Phase Equilibrium on Extraction Methylphenols from Aqueous

Mar 27, 2018 - The phenols recovery process is a significant part of treating coal chemical wastewater with highly concentrated phenols and ammonia. S...
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Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Phase Equilibrium on Extraction Methylphenols from Aqueous Solution with 3,3-Dimethyl-2-butanone at 333.2 K and 353.2 K Kangning Xiong, Xiuyu Zheng, Meiling Jiang, Dan Gao, Furong Wang, and Yun Chen* Department of Chemistry and Chemical Engineering, and State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640, P. R. China ABSTRACT: The phenols recovery process is a significant part of treating coal chemical wastewater with highly concentrated phenols and ammonia. Solvent extraction is an important unit for phenol recovery section. The accurate measurement of liquid−liquid equilibrium (LLE) data is essential for realizing partitioning. In this paper, the LLE data for the ternary system water + 2-, 3-, 4-methylphenol +3,3-dimethyl-2-butanone (also known as methyl tert-butyl ketone, MTBK) were studied at the temperatures of 333.2 K and 353.2 K under 101.3 kPa. The extraction performance of MTBK was estimated by partition coefficients and separation factors. The extraction efficiencies of MTBK were compared with those of MIBK, mesityl oxide, and those results of MTBK at five different temperatures from 298.2 K to 353.2 K were also contrasted with each other. In addition, the nonrandom two-liquid (NRTL) and universal quasi chemical (UNIQUAC) models were applied to fit the measured LLE data. The results indicate that the calculated data based on the NRTL and UNIQUAC equations are good as reported by the experimental data, and the root-mean-square error (RMSE) values are lower than 2.50%. The obtained binary interaction parameters in this study can be used in the calculation of the LLE about the ternary system (water + 2-, 3-, 4-methylphenol + MTBK) as well as for the design and optimization of industrial process to remove methylphenols from effluents.

1. INTRODUCTION A large amount wastewater with a high phenol concentration is generated in the coal chemical fields such as coal to hydrogen, coal to synthetic natural gas, low-temperature carbonization of coal, and lignite quality improvement.1,2 This kind of wastewater needs several treatment sections to reach the standard for discarding or recycle. Furthermore, phenol and ammonia recovery is the crucial part of the process that can decrease chemical oxygen demand from 20000 to 50000 mg·L−1 to 2000−4000 mg·L−1, and remove large amounts of organic pollutants from wastewater.2−5 The flow diagram of the phenol and ammonia recycle process is shown in Figure 14,5 and is briefly described as follows: ammonia, carbon dioxide, and hydrogen sulfide in the pretreated coal chemical wastewater were removed in the wastewater stripper. Then, the temperature of wastewater from the stripper column bottom was lowered to the extraction temperature by three heat exchanges. The wastewater was pumped into the packed extraction column, and subsequently underwent a continuous countercurrent extraction with extracting agent. The aqueous phase and the organic phase in the extraction column is pumped into the solvent stripper and the solvent distillation column to recover the extractant, respectively. The crude phenols product is obtained from the bottom of the solvent distillation column. The treated wastewater from the bottom of the solvent stripper was already free of ammonia, carbon dioxide, hydrogen sulfide, phenols, and other organic pollutants and ready to be treated in the following section of biochemical process. Methylphenols are one of the major phenolic pollutants in the above-mentioned wastewater.2 They are also produced during © XXXX American Chemical Society

cigarette smoking, burning of liquid fuels, and other natural materials.6,7 Methylphenols as highly toxic pollutants are greatly harmful to animals, plants, and the environment even at a low concentrations. In addition, methylphenols are also a significant chemical intermediate, widely used in medicine, pesticides, dyes, and antioxidants and other chemical industries.8,9 Solvent extraction is an efficient method widely used in industry to reduce the concentration of methylphenol from phenolic wastewater.10,11 Solvent extraction is a vital unit in phenol and ammonia recovery process shown in Figure 1, and its function is to extract large amounts of organic pollutants from wastewater and reduce chemical oxygen demand by around 90%. Methylphenols in wastewaters are not only eliminated from highly phenolic wastewater but also recycled as byproducts through solvent extraction technology. Therefore, extraction of methylphenols from wastewater using organic solvent is an effective technology generating enormous environmental and economic benefits. Industrial processes similar to those of Figure 1 have been implemented in many large-scale coal chemical companies such as China Coal Longhua Harbin Industry Co. Ltd., China Coal Ordos Energy Chemical Industry Co. Ltd., Xinjiang Guanghui Energy Co. Ltd., China Datang Corporation, and the Xinjiang Kingho Group. Methyl isobutyl ketone (MIBK) and diisopropyl Special Issue: Emerging Investigators Received: October 27, 2017 Accepted: March 21, 2018

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DOI: 10.1021/acs.jced.7b00932 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Figure 1. Flow diagram of phenols and ammonia recovery from coal chemical wastewater.

ether (DIPE) were the two most commonly used extractants in these industries. The azeotropic temperature of DIPE and water is about 66 °C, so the extraction temperature must be lower than this value and is usually set as 45 °C when the extraction process is designed. However, when the extraction temperature is lower than 60 °C, a certain amount of binders containing fly ash and coal tar from wastewater sticks and deposits in Heater 5 as illustrated in Figure 1, which results in heat exchanger blockage. The use of MIBK as an extractant did not present these problems, but energy consumption of the solvent recovery was too large.5,12,13 So the screening of suitable extractants is very essential. Liquid−liquid equilibrium (LLE) data of ternary and binary systems were usually correlated using nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) activity coefficient models in order to determine the binary interaction parameters used in process simulation. There are many available references reporting the results of solubility measurements in aqueous solutions since accurate solubility data are important for product and process design.14−17 Many organic solvents have been reported to extract methylphenol from wastewater including ketones,18−24 ethers,25−27 aliphatic hydrocarbons,28 and aromatic hydrocarbons.29 However, most of those references focused on temperatures below 323.15 K. Methyl tert-butyl ketone (MTBK) showed good physicochemical properties such as relatively low boiling point, little solubility in water, and high partition coefficient and selectivity for the treatment of phenolic wastewater,20,30,31 which are a benefit for the extraction and solvents recovery process. In this study, the liquid−liquid equilibrium data for the ternary systems of water + methylphenols + MTBK were determined at 333.2 K and 353.2 K under air pressure, for which the LLE data have not been reported so far. Partition coefficients and selectivities of different extractants including MIBK, MTBK, and mesityl oxide, the feedstock in the production of MIBK, were compared. Moreover, the NRTL and UNIQUAC methods were taken to link with the measurement data. Binary interaction parameters were concurrently obtained, which could be applied for optimizing or designing a treatment process to extract methylphenols from wastewater.

Table 1. Suppliers and Purity of Chemicals Used in This Work component

mass fraction

supplier

analysis method

CAS

MTBK 2-methylphenol 3-methylphenol 4-methylphenol 1,3,5-trimethylbenzene n-butyl acetate

0.98 0.99 0.995 0.99 0.995 0.99

Xiya Reagent Xiya Reagent Xiya Reagent Xiya Reagent Xiya Reagent Xiya Reagent

GCa GC GC GC GC GC

75-97-8 95-48-7 108-39-4 106-44-5 108-67-8 123-86-4

a

Gas chromatograph.

The experimental procedure and analysis have been described exhaustively in previous studies.11−13 First, a respectively determined amount of water + 2-, 3-, 4-methylphenol + MTBK was put into a 100 cm3 glass equilibrium vessel (Figure 2) in each

Figure 2. Equilibria vessel: (1) sample outlet of organic phase; (2) sample outlet of aqueous phase; (3) organic phase; (4) aqueous phase

experiment, and solution temperature was regulated by immersing the vessel in a thermostat with a variation of ±0.1 K. Then, the mixed solution was agitated vigorously to accelerate the distribution of 2-, 3-, 4-methylphenol in the aqueous phase and the organic phase. At least 2 h later, the agitation was terminated, and the mixture remained in the container for more than 20 hours to make sure that it reached phase equilibrium, at which time two layers clearly formed (Figure 2). The samples in the upper phase and the lower phase were collected by different syringes through glass catheters attached to an equilibria vessel, accurately weighed, and then analyzed by the gas chromatograph (GC6820, Agilent Technologies) with a DB-5MS capillary column (30 m × 0.32 mm × 0.50 μm) and a flame ionization detector (FID). In this work, the mole fractions of MTBK and 2-, 3-, 4-methylphenol were determined by internal standard method. The mole fraction of water in the lower phase was calculated by deducting those of methylphenol and MTBK from 1, while the water content in the upper phase was measured by

2. EXPERIMENT 2.1. Materials. In this work, the purities of all chemicals used in this paper and corresponding suppliers were given in Table 1. The purities of all organic solvents were determined by gas chromatography. All compounds were not further purified due to their purities being over 98%. The distilled water in the experiments was prepared from ultrapure water equipment. 2.2. Experimental Procedure and Analysis. The LLE data of the ternary systems, water + 2-, 3-, 4-methylphenol + MTBK, were measured at 332.2 K and 353.2 K under air pressure. B

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Table 2. Experimental LLE Data (Mole Fraction) for the Ternary System, Water(1) + 2-Methylphenol(2) + MTBK(3) at 333.2 K and 353.2 K under 101.3 kPaa aqueous phase xI1

xI2

organic phase xI3

{Water(1) + 2-Methylphenol(2) + MTBK(3)} at 333.2 K 0.99782 0.00005 0.00213 0.99780 0.00009 0.00211 0.99777 0.00022 0.00202 0.99774 0.00031 0.00196 0.99769 0.00052 0.00178 0.99763 0.00081 0.00155 0.99715 0.00159 0.00126 0.99685 0.00199 0.00115 {Water(1) + 2-Methylphenol(2) + MTBK(3)} at 353.2 K 0.99767 0.00005 0.00227 0.99764 0.00011 0.00225 0.99753 0.00025 0.00222 0.99740 0.00043 0.00216 0.99715 0.00073 0.00212 0.99686 0.00108 0.00206 0.99618 0.00185 0.00198 0.99561 0.00257 0.00182

xII1

xII2

xII3

P

S

0.14499 0.18340 0.24427 0.27997 0.32145 0.34895 0.38174 0.40692

0.05179 0.08706 0.17440 0.22794 0.29027 0.31898 0.36532 0.39659

0.80323 0.72954 0.58133 0.49209 0.38828 0.33207 0.25294 0.19649

1088.1 943.1 800.6 746.0 555.4 391.6 229.2 199.0

7521 5153 3285 2671 1732 1125 602 491

0.15053 0.18181 0.24277 0.26292 0.33144 0.35685 0.39178 0.41409

0.04661 0.08548 0.15811 0.21741 0.27699 0.30052 0.32915 0.34876

0.80286 0.73271 0.59912 0.51967 0.39157 0.34263 0.27907 0.23715

894.0 743.4 630.4 503.2 379.2 278.3 178.0 135.9

5925 4079 2590 1909 1141 777 453 327

a Standard uncertainties u are u(T) = 0.1 K, u(P) = 1 kPa, u(xI1) = 0.0002, u(xI2) = 0.0002, u(xI3) = 0.0001, u(xII1 ) = 0.0230, u(xII2 ) = 0.0291, u(xII3 ) = 0.0520.

Table 3. Experimental LLE Data (Mole Fraction) for the Ternary System, Water(1) + 3-Methylphenol(2) + MTBK(3) at 333.2 K and 353.2 K under 101.3 kPaa aqueous phase xI1

xI2

organic phase xI3

{Water(1) + 3-Methylphenol(2) + MTBK(3)} at 333.2 K 0.99773 0.00005 0.00222 0.99768 0.00014 0.00218 0.99761 0.00023 0.00216 0.99755 0.00032 0.00213 0.99739 0.00053 0.00207 0.99727 0.00070 0.00203 0.99707 0.00100 0.00193 0.99653 0.00166 0.00181 {Water(1) + 3-Methylphenol(2) + MTBK(3)} at 353.2 K 0.99772 0.00005 0.00223 0.99766 0.00014 0.00220 0.99759 0.00026 0.00215 0.99751 0.00041 0.00208 0.99734 0.00066 0.00201 0.99697 0.00110 0.00193 0.99638 0.00177 0.00185 0.99572 0.00257 0.00171

xII1

xII2

xII3

P

S

0.13091 0.17883 0.21051 0.24632 0.28125 0.31500 0.33290 0.38282

0.05067 0.11330 0.17749 0.22824 0.27044 0.30142 0.33686 0.38397

0.05067 0.11330 0.17749 0.22824 0.27044 0.30142 0.33686 0.38397

966.9 803.5 765.2 703.7 509.3 431.1 335.5 231.1

7369 4483 3626 2850 1806 1365 1005 602

0.15092 0.19278 0.24391 0.27078 0.33187 0.36734 0.40303 0.42355

0.03989 0.10448 0.15514 0.20954 0.26343 0.29107 0.31552 0.33658

0.80919 0.70274 0.60095 0.51968 0.40470 0.34159 0.28145 0.23987

877.3 738.0 603.0 511.1 399.9 264.6 178.4 131.2

5800 3819 2466 1883 1202 718 441 308

a Standard uncertainties u are u(T) = 0.1 K, u(P) = 1 kPa, u(xI1) = 0.0001, u(xI2) = 0.0002, u(xI3) = 0.0001, u(xII1 ) = 0.0228, u(xII2 ) = 0.0267, u(xII3 ) = 0.0488.

Table 4. Experimental LLE Data (Mole Fraction) for the Ternary System, Water(1) + 4-Methylphenol(2) + MTBK(3) at 333.2 K and 353.2 K under 101.3 kPaa aqueous phase xI1

xI2

organic phase xI3

{Water(1) + 4-Methylphenol(2) + MTBK(3)} at 333.2 K 0.99782 0.00005 0.00213 0.99778 0.00014 0.00208 0.99773 0.00023 0.00204 0.99769 0.00034 0.00197 0.99762 0.00048 0.00190 0.99746 0.00073 0.00181

xII1

xII2

xII3

P

S

0.15334 0.20952 0.24067 0.26680 0.31678 0.33914

0.05248 0.11789 0.16198 0.20786 0.26265 0.28969

0.79418 0.67259 0.59735 0.52534 0.42057 0.37117

999.2 860.4 709.1 619.0 545.5 397.2

6502 4097 2940 2315 1718 1168

C

DOI: 10.1021/acs.jced.7b00932 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 4. continued aqueous phase xI1

xI2

organic phase xI3

{Water(1) + 4-Methylphenol(2) + MTBK(3)} at 333.2 K 0.99738 0.00096 0.00166 0.99693 0.00151 0.00156 {Water(1) + 4-Methylphenol(2) + MTBK(3)} at 353.2 K 0.99775 0.00004 0.00221 0.99769 0.00012 0.00219 0.99760 0.00024 0.00216 0.99749 0.00039 0.00212 0.99730 0.00065 0.00205 0.99707 0.00098 0.00195 0.99646 0.00168 0.00187 0.99583 0.00247 0.00170

xII1

xII2

xII3

P

S

0.36048 0.38573

0.32094 0.35758

0.31858 0.25669

335.5 236.8

928 612

0.17072 0.20242 0.24738 0.29393 0.34719 0.38762 0.41500 0.44056

0.03961 0.09062 0.15266 0.20909 0.25537 0.28632 0.31754 0.34269

0.78967 0.70696 0.59996 0.49698 0.39744 0.32606 0.26746 0.21675

899.9 763.3 636.1 536.1 394.6 293.2 189.3 138.7

5259 3762 2565 1819 1134 754 454 313

a

Standard uncertainties u are u(T) = 0.1 K, u(P) = 1 kPa, u(xI1) = 0.0001, u(xI2) = 0.0002, u(xI3) = 0.0001, u(xII1 ) = 0.0223, u(xII2 ) = 0.0260, u(xII3 ) = 0.0479.

Karl Fischer Volumetric Moisture Titrator (New 870 Titrino plus, Metrohm). Methanol was decided as the solvent for GC analysis. n-Butyl acetate was selected as the internal standard for MTBK and 1,3,5-trimethylbenzene was used for methylphenols. The column temperature was programmed as follows: keeping up 313.2 K for 2 min, and then reaching 463.2 K at the speed of 30 K· min−1. The injection temperature was placed at 523.2 K, while the detector temperature was set at 543.2 K. Nitrogen gas was manipulated as the carrier at a speed of 30 cm3·min−1. Each sample was analyzed three times, and the uncertainty for the overall composition determination in mole fraction was smaller than 0.2%. Hence, the average value was published in this paper.

3. RESULTS AND DISCUSSIONS 3.1. Experimental LLE Data. The measured LLE data in mole fraction of the ternary systems, water + 2-, 3-, 4-methylphenol + MTBK, at 333.2 K and 353.2 K were presented in Tables 2−4, and the tie-lines of these systems at different temperatures were shown in the triangle phase diagrams of Figures 3 and 4. To evaluate MTBK’s efficiency of separating methylphenols from effluents, the partition coefficients (P) and separation factors (S), also named as selectivity, in Tables 2−4, were calculated by the equations: P=

S=

x 2II x 2I

(1)

x 2II/x 2I x1II/x1I

(2)

in which xII2 and xI2 are the mole fraction of methylphenols in the upper phase and the lower phase, separately; the mole fraction of water in both phases is individually denoted by xII1 and xI1. According to these tables, it can be found that the partition coefficients (≥131.2) and separation factors (≥308) are very high within the determined range, which indicate that MTBK as an excellent solvent has a strong ability to remove methylphenols from aqueous solutions. As described in Figures 3 and 4, the slopes of the tie-lines in this work are positive, which means that the solubility of methylphenol in MTBK is higher than that in water. The relationship between the partition coefficients, selectivities, and the concentration of methylphenols in the aqueous phase at 333.2 K and 353.2 K is illustrated in Figures 5 and 6.

Figure 3. Ternary diagram for experimental LLE data and the corresponding NRTL and UNIQUAC calculated data of the ternary system, MTBK(1) + methylphenols(2) + water(3), at 333.2 K: (a) 2-methylphenol, (b) 3-methylphenol, (c) 4-methylphenol.

The partition coefficients and selectivities decrease as the concentration of methylphenols in the aqueous phase increases, or equilibrium temperature rises. However, the partition coefficients D

DOI: 10.1021/acs.jced.7b00932 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Figure 4. Ternary diagram for experimental LLE data and the corresponding NRTL and UNIQUAC calculated data of the ternary system, MTBK(1) + methylphenols(2) + water(3), at 353.2 K: (a) 2-methylphenol, (b) 3-methylphenol, (c) 4-methylphenol.

Figure 5. Partition coefficient (P) of 2-, 3-, 4-methylphenol versus the mole fraction of 2-, 3-, 4-methylphenol in the aqueous phase at 298.2, 313.2, 323.2, 333.2 and 353.2 K with MTBK.

are still high when the mole fractions of methylphenols are below 0.025 in the aqueous phase. In a large concentration range, MTBK always maintains a high partition coefficient. This indicates that MTBK is powerful for extracting methylphenols from highly concentrated phenolic wastewater. 3.2. Comparing at Different Temperatures and with Other Solvents. Methylphenols are a type of phenol which are relatively easier to extract from wastewater than phenol or polyphenols. The partition coefficients (P) and separation factors (S) could reach 131.2−1088.1 and 308−7521, which are very high values for liquid−liquid separation. The ranges of those values with MTBK have no big difference with those of other solvents such as methyl isopropyl ketone, methyl isobutyl ketone, methyl butyl ketone and 2-methoxy-2-methylpropane. Previously, liquid−liquid equilibria of the ternary system water−methylphenol−MTBK were measured at 298.2, 313.2, and 323.2 K which are defined as low temperatures. In this paper, further wider concentration ranges were determined with the same ternary system at 333.2 K and 353.2 K as high temperatures. The variation rules of P and S with the concentration of methylphenol in the aqueous phase at high temperatures are

analogous to those at low temperatures as presented in Figures 5 and 6. They all indicate that P and S would decrease with the concentration of methylphenol as the aqueous phase increased. When the temperature changes from 298.2 K to 353.2 K, the P and S values decrease with the rise of the temperature. The change rule of MTBK is also like that of other extractants. So if the extraction temperature was set as a high temperature, extraction efficiency would decrease. However, if the temperature was lower than 333.2 K in the phenol recovery process of coal chemical wastewater with highly concentrated phenols, the paraffin would solidify, which is a change from the liquid phase in wastewater to a solid phase cohering with fly ash and coal tar, etc. To prolong the operation period of the wastewater treatment system, the extraction temperature was set to be more than 333.2 K to properly reduce the extraction performance cost. The partition coefficients (P) and separation factors (S) of MTBK compared with those of mesityl oxide and MIBK were E

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Figure 7. Partition coefficient (P) and selectivity (S) of methylphenols versus that of methylphenol in aqueous phase for different solvents at 333.2 K: (a) 2-methylphenol, (b) 3-methylphenol, (c) 4-methylphenol with different solvents.

was given as 0.2. The UNIQUAC structure parameters of pure components from the literature are presented in Table 5. The objective function was used to obtain the six binary interaction parameters in the NRTL and UNIQUAC equations by the experimental LLE data, which could be described as

Figure 6. Selectivity (S) of 2-, 3-, 4-methylphenol versus the mole fraction of 2-, 3-, 4-methylphenol in aqueous phase at 298.2, 313.2, 323.2, 333.2 and 353.2 K with MTBK.

3

reported in Figure 7. In general, the extraction efficiency of MTBK is stronger than that of mesityl oxide and close to or lightly weaker than that of MIBK. The change law of the P and S values with the change of the concentration of methylphenol in the aqueous phase using MTBK is consistent to those of others. No matter what kind of extrantant is used, the P and S values of 2-methylphenol are the largest of the three kinds of methylphenols at the same solute concentration in the aqueous phase. The water-solubility of MTBK is quite lower than that of MIBK at same temperature.32 The boiling point of MTBK is 10 degrees below that of MIBK. Therefore, methyl tert-butyl ketone is also a promising solvent for extracting phenols from wastewater with highly concentrated phenols. 3.3. Data Correlation. The measured LLE data of the ternary systems (water + 2-, 3-, 4-methylphenol + MTBK) were exactly fitted by using UNIQUAC and NRTL models. In this work, the nonrandomness parameter (α) in the NRTL equation

OF =

2

n

∑ ∑ ∑ (xijkexp − xijkcal) (3)

i=1 j=1 k=1

in which n represents the total of the tie-lines, and x refers to the mole fraction. Subscripts exp and cal stand for experimental value and calculated value, respectively, and subscripts i, j, and k denote the components, the phases, and the tie-lines. The root-mean-square-error (RMSE) as stated in eq 4 was often applied to estimate the similarity between the model and experimental data. ⎡ ∑3 ∑2 ∑n (x exp − x cal)2 ⎤1/2 ijk i=1 j=1 k = 1 ijk ⎥ RMSE = ⎢ ⎢ ⎥ 6 n ⎣ ⎦

(4)

where the content of these symbols is corresponding with the above annotations. The RMSE values in the NRTL and F

DOI: 10.1021/acs.jced.7b00932 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 5. Binary Interaction Parameters in the NRTL and UNIQUAC Equations for the Ternary System Water(1) + Methylphenol(2) + MTBK(3) at 333.32 K and 353.2 K under 101.3 kPa components T/K 333.2

353.2

333.2

353.2

333.2

353.2

i−j

UNIQUAC uij−ujj/ J/mol

1−2 1−3 2−3 1−2 1−3 2−3

−5072.0 −862.3 2965.9 −5095.5 −802.7 2761.8

1−2 1−3 2−3 1−2 1−3 2−3

−4603.4 −743.6 2283.8 −5229.7 −864.9 2828.2

1−2 1−3 2−3 1−2 1−3 2−3

−4902.0 −893.9 2369.2 −5553.4 −917.0 2779.2

uji−uii/ J/mol

Water (1) + 2-Methylphenol(2) + MTBK(3) 2072.0 0.02174 −4443.4 −4005.3 2235.5 0.02259 −4783.6 −2963.8 Water (1) + 3-Methylphenol(2) + MTBK(3) 1705.0 0.01698 −4798.4 −2561.0 2293.3 0.02014 −4670.6 −3249.8 Water (1) + 4-Methylphenol(2) + MTBK(3) 1884.4 0.01472 −4221.5 −2658.7 2425.8 0.02117 −4326.4 −3068.0

gij−gjj/ J/mol

gji−gii/ J/mol

RMSE

21201.8 14563.1 −7643.9 21738.7 14979.6 −7317.1

−5472.6 1553.3 12348.8 −5809.4 1696.7 8249.8

0.02483

17382.4 14131.3 −6118.6 22315.7 15199.6 −8368.5

−2288.1 1814.2 6965.0 −6527.0 1637.8 13309.0

21187.4 14575.6 −5986.6 22266.8 15356.4 −7328.2

−4879.1 1451.4 6389.9 −6078.4 1323.8 8420.7

0.02327

0.01830

0.02177

0.01610

0.02161

Funding

UNIQUAC equations at different temperatures were listed in Table 5. As demonstrated in Table 5, all the RMSE values in the NRTL and UNIQUAC equations were less than 2.5%, which indicated the determined data of the ternary system (water + 2-, 3-, 4-methylphenol + MTBK) were successfully correlated. Figures 3 and 4 also demonstrate a good agreement of the measured data with the fitted data from the NRTL and UNIQUAC models.

Financial support from State Key Laboratory of Pulp and Paper Engineering (201703 and 201708) in China is gratefully acknowledged. Notes

The authors declare no competing financial interest.

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4. CONCLUSIONS The tie-line data of the ternary system water + 2-, 3-, 4-methylphenol + MTBK were determined at the temperatures of 333.2 K and 353.2 K under air pressure. The partition coefficients (P) and separation factors (S) were from 131 to 1049.6, and from 308 to 7724, separately. The P and S values decrease with increasing temperature or concentration of methylphenol in the aqueous phase when the temperature changes from 298.2 K to 353.2 K. Compared with mesityl oxide and MIBK, the extraction efficiency of MTBK is better than that of mesityl oxide and close to or lightly weaker than that of MIBK. Considered boiling point, solubility in water, and other factors, MTBK is an excellent solvent for the extraction of methylphenols from coal chemical wastewater with highly concentrated phenols. The measured LLE data were accurately fitted by the NRTL and UNIQUAC equations with a RMSE less than 2.5%, which indicated good agreement between the fitted values and the measured data. The obtained binary interaction parameters in this research can be employed in the calculation of LLE for the ternary system (water + 2-, 3-, 4-methylphenol + MTBK) besides for the design and optimization of industrial processes to remove methylphenols from effluents.

■

NRTL RMSE

REFERENCES

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*Tel.: + 86 13632384249. E-mail: [email protected]. ORCID

Yun Chen: 0000-0001-5784-2602 G

DOI: 10.1021/acs.jced.7b00932 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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DOI: 10.1021/acs.jced.7b00932 J. Chem. Eng. Data XXXX, XXX, XXX−XXX