Article pubs.acs.org/jced
Experimental Determination and Correlation of Liquid−Liquid Equilibria for the Ternary System 2‑Methoxy-2-methylpropane + o‑Cresol + Water at 298.15 K and 313.15 K Liejin Luo, Dong Liu, Libo Li, and Yun Chen* School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, P. R. China ABSTRACT: Liquid−liquid equilibrium (LLE) data for the ternary system 2-methoxy-2methylpropane (methyl tert-butyl ether) + o-cresol + water were experimentally measured at atmospheric pressure and temperatures of 298.15 K and 313.15 K. From the resulted distribution coefficient and selectivity, we can find that 2-methoxy-2-methylpropane is an efficient solvent to extract o-cresol. The consistency of experimental tie-line data was verified by the Hand and Bachman equations. The binary interaction parameters among these compounds were obtained through correlation of the experimental data with the nonrandom (NRTL) and universal quasichemical (UNIQUAC) models. Both models yielded results in good agreement with experimental data, and the average deviation of the NRTL model was even smaller than that from the UNIQUAC model.
■
INTRODUCTION o-Cresol, an important chemical material, is widely used in industry as a solvent, disinfectant, oil additive, and component of creosote. It is also one main phenolic pollutant in wastewater generated from coal gasification, petrochemical, petroleum, or phenol producing industries. However, o-cresol, together with other phenols, are toxic organic compounds identified as priority pollutants in many environmental protection laws and regulations.1,2 Thus, removing phenols, especially o-cresol, from aqueous solutions is of great environmental interest. A solvent extraction process is frequently used to remove phenols from high concentration phenolic wastewater.3,4 The solvent extraction process consists of three steps: solvent extraction, solvent recovery, and solvent stripping. Solvent recovery is applied to recover the extractant from the phenol solution and solvent stripping is used to recover the extractant from wastewater. After the solvent extraction process, the wastewater will be sent to biochemical treatment. There have been many solvents developed for phenols’ extraction, such as toluene, ethylbenzene, cumene, heptane, and octane, etc. The extraction solvents widely used in industry are 2,2′-oxybis (propane) (diisopropyl ether) and 4-methylpentan-2-one (methyl isobutyl ketone). However, these two solvents have several limitations in practical application. For 2,2′-oxybis (propane), the subsequent treatment becomes difficult due to the low efficiency. In contrast, 4-methylpentan-2-one has been broadly accepted as an effective solvent, but its application, however, is limited by the high energy consumption.5 Liquid−liquid equilibria (LLE) data are essential for properly designing solvent extraction processes.6 There have been many liquid−liquid equilibria studies about ternary systems of water + phenols + extraction solvent. Lei et al.5 reported LLE data for the ternary system 2-methoxy-2-methylpropane + phenol + water. Martin et al.7 researched LLE data for the ternary © 2015 American Chemical Society
systems of aromatic hydrocarbons (toluene or ethylbenzene) + phenols + water. The purpose of this study is to report recovering o-cresol from dilute aqueous solutions using an effective solvent which has a low boiling point. Thus, we selected 2-methoxy-2methylpropane, a fuel additive, as the extraction solvent because of its high distribution coefficients,8 low energy consumption for phenols’ recovery, and low cost. The LLE results were measured for the ternary system 2-methoxy-2-methylpropane + o-cresol + water at (298.15 and 313.15) K and at atmospheric pressure in this paper, which have not been reported by others yet. The experimental tie-line data were correlated to verify the consistency with the Hand9 and Bachman10 equations. These experimental LLE data also agree with those calculated from the nonrandom two-liquid (NRTL)11 and universal quasichemical activity coefficient (UNIQUAC)12 models.
■
EXPERIMENTAL SECTION
Chemicals. 2-Methoxy-2-methylpropane was supplied by Sinpharm Chemical Reagent Co., Ltd. o-Cresol and 1,3,5trimethylbenzene were obtained from Xiya Reagent Research Center. Methanol was purchased from ShangHai LingFeng Chemical Reagent Co., Ltd. n-Butanol was supplied by JiangSu Qiangsheng Functional Chemistry Co., Ltd. The purities of these liquids were higher than 0.99. Distilled and deionized water was prepared in our laboratory and used throughout all experiments. All these materials were tested by gas chromatography but no impurity peaks were detected, thus they were used without further purification. Received: December 8, 2014 Accepted: April 20, 2015 Published: April 29, 2015 1396
DOI: 10.1021/je501114q J. Chem. Eng. Data 2015, 60, 1396−1400
Journal of Chemical & Engineering Data
Article
Table 1. Experimental LLE Data (Mass Fraction) for the Ternary System, 2-Methoxy-2-methylpropane (1) + o-Cresol (2) + Water (3) at T = 298.15 K and T = 313.15 Ka organic phase w1
a
w2
aqueous phase w3
0.40578 0.48283 0.54284 0.58823 0.61840 0.66201 0.70526 0.77102 0.79690 0.88456 0.98831
0.49871 0.43424 0.38377 0.34586 0.32046 0.28377 0.24613 0.19456 0.17258 0.09341 0.00000
0.09551 0.08293 0.07339 0.06590 0.06114 0.05422 0.04861 0.03442 0.03051 0.02203 0.01169
0.38040 0.49594 0.58555 0.65782 0.71991 0.73808 0.77754 0.82689 0.86507 0.90739 0.98530
0.53550 0.43766 0.35933 0.29483 0.23885 0.22238 0.18633 0.14108 0.10583 0.06642 0.00000
0.08411 0.06640 0.05512 0.04735 0.04124 0.03954 0.03613 0.03202 0.02910 0.02619 0.01470
w1
w2
T/K = 298.15 0.00994 0.00561 0.01411 0.00382 0.01729 0.00272 0.01995 0.00223 0.02142 0.00196 0.02357 0.00150 0.02565 0.00120 0.02878 0.00086 0.03036 0.00072 0.03444 0.00030 0.03680 0.00000 T/K = 313.15 0.00451 0.00567 0.00824 0.00320 0.01104 0.00212 0.01309 0.00153 0.01472 0.00112 0.01518 0.00102 0.01612 0.00082 0.01722 0.00059 0.01801 0.00043 0.01960 0.00025 0.02500 0.00000
w3
D
S
0.98445 0.98207 0.97999 0.97781 0.97662 0.97493 0.97315 0.97036 0.96892 0.96526 0.96320
88.96 113.75 141.27 154.96 163.62 188.57 204.96 226.52 239.76 311.53
917.00 1347.11 1886.37 2299.23 2613.46 3390.94 4103.02 6386.59 7613.65 13647.55
0.98982 0.98856 0.98684 0.98538 0.98415 0.98380 0.98306 0.98219 0.98156 0.98014 0.97500
94.44 136.94 169.36 193.19 212.81 217.52 227.14 238.94 244.98 264.15
1111.45 2038.85 3032.02 4020.67 5078.79 5412.19 6180.57 7328.27 8264.27 9885.51
Standard uncertainties u are u(T) = 0.1 K, u(w) = 0.0019 for w > 0.1, u(w) = 0.0001 for w < 0.1.
■
Procedure. A 100 mL glass-sealed cell surrounded by a thermostatted water jacket was used to prepare LLE samples, whose temperature was controlled by a thermostatic bath with a uncertainty of about 0.1 K. A 55 mL, 2-methoxy-2methylpropane + o-cresol + water ternary mixture loaded in the glass cell was stirred vigorously by using a magnetic stirrer for more than 2 h, and then was allowed to settle for at least 18 h to reach the phase equilibrium. After this ternary mixture reached the phase equilibrium and formed two liquid layers, the sample from each phase was taken by a syringe and was analyzed by a gas chromatography (GC6820, Agilent Technologies) consisting of a flame ionization detector (FID, with the sensitivity of 10−100 ppb) and a DB-5MS capillary column (30 m × 0.32 mm × 0.25 μm). This sample’s composition was determined by an internal standard method, where an internal standard was added into the sample before GC analysis. Both the sample and the internal standard were weighed by an analytical balance (Shimadzu, AUW220D) to an accuracy of 0.1 mg. In the experiments, the internal standard for o-cresol was 1,3,5-trimethylbenzene and that for 2-methoxy-2methylpropane was methanol. n-Butanol was used as the organic solvent for GC analysis. Water concentration was obtained by mass balance. In GC analysis, the initial temperature of the oven was kept at 313.15 K for 2 min, then was increased to 473.15 K at a rate of 30 K·min−1. The carrier gas was nitrogen, whose flow rate is 30 mL·min−1. The temperatures of the injector and the detector were kept at 523.15 K and 543.15 K, respectively. Each sample was measured at least three times and the resulting standard deviation is less than 0.5 %. Thus, the mean value was shown in this work.
RESULTS AND DISCUSSION LLE Experimental Data. Table 1 lists the LLE data for the ternary system: 2-methoxy-2-methylpropane + o-cresol + water, at 298.15 K and 313.15 K with all concentrations expressed in mass fraction. Ternary diagrams of Figure 1 show the phase behavior of the corresponding systems. The distribution coefficient (D) and the selectivity (S) were calculated to estimate the ability of 2-methoxy-2-methylpropane to extract ocresol from wastewater: D=
S=
w2O w2W
(1)
(w2 /w3)O (w2 /w3)W
(2)
where superscripts O and W denote organic solvent phase and aqueous phase, respectively, w2 is the mass fraction of o-cresol and w3 is that of water. The distribution coefficient and the selectivity for o-cresol at different temperatures are also shown in Table 1, which indicates 2-methoxy-2-methylpropane is an excellent solvent for extracting o-cresol. In addition, we found that, in the temperature range of our study, temperature has an insignificant effect on the distribution coefficients of 2methoxy-2-methylpropane. The reliability of the experimental tie-line data was assessed with the Hand and Bachman correlation equations, given by eqs 3 and 4, respectively: ⎛ w ⎞W ⎛ w2 ⎞O ln⎜ ⎟ = a1 + b1 ln⎜ 2 ⎟ ⎝ w1 ⎠ ⎝ w3 ⎠ 1397
(3) DOI: 10.1021/je501114q J. Chem. Eng. Data 2015, 60, 1396−1400
Journal of Chemical & Engineering Data
Article
Figure 2. Hand plot for LLE data measured in this work: ●, the 2methoxy-2-methylpropane + o-cresol + water system at T = 298.15 K; ■, the 2-methoxy-2-methylpropane + o-cresol + water system at T = 313.15 K.
Figure 1. Ternary diagram of LLE (mass fraction) for the ternary system: 2-methoxy-2-methylpropane + o-cresol + water at T = 298.15 K (a) and T = 313.15 K (b); ■-■, experimental data tie-lines; ★, calculated NRTL data; □, calculated UNIQUAC data.
⎛ wO ⎞ w1O = a 2 + b2⎜ 1W ⎟ ⎝ w3 ⎠
Figure 3. Bachman plot for LLE data measured in this work: ●, the 2methoxy-2-methylpropane + o-cresol + water system at T = 298.15 K; ■, the 2-methoxy-2-methylpropane + o-cresol + water system at T = 313.15 K.
Table 2. Fitting Parameters in Hand or Bachman Equations
(4)
Hand
where a1, b1 and a2, b2 are parameters for the Hand and Bachman equations, w1 is the mass fraction of 2-methoxy-2methylpropane, w2 is the mass fraction of o-cresol, and w3 is that of water. Figure 2 and Figure 3 show the straight lines fitted from Hand or Bachman equations. Table 2 lists the fitting parameters and corresponding linear correlation coefficient R2. All R2 are greater than 0.99, which indicates a good consistency of our LLE data. Data Correlation. The experimental LLE data in this work were correlated by using the NRTL11 and UNIQUAC12 models. The UNIQUAC structural parameters r (the number of segments per molecules) and q (the relative surface area per molecules) are taken from literature13,14 and are listed in Table 3. The NRTL and UNIQUAC binary interaction parameters for the 2-2-methoxy-2-methylpropane + o-cresol + water
Bachman 2
T/K
a1
b1
R
298.15 313.15
4.6481 5.3390
0.8538 0.9605
0.9989 0.9982
a2
b2
R2
0.0164 0.0098
0.9494 0.9699
0.9999 0.9999
Table 3. UNIQUAC Structural (Area and Volume) Parameters component
r
q
water 2-methoxy-2-methylpropane o-cresol
0.9200 4.0678 4.8180
1.4000 3.6320 3.6480
ternary system were calculated from minimizing the objective function (OF), given as follows: 1398
DOI: 10.1021/je501114q J. Chem. Eng. Data 2015, 60, 1396−1400
Journal of Chemical & Engineering Data exp cal 2 ⎤ ⎡ exp (wijk ) − wijk (Tk − Tkcal)2 ⎢ ⎥ + ∑∑∑⎢ 2 2 ⎥⎦ σT σw i=1 j=1 k=1 ⎣ 3
OF =
Article
n
2
(5) cal
cal
where n is the number of tie-lines w and T are calculated mass fraction and temperature, wexp and Texp are experimental mass fraction and temperature. Subscripts i, j, and k refer to the components, the phases, and the tie-lines, respectively. σT and σw are standard deviations for experimental temperatures and mass fractions. These NRTL and UNIQUAC binary interaction parameters are shown in Tables 4 and 5, respectively. Table 4. NRTL Binary Interaction Parameters and RMSD Values for the Ternary System: 2-Methoxy-2-methylpropane (1) + o-Cresol (2) + Water (3) components
NRTL
T/K
i−j
bij/K
bji/K
αij
RMSD
298.15
1−2 1−3 2−3 1−2 1−3 2−3
−611.93 3325.68 −447.92 −2603.87 3344.47 −467.42
−271.58 −3635.15 1934.87 4791.17 −3537.56 383.14
0.3 0.2 0.2 0.3 0.2 0.2
0.001809
313.15
Figure 4. Mass fraction of o-cresol in organic phase versus that in aqueous phase for the 2-methoxy-2-methylpropane + o-cresol + water system: ●, experimental data at 298.15 K; ···, calculated results from the NRTL model at 298.15 K; bold line, calculated results from the UNIQUAC model at 298.15 K. ■, Experimental data at 313.15 K; , calculated results from the NRTL model at 313.15 K; ---, calculated results from the UNIQUAC model at 313.15 K.
0.001736
Table 5. UNIQUAC Binary Interaction Parameters and RMSD Values for the Ternary System: 2-Methoxy-2methylpropane (1) + o-Cresol (2) + Water (3) components
UNIQUAC
T/K
i−j
bij/K
bji/K
RMSD
298.15
1−2 1−3 2−3 1−2 1−3 2−3
2110.85 −620.86 −10.58 603.48 −473.59 −16.80
−21395.42 −51.60 1374.98 −5366.17 −132.14 −132.35
0.004248
313.15
line data show high reliability, as assessed by the Hand and Bachman equations. The resulting distribution coefficients and selectivity values indicate 2-methoxy-2-methylpropane has great potential to serve as a solvent to extract o-cresol from the wastewater. In addition, the NRTL and UNIQUAC models were used to correlate the experimental LLE data, and yield the relevant binary interaction parameters. Both models correlated the experimental data very well, as indicated by RMSD values and figures.
■
0.003275
AUTHOR INFORMATION
Corresponding Author
*Tel.: +86 13632384249. E-mail:
[email protected]. Funding
The quality of the correlation is assessed by the root-meansquare-deviation (RMSD), calculated from the difference between experimental mass fractions and predictions from NRTL or UNIQUAC models according to the following equation: ⎡ ∑3 ∑2 ∑n (w exp − w cal)2 ⎤1/2 ijk ijk i=1 j=1 k=1 ⎥ RMSD = ⎢ ⎢ ⎥ 6 n ⎣ ⎦
Financial support from Project of the Science & Technology New Star of Pearl River in Guangzhou (2011J2200056), the Fundamental Research Funds for the Central Universities, SCUT (2014ZZ0057), Guangdong Science Foundation (2014A030310260), and National Science Foundation of China (20906028) is gratefully acknowledged. Notes
The authors declare no competing financial interest.
■
(6)
These RMSD values for NRTL and UNIQUAC models are listed in Tables 4 and 5, which indicate both models correlate the tie-line data well for the studied system. The experimental data and calculated data from NRTL and UNIQUAC models for o-cresol at 298.15 K and 313.15 K are plotted in Figure 4. According to these figures, the calculated data are in good agreement with the experimental ones. This indicates both NRTL and UNIQUAC models are suitable for simulating o-cresol extraction.
REFERENCES
(1) Kohl, A. I.; Nielsen, R. Gas Purification, 5th ed.; Gulf Publishing Company: Houston, Texas, 1997. (2) Toxic Substances Control Act (TSCA); US Environmental Protection Agency (EPA): Washington, DC, 1979. (3) González-Muñoz, M. J.; Luque, S.; Á lvarez, J. R.; Coca, J. Recovery of phenol from aqueous solutions using hollow fibre contactors. J. Membr. Sci. 2003, 213, 181−193. (4) Chen, Y.; Wang, Z.; Li, L. Liquid−liquid equilibria for ternary systems: Methyl butyl ketone + phenol + water and methyl butyl ketone + hydroquinone + water at 298.15 K and 323.15 K. J. Chem. Eng. Data 2014, 59, 2750−2755. (5) Lei, Y.; Chen, Y.; Li, X.; Qian, Y.; Yang, S.; Yang, C. Liquid− liquid equilibria for the ternary system 2-methoxy-2-methylpropane + Phenol + Water. J. Chem. Eng. Data 2013, 58, 1874−1878.
■
CONCLUSIONS LLE data for the ternary system 2-methoxy-2-methylpropane + o-cresol + water were measured at temperatures of 298.15 K and 313.15 K and atmospheric pressure. The experimental tie1399
DOI: 10.1021/je501114q J. Chem. Eng. Data 2015, 60, 1396−1400
Journal of Chemical & Engineering Data
Article
(6) Mohammad Doulabi, F. S.; Mohsen-Nia, M. Ternary liquid− liquid equilibria for systems of (sulfolane + toluene or chloronaphthalene + octane). J. Chem. Eng. Data 2006, 51, 1431−1435. (7) Martin, A.; Klauck, M.; Taubert, K.; Precht, A.; Meinhardt, R.; Schmelzer, J. Liquid−liquid equilibria in ternary systems of aromatic hydrocarbons (toluene or ethylbenzene) + phenols + water. J. Chem. Eng. Data 2011, 56, 733−740. (8) Kujawski, W.; Warszawski, A.; Ratajczak, W.; Porębski, T.; Capała, W.; Ostrowska, I. Removal of phenol from wastewater by different separation techniques. Desalination 2004, 163, 287−296. (9) Hand, D. Dineric distribution. J. Phys. Chem. 1929, 34, 1961− 2000. (10) Bachman, I. Tie lines in ternary liquid systems. Ind.Eng. Chem., Anal. Ed. 1940, 12, 38−39. (11) Renon, H.; Prausnitz, J. M. Local compositions in thermodynamic excess functions for liquid mixtures. AIChE J. 1968, 14, 135−144. (12) Abrams, D. S.; Prausnitz, J. M. Statistical thermodynamics of liquid mixtures: A new expression for the excess Gibbs energy of partly or completely miscible systems. AIChE J. 1975, 21, 116−128. (13) Mafra, M. R.; Krähenbühl, M. A. Liquid−liquid equilibrium of (water + acetone) with cumene or α-methylstyrene or phenol at temperatures of (323.15 and 333.15) K. J. Chem. Eng. Data 2006, 51, 753−756. (14) Magnussen, T.; Rasmussen, P.; Fredenslund, A. UNIFAC parameter table for prediction of liquid−liquid equilibria. Ind. Eng. Chem. Process. Des. Dev. 1981, 20, 331−339.
1400
DOI: 10.1021/je501114q J. Chem. Eng. Data 2015, 60, 1396−1400
