms + 3υνISSms2

(7) E

(10)



Article

Table 5. Values of Various Coefficients of Equations 7 and 8 and Limiting Partial Molar Expansibility, Eφ0, for [Emim][Cl] in Aqueous LiCl, LiBr, and LiNO3 Solutions at Different Temperatures in P = 0.087 MPaa T

a0

a1

106·E0ϕ

a2


K 298.15 303.15 308.15 313.15 318.15

34.1240

298.15 303.15 308.15 313.15 318.15

462.6479

298.15 303.15 308.15 313.15 318.15

218.2111

298.15 303.15 308.15 313.15 318.15

49.6099

298.15 303.15 308.15 313.15 318.15

127.4629

298.15 303.15 308.15 313.15 318.15

−29.0151

298.15 303.15 308.15 313.15 318.15

49.6710

298.15 303.15 308.15 313.15 318.15

−69.2995

298.15 303.15 308.15 313.15 318.15

−1

m ·mol ·K 3

80.1858

[Emim][Cl] + H2O + LiCl (wLiCl = 0.05) 0.14 0.14 0.5006 −0.0006 0.13 0.12 0.11 [Emim][Cl] + H2O + LiBr (wLiBr = 0.05) 0.05 0.03 −2.2111 0.0037 0.07 0.11 0.14 [Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.05) 0.04 0.05 −0.5945 0.0011 0.06 0.07 0.08 [Emim][Cl] + H2O + LiCl (wLiCl = 0.1) 0.06 0.05 0.4182 −0.0006 0.05 0.04 0.04 [Emim][Cl] + H2O + LiBr (wLiBr = 0.1) 0.09 0.07 0.1520 −0.0013 0.06 0.05 0.03 [Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.1) 0.09 0.08 0.9884 −0.0015 0.06 0.05 0.03 [Emim][Cl] + H2O + LiCl (wLiCl = 0.15) 0.09 0.08 0.3871 −0.0005 0.08 0.07 0.07 [Emim][Cl] + H2O + LiBr (wLiBr = 0.15) 0.17 0.15 1.1859 −0.0017 0.14 0.12 0.10 [Emim][Cl] + H2O + LiNO3 (wLiNO3 = 0.15)

0.2823

−0.0004

0.04 0.04 0.03 0.03 0.03

106·σ(E0ϕ)

2a2 −1

m3·mol−1·K−1

−0.0012

0.05

0.0074

0.04

0.0022

0.05

−0.0012

0.05

−0.0026

0.05

−0.0030

0.05

−0.0010

0.03

−0.0034

0.03

−0.0008

0.04

a

Standard uncertainties u are u(P) = 5 kPa, u(T) = 0.01 K, (0.68 level of confidence), and combined expanded uncertainties Uc are Uc (E0ϕ) = 0.05 m3·mol−1·K−1, (0.95 level of confidence). F



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4. CONCLUSION The apparent molar volumes have been determined from the experimental density data. The apparent molar volumes at infinite dilution were obtained from fitted apparent molar volume values to Redlich−Meyer and Pitzer equations for binary systems and Redlich−Meyer equation for ternary systems. These values have been applied to calculate the corresponding transfer parameters for the studied ionic liquid from water to the aqueous LiCl, LiBr, and LiNO3 solutions. The result shows a negative transfer volume of [Emim][Cl] from water to the aqueous LiCl, LiBr, and LiNO3 solution that decreases by increasing concentration of lithium salts. The volumetric interaction parameter νIS obtained from McMillan− Mayer theory is positive, show that the interactions between the [Emim][Cl] and lithium salts are mainly pairwise. The infinite dilution apparent molar expansibility of [Emim][Cl] was positive, whereas the value of its temperature derivatives were close to zero, which means that it acts predominantly as a structure maker in the studied aqueous lithium salts solutions.

Table 6. Volumetric Interaction Parameters for Investigated Systems at Different Temperatures at P = 0.087 MPaa T

2υνIS

3υνISS

3υ2νIIS

σ

−0.080 −0.078 −0.074 −0.076 −0.080

0.450 0.433 0.251 0.209 0.251

−0.061 −0.067 −0.073 −0.088 −0.092

0.119 0.100 0.100 0.132 0.246

0.031 0.042 0.030 0.041 0.020

0.100 0.186 0.244 0.158 0.323

−0.076 −0.072 −0.071 −0.071 −0.074

0.377 0.364 0.210 0.202 0202

−0.046 −0.054 −0.061 −0.071 −0.072

0.207 0.124 0.166 0.232 0.368

0.044 0.053 0.041 0.056 0.038

0.100 0.128 0.189 0.100 0.234


K

298.15 303.15 308.15 313.15 318.15

0.915 0.894 0.867 0.882 0.916

298.15 303.15 308.15 313.15 318.15

0.550 0.550 0.556 0.618 0.649

298.15 303.15 308.15 313.15 318.15

0.099 0.053 0.092 0.068 0.171

298.15 303.15 308.15 313.15 318.15

0.875 0.853 0.834 0.837 0.861

298.15 303.15 308.15 313.15 318.15

0.477 0.484 0.493 0.533 0.547

298.15 303.15 308.15 313.15 318.15

0.030 0.009 0.033 0.011 0.075

The V0φ values for binary (IL + H2O) system obtained from Redlich−Meyer equation ([Emim][Cl] + H2O + LiCl) 0.002 0.002 0.001 0.001 0.001 ([Emim][Cl] + H2O + LiBr) 1.100 × 10−5 1.000 × 10−5 0.800 × 10−5 0.700 × 10−5 0.700 × 10−5 ([Emim][Cl] + H2O + LiNO3) 1.000 × 10−5 1.000 × 10−5 1.000 × 10−5 1.000 × 10−5 1.000 × 10−5 The Vφ0 values for binary (IL+H2O) system obtained from Pitzer equation ([Emim][Cl] + H2O + LiCl) 0.001 0.001 0.001 0.001 0.001 ([Emim][Cl] + H2O + LiBr) 1.100 × 10−5 1.000 × 10−5 0.800 × 10−5 0.700 × 10−5 0.659 × 10−5 ([Emim][Cl] + H2O + LiNO3) 1.000 × 10−5 1.000 × 10−5 1.000 × 10−5 1.000 × 10−5 1.000 × 10−5

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.5b00329. Tables S1 to S4, listing the molality m, density ρ and apparent molar volume Vφ, for [Emim][Cl] in water, LiCl, LiBr, and LiNO3 aqueous solutions at different temperatures in P = 0.087 MPa, respectively. (PDF)

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AUTHOR INFORMATION

Corresponding Author

*Tel./Fax: +98-833-4274559. E-mail: rafi[email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

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a Standard uncertainties u are u(P) = 5 kPa, u(T) = 0.01 K, (0.68 level of confidence).

where ΔV0φ,IL is the transfer volumes of [Emim][Cl] at molality mIL from water to aqueous salt solution at molality mS. In this equation, υ is the number of ions into which the electrolyte dissociates, and νIS, νIIS, and νISS are pair and triplet interaction parameters, respectively. The interaction parameters calculated by least-squares regression for this equation along with their standard deviations are given in Table 6. The results demonstrate that νIS values are positive. This may be explained according to the structural interaction model proposed by Desnoyers et al.26 and the hydration model by Conway.27 The positive νIS values are essentially due to the ionic−hydrophilic or ionic−ionic interactions because the dehydration of ions impose a positive value to the volume of solution.28,29 G




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