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Suitability of dihydrogen phosphate anion to salt out cholinium-based ionic liquids
Accepted Manuscript Suitability of dihydrogenphosphate anion to salt out cholinium-based ionic liquids María S. Álvarez, Yanfei Zhang, M. Ángeles Sanromán, Francisco J. Deive, Ana Rodríguez PII: DOI: Reference:
S0021-9614(18)31201-1 https://doi.org/10.1016/j.jct.2019.02.009 YJCHT 5715
To appear in:
J. Chem. Thermodynamics
Received Date: Revised Date: Accepted Date:
29 November 2018 11 February 2019 12 February 2019
Please cite this article as: M.S. Álvarez, Y. Zhang, M. Ángeles Sanromán, F.J. Deive, A. Rodríguez, Suitability of dihydrogenphosphate anion to salt out cholinium-based ionic liquids, J. Chem. Thermodynamics (2019), doi: https:// doi.org/10.1016/j.jct.2019.02.009
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Suitability of dihydrogenphosphate anion to salt out cholinium-based ionic liquids María S. Álvarez1,2*, Yanfei Zhang2, M. Ángeles Sanromán1, Francisco J. Deive1, Ana Rodríguez1* 1
Department of Chemical Engineering, University of Vigo, P. O. Box 36310, Vigo, Spain
2
Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey
08544, USA * Corresponding author: +34 986812304; E-mail addresses: [email protected]; [email protected]
ABSTRACT
The segregation capacity of cholinium dihydrogen phosphate (N 1112OHDHP) in aqueous solutions of two non-ionic surfactants belonging to Triton X family (Triton X-100 and Triton X-102) was explored at different temperatures from T = (298.15 to 333.15) K. The experimental data for each binodal curve have been correlated using three empirical models based on exponential and polynomial equations. The tie-line data were suitably described by applying the Othmer-Tobias and Bancroft models. The data obtained demonstrated the great ability of N1112OHDHP to act as phase promoter in aqueous solutions of non-ionic surfactants in comparison with other ionic liquids like N1112OHCl, N1112OHDHC or C2C1imC2SO4. Keywords: Aqueous two-phase systems; Cholinium dihydrogen phosphate; Ionic liquids; Non-ionic surfactants; Triton X
1. Introduction The awareness for the development of more sustainable chemical processes has prompted the investment of great research efforts in neoteric solvents like liquid polymers, perfluorocarbons, supercritical fluids or ionic liquids [1]. The latter have been
the subject of a great interest since the last decade, due to appealing properties like their negligible volatility, thermal stability and excellent solubilisation capacity [2, 3]. Apart from that, one of the important aspects to attain truly green, competitive and efficient industrial processes is the finding of an appropriate solvent for a specific application, or the so-called task specific ionic liquid. In this sense, thousands of new molten salts can be designed by combining a particular cation and anion, making it possible to label them as neoteric solvents [4]. This fact has contributed the application of ionic liquids in an array of sectors ranging from electrochemistry [5], analytical chemistry [6], biotechnology [7], environmental engineering [8] to separation processes [9]. More specifically, the application of ionic liquids in separation processes has find a promising niche in the development of aqueous biphasic systems (ATPS), as their low vapour pressure makes up an advance regarding conventional volatile organic solvents commonly employed in extraction units [10]. These systems are traditionally composed of a salt and a hydrophilic polymer [11-13], although two salts [14], two polymers [15] or even surfactants [16] may be employed as components in aqueous solutions. The chemical explanation for aqueous phase segregation is based on the different hydrogen bonding capacity of the components to interact with water molecules. These separation systems possess advantages like their short time, easy operation and low energy demand [17], although the lack of knowledge of the partition mechanisms, or the deactivating effects on enzymes of some of them makes it necessary to invest more research efforts. The successful application of this separation method has already been demonstrated for enzymes [18], antioxidants [19], heavy metals [20], or dyes [21]. Additionally, since the addition of surfactants like Triton could entail additional benefits for several applications like biomass solubilisation [22], we have already demonstrated the suitable role of imidazolium-based ionic liquids as agents leading to phase
disengagement [23]. However, the environmental persistence and toxicity of this family of ionic liquids [24] has furthered the research of more biocompatible ionic liquids like those bearing cholinium cation [25], whose complete biodegradability has already been demonstrated [26]. Therefore, in this research work, the role of cholinium dihydrogen phosphate (N1112OHDHP) as salting out agent in aqueous solutions of model non-ionic surfactants with different hydrophilicities like Triton X-100 and Triton X-102, has been demonstrated at four temperatures. All the experimental data for the systems (Triton X100 or Triton X-102 + N1112OHDHP + H2O) have been determined and correlated with known equations. Analogously, the tie-lines were empirically ascertained and OthmerTobias and Bancroft equations were employed to further characterize them. 2. Experimental 2.1. Materials The ionic liquid cholinium dihydrogen phosphate N1112OHDHP was purchased from IoLiTec. In order to reduce potential traces of solvents and moisture, vacuum drying (210−1 Pa) and moderate temperature (T = 323.15 K) were applied for 5 days always immediately prior to its use up to a mass fraction of water of 0.02, after KarlFisher titration. This water content was accounted for in the experimental determinations and added to the water composition in the ternary mixtures. The nonionic surfactants belonging to the polyethylene glycol tert-octylphenyl ether family (Triton X-100 and Triton X-102) were purchased from Sigma-Aldrich, and used without further purification. Their water content was also determined by Karl-Fisher titration and was lower than 0.001 (w/w). Double-distilled deionized water was used for
preparation of the solutions. The main data referring to chemicals are summarized in Table 1. 2.2. Apparatus and experimental procedure The cloud point titration method was used to ascertain the binodal data of the different ATPS at temperatures from T = (298.15 to 333.15) K and atmospheric pressure according to the procedure described previously [27]. As a short overview, the binodal curves were accomplished in a jacketed glass vessel containing a magnetic stirrer and double-distiller deionized water was dropwise-added to binary mixtures containing known concentrations of surfactant and ionic liquid (ranging from 0.1:0.99 to 0.99:0.1 ratios of ionic liquid: surfactant) until solids disappear. Thereby, the solid-liquid and the liquid-liquid regions were delineated. The ternary system compositions were determined by the mass quantification of all components (Mettler Toledo XS104 balance, ± 10-4 g) and the temperature was controlled with a F200 ASL digital thermometer with an uncertainty of ± 0.01 K. The tie-lines (TLs) data determination was carried out in the previously described thermostatted glass vessel where a ternary mixture with known composition from the biphasic region was added to the cell, stirred vigorously for 1 h, and left to settle for 48 h to guarantee a complete separation of the two phases. Each layer was harvested through a syringe and analysed by means of density and refractive index measurements. An Anton Paar DSA-48 digital vibrating tube densimeter was used for density measurements (uncertainty of ± 210-4 gcm-3). On the other hand, refractive indices were determined by means of a Dr. Kernchen ABBEMAT WR refractometer (uncertainty of ± 410-5). Both densimeter and refractometer were calibrated beforehand following the manufacturer recommendations.
3. Results and discussion 3.1 Binodal curves determination and modelling At first, the salting out potential of the systems formed by the ionic liquid N1112OHDHP and aqueous solutions of the non-ionic surfactants Triton X-100 and Triton X-102 was researched at temperatures ranging from T = (298.15 to 333.15) K. The experimental solubility data in mass composition for the ternary mixture are listed in Tables 2 and 3, and displayed as triangular representation in Figures 1 and 2. A visual inspection of the experimental binodal data discloses that the biphasic region is expanded with increasing temperature for both non-ionic surfactants. A plausible reason to understand this behaviour is that the interactions between the nonionic surfactants and the water molecules are debilitated at high temperatures, thus leading to greater surfactant hydrophobicity and a consequent increase of the biphasic area. These results are in agreement with previous research studies in this field [23, 2830]. On the other hand, a careful analysis of the data in terms of the hydrophilicity of the surfactant can be carried out by comparing the systems displayed in Figures 1 and 2. Hence, it is clear that the use of the surfactant Triton X-100 entails higher immiscibility regions than Triton X-102. This response is in accordance with the hydrophobic nature of the former, which is justified by the hydrophilic-lipophilic balance (HLB) parameter. This empirical number, varying between 0 and 20 for non-ionic surfactants, allows evaluating the balance of the strength and size of hydrophilic and lipophilic groups present in emulsifying compounds [31]. In this context, Triton X-100, with the lower HLB value (cf. Table 1), displays less favourable interactions with water molecules, making it easier to trigger phase segregation. The same pattern was found for other
ATPS, where different surface active compounds like those belonging to Tween family were used [32-34]. In general, it is observed that the use of the less hydrophilic surfactant Triton X100 and the operation at T = 333.15K involve the existence of biphasic area occupying almost all the surface of the triangular diagram. In relation to that, it should be noted that DHP anion plays an important role in the phase segregation. This salting out potential can be evaluated in terms of the Hofmeister series, which classifies the anions in accordance with the lyotropic number of the anion. In general, hydration radius, charge to size ratio, charge and lyotropic number can all be related to an ion Gibbs free energy of hydration (hydG), which can be a useful tool to quantitatively verify the experimental results obtained. This trend confirms that anions with higher phase promotion capacity show more negative hydG values. Thus, dihydrogen phosphate anion displays lower values (−465 kJmol-1) than other recently reported systems using cholinium cation combined with chloride anion (−340 kJmol-1) or dihydrogen citrate anion (−81 kJmol-1) [35, 36]. An analogous classification may be done when analysing the Jones-Dole B coefficient, which is higher for dihydrogen phosphate (0.340 dm3mol1
) than for chloride anion (-0.005 dm3mol-1) [37, 38], thus confirming the sequence
obtained when the solubility data reported recently is compared with the present results, as shown in Figure 3. All experimental solubility data for the systems were suitably correlated using three empirical mathematical models commonly applied to several types of ATPS [39, 40]. 3 w1 =α∙exp (βw0.5 2 -λw2 )
(1)
2 w1 =α+βw0.5 2 +λw2 +δw2
(2)
2 w1 =exp(α+βw0.5 2 +λw2 +δw2 )
(3)
The w1 and w2 the mass fraction of surfactant and N1112OHDHP, respectively. On the other hand, , , and are the fitting parameters, which values were determined by minimizing the standard deviation ( ): n DAT z exp z adjust σ i n DAT
1/ 2
2
(4)
Here zexp and zadjust represent the experimental and the theoretical values, respectively and nDAT equals the number of data. All the values of the fitting parameters and standard deviations are listed in Tables 4 to 6. From the deviation data, it is possible to conclude that Eq. (3) is the one leading to the more appropriate description of the binodal curves, in line with previous results reported in literature [27, 40]. 3.2. Tie-lines and modelling The tie-lines of each system, which procedure was described beforehand, were carried out at T = (298.15 to 333.15) K and 0.1 MPa. The tie-line length (TLL) and the slope (S) were calculated using the following equations:
TLL w1I w1II
S
w1I w1II w2I w2II
w 2
I 2
2 w2II
0.5
(5)
(6)
where w1 refers to the mass fraction of Triton X-100 or Triton X-102 and w2 refers to N1112OHDHP. The superscripts I and II refer to top and bottom phases, respectively. The TL data obtained for each ternary system and the abovementioned parameters are given in Tables 7 and 8. Furthermore, the phase diagrams containing the tie-lines for both
non-ionic surfactants are shown in Figures 4 and 5. From the data obtained, it seems clear that the increase in the ionic liquid concentration in the bottom phase, leads to more non-ionic surfactant being salted out to the top phase, which in turn is associated with an increase in the TLL values. The component compositions between the surfactant and ionic liquid-rich phases can be suitably described by means of two well-known models like Othmer-Tobias (Eq. 7) and Bancroft (Eq. 8) equations [41].
1 w1I I w1 w3II II w 2
1 w2II II w2
w3I I w 1
(7)
(8)
The w1, w2 and w3 the Triton X, N1112OHDHP and water mass fraction, respectively, (I and II refer to top and bottom phases) while , , , and are the fitting parameters. The values of these parameters are listed in Table 9, and the regression coefficients greater than 0.98 indicate the suitability of the abovementioned equations to describe the experimental tie-line data. 4. Conclusion The present study demonstrates the greater suitability of cholinium dihydrogen phosphate anion to trigger phase segregation in aqueous solutions of non-ionic surfactants, regarding previous studies using chloride or dihydrogencitrate anions. Additionally, the operation at high temperatures contributes to maximize the biphasic area, as it weakens the interplays between surfactant and water molecules. The use of a polynomial equation allowed describing the binodal curves for both Triton X-100 and Triton X-102 at the temperatures under study. In the same vein, Othmer Tobias and
Bancroft models were successfully employed to model the experimental tie-line data, as the regression coefficients were always close to the unit. Acknowledgements The authors thank Xunta de Galicia and ERDF for funding through a postdoctoral grant (ED481B-2016/140-0) and project ED431F 2016/007. The authors are grateful to the Spanish Ministry of Economy and Competitiveness for the financial support of F.J. Deive under the Ramón y Cajal program (RyC-2013-14225). References [1] P. Lozano, Green Chem. 12 (2012) 555-569. [2] K.R. Seddon, J. Chem. Technol. Biotechnol. 68 (1997) 351-356. [3] M.J. Earle, J.M.S.S. Esperança, M.A. Gilea, J.N. Canongia Lopes, L.P.N. Rebelo, J.W. Magee, K.R. Seddon, J.A. Widegren, Nature 439 (2006) 831-834. [4] K.D. Clark, O. Nacham, H. Yu, T. Li, M.M. Yamsek, D.R. Ronning, J.L. Anderson, Anal. Chem. 87 (2015) 1552-1559. [5] M.C. Lin, M. Gong, B. Lu, Y. Wu, D.Y. Wang, M. Guan, M. Angell, C. Chen, J. Yang., B.J. Hwang, H. Dai, Nature 520 (2015) 324-328. [6] T.D. Ho, C. Zhang, L.W. Hantao, J.L. Anderson, Anal. Chem. 86 (2014) 262-285. [7] J.V. Rodrigues, D. Ruivo, A. Rodríguez, F.J. Deive, J.M.S.S. Esperança, I.M. Marrucho, C.M. Gomes, L.P.N. Rebelo, Green Chem. 16 (2014) 4520-4523. [8] A.B. Pereiro, F.J. Deive, A. Rodríguez, Sep. Purif. Technol. 47 (2012) 377-385. [9] L. Morandeira, M.S.Álvarez, F.J.Deive, M.A. Sanromán, A. Rodríguez, Sep. Purif. Technol. 174 (2017) 29-38.
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Figure Captions
Figure 1. Plot of solubility data for {Triton X-100 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa. Dashed lines represent the fitting to Eq. (3) and solid lines are a guide to the eye. Figure 2. Plot of solubility data for {Triton X-102 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa . Dashed lines represent the fitting to Eq. (3) and solid lines are a guide to the eye. Figure 3. Comparison of solubility data for {Triton X-100 (1) or Triton X-102 + ionic liquid (2) +H2O (3)} at T = 298.15 K: dihydrogencitrate (), chloride () and DHP () anions combined with N1112OH cation. Figure 4. Plot of tie-lines for {Triton X-100 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa.
Figure 5. Plot of tie-lines for {Triton X-102 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa.
FIGURE 1
H2O 0
100
10 20
90
L 80
30
70
40
60
50
50 L+L
60
40
70
30
80
20
90
S+L
10
100
Triton X-100 0
0 10
20
30
40
50
60
70
80
90
100
N1112OHDHP
FIGURE 2
H2O 0
100
10 20
90 L
80
30
70
40
60
50
50 L+L
60
40
70
30
80
20
90
10
100
Triton X-102 0
0 10
20
30
40
50
60
70
80
90
100
N1112OHDHP
FIGURE 3
H2O 0
100
10
90
20
80
30
70
40
60
50
50
60
40
70
30
80
20
90
10
100
0
0
10
20
30
40
50
60
70
80
90
100
Ionic Liquids
Triton X-100 H2O 0 10
100 90
20
80
30
70
40
60
50
50
60
40
70
30
80
20
90
10
100 0
0 10
Triton X-102
20
30
40
50
60
70
80
90
100
Ionic Liquids
FIGURE 4
H 2O
H2O 0
0
100
90
90 20
20
80
80 30
30
70
70 40
40
60
60 50
50
50
50 60
60
40
40 70
70
30
30 80
80
20
20 90
90
10
10 100
100
0
0
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
50
10
10
90
50 60 70 80 90 100
0
Triton X-100
30
100
N1112OHDHP
20
90
10
90
40
80
20
80
50
70
30
70
60
60
40
60
70
50
50
50
80
40
60
40
100
90
30
70
40
30
90
100
20
80
30
20
80
H2O 0
100
20
10
70
N1112OHDHP
H2O 0
60
Triton X-100
N1112OHDHP
Triton X-100
0
100
10
10
10
100 0
0 10
Triton X-100
20
30
40
50
60
70
80
90
100
N1112OHDHP
FIGURE 5
H2O
H2O
0
0 100
90
90 20
20
80
80 30
30
70
70 40
40
60
60 50
50
50
50 60
60
40
40 70
70
30
30 80
80
20
20 90
90
10
10 100
100
0
0
0
10
20
30
40
50
60
70
80
90
0
100
N1112OHDHP
Triton X-102
60
10
90
60
30
0 100
N1112OHDHP
20
90
10
100 90
40
80
20
90
80
50
70
30
70
60
60
80
60
70
50
40
70
100
80
40
50
90
90
30
60
80
100
20
80
50
70
N1112OHDHP
0
50
Triton X-102
50
Triton X-102
70
40
40
100
40
30
30
H2O
30
20
20
0
20
10
10
H2O
10
0
100
10
10
10
100 0
0 10
20
Triton X-102
30
40
50
60
70
80
90
100
N1112OHDHP
Table 1 Structures, suppliers and purities of chemicalsa. Compound
N1112OHDHP
Chemical structure
Supplier
IoLiTec
Triton X-100 n = 9.5
CAS number
83846-92-8
9002-93-1 SigmaAldrich
Triton X-102 n = 12 a
9036-19-5
Milli-Q water was used in all the experiments. *HLB: Hydrophilic Lipophilic Balance; ** Ref [25]
IUPAC name Dihydrogen phosphate;2hydroxyethyl (trimethyl) azanium 2-[4-(2,4,4trimethylpenta n-2-yl) phenoxy]ethan ol
Mass fraction purity
HLB*
0.98
-
0.98
13.4**
0.98
14.4**
Table 2 Solubility data for {Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} from T = (298.15-333.15) K and 0.1 MPa .a T = 298.15 K 100 w2
T = 313.15 K
100 w1
100 w2
T = 323.15 K
100 w1
100 w2
100 w1
T = 333.15 K 100 w2
100 w1
Boundaries between solid and liquid region* 1.11
95.74
0.79
94.89
0.99
94.38
1.09
94.01
9.80
82.86
10.30
82.28
9.53
83.14
9.90
82.17
17.02
74.15
20.74
70.10
19.23
72.70
21.28
69.55
24.81
63.79
26.19
61.07
26.26
62.26
25.54
63.05
35.17
51.17
33.44
50.93
34.66
51.92
33.11
52.16
41.92
42.29
41.35
40.85
41.85
42.94
42.23
41.21
49.49
31.52
48.70
31.83
48.14
33.50
47.05
33.81
54.21
24.20
54.72
22.39
50.79
29.45
53.72
23.64
60.79
15.03
59.28
15.90
62.20
14.81
60.16
15.02
67.36
7.46
67.41
6.76
68.17
7.16
66.47
7.41
71.48
0.80
72.08
0.98
73.03
0.85
LLE 65.02
0.53
63.54
0.43
69.54
0.93
71.06
1.02
55.47
0.38
57.37
0.51
62.56
0.57
60.39
0.68
45.39
0.32
43.28
0.56
50.29
0.71
47.91
0.54
35.85
0.46
35.74
0.57
41.46
0.63
39.74
0.82
25.63
0.39
26.53
0.46
35.51
0.55
30.13
0.61
18.57
0.30
15.71
0.65
23.67
0.75
21.67
0.73
17.02
1.88
11.37
0.16
13.35
0.69
9.96
0.56
a
16.78
4.15
11.80
1.25
7.82
0.12
3.63
0.06
15.53
6.93
10.40
2.79
6.70
0.70
3.29
0.39
14.68
9.35
10.53
4.31
6.63
1.58
3.01
0.75
14.82
14.95
10.45
6.83
6.24
3.62
2.86
1.26
13.63
19.83
9.95
9.83
5.70
3.97
2.54
1.82
11.78
30.28
9.86
15.01
6.13
6.29
2.61
2.55
8.95
39.00
9.20
21.47
5.78
8.66
2.36
3.71
5.86
49.54
8.69
29.38
6.10
14.46
2.79
6.89
0.89
76.92
5.85
46.73
6.14
23.21
2.54
8.31
0.64
76.97
5.04
43.97
2.57
29.59
0.78
74.00
0.84
72.51
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.007 (95% level of confidence) * these data correspond to the total composition when the last crystal disappears. The solids have been identified to be N1112OHDHP by NMR
Table 3 Solubility data for {Triton X-102 (1) + N1112OHDHP (2)+ H2O (3)} from T = (298.15-333.15) K and 0.1 MPa.a T = 298.15 K 100 w2
100 w1
T = 313.15 K 100 w2
T = 323.15 K
100 w1
100 w2
100 w1
T = 333.15 K 100 w2
100 w1
Boundaries between solid and liquid region* 1.06
94.92
1.00
94.76
0.92
95.14
0.63
94.87
9.18
84.31
9.81
84.31
10.19
83.72
8.89
84.27
18.03
72.83
18.18
73.49
17.84
72.23
17.45
73.55
25.91
61.97
26.37
60.76
26.85
61.64
25.01
64.17
34.13
51.03
32.63
52.38
33.73
51.18
34.17
51.77
39.67
41.85
41.19
39.90
41.19
41.44
41.53
41.87
47.11
31.07
46.57
31.59
46.21
32.78
48.01
31.83
53.01
22.36
54.34
22.64
52.27
23.90
52.30
25.70
59.23
14.82
59.94
15.06
59.34
13.70
59.70
15.73
64.84
8.30
66.75
7.05
64.78
6.95
66.81
7.43
71.19
0.71
71.22
0.96
69.28
0.91
71.00
0.93
LLE 67.36
0.56
65.21
0.51
66.08
0.56
68.03
0.75
60.52
0.61
54.30
0.64
52.46
0.61
58.61
0.69
51.74
0.43
43.41
0.58
42.68
0.73
49.84
0.71
40.09
0.88
36.18
0.63
33.86
0.46
41.81
0.55
30.28
0.53
25.37
0.46
26.09
0.53
33.22
0.62
24.18
0.32
20.60
0.31
17.39
0.63
25.95
0.57
23.33
2.99
18.75
1.98
15.30
0.22
16.15
0.65
20.93
5.24
18.15
4.56
13.90
1.49
11.67
0.15
20.37
8.59
16.68
6.95
13.80
3.19
11.15
1.24
18.64
12.29
15.63
10.61
13.37
6.11
10.88
2.87
a
16.73
17.65
14.98
14.51
12.79
9.08
10.60
5.21
15.50
23.18
12.68
20.35
12.10
12.17
9.73
6.45
13.32
31.85
11.55
26.60
10.76
16.33
9.87
9.95
9.53
38.48
9.19
37.16
10.37
23.79
8.73
13.23
5.29
48.54
5.47
47.03
8.25
33.39
8.09
20.75
0.79
70.90
0.80
75.75
5.32
43.76
7.30
30.75
0.74
76.47
4.60
43.65
0.51
76.82
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.009 (95% level of confidence) * These data correspond to the total composition when the last crystal disappears. The solids have been identified to be N1112OHDHP by NMR
Table 4 Parameters of Eq. (1) and standard deviation for {non-ionic surfactant (1) + N1112OHDHP (2) +H2O (3)}.a T/K
{Triton X-100 (1) + N1112OHDHP (2) +H2O (3) 298.15
0.9093
-1.8854
400.86
0.0317
313.15
0.7886
-0.3544
1842.96
0.0416
323.15
0.9851
-2.9906
5994.00
0.0915
333.15
18.775
-34.284
9800.75
0.0790
{Triton X-102 (1) + N1112OHDHP (2) +H2O (3) 298.15
0.8297
-1.9504
162.12
0.0213
313.15
0.9356
-2.4522
311.78
0.0164
323.15
0.9421
-2.5119
711.01
0.0260
333.15
0.8961
-2.2271
1737.39
0.0263
a
Standard deviation () was calculated by means of Eq. (4).
Table 5 Parameters of Eq. (2) and standard deviation for {Non-ionic surfactant (1) + N1112OHDHP (2) +H2O (3)}.a T/K
{Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} 298.15
0.8766
-0.9716
-1.9636
-3.6164
0.0257
313.15
0.7682
0.6610
-7.1885
-13.466
0.0339
323.15
0.7271
0.7884
-9.3123
-59.080
0.0957
333.15
2.1344
-20.142
47.619
-66.496
0.0786
{Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} 298.15
0.8318
-1.4398
0.2300
-3.2385
0.0184
313.15
0.8526
-0.8005
-3.3496
4.3419
0.0166
323.15
0.9180
-1.7049
-1.0414
-5.0624
0.0195
333.15
0.8007
0.1858
-9.1209
13.578
0.0218
a
Standard deviation () was calculated by means of Eq. (4).
Table 6 Parameters of Eq. (3) and standard deviation for {Non-ionic surfactant (1) + + N1112OHDHP (2) +H2O (3)}.a T/K
{Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} 298.15
1.4535
-26.091
88.130
-301.49
0.0241
313.15
0.4385
-13.680
64.909
-478.26
0.0431
323.15
-0.2013
-2.9069
30.544
-830.88
0.0895
333.15
-0.4113
17.209
-169.51
-883.08
0.0748
{Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} 298.15
0.5315
-13.338
40.542
-127.85
0.0142
313.15
0.8158
-17.012
55.222
-204.72
0.0095
323.15
1.0444
-21.841
79.018
-355.50
0.0200
333.15
1.1631
-28.111
120.04
-685.80
0.0201
a
Standard deviation () was calculated by means of Eq. (4).
Table 7 Experimental tie–lines in mass percentage for {Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} at T = (298.15 to 333.15) K and 0.1MPa a Surfactant-rich phase 100 w1I
100 w2I
Ionic liquid-rich phase 100 w1II
100 w2II
Feed composition 100w1
100w2
TLL
S
T = 298.15 K 89.10
0.86
0.18
62.50
10.08
54.95
108.20
-1.4424
75.87
1.46
0.24
54.68
10.47
47.28
92.48
-1.4210
60.06
5.69
0.27
46.38
9.93
40.31
72.31
-1.4696
48.19
6.61
0.32
35.91
10.05
30.10
56.13
-1.6336
T = 313.15 K 87.80
0.83
0.21
60.96
10.26
54.34
106.25
-1.4567
74.95
1.44
0.26
51.55
9.77
44.59
89.93
-1.4906
60.00
3.48
0.33
39.78
9.92
33.97
69.84
-1.6441
41.30
6.37
0.42
32.58
10.02
26.75
48.57
-1.5601
26.21
9.00
0.48
21.83
10.25
16.95
28.76
-2.0060
T = 323.15 K 87.36
1.18
0.20
59.26
9.95
52.92
104.74
-1.5006
74.12
1.47
0.28
47.58
10.68
40.96
87.05
-1.6015
57.58
3.60
0.39
37.49
10.25
31.62
66.48
-1.6877
38.65
5.40
0.44
26.38
10.70
20.65
43.59
-1.8212
20.70
6.51
0.46
15.14
10.80
11.00
22.00
-2.3420
T = 333.15 K
a
87.54
0.51
0.16
63.44
10.73
55.80
107.69
-1.3886
75.19
0.88
0.24
52.56
9.88
45.65
91.04
-1.4501
63.60
1.97
0.28
44.50
10.31
37.17
76.28
-1.4889
50.67
2.18
0.45
32.85
10.13
26.83
58.85
-1.6374
35.79
3.38
0.57
20.24
10.34
15.62
39.04
-2.0886
21.62
3.61
0.65
11.86
10.15
8.23
22.54
-2.5412
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.010 (95% level of confidence)
Table 8
Experimental tie–lines in mass percentage for {Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} at T = (298.15 to 333.15) K and 0.1 MPa a Surfactant-rich phase Ionic liquid-rich phase Feed composition 100 w1I
100 w2I
100 w1II
100 w2II
100w1
100w2
TLL
S
T = 298.15 K 86.08
0.75
0.24
63.12
10.93
55.60
106.10
-1.3763
75.11
1.21
0.36
53.48
9.76
47.24
91.22
-1.4301
57.19
4.46
0.42
43.38
10.20
35.80
68.83
-1.4590
30.09
14.19
0.46
31.60
10.51
25.96
34.36
-1.7026
T = 313.15 K 90.00
0.61
0.20
63.89
10.42
56.35
109.86
-1.4191
79.10
1.37
0.25
52.48
10.86
45.53
93.96
-1.5428
63.26
3.30
0.31
45.34
10.20
37.88
75.70
-1.4974
49.78
5.51
0.43
34.70
9.71
29.34
57.33
-1.6907
26.09
12.71
0.47
27.09
9.96
21.14
29.38
-1.7818
T = 323.15 K 89.57
0.43
0.16
62.95
10.20
56.10
109.10
-1.4301
78.06
1.19
0.27
50.87
10.33
43.98
92.30
-1.5659
58.00
3.16
0.30
41.20
9.67
34.87
69.12
-1.5167
34.89
8.43
0.34
29.77
10.67
23.59
40.61
-1.6192
21.44
10.62
0.41
19.68
9.46
15.74
22.89
-2.3217
T = 333.15 K
a
89.46
0.31
0.14
66.39
10.29
59.18
111.11
-1.3516
79.12
0.74
0.16
56.92
10.68
49.00
96.91
-1.4055
64.03
2.16
0.19
47.78
10.76
40.14
78.47
-1.3992
53.71
3.06
0.23
36.61
10.34
30.42
63.13
-1.5939
38.32
5.26
0.27
27.07
10.29
21.67
43.85
-1.7440
21.71
8.54
0.34
18.05
9.47
13.45
23.39
-2.2454
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.013 (95% level of confidence)
Table 9 Othmer-Tobias and Bancroft fitting parameters Eq. (7) and Eq. (8) and correlation coefficient for {Non-ionic surfactant (1) + N1112OHDHP (2) +H2O (3)} T/K
µ
R2
R2
{Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} 298.15
1.7963
0.4538
0.961
1.8076
0.6685
0.961
313.15
1.7282
0.3506
0.990
1.9489
0.6381
0.966
323.15
1.5465
0.3093
0.995
2.2344
0.7189
0.976
333.15
1.1662
0.3847
0.987
2.3278
0.9307
0.961
{Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} 298.15
2.0816
0.4483
0.998
1.5693
0.5162
0.997
313.15
1.9895
0.3444
0.984
1.7911
0.4898
0.965
323.15
1.8458
0.3440
0.991
1.8348
0.6694
0.989
333.15
1.4297
0.4094
0.994
1.9976
0.7027
0.961
Highlights Cholinium dihydrogenphosphate efficiently salts out Triton aqueous solutions The biphasic area covers almost all the ternary diagram at elevated temperatures DHP anion is pointed out as a more suitable anion than chloride or dihydrogen citrate The experimental data was successfully correlated with well-known empirical equations
S0021-9614(18)31201-1 https://doi.org/10.1016/j.jct.2019.02.009 YJCHT 5715
To appear in:
J. Chem. Thermodynamics
Received Date: Revised Date: Accepted Date:
29 November 2018 11 February 2019 12 February 2019
Please cite this article as: M.S. Álvarez, Y. Zhang, M. Ángeles Sanromán, F.J. Deive, A. Rodríguez, Suitability of dihydrogenphosphate anion to salt out cholinium-based ionic liquids, J. Chem. Thermodynamics (2019), doi: https:// doi.org/10.1016/j.jct.2019.02.009
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Suitability of dihydrogenphosphate anion to salt out cholinium-based ionic liquids María S. Álvarez1,2*, Yanfei Zhang2, M. Ángeles Sanromán1, Francisco J. Deive1, Ana Rodríguez1* 1
Department of Chemical Engineering, University of Vigo, P. O. Box 36310, Vigo, Spain
2
Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey
08544, USA * Corresponding author: +34 986812304; E-mail addresses: [email protected]; [email protected]
ABSTRACT
The segregation capacity of cholinium dihydrogen phosphate (N 1112OHDHP) in aqueous solutions of two non-ionic surfactants belonging to Triton X family (Triton X-100 and Triton X-102) was explored at different temperatures from T = (298.15 to 333.15) K. The experimental data for each binodal curve have been correlated using three empirical models based on exponential and polynomial equations. The tie-line data were suitably described by applying the Othmer-Tobias and Bancroft models. The data obtained demonstrated the great ability of N1112OHDHP to act as phase promoter in aqueous solutions of non-ionic surfactants in comparison with other ionic liquids like N1112OHCl, N1112OHDHC or C2C1imC2SO4. Keywords: Aqueous two-phase systems; Cholinium dihydrogen phosphate; Ionic liquids; Non-ionic surfactants; Triton X
1. Introduction The awareness for the development of more sustainable chemical processes has prompted the investment of great research efforts in neoteric solvents like liquid polymers, perfluorocarbons, supercritical fluids or ionic liquids [1]. The latter have been
the subject of a great interest since the last decade, due to appealing properties like their negligible volatility, thermal stability and excellent solubilisation capacity [2, 3]. Apart from that, one of the important aspects to attain truly green, competitive and efficient industrial processes is the finding of an appropriate solvent for a specific application, or the so-called task specific ionic liquid. In this sense, thousands of new molten salts can be designed by combining a particular cation and anion, making it possible to label them as neoteric solvents [4]. This fact has contributed the application of ionic liquids in an array of sectors ranging from electrochemistry [5], analytical chemistry [6], biotechnology [7], environmental engineering [8] to separation processes [9]. More specifically, the application of ionic liquids in separation processes has find a promising niche in the development of aqueous biphasic systems (ATPS), as their low vapour pressure makes up an advance regarding conventional volatile organic solvents commonly employed in extraction units [10]. These systems are traditionally composed of a salt and a hydrophilic polymer [11-13], although two salts [14], two polymers [15] or even surfactants [16] may be employed as components in aqueous solutions. The chemical explanation for aqueous phase segregation is based on the different hydrogen bonding capacity of the components to interact with water molecules. These separation systems possess advantages like their short time, easy operation and low energy demand [17], although the lack of knowledge of the partition mechanisms, or the deactivating effects on enzymes of some of them makes it necessary to invest more research efforts. The successful application of this separation method has already been demonstrated for enzymes [18], antioxidants [19], heavy metals [20], or dyes [21]. Additionally, since the addition of surfactants like Triton could entail additional benefits for several applications like biomass solubilisation [22], we have already demonstrated the suitable role of imidazolium-based ionic liquids as agents leading to phase
disengagement [23]. However, the environmental persistence and toxicity of this family of ionic liquids [24] has furthered the research of more biocompatible ionic liquids like those bearing cholinium cation [25], whose complete biodegradability has already been demonstrated [26]. Therefore, in this research work, the role of cholinium dihydrogen phosphate (N1112OHDHP) as salting out agent in aqueous solutions of model non-ionic surfactants with different hydrophilicities like Triton X-100 and Triton X-102, has been demonstrated at four temperatures. All the experimental data for the systems (Triton X100 or Triton X-102 + N1112OHDHP + H2O) have been determined and correlated with known equations. Analogously, the tie-lines were empirically ascertained and OthmerTobias and Bancroft equations were employed to further characterize them. 2. Experimental 2.1. Materials The ionic liquid cholinium dihydrogen phosphate N1112OHDHP was purchased from IoLiTec. In order to reduce potential traces of solvents and moisture, vacuum drying (210−1 Pa) and moderate temperature (T = 323.15 K) were applied for 5 days always immediately prior to its use up to a mass fraction of water of 0.02, after KarlFisher titration. This water content was accounted for in the experimental determinations and added to the water composition in the ternary mixtures. The nonionic surfactants belonging to the polyethylene glycol tert-octylphenyl ether family (Triton X-100 and Triton X-102) were purchased from Sigma-Aldrich, and used without further purification. Their water content was also determined by Karl-Fisher titration and was lower than 0.001 (w/w). Double-distilled deionized water was used for
preparation of the solutions. The main data referring to chemicals are summarized in Table 1. 2.2. Apparatus and experimental procedure The cloud point titration method was used to ascertain the binodal data of the different ATPS at temperatures from T = (298.15 to 333.15) K and atmospheric pressure according to the procedure described previously [27]. As a short overview, the binodal curves were accomplished in a jacketed glass vessel containing a magnetic stirrer and double-distiller deionized water was dropwise-added to binary mixtures containing known concentrations of surfactant and ionic liquid (ranging from 0.1:0.99 to 0.99:0.1 ratios of ionic liquid: surfactant) until solids disappear. Thereby, the solid-liquid and the liquid-liquid regions were delineated. The ternary system compositions were determined by the mass quantification of all components (Mettler Toledo XS104 balance, ± 10-4 g) and the temperature was controlled with a F200 ASL digital thermometer with an uncertainty of ± 0.01 K. The tie-lines (TLs) data determination was carried out in the previously described thermostatted glass vessel where a ternary mixture with known composition from the biphasic region was added to the cell, stirred vigorously for 1 h, and left to settle for 48 h to guarantee a complete separation of the two phases. Each layer was harvested through a syringe and analysed by means of density and refractive index measurements. An Anton Paar DSA-48 digital vibrating tube densimeter was used for density measurements (uncertainty of ± 210-4 gcm-3). On the other hand, refractive indices were determined by means of a Dr. Kernchen ABBEMAT WR refractometer (uncertainty of ± 410-5). Both densimeter and refractometer were calibrated beforehand following the manufacturer recommendations.
3. Results and discussion 3.1 Binodal curves determination and modelling At first, the salting out potential of the systems formed by the ionic liquid N1112OHDHP and aqueous solutions of the non-ionic surfactants Triton X-100 and Triton X-102 was researched at temperatures ranging from T = (298.15 to 333.15) K. The experimental solubility data in mass composition for the ternary mixture are listed in Tables 2 and 3, and displayed as triangular representation in Figures 1 and 2. A visual inspection of the experimental binodal data discloses that the biphasic region is expanded with increasing temperature for both non-ionic surfactants. A plausible reason to understand this behaviour is that the interactions between the nonionic surfactants and the water molecules are debilitated at high temperatures, thus leading to greater surfactant hydrophobicity and a consequent increase of the biphasic area. These results are in agreement with previous research studies in this field [23, 2830]. On the other hand, a careful analysis of the data in terms of the hydrophilicity of the surfactant can be carried out by comparing the systems displayed in Figures 1 and 2. Hence, it is clear that the use of the surfactant Triton X-100 entails higher immiscibility regions than Triton X-102. This response is in accordance with the hydrophobic nature of the former, which is justified by the hydrophilic-lipophilic balance (HLB) parameter. This empirical number, varying between 0 and 20 for non-ionic surfactants, allows evaluating the balance of the strength and size of hydrophilic and lipophilic groups present in emulsifying compounds [31]. In this context, Triton X-100, with the lower HLB value (cf. Table 1), displays less favourable interactions with water molecules, making it easier to trigger phase segregation. The same pattern was found for other
ATPS, where different surface active compounds like those belonging to Tween family were used [32-34]. In general, it is observed that the use of the less hydrophilic surfactant Triton X100 and the operation at T = 333.15K involve the existence of biphasic area occupying almost all the surface of the triangular diagram. In relation to that, it should be noted that DHP anion plays an important role in the phase segregation. This salting out potential can be evaluated in terms of the Hofmeister series, which classifies the anions in accordance with the lyotropic number of the anion. In general, hydration radius, charge to size ratio, charge and lyotropic number can all be related to an ion Gibbs free energy of hydration (hydG), which can be a useful tool to quantitatively verify the experimental results obtained. This trend confirms that anions with higher phase promotion capacity show more negative hydG values. Thus, dihydrogen phosphate anion displays lower values (−465 kJmol-1) than other recently reported systems using cholinium cation combined with chloride anion (−340 kJmol-1) or dihydrogen citrate anion (−81 kJmol-1) [35, 36]. An analogous classification may be done when analysing the Jones-Dole B coefficient, which is higher for dihydrogen phosphate (0.340 dm3mol1
) than for chloride anion (-0.005 dm3mol-1) [37, 38], thus confirming the sequence
obtained when the solubility data reported recently is compared with the present results, as shown in Figure 3. All experimental solubility data for the systems were suitably correlated using three empirical mathematical models commonly applied to several types of ATPS [39, 40]. 3 w1 =α∙exp (βw0.5 2 -λw2 )
(1)
2 w1 =α+βw0.5 2 +λw2 +δw2
(2)
2 w1 =exp(α+βw0.5 2 +λw2 +δw2 )
(3)
The w1 and w2 the mass fraction of surfactant and N1112OHDHP, respectively. On the other hand, , , and are the fitting parameters, which values were determined by minimizing the standard deviation ( ): n DAT z exp z adjust σ i n DAT
1/ 2
2
(4)
Here zexp and zadjust represent the experimental and the theoretical values, respectively and nDAT equals the number of data. All the values of the fitting parameters and standard deviations are listed in Tables 4 to 6. From the deviation data, it is possible to conclude that Eq. (3) is the one leading to the more appropriate description of the binodal curves, in line with previous results reported in literature [27, 40]. 3.2. Tie-lines and modelling The tie-lines of each system, which procedure was described beforehand, were carried out at T = (298.15 to 333.15) K and 0.1 MPa. The tie-line length (TLL) and the slope (S) were calculated using the following equations:
TLL w1I w1II
S
w1I w1II w2I w2II
w 2
I 2
2 w2II
0.5
(5)
(6)
where w1 refers to the mass fraction of Triton X-100 or Triton X-102 and w2 refers to N1112OHDHP. The superscripts I and II refer to top and bottom phases, respectively. The TL data obtained for each ternary system and the abovementioned parameters are given in Tables 7 and 8. Furthermore, the phase diagrams containing the tie-lines for both
non-ionic surfactants are shown in Figures 4 and 5. From the data obtained, it seems clear that the increase in the ionic liquid concentration in the bottom phase, leads to more non-ionic surfactant being salted out to the top phase, which in turn is associated with an increase in the TLL values. The component compositions between the surfactant and ionic liquid-rich phases can be suitably described by means of two well-known models like Othmer-Tobias (Eq. 7) and Bancroft (Eq. 8) equations [41].
1 w1I I w1 w3II II w 2
1 w2II II w2
w3I I w 1
(7)
(8)
The w1, w2 and w3 the Triton X, N1112OHDHP and water mass fraction, respectively, (I and II refer to top and bottom phases) while , , , and are the fitting parameters. The values of these parameters are listed in Table 9, and the regression coefficients greater than 0.98 indicate the suitability of the abovementioned equations to describe the experimental tie-line data. 4. Conclusion The present study demonstrates the greater suitability of cholinium dihydrogen phosphate anion to trigger phase segregation in aqueous solutions of non-ionic surfactants, regarding previous studies using chloride or dihydrogencitrate anions. Additionally, the operation at high temperatures contributes to maximize the biphasic area, as it weakens the interplays between surfactant and water molecules. The use of a polynomial equation allowed describing the binodal curves for both Triton X-100 and Triton X-102 at the temperatures under study. In the same vein, Othmer Tobias and
Bancroft models were successfully employed to model the experimental tie-line data, as the regression coefficients were always close to the unit. Acknowledgements The authors thank Xunta de Galicia and ERDF for funding through a postdoctoral grant (ED481B-2016/140-0) and project ED431F 2016/007. The authors are grateful to the Spanish Ministry of Economy and Competitiveness for the financial support of F.J. Deive under the Ramón y Cajal program (RyC-2013-14225). References [1] P. Lozano, Green Chem. 12 (2012) 555-569. [2] K.R. Seddon, J. Chem. Technol. Biotechnol. 68 (1997) 351-356. [3] M.J. Earle, J.M.S.S. Esperança, M.A. Gilea, J.N. Canongia Lopes, L.P.N. Rebelo, J.W. Magee, K.R. Seddon, J.A. Widegren, Nature 439 (2006) 831-834. [4] K.D. Clark, O. Nacham, H. Yu, T. Li, M.M. Yamsek, D.R. Ronning, J.L. Anderson, Anal. Chem. 87 (2015) 1552-1559. [5] M.C. Lin, M. Gong, B. Lu, Y. Wu, D.Y. Wang, M. Guan, M. Angell, C. Chen, J. Yang., B.J. Hwang, H. Dai, Nature 520 (2015) 324-328. [6] T.D. Ho, C. Zhang, L.W. Hantao, J.L. Anderson, Anal. Chem. 86 (2014) 262-285. [7] J.V. Rodrigues, D. Ruivo, A. Rodríguez, F.J. Deive, J.M.S.S. Esperança, I.M. Marrucho, C.M. Gomes, L.P.N. Rebelo, Green Chem. 16 (2014) 4520-4523. [8] A.B. Pereiro, F.J. Deive, A. Rodríguez, Sep. Purif. Technol. 47 (2012) 377-385. [9] L. Morandeira, M.S.Álvarez, F.J.Deive, M.A. Sanromán, A. Rodríguez, Sep. Purif. Technol. 174 (2017) 29-38.
[10] M.G. Freire, A.F.M. Claúdio, J.M.M. Araúo, J.A.P. Coutinho, I.M. Marrucho, J.N. Canongia Lopes, L.P.N. Rebelo, Chem. Soc. Rev. 41 (2012) 4966-4995. [11] M.T. Zafarani-Moattar, H. Shekaari, F. Gharekhani, J. Chem. Thermodyn. 113 (2017) 20-28. [12] P.A. Albertsson, Partition of Cell Particles and Macromolecules, John Wiley and Sons, New York, 1986. [13] B.Y. Zaslavsky, Aqueous Two-Phase Partitioning: Physical Chemistry and Bioanalytical Applications, Marcel Dekker, New York, 1994. [14] S.P.M. Ventura, F.A. Silva, M.V. Quental, D. Mondal, M.G. Freire, J.A.P. Coutinho, Chem. Rev. 117 (2017) 6984-7052. [15] R. Sadeghi, M. Maali, Polymer 83 (2016) 1-11. [16] M.S. Álvarez, F. Moscoso, F.J. Deive, M.A. Sanromán, A. Rodríguez, J. Chem. Thermodyn. 55 (2012) 151-158. [17] A. Salabat, S.T. Moghadam, M.R. Far, Calphad-Comput. Coupling Ph. Diagrams Thermochem. 34 (2010) 81-83. [18] V.E. Wolf-Márquez, M.A Martínez-Trujillo, G. Aguilar Osorio, F. Patiño, M.S. Álvarez, A. Rodríguez, M.A. Sanromán, F.J. Deive, Bioresour. Technol. 225 (2017) 326-335. [19] G. Ulloa, C. Coutens, M. Sánchez, J. Sineiro, J. Fábregas, F.J. Deive, A. Rodríguez, M.J. Núñez, Green Chem. 14 (2012) 1044-1051. [20] M.S. Álvarez, E. Gutiérrez, A. Rodríguez, M.A. Sanromán, F.J. Deive, Ind. Eng. Chem. Res. 53 (2014) 8615-8620.
[21] M.S. Álvarez, F. Moscoso, A. Rodríguez, M.A. Sanromán, F.J. Deive, Bioresour. Technol. 146 (2013) 689-695. [22] E. Gutiérrez-Arnillas, F.J. Deive, M.A. Sanromán, A. Rodríguez, Bioresour. Technol. 186 (2015) 303-308. [23] M.S. Álvarez, M. Rivas, F.J. Deive, M.A. Sanromán, A. Rodríguez, RSC Adv. 4 (2014) 32698-32700. [24] M. Petkovic, K.R. Seddon, L.P.N. Rebelo, C. Silva Pereira, Chem. Soc. Rev. 40 (2011) 1383-1403. [25] M.S. Álvarez, F. Moscoso, A. Rodríguez, M.A. Sanromán, F.J. Deive, J. Chem. Thermodyn. 54 (2012) 385-392. [26] L. Morandeira, M.S. Álvarez, M. Markiewicz, S. Stolte, A. Rodríguez, M.A. Sanromán, F.J. Deive, ACS Sust. Chem. Eng. 5 (2017) 8302-8309. [27] M.S. Álvarez, F. Patiño, F.J. Deive, M.A. Sanromán, A. Rodríguez, J. Chem. Thermodyn. 91 (2015) 86-93. [28] N. Escudero, L. Morandeira, M.A. Sanromán, F. J. Deive, A. Rodríguez, J. Chem. Thermodyn. 118 (2018) 235-243. [29] M.S. Álvarez, J. M.S.S. Esperança, F.J. Deive, M.Á. Sanromán, A. Rodríguez, Sep. Purif. Technol. 153 (2015) 91-98. [30] H. Rasa, M. Mohsen-Nia , H. Modarress, J. Chem. Thermodyn. 40 (2008) 573579. [31] W. C. Griffin, J. Soc. Cosmet. Chem. 5 (1954) 249-256. [32] G. Ulloa, C. Coutens, M. Sánchez, J. Sineiro, A. Rodríguez, F.J. Deive, M.J. Núñez, J. Chem. Thermodyn. 47 (2012) 62-67.
[33] F.J. Deive, A. Rodríguez, I.M. Marrucho, L.P.N. Rebelo, J. Chem. Thermodyn. 43 (2011) 1565-1572. [34] J.P. Martins, J.S.R. Coimbra, F.C. Oliveira, G. Sanaiotti, C.A.S. Silva, L.H.M. Silva, M.C.H. Silva, J. Chem. Eng. Data 55 (2010) 1247-1251. [35] Y. Marcus, J. Chem. Soc. Faraday Trans. 87 (1991) 2995-2999. [36] M.T. Zafarani-Moattar, S. Hamzehzadeh, Fluid Phase Equilib. 304 (2011) 110-120. [37] H. Zhao, S. Campbell, L. Jackson, Z. Song, O. Olubajo, Tetrahedron: Asymmetry 17 (2006) 377-383. [38] H.D.B. Jenkins, Y. Marcus, Chem. Rev. 95 (1995) 2695-2724. [39] J.C. Merchuk, B.A. Andrews, J.A. Asenjo, J. Chromatogr. B 711 (1998) 285-293. [40] S. Hamzehzadeh, M.T. Zafarani-Moattar, Fluid Phase Equilib. 385 (2015) 37-47. [41] D.F. Othmer, P.E. Tobias, Ind. Eng. Chem. 34 (1942) 693-696.
Figure Captions
Figure 1. Plot of solubility data for {Triton X-100 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa. Dashed lines represent the fitting to Eq. (3) and solid lines are a guide to the eye. Figure 2. Plot of solubility data for {Triton X-102 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa . Dashed lines represent the fitting to Eq. (3) and solid lines are a guide to the eye. Figure 3. Comparison of solubility data for {Triton X-100 (1) or Triton X-102 + ionic liquid (2) +H2O (3)} at T = 298.15 K: dihydrogencitrate (), chloride () and DHP () anions combined with N1112OH cation. Figure 4. Plot of tie-lines for {Triton X-100 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa.
Figure 5. Plot of tie-lines for {Triton X-102 (1) + N1112OHDHP (2) +H2O (3)} at T = 298.15 K (), 313.15 K (), 323.15 K (), 333.15 K () and 0.1 MPa.
FIGURE 1
H2O 0
100
10 20
90
L 80
30
70
40
60
50
50 L+L
60
40
70
30
80
20
90
S+L
10
100
Triton X-100 0
0 10
20
30
40
50
60
70
80
90
100
N1112OHDHP
FIGURE 2
H2O 0
100
10 20
90 L
80
30
70
40
60
50
50 L+L
60
40
70
30
80
20
90
10
100
Triton X-102 0
0 10
20
30
40
50
60
70
80
90
100
N1112OHDHP
FIGURE 3
H2O 0
100
10
90
20
80
30
70
40
60
50
50
60
40
70
30
80
20
90
10
100
0
0
10
20
30
40
50
60
70
80
90
100
Ionic Liquids
Triton X-100 H2O 0 10
100 90
20
80
30
70
40
60
50
50
60
40
70
30
80
20
90
10
100 0
0 10
Triton X-102
20
30
40
50
60
70
80
90
100
Ionic Liquids
FIGURE 4
H 2O
H2O 0
0
100
90
90 20
20
80
80 30
30
70
70 40
40
60
60 50
50
50
50 60
60
40
40 70
70
30
30 80
80
20
20 90
90
10
10 100
100
0
0
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
50
10
10
90
50 60 70 80 90 100
0
Triton X-100
30
100
N1112OHDHP
20
90
10
90
40
80
20
80
50
70
30
70
60
60
40
60
70
50
50
50
80
40
60
40
100
90
30
70
40
30
90
100
20
80
30
20
80
H2O 0
100
20
10
70
N1112OHDHP
H2O 0
60
Triton X-100
N1112OHDHP
Triton X-100
0
100
10
10
10
100 0
0 10
Triton X-100
20
30
40
50
60
70
80
90
100
N1112OHDHP
FIGURE 5
H2O
H2O
0
0 100
90
90 20
20
80
80 30
30
70
70 40
40
60
60 50
50
50
50 60
60
40
40 70
70
30
30 80
80
20
20 90
90
10
10 100
100
0
0
0
10
20
30
40
50
60
70
80
90
0
100
N1112OHDHP
Triton X-102
60
10
90
60
30
0 100
N1112OHDHP
20
90
10
100 90
40
80
20
90
80
50
70
30
70
60
60
80
60
70
50
40
70
100
80
40
50
90
90
30
60
80
100
20
80
50
70
N1112OHDHP
0
50
Triton X-102
50
Triton X-102
70
40
40
100
40
30
30
H2O
30
20
20
0
20
10
10
H2O
10
0
100
10
10
10
100 0
0 10
20
Triton X-102
30
40
50
60
70
80
90
100
N1112OHDHP
Table 1 Structures, suppliers and purities of chemicalsa. Compound
N1112OHDHP
Chemical structure
Supplier
IoLiTec
Triton X-100 n = 9.5
CAS number
83846-92-8
9002-93-1 SigmaAldrich
Triton X-102 n = 12 a
9036-19-5
Milli-Q water was used in all the experiments. *HLB: Hydrophilic Lipophilic Balance; ** Ref [25]
IUPAC name Dihydrogen phosphate;2hydroxyethyl (trimethyl) azanium 2-[4-(2,4,4trimethylpenta n-2-yl) phenoxy]ethan ol
Mass fraction purity
HLB*
0.98
-
0.98
13.4**
0.98
14.4**
Table 2 Solubility data for {Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} from T = (298.15-333.15) K and 0.1 MPa .a T = 298.15 K 100 w2
T = 313.15 K
100 w1
100 w2
T = 323.15 K
100 w1
100 w2
100 w1
T = 333.15 K 100 w2
100 w1
Boundaries between solid and liquid region* 1.11
95.74
0.79
94.89
0.99
94.38
1.09
94.01
9.80
82.86
10.30
82.28
9.53
83.14
9.90
82.17
17.02
74.15
20.74
70.10
19.23
72.70
21.28
69.55
24.81
63.79
26.19
61.07
26.26
62.26
25.54
63.05
35.17
51.17
33.44
50.93
34.66
51.92
33.11
52.16
41.92
42.29
41.35
40.85
41.85
42.94
42.23
41.21
49.49
31.52
48.70
31.83
48.14
33.50
47.05
33.81
54.21
24.20
54.72
22.39
50.79
29.45
53.72
23.64
60.79
15.03
59.28
15.90
62.20
14.81
60.16
15.02
67.36
7.46
67.41
6.76
68.17
7.16
66.47
7.41
71.48
0.80
72.08
0.98
73.03
0.85
LLE 65.02
0.53
63.54
0.43
69.54
0.93
71.06
1.02
55.47
0.38
57.37
0.51
62.56
0.57
60.39
0.68
45.39
0.32
43.28
0.56
50.29
0.71
47.91
0.54
35.85
0.46
35.74
0.57
41.46
0.63
39.74
0.82
25.63
0.39
26.53
0.46
35.51
0.55
30.13
0.61
18.57
0.30
15.71
0.65
23.67
0.75
21.67
0.73
17.02
1.88
11.37
0.16
13.35
0.69
9.96
0.56
a
16.78
4.15
11.80
1.25
7.82
0.12
3.63
0.06
15.53
6.93
10.40
2.79
6.70
0.70
3.29
0.39
14.68
9.35
10.53
4.31
6.63
1.58
3.01
0.75
14.82
14.95
10.45
6.83
6.24
3.62
2.86
1.26
13.63
19.83
9.95
9.83
5.70
3.97
2.54
1.82
11.78
30.28
9.86
15.01
6.13
6.29
2.61
2.55
8.95
39.00
9.20
21.47
5.78
8.66
2.36
3.71
5.86
49.54
8.69
29.38
6.10
14.46
2.79
6.89
0.89
76.92
5.85
46.73
6.14
23.21
2.54
8.31
0.64
76.97
5.04
43.97
2.57
29.59
0.78
74.00
0.84
72.51
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.007 (95% level of confidence) * these data correspond to the total composition when the last crystal disappears. The solids have been identified to be N1112OHDHP by NMR
Table 3 Solubility data for {Triton X-102 (1) + N1112OHDHP (2)+ H2O (3)} from T = (298.15-333.15) K and 0.1 MPa.a T = 298.15 K 100 w2
100 w1
T = 313.15 K 100 w2
T = 323.15 K
100 w1
100 w2
100 w1
T = 333.15 K 100 w2
100 w1
Boundaries between solid and liquid region* 1.06
94.92
1.00
94.76
0.92
95.14
0.63
94.87
9.18
84.31
9.81
84.31
10.19
83.72
8.89
84.27
18.03
72.83
18.18
73.49
17.84
72.23
17.45
73.55
25.91
61.97
26.37
60.76
26.85
61.64
25.01
64.17
34.13
51.03
32.63
52.38
33.73
51.18
34.17
51.77
39.67
41.85
41.19
39.90
41.19
41.44
41.53
41.87
47.11
31.07
46.57
31.59
46.21
32.78
48.01
31.83
53.01
22.36
54.34
22.64
52.27
23.90
52.30
25.70
59.23
14.82
59.94
15.06
59.34
13.70
59.70
15.73
64.84
8.30
66.75
7.05
64.78
6.95
66.81
7.43
71.19
0.71
71.22
0.96
69.28
0.91
71.00
0.93
LLE 67.36
0.56
65.21
0.51
66.08
0.56
68.03
0.75
60.52
0.61
54.30
0.64
52.46
0.61
58.61
0.69
51.74
0.43
43.41
0.58
42.68
0.73
49.84
0.71
40.09
0.88
36.18
0.63
33.86
0.46
41.81
0.55
30.28
0.53
25.37
0.46
26.09
0.53
33.22
0.62
24.18
0.32
20.60
0.31
17.39
0.63
25.95
0.57
23.33
2.99
18.75
1.98
15.30
0.22
16.15
0.65
20.93
5.24
18.15
4.56
13.90
1.49
11.67
0.15
20.37
8.59
16.68
6.95
13.80
3.19
11.15
1.24
18.64
12.29
15.63
10.61
13.37
6.11
10.88
2.87
a
16.73
17.65
14.98
14.51
12.79
9.08
10.60
5.21
15.50
23.18
12.68
20.35
12.10
12.17
9.73
6.45
13.32
31.85
11.55
26.60
10.76
16.33
9.87
9.95
9.53
38.48
9.19
37.16
10.37
23.79
8.73
13.23
5.29
48.54
5.47
47.03
8.25
33.39
8.09
20.75
0.79
70.90
0.80
75.75
5.32
43.76
7.30
30.75
0.74
76.47
4.60
43.65
0.51
76.82
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.009 (95% level of confidence) * These data correspond to the total composition when the last crystal disappears. The solids have been identified to be N1112OHDHP by NMR
Table 4 Parameters of Eq. (1) and standard deviation for {non-ionic surfactant (1) + N1112OHDHP (2) +H2O (3)}.a T/K
{Triton X-100 (1) + N1112OHDHP (2) +H2O (3) 298.15
0.9093
-1.8854
400.86
0.0317
313.15
0.7886
-0.3544
1842.96
0.0416
323.15
0.9851
-2.9906
5994.00
0.0915
333.15
18.775
-34.284
9800.75
0.0790
{Triton X-102 (1) + N1112OHDHP (2) +H2O (3) 298.15
0.8297
-1.9504
162.12
0.0213
313.15
0.9356
-2.4522
311.78
0.0164
323.15
0.9421
-2.5119
711.01
0.0260
333.15
0.8961
-2.2271
1737.39
0.0263
a
Standard deviation () was calculated by means of Eq. (4).
Table 5 Parameters of Eq. (2) and standard deviation for {Non-ionic surfactant (1) + N1112OHDHP (2) +H2O (3)}.a T/K
{Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} 298.15
0.8766
-0.9716
-1.9636
-3.6164
0.0257
313.15
0.7682
0.6610
-7.1885
-13.466
0.0339
323.15
0.7271
0.7884
-9.3123
-59.080
0.0957
333.15
2.1344
-20.142
47.619
-66.496
0.0786
{Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} 298.15
0.8318
-1.4398
0.2300
-3.2385
0.0184
313.15
0.8526
-0.8005
-3.3496
4.3419
0.0166
323.15
0.9180
-1.7049
-1.0414
-5.0624
0.0195
333.15
0.8007
0.1858
-9.1209
13.578
0.0218
a
Standard deviation () was calculated by means of Eq. (4).
Table 6 Parameters of Eq. (3) and standard deviation for {Non-ionic surfactant (1) + + N1112OHDHP (2) +H2O (3)}.a T/K
{Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} 298.15
1.4535
-26.091
88.130
-301.49
0.0241
313.15
0.4385
-13.680
64.909
-478.26
0.0431
323.15
-0.2013
-2.9069
30.544
-830.88
0.0895
333.15
-0.4113
17.209
-169.51
-883.08
0.0748
{Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} 298.15
0.5315
-13.338
40.542
-127.85
0.0142
313.15
0.8158
-17.012
55.222
-204.72
0.0095
323.15
1.0444
-21.841
79.018
-355.50
0.0200
333.15
1.1631
-28.111
120.04
-685.80
0.0201
a
Standard deviation () was calculated by means of Eq. (4).
Table 7 Experimental tie–lines in mass percentage for {Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} at T = (298.15 to 333.15) K and 0.1MPa a Surfactant-rich phase 100 w1I
100 w2I
Ionic liquid-rich phase 100 w1II
100 w2II
Feed composition 100w1
100w2
TLL
S
T = 298.15 K 89.10
0.86
0.18
62.50
10.08
54.95
108.20
-1.4424
75.87
1.46
0.24
54.68
10.47
47.28
92.48
-1.4210
60.06
5.69
0.27
46.38
9.93
40.31
72.31
-1.4696
48.19
6.61
0.32
35.91
10.05
30.10
56.13
-1.6336
T = 313.15 K 87.80
0.83
0.21
60.96
10.26
54.34
106.25
-1.4567
74.95
1.44
0.26
51.55
9.77
44.59
89.93
-1.4906
60.00
3.48
0.33
39.78
9.92
33.97
69.84
-1.6441
41.30
6.37
0.42
32.58
10.02
26.75
48.57
-1.5601
26.21
9.00
0.48
21.83
10.25
16.95
28.76
-2.0060
T = 323.15 K 87.36
1.18
0.20
59.26
9.95
52.92
104.74
-1.5006
74.12
1.47
0.28
47.58
10.68
40.96
87.05
-1.6015
57.58
3.60
0.39
37.49
10.25
31.62
66.48
-1.6877
38.65
5.40
0.44
26.38
10.70
20.65
43.59
-1.8212
20.70
6.51
0.46
15.14
10.80
11.00
22.00
-2.3420
T = 333.15 K
a
87.54
0.51
0.16
63.44
10.73
55.80
107.69
-1.3886
75.19
0.88
0.24
52.56
9.88
45.65
91.04
-1.4501
63.60
1.97
0.28
44.50
10.31
37.17
76.28
-1.4889
50.67
2.18
0.45
32.85
10.13
26.83
58.85
-1.6374
35.79
3.38
0.57
20.24
10.34
15.62
39.04
-2.0886
21.62
3.61
0.65
11.86
10.15
8.23
22.54
-2.5412
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.010 (95% level of confidence)
Table 8
Experimental tie–lines in mass percentage for {Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} at T = (298.15 to 333.15) K and 0.1 MPa a Surfactant-rich phase Ionic liquid-rich phase Feed composition 100 w1I
100 w2I
100 w1II
100 w2II
100w1
100w2
TLL
S
T = 298.15 K 86.08
0.75
0.24
63.12
10.93
55.60
106.10
-1.3763
75.11
1.21
0.36
53.48
9.76
47.24
91.22
-1.4301
57.19
4.46
0.42
43.38
10.20
35.80
68.83
-1.4590
30.09
14.19
0.46
31.60
10.51
25.96
34.36
-1.7026
T = 313.15 K 90.00
0.61
0.20
63.89
10.42
56.35
109.86
-1.4191
79.10
1.37
0.25
52.48
10.86
45.53
93.96
-1.5428
63.26
3.30
0.31
45.34
10.20
37.88
75.70
-1.4974
49.78
5.51
0.43
34.70
9.71
29.34
57.33
-1.6907
26.09
12.71
0.47
27.09
9.96
21.14
29.38
-1.7818
T = 323.15 K 89.57
0.43
0.16
62.95
10.20
56.10
109.10
-1.4301
78.06
1.19
0.27
50.87
10.33
43.98
92.30
-1.5659
58.00
3.16
0.30
41.20
9.67
34.87
69.12
-1.5167
34.89
8.43
0.34
29.77
10.67
23.59
40.61
-1.6192
21.44
10.62
0.41
19.68
9.46
15.74
22.89
-2.3217
T = 333.15 K
a
89.46
0.31
0.14
66.39
10.29
59.18
111.11
-1.3516
79.12
0.74
0.16
56.92
10.68
49.00
96.91
-1.4055
64.03
2.16
0.19
47.78
10.76
40.14
78.47
-1.3992
53.71
3.06
0.23
36.61
10.34
30.42
63.13
-1.5939
38.32
5.26
0.27
27.07
10.29
21.67
43.85
-1.7440
21.71
8.54
0.34
18.05
9.47
13.45
23.39
-2.2454
Standard uncertainties are u(T) = ± 0.01 K; u(P) = ± 2kPa. Expanded uncertainty for Uc(w) = 0.013 (95% level of confidence)
Table 9 Othmer-Tobias and Bancroft fitting parameters Eq. (7) and Eq. (8) and correlation coefficient for {Non-ionic surfactant (1) + N1112OHDHP (2) +H2O (3)} T/K
µ
R2
R2
{Triton X-100 (1) + N1112OHDHP (2) + H2O (3)} 298.15
1.7963
0.4538
0.961
1.8076
0.6685
0.961
313.15
1.7282
0.3506
0.990
1.9489
0.6381
0.966
323.15
1.5465
0.3093
0.995
2.2344
0.7189
0.976
333.15
1.1662
0.3847
0.987
2.3278
0.9307
0.961
{Triton X-102 (1) + N1112OHDHP (2) + H2O (3)} 298.15
2.0816
0.4483
0.998
1.5693
0.5162
0.997
313.15
1.9895
0.3444
0.984
1.7911
0.4898
0.965
323.15
1.8458
0.3440
0.991
1.8348
0.6694
0.989
333.15
1.4297
0.4094
0.994
1.9976
0.7027
0.961
Highlights Cholinium dihydrogenphosphate efficiently salts out Triton aqueous solutions The biphasic area covers almost all the ternary diagram at elevated temperatures DHP anion is pointed out as a more suitable anion than chloride or dihydrogen citrate The experimental data was successfully correlated with well-known empirical equations