Application of Buffer-Based Ionic Liquid in the ... - ACS Publications

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

pubs.acs.org/jced

Application of Buffer-Based Ionic Liquid in the Separation of 1,4Dioxane from Its Azeotropic Aqueous Solution Bhupender S. Gupta, Mei-Yueh Fang, and Ming-Jer Lee* Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106-07, Taiwan S Supporting Information *

ABSTRACT: We have found that the ionic liquid (IL) [TMA][EPPS] could induce liquid−liquid phase splitting in the aqueous solution of 1,4-dioxane at ambient conditions. This IL is composed of tetramethylammonium (TMA) as a cation and a biological buffer, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS), as an anion. The efficiency of this buffer-based IL for separating 1,4-dioxane from its aqueous solution has been evaluated on the basis of the liquid−liquid equilibrium (LLE) and solid−liquid−liquid equilibrium (SLLE) data of 1,4-dioane + water + [TMA][EPPS] at 298.15 K and under atmospheric pressure. The experimental LLE phase boundary data were correlated with an empirical equation and the effective excluded volume (EEV) model, respectively. The consistency of the LLE tie-line data was confirmed by using the Othmer−Tobias model. The binary interaction parameters of the NRTL model for each pair were obtained by correlating the experimental LLE and SLLE tie-line data. By using [TMA][EPPS] as an auxiliary agent, the maximum concentrations of 1,4-dioxane (97.8 wt %) in the organic-rich phase is greater than the azeotropic compositions (87.82 wt %) of the corresponding aqueous system. It clearly indicates that [TMA][EPPS] can be served as a high efficiency, noncorrosive, and biocompatible green agent for recovering high purity of 1,4-dioxane from its aqueous solution.

1. INTRODUCTION Volatile organic components (VOCs) such as 1,4-dioxane are widely used in various industries. But, because of their volatile nature, they create a potential threat to our environment.1−3 To recover the organics from the waste not only is desirable from an environmental point of view but also could make the overall process more economical. Therefore, in the present work we focus on the separation of 1,4-dioxane from its aqueous solution. 1,4-Dioxane serves as a solvent, reactive intermediate, and cleansing agent in various chemical processes.4 The binary mixture of 1,4-dioxane and water is known to form a homogeneous solution over the entire composition range. But, the aqueous solution containing about 82 wt % of 1,4-dioxane forms an azeotrope at atmospheric pressure.5 Because of the formation of the azeotrope, the recovery of high purity 1,4-dioxane from its aqueous solution becomes a challenging task when simple distillation methods are used. An alternative method by taking advantage of liquid−liquid phase splitting could be effective for the separation of the azeotropic aqueous solution.6 In this method, a suitable auxiliary agent is added into the homogeneous aqueous solution. Because the auxiliary agent may interact preferentially with one component of the mixture, it may lead to the splitting of the aqueous solution into different liquid phases. Then, a high purity of the organic from the organic-rich phase can be easily obtained via decantation and simple distillation. Since this whole process of phase-splitting occurs at ambient © XXXX American Chemical Society

conditions of temperature and pressure, the utilization of this method is considered as highly energy efficient. However, the development of this new separation process requires experimental phase equilibrium data such as LLE, SLLE, SLE (solid− liquid equilibrium), and VLE (vapor−liquid equilibrium) of the related mixtures. To find a suitable auxiliary agent for a particular mixture is still a challenging task for chemical engineers. The main expectation with an ideal auxiliary agent is, in addition to the high extraction efficiency and easy recyclability, that it should also possess high chemical and thermal stability without any potential threat to our environment. Various inorganic salts have been recognized as a potential auxiliary agent to induce liquid−liquid phase splitting for aqueous solutions of organics, such as alcohols, 1,4-dioxane, acetonitrile, and acetone. Because of their ionic nature, the inorganic salts strongly and preferentially interact electrostatically with water. Thus, the salt-based extractive method was also employed in other processes such as purification of biomolecules such as nucleic acid, protein, enzyme, and others,7−9 extractive crystallization,10 and extractive fermentation.11−14 However, several disadvantages are reported with the use of salts. For instance, salts are found corrosive in nature, which limits the average life of the Received: October 15, 2017 Accepted: February 13, 2018

A

DOI: 10.1021/acs.jced.7b00905 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Description of the Materials chemical name 1,4-dioxane EPPSa tetra-methylammonium hydroxide ethanol acetonitrile deionized water [TMA][EPPS] a

source Sigma Chemical Sigma Chemical Sigma Chemical Sigma Chemical Sigma Chemical our lab synthesize

Co. Co. Co. Co. Co.

(USA) (USA) (USA) (USA) (USA)

EPPS = 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid. GC = Gas chromatograph.

d

b1

CAS no.

purification method

mass fraction purity

analysis method

123-91-1 16052-06-5 75-59-2 64-17-5 75-05-8 7732-18-5

none none none none none none recrystallization

0.995 0.998 0.250 0.998 0.998

GCd none none GCd GCd none 1 HNMRb and KFc

0.998

H NMR = Proton nuclear magnetic resonance spectra. cKF = Karl Fischer titration.

distillation equipment.15 Moreover, the high concentration of salt used in the separation process changes the optimum pH of the medium, and thus it may cause the damage to the biological molecules.16 To overcome the above-mentioned problems associated with conventional salts, in our previous works17,18 we have reported a biocompatible and self-buffering IL, tetra-methylammonium 4-(2-hydroxyethyl)-1-piperazinepropanesulfonate [TMA][EPPS] as an alternative to the corrosive salt. This IL is synthesized by using a commonly used buffer, EPPS, as an anion and terta-methylammonium as a cation. This new IL is found to induce liquid−liquid phase splitting in aqueous solutions of 1,3-dioxolane and is also observed to form an aqueous-two-phase system (ATPS).17,18 Because of its selfbuffering and biocompatible nature, the extractive medium formed by this IL did not require any external buffering compound and thus it could be more advantageous over the conventional immidazoilium-based ILs and inorganic salts used in biological studies. To confirm the applicability of [TMA][EPPS] in the separation of the 1,4-dioxane from its aqueous solution, we measure the experimental liquid−liquid equilibrium (LLE) and solid−liquid−liquid equilibrium (SLLE) tie-lines data for the ternary system of 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPa in the present work. The LLE phase boundaries data are correlated with a semiempirical polynomial equation and also with the effective excluded volume (EEV) equations of Gun et al.19 The consistency of our experimental LLE-tie line data is checked with the well-known Othmer−Tobias equation.20 Moreover, the LLE and SLLE tieline data are also correlated with the NRTL model21 and the optimal values of the NRTL parameters for each pair are determined simultaneously.

Supporting Information. The water contained in the synthesized IL is measured by using Karl Fischer titration method, which shows the presence of water as low as 0.0085 wt %. The description of the materials is provided in Table 1. The highly pure water (double-deionized) with a resistivity of 18.3 MΩ·cm was prepared by using a Nano-Pure-Ultra pure water purifying system. This deionized water was used in the sample preparation. All the sample mixtures were prepared gravimetrically by using a digital balance (model GR-200, A&D, Japan) with an uncertainty of 0.1 mg. 2.2. Measurement of Tie-Line Data. The experimental LLE and SLLE tie-line data for the investigated ternary system of (1,4-dioxane + water + [TMA][EPPS]) were measured at 298.15 K and 101 kPa by using the similar method as explained in our previous articles.18,22 The schematic diagram of the apparatus is available in the literature.23 The experimental setup includes an equilibrium cell made of glass, a magnetic stirrer, a thermostatic water bath, and a precise temperature probe. The total volume of the equilibrium cell is 50 cm3. The cell was provided with a jacket to circulate thermostatic water for keeping constant temperature for the equilibrium cell throughout the experiment. The temperature was measured by using a platinum (Pt-100Ω) sensor connected to a digital precision sensor (TM-907A, Lutron). The use of platinum digital sensor, compared to mercury thermometer, gives a bit more precise value of the temperature. Prior to use, this probe was calibrated by using a highly precise digital thermometer (model 1560, Hart Scientific Co., USA) to an uncertainty of 0.1 K. A freshly prepared solution with a prespecified fixed composition of 1,4-dioxane + water + [TMA][EPPS] was charged into the equilibrium cell. The equilibrium cell was carefully capped and connected with the water bath, and the loaded mixture was stirred uniformly. After about 12 h mixing, the mixture was left for 8 h to ensure that the phase splitting was completed and that the two-split phases, the upper organicrich phase, and the lower aqueous-rich phase were in equilibrium. The mixing and settling time periods were optimized by collecting samples at different time intervals. At least five samples from each phase (upper and lower) were carefully collected by using an airtight glass syringe for the composition analysis. 2.3. Method of Composition Analysis. The equilibrium compositions of 1,4-dioxane and water in the upper and the lower phases were determined by using a gas chromatograph (GC, model 9800, China Chromatography Co., Taiwan). The collected sample of about 0.001 cm3 was injected into the GC by using an airtight glass syringe. To separate the injected mixture into its individual components of 1,4-dioxane and water, a 2-m-long stainless steel Porapak QS column with 80/

2. EXPERIMENTAL SECTION 2.1. Materials. 1,4-Dioxane (mass fraction purity > 0.995) and the buffer EPPS (mass fraction purity, 0.998) were supplied by Sigma Chemical Co. (USA). The aqueous solution of tetramethylammonium hydroxide (25 wt % in water) was purchased from Sigma Chemical Co. (USA). Ethanol (mass fraction purity, 0.998) and acetonitrile (mass fraction purity, 0.995) were also purchased from Sigma Chemical Co. (USA). All these chemicals were used without any further purification. The ionic liquid [TMA][EPPS] was synthesized by using the method as described in our previous work.17 To remove the unreacted material and other impurities, the synthesized ionic liquid was washed many times by using the 1:1 solution of ethanol and acetonitrile. After washing was completed, the IL was dried under vacuum. The 1H NMR spectra for the synthesized IL is measured and provided in Figure S1 of the B



Article

Table 2. Tie-line Data, Distribution Coefficients (D1 and D2), and Separation Factor (S) for 1,4-Dioxane (1) + Water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPaa organic-rich phase wI1

a

wI2

water-rich phase wI3

wII1

0.8308 0.8612 0.8883 0.9518 0.9552 0.9645

0.1597 0.1337 0.1092 0.0480 0.0441 0.0353

0.0095 0.0051 0.0025 0.0002 0.0007 0.0002

0.4409 0.3652 0.3011 0.1787 0.1532 0.1105

0.9776

0.0224

0.0000

0.0796

wI2 b

LLE 0.3752 0.4036 0.4253 0.4024 0.3929 0.3911 SLLEb 0.3322

distribution coefficients and separation factor wII3

D1

D2

S

0.1839 0.2312 0.2736 0.4189 0.4539 0.4984

1.884 2.358 2.950 5.326 6.235 8.729

0.426 0.331 0.257 0.119 0.112 0.090

4.4 7.1 11.5 44.7 55.5 96.7

0.5882

12.281

0.067

182.1

Standard uncertainty are u(T) = 0.05 K and u(P) = 2 kPa. bStandard uncertainty is u(wi) = 0.005

100 mess was used. To prevent the IL from entering the GC column, a filter composed of a stainless steel tube (aperture 0.1 mm) packed with glass wool was used in the injector section of the GC. This filter was cleaned routinely after the injection of about 30 samples. This period of cleaning filter is estimated by a hit and trial method to ensure that no ionic liquid enters in the column of the GC. To carry the injected sample from the injector section to the thermal conductivity detector (TCD) section, highly pure helium (mass fraction purity >0.9995) was used as a carrier gas. Prior to the composition analysis of the 1,4-dioxane and water in the collected samples, the GC was calibrated by using a series of binary solution of 1,4-dioxane + water prepared gravimetrically in the entire composition range (0 to 1 mass fraction of 1,4-dioxane) with an uncertainty of 0.001. The equilibrium composition of IL, [TMA][EPPS] in 1,4dioxane-rich phase and aqueous-rich phase was estimated by using the gravimetric method. About 2 g of the sample taken from either the upper or the lower phases was placed on a watch glass. To remove the solvents (1,4-dioxane and water) the watch glass was kept carefully inside the oven at 120 °C. After the collected sample was dried, the mass of [TMA][EPPS] was determined. The equilibrium composition was calculated from an average of at least five replicated samples with the standard uncertainty u(wi) of 0.005 for each component.

Figure 1. Phase diagram of 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPa. (-■-), tie-line (LLE); (-△-), tie-line (SLLE); (−), empirical equation; (···), EEV model.

as a dashed line) in the phase diagram. The first (S + L) region at the bottom of the phase diagram represents [TMA][EPPS] saturated in 1,4-dioxane-rich phase. The other (S + L) region at the right of the SLLE region represents [TMA][EPPS] saturated in aqueous phase. The region 2L in the phase diagram provides the information that the concentration ranges of [TMA][EPPS] to induce the 1,4-dioxane aqueous solution into two liquid phases: the upper phase rich in organics and the lower phase rich in water. The majority of [TMA][EPPS] remains in the lower aqueous-rich phase and only a trace amount of [TMA][EPPS] in the upper 1,4-dioxane-rich phase, as can be seen clearly from the mass fractions of the IL in aqueous-rich-phase (w3I) and organic-rich phase (w3II) in Table 2. In our recent article,24 we have investigated the mechanism of the liquid−liquid phase splitting for the aqueous solution of tetrahydrofuran (THF) in the presence of a zwitterionic buffer 4-(2-hydroxyethyl) piperazine1-ethanesulfonic acid (HEPES). The study found that the buffer molecule interacted strongly with water molecule and thus forming various hydrogen bonds. This preferential interaction between buffer and water forced the organic molecule to be squeezed out from the network of water and formed a separated organic phase. A similar mechanism was also noticed for inducing the liquid−liquid phase splitting in the ternary mixture of organic + water + salt.25−30 Certainly, in the present case, this IL, [TMA][EPPS], a derivative of buffer EPPS, behaved similar in nature and interacted preferentially

3. RESULTS AND DISCUSSION The experimental LLE and SLLE tie-line data for the ternary system of 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) were measured at 298.15 K under 101 kPa and are reported in Table 2. Using those experimental data, we plot the phase diagram for the investigated ternary system as shown in Figure 1. The LLE tie-line data and the SLLE tie-line data are represented by a closed square symbol and an open triangle symbol, respectively. The phase diagram shows five distinct phase regions for this ternary system. The homogeneous liquid phase (L) in which the ternary solution is miscible at all compositions of its constituent components in region L. The region (2L) represents the coexistence of the liquid−liquid equilibria (LLE), while the region (2L + S) denotes the coexistence of the solid−liquid−liquid equilibria (SLLE). It also shows that in the (2L + S) region, the biphasic solution of aqueous 1,4-dioxane became saturated with solid [TMA][EPPS]. In this work, we did not measure phase boundaries of the S + L regions. However, two possible (S + L) regions are qualitatively marked by extrapolating the SLLE tie-line (shown C



Article

correlation curve in Figure 1 and the obtained lower value of the RMSD in Table 3, confirm that this polynomial equation can convincingly represent the phase boundaries of the investigated system. Previously, the effective excluded volume model (EEV) was developed for representing the polymer-based biphasic systems. Later, this model was also found highly useful in correlating the LLE phase boundaries data for the ternary systems of organic + water + salts.33−35 Therefore, we also employ this model to correlate the LLE phase boundaries data for 1,4-dioxane + water + [TMA][EPPS]. The mathematical form of this EEV model is given below:

with water over 1,4-dioxane. Because of the high electrostatic nature of the TMA cation and EPPS anion, they should be strongly interacting with water molecules. Moreover, the anion EPPS possesses various hydrogen-bond donor and acceptor sites, which should enhance the network of hydrogen bonds in the aqueous phase. The preferential interaction between IL and water was also evident from the observed high concentration of IL in the aqueous phase compared with its concentration in the organic-rich phase (Table 2). In the present study, we adopt two semiempirical models, a polynomial equation and the effective excluded volume (EEV) equation to correlate the LLE phase boundary data of the ternary system of 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3). The suitability of the semiempirical polynomial equation to correlate the experimental LLE phase boundaries data for the similar ternary systems (organic solvent + water + buffer) has also been shown in the literature.24,31,32 The mathematical form of this polynomial equation is w1 = a +

bw31/2

+ cw3 +

dw33

⎛ w ⎞ w ln⎜V * 3 + f *⎟ + V * 1 = 0 M1 ⎝ M3 ⎠

where wi and Mi represent the mass fraction and the molar mass of component i, respectively. The subscripts 1 and 3 represent 1,4-dioxane and [TMA][EPPS], respectively. The parameters, V* and f * are the fitting parameters of the EEV model. The parameter f * represents the volume fraction of an unfilled effective available volume after the packing [TMA][EPPS] molecule into the network of 1,4-dioxane molecule in water. The parameter V* is also known as scaled effective excluded volume and its value directly implies the tendency of the phase forming agent to split the homogeneous aqueous organic solution into two separate phases. The values of the parameters (V* and f *) were determined by correlating the experimental LLE phase boundary data to the EEV model. The obtained values along with RMSD are presented in Table 3. The high value of V* indicates that even a lower mass fraction of [TMA][EPPS] could induce the liquid−liquid phase splitting for the aqueous 1,4-dioxane system. The correlated results from the EEV model are shown as the red dashed line in Figure 1. The deviations from the EEV model are obviously larger than those from the empirical model of eq 1. To ascertain the thermodynamic consistency of experimental LLE tie-line data, we used the well-known Othmer−Tobias equation.20,36−39 The expression of this equation is given below:

(1)

where a, b, c, and d represent the fitting parameters and w1 and w3 are the mass fraction of 1,4-dioxane and [TMA][EPPS], respectively. The results of the correlation are shown in Figure 1 as the blue solid curve. The best-fitted values of the parameters (a, b, c, and d) and the corresponding root-meansquare deviations (RMSD) are given in Table 3. The Table 3. Correlated Parameters for 1,4-Dioxane (1) + Water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPa Empirical eq 1 a

b

0.9729

−1.3622

c

RMSDa

d

0.1721 0.2101 Othmer-Tobias model

0.0114

m*

n*

R2

2.7519

0.8308 effective excluded volume (EEV) model

0.9925

f*

V* 347.5759 i−j 1−2 1−3 2−3 aqueous phase organic phase

RMSDa

0.0238 NRTL model αij

bijb (K)

0.20 0.20 0.20 AAD Δx1

318.58 1617.39 97.86 AAD Δx2

0.0201 0.0163

0.0195 0.0160

0.0290 bjibK)

⎛ 1 − w II ⎞ ⎛ 1 − wI ⎞ 3 1 ⎟ = m* + n*ln⎜ ⎟ ln⎜ II I ⎝ w1 ⎠ ⎝ w3 ⎠

222.39 −1504.08 −220.77 AAD Δx3 grand AADc 0.0008 0.0005

(2)

(3)

where w represents the mass fraction. While the superscripts I and II denote the organic-rich phase and aqueous-rich phase, respectively, the subscripts 1 and 3 are for 1,4-dioxane and [TMA][EPPS], respectively. The variables m* and n* are the adjustable parameters of the Othmer−Tobias equation. The optimal values of the model parameters and the correlation coefficient (R2) are tabulated in Table 3. In addition to R2 = 0.9925 from this correlation, the graphical comparison made in Figure 2 confirms that our LLE tie-line data are consistently good. The LLE and SLLE tie-line data of 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) were correlated with the activity coefficient model, NRTL (nonrandom two-liquid).21 For multicomponent systems, the NRTL model is represented by the following equations:

0.0122

a

In the following calculation np is the number of data points; w1expt and w1calc are the experimental and the calculated mass fractions of 1,4dioxane. ⎡ np ⎤0.5 RMSD = ⎢∑ (w1calc − w1expt)2 /np⎥ ⎢⎣ i = 1 ⎥⎦

b τij = bij/T. cIn the following calculation, n is the number of tie-lines and i, j, and k represent, ith component in jth phase on the kth tie-line.

⎧ ⎫ n 2 3 ⎪ exp t ⎪ calc AAD = ⎨∑ ∑ ∑ |xijk − xijk |⎬/6n ⎪ ⎪ ⎩k=1 j=1 i=1 ⎭ D



Article

Figure 3. Correlated results from the NRTL model for 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPa. (-■-), tieline (LLE); (-△-), tie-line (SLLE); (-·-), the NRTL model.

Figure 2. Correlation of LLE tie-line data with the Othmer−Tobias model for 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPa: (■), experimental; (−), Othmer−Tobias model.

separation factor (S) for the ternary system of (1,4-dioxane + water + [TMA][EPPS]) with the increase of mass fraction of IL in aqueous phase (w3II) is shown in Figure 4. The nonlinear

n

ln γi =

∑ j c= 1 xjτijGji n

∑kc= 1 xkGkj nc

+

∑ j=1

n ⎛ ∑mc = 1 xmτmjGmj ⎞ ⎜ ⎟ τij − n n ∑kc= 1 xkGkj ⎟⎠ ∑k = 1 xkGkj ⎜⎝

xjGij

(4)

with Gij = exp( −αijτij)

(5)

and τij = bij /T

(6)

where γi represents the activity coefficient for component i. αij is known as the nonrandomness parameter and its value is fixed to 0.2 for each (i−j) pair. The adjustable parameter of the NRTL model (bij) represents the interaction energy difference between (i−j) pair and (j−j) pair. Therefore, the values of those adjustable parameters are essentially needed for conducting the process simulation and design. In the present case, the best-fitted values of the six adjustable parameters (b12, b13, b23, b21, b31, and b32) are obtained by fitting the experimental data to the NRTL model via LLE calculation. The results of correlation are presented in Table 3 along with the values of the absolute average deviations (AAD). The correlated results from the NRTL model for the LLE and SLLE tie-lines are graphically shown in Figure 3 as red dashed-dotted line. Figure 3 shows that the NRTL model correlates our experimental tie-lines data satisfactorily. To evaluate the separation efficiency of the IL to separate 1,4-dioxane from its aqueous solution, via liquid−liquid phase splitting induced by IL, is one of our major concerns in this work. For this purpose, we calculate the distribution coefficient of component i (Di) and the separation factor (S) by using the following equations:40 Di = wiI/wiII

Figure 4. Separation factor (S) varying with the mass fraction of [TMA][EPPS] in aqueous phase (wII3 ) for 1,4-dioxane (1) + water (2) + [TMA][EPPS] (3) at 298.15 K and 101 kPa: (●) experimental; (−) smoothed curve.

increase in the separation factor S with the increase of w3II indicates that the separation efficiency increases with the increase of the IL concentration in the mixture. The calculated distribution coefficients (D1 and D2) and the separation factor (S) are given in Table 2. The value of S can be as high as 182.1 for the investigated ternary system, revealing that the use of [TMA][EPPS] could be very effective in the recovery of 1,4dioxane from its aqueous solution. At 101 kPa, the binary mixture of 1,4-dioxane + water forms an azeotrope at 87.82 °C and 0.82 in mass fraction of 1,4-dioxane.5 In the present work, we have found that the maximum mass fraction of 1,4-dioxane at SLLE is 0.9776 (Table 2) which is significantly greater than its binary azeotropic composition. It indicates that the [TMA][EPPS] could serve as a powerful auxiliary agent to overcome the separation barrier of the azeotrope. Several reports are available in the literature28,41−43 highlighting the phase-separation phenomenon in the aqueous 1,4dioxane system by adding various additives such as sodium

(7)

S = D1/D2

(8)

wIi

wIIi

where the symbols and in eq 7 represent the mass fraction of component i in the organic-rich and the aqueousrich phases, respectively. The variation of the calculated E



Article

bij = binary interaction parameter of the NRTL model for i-j pair in the mixture (K) Di = distribution coefficient of component i in the mixture EEV = effective exclude volume model f *, V* = parameters of the EEV model IL = ionic liquid m*, n* = coefficients of Othmer-Tobias equation Mi = molecular mass of component i (g. mol−1) n = number of tie-lines nc = number of components np = number of data points NRTL = nonrandom two liquid model R2 = square of correlation coefficient AAD = absolute average deviation S = separation factor wi = mass fraction of component i xijk = mole fraction of the component i in the phase j on the tie-line k

chloride, salicylic acid, cyclohexanol, 2,6-dimethyloct-7-en-2-ol etc. However, those studies are lacking information about the recovery of the maximum mass fraction of 1,4-dioxane from its azeotropic aqueous solution and thus the tendency of those additives as suitable auxiliary agents cannot be compared. In our previous lab reports,32,44 it is found on adding a suitable concentration of the biological buffers such as EPPS and MOBS, that the aqueous solution of 1,4-dioxane split into two separate phases and the maximum mass fraction of 1,4-dioxane is found as 0.945 and 0.843 for EPPS and MOPS, respectively. By using our proposed ionic liquid as an auxiliary agent, a higher concentration of 1,4-dioxane (the mass fraction of 0.9776) can be obtained. These results further indicate that compared with other reported additives, our proposed ionic liquid possess greater potential to recover highly pure 1,4dioxane from its azeotropic solution. In our previous work,23 we already proposed a conceptual flowsheet to separate the organics from its aqueous solution via the liquid−liquid splitting method induced by the buffer HEPES-Na and almost totally recycle the buffer. A similar flowsheet can also be employed in the present case.

Greek Symbols

αij = nonrandomness parameter of the NRTL model for i−j pair γi = activity coefficient of component i

4. CONCLUSIONS Our experimental results confirm that the ionic liquid [TMA][EPPS] can induce liquid−liquid phase splitting for the aqueous solution of 1-4 dioxane at 298.15 K under atmospheric pressure in a certain phase region. The LLE and SLLE tie-line data have been determined experimentally from this study and found to be consistently good. The experimental results also reveal that [TMA][EPPS] can be served as a green and powerful auxiliary agent to overcome the azeotrope barrier for recovery of 1,4-dioxane from its aqueous solution. The LLE tie-line data were well correlated with the NRTL model and the optimal values of the model parameters have also been determined. These model parameters will be applied to the process simulation and design for development of this green separation process in the near future.

■

Superscripts

calc = calculated value expt = experimental value I = liquid phase I (organic-rich phase) II = liquid phase II (water-rich phase) Subscripts

■

REFERENCES

(1) Ozturk, B.; Kuru, C.; Aykac, H.; Kaya, S. VOC separation using immobilized liquid membranes impregnated with oils. Sep. Purif. Technol. 2015, 153, 1−6. (2) Rudd, J. H.; Hill, N. Measures to reduce emission of VOCs during loading and un-loading of ship in the EU; AEA Technology Environment: Oxfordshire, 2001. (3) Rao, R.; Chandrababu, J.; Muralidharan, N. K.; Nair, C. Recouping the wastewater: A way forward for cleaner leather processing. J. Cleaner Prod. 2003, 11, 591−609. (4) Cheremisinoff, N. P. Industrial solvents handbook. 2nd ed.; Marcel Dekker Inc; 2003. (5) Horsley, L. H. Tables of azeotropes and nonazeotropes, in azeotropic Data-III; American Chemical Society, 1973. (6) Mohanty, S. Modelling of liquid−liquid extraction column: A review. Rev. Chem. Eng. 2000, 16, 199−248. (7) Taboda, M. E.; Graber, T. A.; Andrew, B. A.; Asenjo, J. A. Drowning-out crystallization of sodium sulphate using aqueous twophase systems. J. Chromatogr., Biomed. Appl. 2000, 743, 101−105. (8) Al-Sahhaf, T. A.; Kapetanovic, E. Salt effects of lithium chloride, sodium bromide, or potassium iodide on liquid−liquid equilibrium in the system water + 1-butanol. J. Chem. Eng. Data 1997, 42, 74−77. (9) Andrews, B. A.; Asenjo, J. A. In: Handbook of Chemistry; Harris, E. L., Angal, S., Eds. Plenum Press: New York, 1979. (10) Lynn, S.; Schiozer, A. L.; Jaecksch, W. L.; Cos, R.; Prausnitz, J. M. Recovery of anhydrous Na2SO4 from SO2-scrubbing liquor by extractive crystallization: liquid−liquid equilibria for aqueous solutions of sodium carbonate, sulfate, and/or sulfite plus acetone, 2-propanol, or tert-butyl alcohol. Ind. Eng. Chem. Res. 1996, 35, 4236−4245. (11) Demirci, A.; Pometto, A. L., III; Hok, K. L. G. Ethanol production by Saccharomyces cerevisiae in biofilm reactors. J. Ind. Microbiol. Biotechnol. 1997, 19, 299−304.

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.7b00905. The 1H NMR spectrum of [TMA][EPPS] (PDF)

■

i = component i 1 = 1,4-dioxane 2 = water 3 = [TMA][EPPS]

AUTHOR INFORMATION

Corresponding Author

*Tel.: +886-2-2737-6626. Fax: +886-2-2737-6644. E-mail: [email protected]. ORCID

Ming-Jer Lee: 0000-0001-7586-7379 Funding

The authors are grateful for financing provided by the Ministry of Science and Technology (MOST), Taiwan, through MOST 105-2221-E-011-144-MY3, MOST 105-2811-E-011-012, and MOST 106-2811-E-011-014. Notes

The authors declare no competing financial interest.

■

NOMENCLATURE a, b, c, d = fitting parameters of eq 1 RMSD = root-mean square deviation F



Article

(12) Malinowski, J. J.; Daugulis, A. J. Liquid−liquid and vapor−liquid behavior of oleyl alcohol applied to extractive fermentation processing. Can. J. Chem. Eng. 1993, 71, 431−436. (13) Malinowski, J. J.; Daugulis, A. J. Salt effects in extraction of ethanol, 1-butanol and acetone from aqueous solutions. AIChE J. 1994, 40, 1459−1460. (14) Veljkovic, V. B.; Lazic, M. L.; Stankovic, M. Z. Repeated use of yeast biomass in ethanol fermentation of juniper berry sugars. World J. Microbiol. Biotechnol. 2006, 22, 519−523. (15) Piehl, R. L. Correlation of corrosion in a crude distillation unit with chemistry of the crudes. Corrosion 1960, 16, 305−307. (16) Taha, M.; Teng, H. L.; Lee, M. J. Phase diagrams of acetonitrile or (acetone + water + EPPS) buffer phase separation systems at 298.15 K and quantum chemical modeling. J. Chem. Thermodyn. 2012, 54, 134−141. (17) Gupta, B. S.; Taha, M.; Lee, M. J. Extraction of an active enzyme by self-buffering ionic liquids: a green medium for enzymatic research. RSC Adv. 2016, 6, 18567−18576. (18) Gupta, B. S.; Fang, M. Y.; Lee, M. J. Separation of 1,3-dioxolane from its azeotropic aqueous solution by using Good’s buffer ionic liquid [TMA][EPPS]. Fluid Phase Equilib. 2016, 418, 119−124. (19) Guan, Y.; Lilleyand, T. H.; Treffry, T. E. A new excludedvolume theory and its application to the co-existence curve polymer two-phase systems. Macromolecules 1993, 26, 3971−3979. (20) Othmer, D. F.; Tobias, P. E. Liquid−liquid extraction data-the line correlation. Ind. Eng. Chem. 1942, 34, 693−696. (21) Renon, H.; Prausnitz, J. M. Local compositions in thermodynamic excess functions for liquid mixtures. AIChE J. 1968, 14, 135−144. (22) Altway, S.; Taha, M.; Lee, M. J. Liquid−liquid, solid−liquid, and solid−liquid−liquid equilibria of systems containing cyclic ether (tetrahydrofuran or 1,3-dioxolane), water, and a biological buffer MOPS. J. Chem. Thermodyn. 2015, 82, 93−98. (23) Gupta, B. S.; Fang, M. Y.; Taha, M.; Lee, M. J. Separation of 1,3dioxolane, 1,4-dioxane, acetonitrile and tert-butanol from their aqueous solutions by using Good’s buffer HEPES-Na as an auxiliary agent. J. Taiwan Inst. Chem. Eng. 2016, 66, 43−53. (24) Taha, M.; Khoiroh, I.; Lee, M. J. Phase behavior and molecular dynamics simulation studies of new aqueous two-phase separation systems induced by HEPES buffer. J. Phys. Chem. B 2013, 117, 563− 582. (25) Haugen, G. R.; Friedman, H. L. Ionwater interaction (“salting out”) in nitromethane and the free energy of transfer of some electrolytes to pure nitromethane from nitromethane saturated with water. J. Phys. Chem. 1963, 67, 1757−1761. (26) Hall, D. G. Kirkwood-Buff theory of solutions. An alternative derivation of part of it and some applications. Trans. Faraday Soc. 1971, 67, 2424−2516. (27) Long, F. A.; McDevit, W. F. Activity coefficients of nonelectrolyte solutes in aqueous salt solutions. Chem. Rev. 1952, 51, 119−169. (28) Takamuku, T.; Yamaguchi, A.; Matsuo, D.; Tabata, M.; Yamaguchi, T.; Otomo, T.; Adachi, T. NaCl-induced phase separation of 1,4-dioxane−water mixtures studied by large-angle x-ray scattering and small-angle neutron scattering techniques. J. Phys. Chem. B 2001, 105, 10101−10110. (29) Takamuku, T.; Noguchi, Y.; Yoshikawa, E.; Kawaguchi, T.; Matsugami, M.; Otomo, T. Alkali chlorides-induced phase separation of acetonitrile−water mixtures studied by small-angle neutron scattering. J. Mol. Liq. 2007, 131−132, 131−138. (30) Takamuku, T.; Yamaguchi, A.; Matsuo, D.; Tabata, M.; Kumamoto, M.; Nishimoto, J.; Yoshida, K.; Yamaguchi, T.; Nagao, M.; Otomo, T.; Adachi, T. Large-angle x-ray scattering and small-angle neutron scattering study on phase separation of acetonitrile−water mixtures by addition of NaCl. J. Phys. Chem. B 2001, 105, 6236−6245. (31) Taha, M.; Teng, H. L.; Lee, M. J. The buffering-out effect and phase separation in aqueous solutions of EPPS buffer with 1-propanol, 2-propanol, or 2-methyl-2-propanol at T = 298.15 K. J. Chem. Thermodyn. 2012, 47, 154−161.

(32) Taha, M.; Teng, H. L.; Lee, M. J. Buffering-out: separation of tetrahydrofuran, 1,3-dioxolane, or 1,4-dioxane from their aqueous solutions using EPPS buffer at 298.15 K. Sep. Purif. Technol. 2013, 105, 33−40. (33) Wang, Y.; Yan, Y.; Hu, S.; Han, J.; Xu, X. Phase diagrams of ammonium sulfate + ethanol/1-propanol/2-propanol + water aqueous two-phase systems at 298.15 K and correlation. J. Chem. Eng. Data 2010, 55, 876−881. (34) Wang, Y.; Wang, J.; Han, J.; Hu, S.; Yan, Y. Liquid−liquid equilibrium of novel aqueous two phase systems and evaluation of salting-out abilities of salts. Cent. Eur. J. Chem. 2010, 8, 886−891. (35) Wang, Y.; Hu, S.; Han, J.; Yan, Y. Measurement and correlation of phase diagram data for several hydrophilic alcohols + citrate aqueous two-phase systems at 298.15 K. J. Chem. Eng. Data 2010, 55, 4574−4579. (36) Lv, R.; Wang, Z.; Li, L.; Chen, Y. Liquid−liquid equilibria in the ternary systems water + cresols + methyl butyl ketone at 298.2 and 313.2 K: Experimental data and correlation. Fluid Phase Equilib. 2015, 403, 89−95. (37) Luo, L.; Liu, D.; Li, L.; Chen, Y. Phase equilibria of (water + propionic acid or butyric acid + 2-methoxy-2-methylpropane) ternary systems at 298.2 and 323.2 K. Fluid Phase Equilib. 2015, 403, 30−35. (38) Wang, H.; Wang, Q.; Xiong, Z.; Chen, C. Liquid−liquid equilibria for ternary system water + toluene + benzaldehyde at (303.2−343.2) K. Fluid Phase Equilib. 2014, 383, 43−48. (39) Sofiya, K.; Karunanithi, B. Liquid−liquid equilibrium of water + acetic acid + butyl butanoate at 298 K and 1 atm. Fluid Phase Equilib. 2015, 403, 114−117. (40) Zhang, H. Measurements and comparative study of ternary liquid−liquid equilibria for water + acrylic acid + cyclopentyl methyl ether at (293.15, 303.15, and 313.15) K and 100.249 kPa. J. Chem. Eng. Data 2015, 60, 1371−1376. (41) Pena, M. A.; Bustamante, P.; Escalera, B.; Reillo, A.; Sendra, J. M. B. Solubility and phase separation of benzocaine and salicylic acid in 1,4-dioxane-water mixtures at several temperatures. J. Pharm. Biomed. Anal. 2004, 36, 571−578. (42) Qiu, T.; Wang, X.-da.; Tian, H.; Huang, Z.-X. Liquid−liquid equilibrium for the system water + 1,4-dioxane + cyclohexanol over the temperature range of 313.2−343.2 K. Fluid Phase Equilib. 2012, 324, 28−32. (43) Wang, B.; Qiu, T.; Li, S. Liquid-liquid equilibrium for the system water + 1,4-dioxane + 2,6-dimethyloct-7-en-2-ol over the temperature range of (343.2 to 358.2) K. J. Chem. Eng. Data 2010, 55, 558−560. (44) Taha, M.; Lee, M. J. Solubility and phase separation of 2-(Nmorpholino)ethanesulfonic acid (MES) and 4-(N-morpholino)butanesulfonic acid (MOBS) in aqueous 1,4-dioxane and ethanol solutions. J. Chem. Eng. Data 2011, 56, 4436−4443.

G


Application of Buffer-Based Ionic Liquid in the ... - ACS Publications

Recommend Documents