Article pubs.acs.org/jced
Measurement and Thermodynamic Modeling of Ternary (Liquid + Liquid) Equilibrium for Extraction of N,N-Dimethylacetamide from Aqueous Solution with Different Solvents Bing Jia, Chao Zhang, Kun Xin, Yingmin Yu, and Qingsong Li* The State Key Lab of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum-East China, Qingdao, Shandong 266580, People’s Republic of China ABSTRACT: Liquid−liquid equilibrium (LLE) data for the water + N,N-dimethylacetamide + solvents (chloroform, methyl isobutyl carbinol, methyl isobutyl ketone, isopropyl acetate, or isopropyl ether) ternary systems were determined at 308.2 and 298.2 K and at 101.3 kPa. Distribution coefficients and separation factors were calculated to evaluate the effectiveness of extracting N,N-dimethylacetamide from aqueous solution. The Othmer−Tobias equation and the Hand equation were used to confirm the reliability of the experimental LLE data. The experimental data were correlated by thermodynamic nonrandom two-liquid and universal quasichemical models, and the binary interaction parameter values were obtained from the data correlation.
1. INTRODUCTION N,N-Dimethylacetamide (DMAC) is an important organic solvent for industrial applications. DMAC has been extensively used in the textile industry for the production of polyacrylate synthetic fibers as well as the production of polyimide film.1,2 DMAC can also be utilized in the production of medical intermediates in the pharmaceutical industry.3,4 Owing to the wide use of DMAC in industry, a large amount of wastewater with different concentrations of DMAC is produced. Direct discharge of DMAC wastewater causes environment pollution and loss of DMAC.5 Therefore, to reduce production costs and solve environmental problems, separation and recovery of DMAC from the wastewater is necessary. Liquid−liquid extraction is a conventional technique from an economic and technical point of view.6 The extraction method is adopted in this work to recover DMAC from the wastewater. The reliable liquid−liquid equilibrium (LLE) data reflect the distribution of DMAC between the solvent phase and the aqueous phase in the extraction process, provide a good understanding of phase behavior and the thermodynamic properties of ternary systems, and thus are important thermodynamic properties for the design and evaluate industrial units for DMAC extraction processes.7,8 However, only a few publications have reported the LLE data for the extraction of DMAC from aqueous solution until now;3,4 searching for new and more suitable solvents for the recovery of DMAC is still the principal consideration. Therefore, in this work, chloroform, methyl isobutyl carbinol (MIBC), methyl isobutyl ketone (MIBK), isopropyl acetate, and isopropyl ether were chosen as new solvents for DMAC extraction from DMAC aqueous solution; and the LLE and phase behavior involved in extracting DMAC from an aqueous solution were investigated adequately. © XXXX American Chemical Society
To explore the multicomponent phase behaviors of DMAC in water + solvents (chloroform, MIBC, MIBK, isopropyl acetate, or isopropyl ether) mixture, the LLE data of the ternary systems water + DMAC + solvents were determined at 308.2 and 298.2 K and at 101.3 kPa. To the best of our knowledge, these data have never been reported in any previous references. Distribution coefficients (D) and separation factors (S) were calculated. Additionally, all experimental LLE data were correlated using the nonrandom two-liquid (NRTL)9 and universal quasi-chemical (UNIQUAC)10 activity models, and the values for the binary interaction parameters were obtained. 2. Materials and Methods. 2.1. Materials. Detailed information on the chemical reagents is listed in Table 1. DMAC, MIBC, MIBK, isopropyl acetate, isopropyl ether, pyridine, and isopropyl alcohol were purchased from Aladdin reagent company (Shanghai, China). Chloroform was purchased from Sinopharm Chemical Reagent. Double distilled water was prepared in our laboratory and employed throughout. All these chemicals were used without further purification as typical LLE studies do.11−13 2.2. Apparatus and Procedure. The experimental LLE data for ternary systems water + N,N-dimethylacetamide + solvents (chloroform, MIBC, MIBK, isopropyl acetate, or isopropyl ether) were carried out at 308.2 and 298.2 K and at 101.3 kPa. The details about experimental equipment were reported in our previous work, and the reliability of the experimental system has been evaluated.14−17The mixture was vigorously stirred for at least 2 h and left to settle for at least 6 h Received: February 20, 2017 Accepted: May 1, 2017
A
DOI: 10.1021/acs.jced.7b00194 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 1. Details of the Chemical Reagents Used in This Work compounda
supplier
DMAC chloroform MIBC MIBK isopropyl acetate isopropyl ether pyridine isopropyl alcohol double-distilled water a
Aladdin Reagent Sinopharm Aladdin Reagent Aladdin Reagent Aladdin Reagent Aladdin Reagent Aladdin Reagent Aladdin Reagent self-made
mass fraction purity
chemical formula
purity analysis methoda
CAS
>0.998 >0.990 >0.990 >0.995 >0.990 >0.990 >0.990 >0.995
C4H9NO CHCl3 C6H14O C6H12O C6H10O2 C6H14O C5H5N C3H8O H2O
GC GC GC GC GC GC GC GC GC
127-19-5 67-66-3 108-11-2 108-10-1 108-21-4 108-20-3 110-86-1 67-63-0 7732-18-5
Company Company Company Company Company Company Company
Notation: GC, gas chromatography; DMAC, N,N-dimethylacetamide; MIBC, methyl isobutyl carbinol; MIBK, methyl isobutyl ketone.
Table 2. Experimental LLE Data in Mass Fraction for Water (1) + DMAC (2) + Solvents (3) Systems at 308.2 and 298.2 K and at 101.3 kPa, Together with the Distribution Coefficient D and Separation Factor Sa water-rich phase wI1
wI2
solvents-rich phase wI3
0.9954 0.9661 0.9309 0.8966 0.8780 0.8423 0.8109 0.7766 0.7549 0.7265 0.6978
0.0239 0.0498 0.0926 0.1094 0.1385 0.1681 0.1991 0.2214 0.2433 0.2715
0.0046 0.0100 0.0194 0.0107 0.0126 0.0192 0.0210 0.0243 0.0237 0.0302 0.0307
0.9941 0.9599 0.9371 0.9085 0.8758 0.8495 0.7858 0.7525 0.7216
0.0331 0.0528 0.0784 0.1074 0.1366 0.1978 0.2243 0.2588
0.0059 0.0070 0.0102 0.0130 0.0167 0.0140 0.0164 0.0232 0.0196
0.9821 0.9390 0.8939 0.8533 0.8132 0.7734 0.7441 0.7097 0.6814
0.0366 0.0792 0.1180 0.1552 0.1909 0.2199 0.2497 0.2760
0.0179 0.0244 0.0269 0.0287 0.0316 0.0356 0.0361 0.0406 0.0426
0.9791 0.9266 0.8790 0.8327 0.7916 0.7505 0.7159 0.6829 0.6513
0.0449 0.0917 0.1321 0.1706 0.2072 0.2411 0.2714 0.2985
0.0209 0.0285 0.0292 0.0352 0.0378 0.0423 0.0430 0.0457 0.0502
0.9676 0.9291 0.8713
0.0371 0.0908
0.0308 0.0338 0.0379
wII1
wII2
Chloroform 308.2 K 0.0009 0.0049 0.0238 0.0060 0.0464 0.0081 0.0687 0.0103 0.0864 0.0107 0.1032 0.0113 0.1189 0.0134 0.1314 0.0164 0.1453 0.0163 0.1572 0.0162 0.1715 Chloroform 298.2 K 0.0008 0.0034 0.0300 0.0034 0.0454 0.0045 0.0627 0.0052 0.0798 0.0069 0.0955 0.0092 0.1276 0.0098 0.1422 0.0133 0.1568 MIBC 298.2 K 0.0602 0.0663 0.0126 0.0682 0.0269 0.0717 0.0399 0.0751 0.0525 0.0797 0.0675 0.0820 0.0798 0.0854 0.0942 0.0878 0.1057 MIBK 298.2 K 0.0185 0.0194 0.0042 0.0195 0.0084 0.0200 0.0124 0.0213 0.0168 0.0219 0.0213 0.0229 0.0271 0.0232 0.0318 0.0242 0.0380 Isopropyl Acetate 298.2 K 0.0127 0.0188 0.0027 0.0192 0.0064 B
wII3
D
S
0.9991 0.9713 0.9475 0.9232 0.9033 0.8860 0.8698 0.8552 0.8382 0.8265 0.8123
0.9958 0.9328 0.7413 0.7890 0.7450 0.7072 0.6601 0.6565 0.6461 0.6318
197.6 144.1 81.92 67.13 58.41 50.60 38.38 30.14 28.82 27.30
0.9992 0.9666 0.9512 0.9328 0.9149 0.8976 0.8632 0.8480 0.8300
0.9077 0.8595 0.7993 0.7433 0.6996 0.6447 0.6338 0.6057
255.3 234.3 160.4 124.7 86.28 54.94 48.82 32.96
0.9398 0.9211 0.9049 0.8884 0.8724 0.8528 0.8382 0.8204 0.8065
0.3451 0.3399 0.3378 0.3385 0.3535 0.3629 0.3773 0.3828
4.887 4.457 4.017 3.667 3.431 3.294 3.137 2.969
0.9815 0.9765 0.9720 0.9675 0.9620 0.9568 0.9500 0.9449 0.9378
0.0926 0.0921 0.0941 0.0983 0.1029 0.1125 0.1173 0.1274
4.435 4.141 3.911 3.660 3.525 3.513 3.450 3.427
0.9873 0.9785 0.9744
0.0737 0.0708
3.644 3.214
DOI: 10.1021/acs.jced.7b00194 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 2. continued water-rich phase wI1
wI2
solvents-rich phase wI3
0.8295 0.7889 0.7468 0.7089 0.6793 0.6495
0.1294 0.1685 0.2077 0.2416 0.2676 0.2941
0.0411 0.0426 0.0455 0.0495 0.0532 0.0564
0.9838 0.9327 0.8847 0.8406 0.7985 0.7628 0.7267 0.6865 0.6449
0.0493 0.0994 0.1375 0.1813 0.2155 0.2500 0.2836 0.3162
0.0162 0.0180 0.0159 0.0219 0.0202 0.0217 0.0233 0.0299 0.0289
wII1
wII2
Isopropyl Acetate 298.2 K 0.0191 0.0091 0.0203 0.0127 0.0205 0.0165 0.0202 0.0198 0.0226 0.0245 0.0233 0.0289 Isopropyl Ether 298.2 K 0.0029 0.0053 0.0010 0.0058 0.0017 0.0059 0.0024 0.0064 0.0035 0.0059 0.0040 0.0060 0.0043 0.0064 0.0063 0.0061 0.0068
wII3
D
0.9717 0.9680 0.9630 0.9604 0.9530 0.9479
0.0705 0.0757 0.0793 0.0818 0.0915 0.0982
3.055 2.947 2.894 2.870 2.754 2.743
0.9971 0.9936 0.9926 0.9916 0.9902 0.9902 0.9897 0.9873 0.9871
0.0209 0.0168 0.0177 0.0191 0.0184 0.0172 0.0221 0.0214
3.653 2.573 2.520 2.399 2.386 2.097 2.381 2.258
S
a
Standard uncertainties u are u(T) = 0.1 K, u(p) =1 kPa, u(w1) = 0.0065, u(w2) = 0.0071, u(wI3) = 0.0074. Notation: w1, mass fraction of water; w2, mass fraction of DMAC; w3, mass fraction of solvents.
to reach the phase equilibrium. The evaporated compounds were completely condensed by the condenser to ensure the mass balance. When the phase equilibrium was reached, three samples were obtained from the two immiscible phases by syringes, respectively. They were analyzed with gas chromatography by applying an internal standard method. Pyridine or isopropyl alcohol was chosen as the internal standard substance. The gas chromatograph (Agilent GC6820) was equipped with a Porapak N column (3 mm × 3 m) and a thermal conductivity detector. The carrier gas was hydrogen with the flow rate of 60 mL min−1. The temperatures of the injector and the detector were set at 523.2 K. The temperature program started at 393.2 K and was held for 1 min, followed by a 20 K per minute ramp to 523.2 K then held for 1.5 min; total run time was 9 min. Every sample was analyzed at least three times to ensure the reliability of the experimental data. The standard uncertainty of the liquid phase compositions was calculated according to the GUM standard18 and associated references.19,20 A series of LLE data were obtained by changing the feed composition.
Figure 1. Ternary phase diagram for the water + DMAC + chloroform system at 308.2 K: (blue ■) experimental data; (☆) feed composition; (△) UNIQUAC model; (○) NRTL model.
3. RESULTS AND DISCUSSION 3.1. Experimental Data. The experimental LLE data for ternary systems water + DMAC + solvents (chloroform, MIBC, MIBK, isopropyl acetate or isopropyl ether) at desired temperatures were listed in Table 2 with all concentrations expressed as mass fraction. The corresponding triangular phase diagrams were presented in Figures 1−6. Using these figures, one could also conclude that the experimental data were reliable because the points of the feed compositions agree with the tie-lines with great accuracy.21 Table 2 listed the distribution coefficients (D) and separation factors (S).22 These were defined as follows: D = w2II/w2I
(1)
S = (w2II/w2I)/(w1II/w1I)
(2)
Figure 2. Ternary phase diagram for the water + DMAC + chloroform system at 298.2 K: (blue ■) experimental data; (☆) feed composition; (△) UNIQUAC model; (○) NRTL model.
mass fractions of DMAC in the above two phases, respectively. The separation factors versus the DMAC mass fraction in the aqueous phase with different solvents were shown in Figure 7. Studies were carried out on the effect of temperature on the extraction with chloroform as extractant. The values of S decrease with increasing temperature, indicating that a lower temperature is preferable. The separation factors tend to decrease as the concentration of DMAC increases at a certain temperature. As presented in Figure 7, the separation capacities of five different solvents are compared. The values of S are much higher than the unity, especially at low content of DMAC,
where wII1 and wI1 denote water’s mass fractions in the solvents phase and the aqueous phase, respectively; wII2 , wI2 denote the C
DOI: 10.1021/acs.jced.7b00194 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Figure 3. Ternary phase diagram for the water + DMAC + MIBC system at 298.2 K: (blue ■) experimental data; (☆) feed composition; (△) UNIQUAC model; (○) NRTL model.
Figure 7. Experimental separation factors versus mass fraction of DMAC in the aqueous phase at 101.3 kPa. (●) chloroform 308.2 K; (▲) chloroform 298.2 K; (▼) MIBC 298.2 K; (△) MIBK 298.2 K; (▽) isopropyl acetate 298.2 K; (■) isopropyl ether 298.2 K.
extractant. Thus, chloroform is an efficient solvent for extracting DMAC. The reliability of the experimental LLE data was verified by the Othmer−Tobias23 and Hand24 equations. These are defined as
Figure 4. Ternary phase diagram for the water + DMAC + MIBK system at 298.2 K: (blue ■) experimental data; (☆) feed composition; (△) UNIQUAC model; (○) NRTL model.
ln[(1 − w3II)/w3II] = a1 + b1 ln[(1 − w1I)/w1I]
(3)
ln(w2II/w3II)
(4)
= a2 +
b2 ln(w2I/w1I)
where a1, b1, a2, and b2 are the parameters of the Othmer− Tobias correlations and the Hand equations; wII2 and wII3 denote the mass fractions of DMAC and solvents in the solvents-rich phase, respectively. While wI1 and wI2 are mass fractions of water and DMAC in the water-rich phase, respectively. The fitting parameters and the regression coefficients (R2) for the six studied ternary systems are presented in Table 3. The calculated results show that the Hand equation was more suitable than the Othmer−Tobias equation for these ternary systems. 3.2. Data Correlation. The experimental LLE date were correlated by the NRTL and UNIQUAC excess Gibbs free energy models. The NRTL and UNIQUAC results were generated using Aspen Plus 8.4 software. The UNIQUAC structural parameters r (molecular-geometric volume) and q (molecular-geometric surface) were taken from the Aspen Plus V 8.4 physical properties data bank and presented in Table 4. During the regression process of the NRTL model, NRTL nonrandomness parameters aij were fixed to 0.3, excepting that value for the (water + solvents) binary pair, which was fixed to 0.2 instead, as listed in Table 5. The corresponding binary interaction parameters in the NRTL and UNIQUAC models were calculated by minimizing the objective function (OF):
Figure 5. Ternary phase diagram for the water + DMAC + isopropyl acetate system at 298.2 K: (blue ■) experimental data; (☆) feed composition; (△) UNIQUAC model; (○) NRTL model.
Figure 6. Ternary phase diagram for the water + DMAC + isopropyl ether system at 298.2 K: (blue ■) experimental data; (☆) feed composition; (△) UNIQUAC model; (○) NRTL model.
M
OF =
2
3
∑ ∑ ∑ (wijkexp − wijkcal)2 k=1 j=1 i=1
(5)
where subscripts i, j, and k refer to the components, the phases, and tie-lines, respectively. M is the number of tie lines, wexp is the experimental mass fraction, and wcal is the calculated mass fraction. The root-mean-square deviation (RMSD) was used as a measure of the agreement between the calculated and experimental data, and was defined as
demonstrating that extraction of DMAC by these solvents is possible. Nevertheless, the distribution coefficients are quite low (
