Article pubs.acs.org/jced
Liquid−Liquid Equilibrium Data of the Ternary Systems Containing 1‑Propanol/2-Propanol + Dipotassium Tartrate/Potassium Sodium Tartrate + Water at T = 298.15 K Mohammed Taghi Zafarani-Moattar,* Vahid Hosseinpour-Hashemi, and Shahram Tolouei Department of Physical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, Iran ABSTRACT: The liquid−liquid equilibrium data of the ternary systems containing 1-propanol/2-propanol + dipotassium tartrate/potassium sodium tartrate + water have been measured at T = 298.15 K. To fit the binodal data an empirical equation was used. The length of the alcohol chain, polarity of the alcohol, and the type of salt are the parameters that have influence on the phase behavior of these systems have been studied. In addition, the obtained experimental tie-line data were fitted using the Setschenow-type equation. Finally, the plait points of these systems were calculated.
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INTRODUCTION The aqueous two-phase system (ATPS) has applications in the partitioning of monosaccharides and proteins, recovery of nanoparticles, and in food industries.1−3 Recently, ATPS’s containing polymer + salt + water have been studied.4−6 The salts are used in these studies are valuable salts such as citrates and tartrates, so recycling of these salts can be economical and useful. For recycling of the used salts, Greve et al. presented a method using ATPS’s containing salts and a suitable aliphatic alcohol.7 In recent years, following Greve et al., liquid−liquid equilibria (LLE) of some aliphatic alcohol + salt + water systems have been studied.8−11 Tartrate salts are biodegradable and nontoxic and could be discharged into biological wastewater treatment plants, but some types of these salts are valuable and they can be recycled. For instance, potassium sodium tartrate has been commonly used in protein crystallization,12−16 medicine,17 electronics,18 and industry.19 In this respect, we have studied the phase behavior of the 1-propanol/2-propanol + dipotassium tartrate/potassium sodium tartrate + water systems at T = 298.15 K. Only the binodal curves for 1-propanol/2-propanol + dipotassium tartrate + water systems have been determined previously.20 In addition, the effect of some factors such as the polarity of alcohol, length of alcohol chain, and the type of salt on the phase forming of these investigated systems have been studied. Moreover, using the linear least-squares regression method, plait points of these investigated systems have been calculated. An empirical21 equation was applied to correlate the obtained binodal data. Furthermore, the experimental tie-line data were correlated with the Setschenow-type22 equation.
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Table 1. Physical Properties of the Used Chemicals chemical 1-propanol 2-propanol dipotassium tartrate hemihydrate potassium sodium tartrate tetra-hydrate H2O
source
country
purity (in mass fraction %)
71-23-8 67-63-0 6100-19-2
Merck Merck Merck
Germany Germany Germany
> 99.5 % > 99.5 % > 99 %
6381-59-5
Merck
Germany
> 99 %
7732-18-5
Zakaria
Iran
> 99.9 %
purification. For preparing solutions, double-distilled deionized water was used. Apparatus and Procedure. The clouding point titration method was used for the determination of binodal data. The determination apparatus was similar to the one used in our previous work.11 A glass vessel with an external jacket was used around which water at constant temperature was circulated using a thermostat (HETO BIRKERØD, Type: 01 TE 623, Denmark) with an uncertainty of ± 0.05 K. The composition of the mixture for each point on the binodal curve was determined from the amount of titrant added until turbidity was observed using an analytical balance (Shimadzu, AW220, Shimadzu Co., Japan) with a precision of ± 1·10−7 kg. The maximum uncertainty in determining of the mass fraction of both alcohol and salt is ± 0.0001. The procedure for determination of the tie-lines has also been described previously.11 The vessels containing appropriate amounts of alcohol, salt, and water were placed in the thermostat (JULABO model MB, Germany) at T = 298.15 K at least 48 h to separate into two clear phases. The accuracy of the thermostat
MATERIALS AND METHODS
Received: January 8, 2013 Accepted: April 11, 2013
Materials. The properties of chemicals used in this work were listed in Table 1. All of these chemicals were used without further © XXXX American Chemical Society
CAS No.
A
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is ± 0.02 K. To determine the mass fractions of salt in the top and bottom phases, the flame photometer (JENWAY model PFP7, England) was used. Using this method the maximum uncertainty was found to be ± 0.002 in determining the mass fraction of salt. The refractive index method was used for the determination of alcohol in both phases using a refractometer (ATAGO DRA-1, ATAGO, Japan) with uncertainty of ± 0.0002. The following relation between refractive index of solution, nD, and the mass fractions of alcohol, wm, and salt, wca, has been proposed by Chegluget et al. to calculate the mass fraction of alcohol in both phases by measuring refractive index.23 The mass fraction of salt determined by flame photometry as mentioned above.
Table 2. Values of the Parameters of Equation 1, ai, for the Alcohol (m) + Salt (ca) + Water (w) Systems chemical
constant
value ± σ
105 SDa
am am aca aca
0.0934 ± 0.0007 0.0897 ± 0.0001 0.1470 ± 0.0001 0.1593 ± 0.0001
6.62 8.03 11.03 3.81
1-propanol 2-propanol dipotassium tartrate hemihydrate potassium sodium tartrate tetrahydrate
2 0.5 SD = (∑Ni=1)(ncal − nexp i i ) /N) , where N and ni represent the number of refractive indexes data and values of refractive index for compound i, respectively.
a
Table 3. Binodal Data as Mass Fraction, wi, for Alcohol (m) + Salt (ca) + Water (w)a dipotassium tartrate 1-propanol
nD = n0 + amwm + acawca
where n0, am, and aca are the refractive index of pure water (1.3325 at T = 298.15 K),24 constants corresponding to alcohol and salt respectively which are obtained from the linear calibration plots of refractive index of the solution. It should be noted that this relation is accurate only for dilute aqueous solutions containing an alcohol and a salt; therefore, it was necessary to dilute the samples before refractive index measurements (our prepared ternary standard solutions for the calibration curves are in the mass fraction range of 0 ≤ wm ≤ 0.1 and 0 ≤ wca ≤ 0.05). Using this method the uncertainty for mass fraction of alcohol was better than ± 0.002. The values of these constants along with the corresponding standard deviations (SD) are reported in Table 2.
potassium sodium tartrate
2-propanol
2-propanolb
1-propanol
100wm
100wca
100wm
100wca
100wm
100wca
100wm
100wca
57.40 45.86 34.54 30.56 26.36 21.44 17.20 8.45
0.99 3.12 5.41 6.54 7.71 9.42 10.93 15.80
65.82 59.87 55.12 48.94 41.84 37.20 33.01 29.16 25.62 22.34 18.84 15.66 13.71 11.11 8.78 6.87 4.88 3.69 2.90 2.09 1.82
0.70 1.01 1.50 2.54 4.33 6.09 7.82 9.46 11.45 13.22 15.35 17.58 19.30 21.81 24.38 26.81 30.72 34.43 37.76 41.61 43.27
55.96 47.98 42.38 32.85 28.96 25.01 20.83 12.43
1.18 2.25 3.37 5.21 6.37 7.36 8.40 11.75
66.8 60.4 56.0 52.0 49.4 46.8 9.4 6.9 4.6 3.2 1.3 0.5
0.3 0.8 1.3 1.6 2.0 2.5 22.4 24.7 27.2 29.1 33.5 37.4
(1)
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RESULTS AND DISCUSSION Experimental Results. The binodal data for the 1-propanol/ 2-propanol + dipotassium tartrate + water and 1-propanol + potassium sodium tartrate + water systems were obtained as listed in Table 3. Detection of turbidity for 2-propanol + potassium sodium tartrate +water system was impossible; therefore, using the tie-line data the binodal curve has been determined as we have done for 2-propanol + disodium succinate + water system previously.11 Moreover, the tie-line data for these investigated systems are reported in Table 4. Figure 1 illustrates the binodal curves for the alcohol (m) + salt (ca) + water (w) systems. In addition, the binodal curves for 1-propanol/2-propanol + dipotassium tartrate + water systems at 298.15 K are compared with the literature,20 and good agreements are obtained between the literature and our experimental data.
Standard uncertainties for mass percent and temperature are ± 0.01 and ± 0.05 K, respectively. bThe binodal curve is determined using the tie-line data. a
Table 4. Experimental Tie-Line Data in Mass Fraction, wi, for Alcohol (m) + Salt (ca) + Water (w) Systemsa dipotassium tartrate top phase 100wmb 63.1 ± 0.3 71.1 ± 0.1 77.2 ± 0.1 80.2 ± 0.1 85.1 ± 0.00 44.2 ± 0.1 53.9 ± 0.1 61.2 ± 0.03 77.2 ± 0.0 82.6 ± 0.0 a
potassium sodium tartrate bottom phase
100wcab
100wmb
1-Propanol 0.8 ± 0.5 10.5 ± 0.5 0.5 ± 0.3 7.6 ± 0.8 0.3 ± 0.1 5.0 ± 1.0 0.2 ± 0.05 2.7 ± 1.3 0.1 ± 0.02 1.0 ± 1.6 2-Propanol 3.8 ± 0.8 12.3 ± 0.7 1.7 ± 0.6 6.7 ± 0.9 1.0 ± 0.3 3.3 ± 1.1 0.1 ± 0.2 0.6 ± 1.5 0.01 ± 0.03 0.2 ± 1.7
top phase
100wcab
100wm
11.8 ± 1.7 24.1 ± 2.0 30.3 ± 2.2 39.8 ± 2.6 51.1 ± 3.0
58.9 ± 0.03 62.0 ± 0.02 66.7 ± 0.02 70.9 ± 0.01 73.9 ± 0.00
21.0 ± 2.0 28.3 ± 2.1 34.6 ± 2.3 45.8 ± 2.5 53.1 ± 2.8
46.8 ± 0.1 49.4 ± 0.1 52.0 ± 0.1 56.0 ± 0.05 60.4 ± 0.03 66.8 ± 0.01
100wca
bottom phase 100wm
1-Propanol 0.9 ± 0.1 9.4 ± 0.5 0.6 ± 0.1 6.3 ± 0.6 0.5 ± 0.1 4.4 ± 0.8 0.2 ± 0.1 3.4 ± 0.9 0.1 ± 0.03 1.5 ± 1.1 2-Propanol 2.5 ± 0.4 9.4 ± 0.8 2.0 ± 0.3 6.9 ± 0.9 1.6 ± 0.3 4.6 ± 1.0 1.3 ± 0.3 3.2 ± 1.0 0.8 ± 0.2 1.3 ± 1.2 0.3 ± 0.1 0.5 ± 1.3
100wca 14.3 ± 0.2 17.4 ± 0.2 22.3 ± 0.2 25.4 ± 0.2 32.4 ± 0.2 22.4 ± 1.3 24.7 ± 1.3 27.2 ± 1.3 29.1 ± 1.4 33.5 ± 1.4 37.4 ± 1.4
The standard uncertainty for temperature is ± 0.02 K. bwm and wca are mass fractions of each alcohol and salt, respectively. B
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alcohol + salt + water8,11,26 systems. Therefore, in this work, we decided to use the Setschenow-type equation to correlate the tieline data of these investigated systems. This equation proposed by Hey et al.22 and has the following form: ⎛ mt ⎞ ln⎜⎜ mb ⎟⎟ = β + kca(mcab − mcat ) ⎝ mm ⎠
(3)
where kca and β are the salting-out coefficient and a constant, respectively. mm and mca represent the molality of alcohol and salt, respectively. The superscripts “t” and “b” stand for the alcohol-rich phase and salt-rich phase, respectively. The experimental LLE data were correlated to eq 3 using the objective function (OF) which has the following form OF =
∑ ∑ ∑ (mpcal,l ,j − mpexp,l ,j)2 p
l
(4)
j
In this equation, mp,l,j represents the molality of the component j in the phase p for lth tie-line and the species j can be alcohol, salt, or solvent molecule. The superscripts “cal” and “exp” stand for the calculated and experimental values, respectively. The values of fitting parameters (kca and β) of eq 3, along with SD values, are reported in Table 6. The results of data correlation for these Table 6. Values of Parameters of Setschenow-Type Equation (eq 3), (β, kca) for Alcohol + Salt + Water Systems kca ± σ
Figure 1. Binodal data for: (a) {red ◆, 1-propanol; green ▲, 2-propanol; purple ×, 1-propanol;20 black∗, 2-propanol20} (m) + dipotassium tartrate (ca) + water; (b) {blue ■, 1-propanol; red ●, 2-propanol} (m) + potassium sodium tartrate (ca) + water systems at T = 298.15 K; (solid lines) calculated from eq 2.
dipotassium tartrate potassium sodium tartrate dipotassium tartrate potassium sodium tartrate
Correlation of Data. For correlation of experimental binodal data, an empirical equation21 was used which gives satisfactory results. This nonlinear equation with three parameters expresses the mass fraction of alcohol, wm, as a function of salt mass fraction, wca, and it has the following form: wm = a + bwca0.5 + cwca
β±σ
salt
1-Propanol 1.9657 ± 0.0258 0.1120 ± 0.0244 2-Propanol 1.3899 ± 0.0542 −1.3928 ± 0.0046
kg·mol−1
SDa
0.8023 ± 0.0160 1.3905 ± 0.0220
0.71 0.23
1.5118 ± 0.0288 2.4512 ± 0.0028
0.23 0.07
a exp 2 0.5 SD = [∑p∑i∑j((mcal p,l,j − mp,l,j) /6N)] , where mp,l,j is the molality of the component j (i.e., alcohol, salt, or water) in the phase p for the lth tie-line and N represents the number of tie-line data points.
(2)
investigated systems are shown in Figures 2 to 5. According to the SD values reported in Table 6, it can be concluded that the performance of eq 3 in fitting the tie-line data is very good. Again it can be seen that eq 3 with only two parameters has a good performance in representing tie-lines for alcohol + salt + water systems considered in this work and other similar systems studied before.8,11,26 Effect of Alcohol. In this section, the effect of alcohols in phase formation of ATPS’s has been studied. To achieve this goal, the binodal curves of systems containing different alcohols and these salts should be compared. For instance, the binodal
where a, b, and c are fitting parameters of eq 2. The obtained fitting parameters along with the corresponding standard deviations listed in Table 5. Reproductions of the binodal curves using eq 2 are also illustrated in Figure 1. The obtained standard deviations show that the performance of this empirical equation is acceptable for correlation of the binodal data for the investigated systems. It was found that the Setschenow-type equation22 with only two parameters usually has a good performance in the correlation of tie-line data for polymer + salt + water4,25 and
Table 5. Values of Parameters of Equation 2 for Alcohol + Salt + Water Systems
a
alcohol
a±σ
1-propanol 2-propanol
77.2616 ± 1.7526 80.7157 ± 0.0894
1-propanol 2-propanol
77.9785 ± 0.5328 78.2740 ± 0.1697
b±σ Dipotassium Tartrate −19.6846 ± 1.3173 −21.3774 ± 0.0476 Potassium Sodium Tartrate −20.4595 ± 0.5731 −22.0730 ± 0.1776
c±σ
SDa
0.5455 ± 0.2478 1.4115 ± 0.0059
0.83 0.88
0.3555 ± 0.1432 1.5305 ± 0.0253
0.46 0.70
exp 2 0.5 SD = (∑Ni=1)(100wcal i − 100ci ) /N) , where N and wi represent the number of binodal data and mass fraction of component i, respectively.
C
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Figure 4. Experimental and calculated tie-line data for 1-propanol (m) + potassium sodium tartrate (ca) + water (w) system: green □, experimental; red ---×---, calculated tie-lines from the Setschenow equation (eq 3); ●, experimental binodal; solid line, the calculated binodal from eq 2.
Figure 2. Experimental and calculated tie-line data for 1-propanol (m) + dipotassium tartrate (ca) + water (w) system: green □, experimental; red ---×---, calculated tie-lines from the Setschenow equation (eq 3); ●, experimental binodal; solid line, the calculated binodal from eq 2.
Figure 3. Experimental and calculated tie-line data for 2-propanol (m) + dipotassium tartrate (ca) + water (w) system: green □, experimental; red ---×---, calculated tie-lines from the Setschenow equation (eq 3); ●, experimental binodal; solid line, the calculated binodal from eq 2.
Figure 5. Experimental and calculated tie-line data for 2-propanol (m) + potassium sodium tartrate (ca) + water (w) system: green □, experimental; red ---×---, calculated tie-lines from the Setschenow equation (eq 3); ●, experimental binodal; solid line, the calculated binodal from eq 2.
curves of ethanol20/1-propanol/2-propanol + dipotassium tartrate + water systems are shown in Figure 6. This obtained behavior can be explained by two factors, which are the number of carbon atoms and the polarity of alcohols. A comparison between ethanol and propanols shows that the solubility and miscibility of alcohols is decreased by increasing the number of carbon atoms. For 1-propanol and 2-propanol, the higher polarity of 2-propanol as compared with 1-propanol also leads the shift of the binodal curve to higher miscibility of 2-propanol. Therefore, the obtained order of alcohol’s phase-forming ability is 1-propanol >2-propanol > ethanol. The similar results are obtained for systems containing ethanol20/1-propanol/2-propanol and potassium sodium tartrate. Effect of Salt. To study the salt effect in phase formation in the presence of alcohols, the binodal curves for 1-propanol + dipotassium tartrate + water and 1-propanol + potassium sodium tartrate + water systems are illustrated in Figure 7. In this study, the effect of cations is important because the salts have the same
anions. To have a complete comparison, the binodal curve of the 1-propanol + disodium tartrate + water system11 is also shown in Figure 7. As seen in Figure 7, in these series of salts, disodium tartrate (Na2C4H4O6) has the highest salting-out ability. Moreover, based on experimental uncertainties there is not an obvious difference between potassium sodium tartrate (NaKC4H4O6) and dipotassium tartrate (K2C4H4O6) salts in regard with their salting-out ability. Plait Point. The plait point is the point in which two liquid phases become identical.27 The plait points were calculated using extrapolation from the auxiliary points, which were fitted with the equation that has the following form wm = a + bwca
(5)
where a and b are fitting parameters. The results of this fitting containing obtained parameters and estimated plait points along with correlation coefficients, R2, are given in Table 7. D
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and the LLE data for these investigated systems were determined. For correlation of the binodals of these systems an empirical equation was used with acceptable results. In addition, the experimental tie-line data reproduced by the Setschenowtype equation. The performance of this equation with only two parameters in data fitting was good. Moreover, effective factors such as the type of salt, polarity, and number of carbon atoms in phase forming were studied. The results show that the phaseforming ability of alcohols follows the ordering 1-propanol > 2-propanol > ethanol. Furthermore, the salting-out ability of investigated salts was studied. The following order was observed: disodium tartrate (Na2C4H4O6) > potassium sodium tartrate (NaKC4H4O6) ≈ dipotassium tartrate (K2C4H4O6). Finally, the plait points of these systems were calculated.
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AUTHOR INFORMATION
Corresponding Author
*Fax: +98 411 3340191. E-mail address:
[email protected].
Figure 6. Comparing the binodal data of {red □, ethanol;20 green ○, 2-propanol; blue ◇, 1-propanol} (m) + dipotassium tartrate (ca) + water (w) systems.
Notes
The authors declare no competing financial interest.
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Figure 7. Plot of the molality of alcohol against the molality of salt to show binodal curves for 1-propanol (m) + {red ●, dipotassium tartrate; green ◆, potassium sodium tartrate; blue ▲, disodium tartrate11} (ca) + water (w) systems.
Table 7. Values of Parameters of Equation 5 and the Plait Points for the Alcohol (m) + Salt (ca) + Water (w) Systems alcohol
a±σ
b±σ
1-propanol
Dipotassium Tartrate 56.0047 ± 1.0495 0.6002 ± 0.0307
2-propanol
18.8400 ± 0.5759
1-propanol
Potassium Sodium Tartrate 47.2275 ± 0.7547 0.8604 ± 0.0394
2-propanol
16.5386 ± 0.3786
1.2293 ± 0.0197
1.3308 ± 0.0140
R
2
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CONCLUSION ATPS’s of 1-propanol/2-propanol + dipotassium tartrate/ potassium sodium tartrate + water systems have been studied, E
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