Extraction of Phenolic Pollutants (Phenol and p-Chlorophenol) from

Article pubs.acs.org/jced

Extraction of Phenolic Pollutants (Phenol and p‑Chlorophenol) from Industrial Wastewater Khalid Farhod Chasib* Chemical Engineering Department, University of Technology, Baghdad, Iraq ABSTRACT: The efficiency of five new solvents as a selective solvent in the extraction of phenol and p-chlorophenol from wastewater was investigated. The phenols samples were collected from real petroleum refinery wastewater and from an experimentaly prepared aqueous phenol solution. In this work, data have been estimated for 10 systems containing, phenol + water or p-chlorophenol + water as a common component liquid and + five solvents [ethylene glycol, diethylene glycol, poly(ethylene glycol) (200), dimethylsulfoxide and tetramethylene sulfolone (sulfolane)]. The consistency and accuracy of the tie-line data were evaluated using three correlation relations namely, Bachman, Hand, and Othmer, and Tobias correlation. The Plait Point for each ternary system was estimated. Among the five solvents used to extract the phenol or p-chlorophenol from wastewater, diethylene glycol (DEG) has the highest selectivity and distribution coefficient and the greatest differences between its boiling point and density and those of phenol or p-chlorophenol. It can therefore, be regarded as an excellent solvent for extracting phenol or p-chlorophenol from wastewater. The liquid−liquid equilibrium data have been predicated using the nonrandom-two-liquid (NRTL) model and universal-quasichemical (UNIQUAC) model. The binary interaction parameters have been calculated using the Maximum Likelihood Principle technique. The experimental data fitted by the NRTL model are more accurate than the UNIQUAC model.

1. INTRODUCTION

If the pollutants are to be recycled, liquid−liquid extraction can be used because it is cost-efficient for the extraction of a wide range of phenol concentrations. For phenol removal from wastewater, liquid−liquid equilibria data of ternary water−phenols−solvent system are important in the modeling and design of the extraction process.11 Solvent extraction is the most economic nondestructive process and has been applied with good results for recovering phenol from industrial effluents when the phenol content in the effluent is above 50 mg/L.12 Various wastewater industries have phenols, such as petrochemicals (3.9 mg/L to 1230 mg/L), coking operations (29 mg/L to 3950 mg/L), wood products, paint, pharmaceutical, pulp and paper industries (0.2 mg/L to 1700 mg/L), plastics, coal processing (10 mg/L to 6900 mg/L), and refineries (5 mg/L to 600 mg/L).13 Several organic solvents, such as diisopropyl ether (DIPE), methyl isobutyl ketone (MIBK), ethylbenzene, cumene, di-isopropyl ether, isopropyl acetate, iso-pentyl-acetate, n-hexane, toluene, methyl-iso-butyl ketone, benzene, n-octylpyrrolidone, ethyl acetate, cyclohexane, n-butyl acetate, n-hexyl acetate, n-pentyl-acetate, cyclo-hexyl acetate, acetate esters, TBP, and butyl acetate are in common use for recovering the phenolic compounds in the wastewater by solvent extraction technology.14−16 It is necessary to study new solvents and new experiments related to the removal of phenolic compounds because the industrial wastewater from petroleum refining and coking plants

Industrial wastewaters including those from petroleum refining and coking plants contain appreciable amounts of phenols (especially phenol or chlorophenol isomers) which have been identified as hazardous compounds for many aquatic organisms by environmental protection agencies.1 Phenols, particularly phenol and chlorophenols can be considered as a serious pollutant of water and soil. They come from the chlorination of water or from industrial and agricultural sources.2,3 Water that has a concentration usually less than 0.02 mg·L−1 of phenols is considered unpolluted water.4 The level of phenols in dinking water is considered by WHO’s guidelines for drinking water quality as 0.001 mg·L−1.5 Phenol and chlorophenols are the starting material for many chemical industries. For example, additives for rubber chemicals, emulsifiers, dyes, detergents, adhesives, flavors and impregnating resins are heavily used.6 Five million tons per year is the phenol worldwide production.7 It is used for the production of caprolactcam and epoxy resins.8 The widespread use of chlorophenols as the chlorination of municipal and industrial wastewater and drinking water, degradation products of chlorinated herbicides, wood preservative, the chlorination of lignin or the use of slimicicles in paper or pulp mill plants were the major sources of environmental contamination.9 Various methods have recently been applied for phenolic compounds removal like biological-based processes, membrane extraction, distillation, adsorption, ozonation, electrochemical methods, fenton, pervaporation, and liquid−liquid extraction.10 © 2013 American Chemical Society

Received: October 16, 2012 Accepted: May 13, 2013 Published: May 29, 2013 1549

dx.doi.org/10.1021/je4001284 | J. Chem. Eng. Data 2013, 58, 1549−1564

Journal of Chemical & Engineering Data

Article

Table 1. Physical Properties of the Pure Chemicals at 298.15 K Compared with Literature Values density ρ/g·cm−3 chemicals P ClP W EG DEG DMSO TMS a

obs. 1.1320 1.2953 0.99713 1.1112 1.1163 1.0959 1.2631

viscosity η/cp

refractive index nD lit.

1.1320 1.3061 0.99707 1.1100 1.1164b 1.0958 1.2623c

obs.

lit. a

1.5411 1.5581 1.3328 1.4317 1.4434 1.4780 1.4813

1.5403 1.5579 1.3329 1.4306 1.4461 1.4773 1.4820

obs.

lit.

b.p./°C

4.110 6.153 1.010 13.542 29.799 2.098 10.211

4.076 6.150a 0.89 13.550 30.000 2.121 10.286c

181.8 220 100 197.3 244.8 189.0 217.3

At 318.15 K. bAt 393.15 K. cAt 303.15 K.

is composed of petrochemicals containing an appreciable amount of phenol or chlorophenols which have been identified as hazardous compounds for many aquatic organisms by Environment Protection Agencies. To our knowledge, the new experimental information available in the literature for liquid− liquid equilibria of ternary mixtures containing the pair phenol− water is limited. Therefore the purpose of the present investigation is to generate the data for the water−phenol pair with new different solvents to aid the correlation of liquid−liquid equilibria, including phase diagrams, distribution coefficients of phenol, tie-lines data, and selectivity of the solvents for the aqueous phenol system. The aim of this study is to extract phenols, mainly phenol or p-chlorophenol, from aqueous and real petroleum refinery wastewater using different solvents. We present new experimental liquid−liquid equilibrium (LLE) data for different ternary systems including phenol or p-chlorophenol + water + solvent. Five different solvents were used, ethylene glycol (EG), diethylene glycol (DEG), poly(ethylene glycol) 200 (PEG), dimethylsulfoxide (DMSO), and tetramethylsulfon (sulfolane) (TMS). The phase equilibrium diagrams, distribution coefficient of phenols, tie-line data, and selectivity and solvency of solvent for each system were generated. To our knowledge there is no literature data on the systems studied. The UNIQUAC and the NRTL models of the liquid-phase activity coefficients for the multicomponent mixtures of nonpolar and polar liquids were used to correlate the experimental data.

Table 2. Characterization of Used Refinery Wastewater characteristic

value

pH COD (mg/L) phenols (mg/L) TSS (g/L) TDS (g/Ll)

8.9 4612 94 0.13 17

Figure 1. Cloud point titrator.

2. EXPERIMENTAL SECTION 2.1. Chemicals. Phenol and p-chlorophenol with purity of 99 % obtained from Aldrich Company were used without further purification. Bidistilled water with conductivity (≤ 1 μs) was used in all experiments. Ethylene glycol (stated purity 99.3 %), diethylene glycol (stated purity 99 %), dimethyl sulfoxide (stated purity 99.5 %), sulfolane (stated purity >99.5 %) were obtained from Fluka Company and were stored under 4 Å molecular sieves and filtered before use. Poly(ethylene glycol) was obtained from Aldrich Company in liquid form and the average molecular weight reported by the manufacturer was 200 and used without further treatment. The physical properties of the chemicals used in this study are listed in Table 1 and compared with values in the literature.17−19 Samples of the wastewater were collected from a local petroleum refinery (Midland Refineries CompanyAl-Daura Refinery, Iraq) and the samples were preserved at room temperature in dark color plastic containers. The refinery wastewater samples characteristics are given in Table 2. Two different initial phenol concentrations from Real refinery wastewater samples were tested namely 94 and 43 (± 0.5) mg/L. A series of different initial concentrations of phenol solution was

prepared from phenol stock solution for the aqueous wastewater ranging from 100 mg/L to 300 mg/L. 2.2. Density Measurements. The densities of the pure chemicals were measured with an Anton Paar Digital Density Meter (model DMA 602) at 298.15 K, except for sulfolane which was measured at 303.15 K (uncertainty ± 1·10−4 g·cm−3). The details of using this instrument were described elsewhere.20 2.3. Refractive Index Measurements. Refractive indices, nD of the pure component liquid and mixtures were measured at 298.15 K using Abbe refractometer (Tafesa, Germany) by the reflection method using sodium line (λ = 589.3 nm) with a precision of the reading of ± 0.0002. It was calibrated before measuring the refractive indices of sample using standard pure liquids (uncertainty ± 5·10−4). In all refractive index measurements, the temperature was kept constant within ± 0.01 K using a Schott-Gerate CT 1150 thermostat water bath, and a Hewlett-Packard model 201 A quartz thermometer. 2.4. Viscosity Measurements. The viscosities of the pure liquids were determined using a suspended Ubbelhode viscometer in a bath controlled to ± 0.01 K at specific 1550



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Figure 2. Determination of the tie lines.

Figure 3. Plots of refractive indices versus concentration of solvents for phenol + water + sulfolane system at 308.15 K.

Figure 4. Equilibrium compositions in a phenol + water binary system with an upper critical solution temperature.

temperature (uncertainty ± 3·10−4 cp). The times were determined electronically using an electronic timer (SchottGerete model AVS300) with a precision ± 0.01 s. 2.5. Apparatus and Procedure. 2.5.1. Determination of the Binodal Curves. The binodal curves of the ternary system were determined by the apparatus of titration as described by Haddad and Admister.21 The cloud point is the temperature at which haziness is first observed at the bottom of the test jar. The apparatus shown diagrammatically in Figure 1 was kept within ± 0.1 °C of the experiment temperature by circulating water through a constant temperature bath. A microburet calibrated to 0.01 mL was used to ensure that the liquid was perfectly titrated. During the addition, the solution in the jacket jar was mixed with a Teflon-coated magnetic rod. The binodal curve of the ternary system was determined by the method of Othmer et al.22 The phenol was placed in the sample

bottle inside the constant temperature water jacket and was titrated using a microburet while the solution was being stirred by a magnetic stirring bar. As soon as the cloud point was reached, the liquid was reclarified by a slow titrating solvent. Water was then added to make the liquid cloudy once again. The procedure was repeated many times, and the successive cloud points were connected up to produce a binodal curve. 2.5.2. Determination of the Tie Lines. To determine lines of conjugate layers, a ternary two phase system was analyzed by the so-called cross-section method by Radecki et al.23 The method consists of plotting the refractive index of a mixture against concentration of the components at a constant ratio of the remaining two components. As known, sections A, B, and C (as shown in Figure 2), developed from a point of triangle representing a solvent concentration in a mixture are loci of 1551



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Figure 5. Binodal curve and tie lines for ternary system (P + W + EG) at 308.15 K.

Figure 6. Binodal curve and tie lines for ternary system (P + W + DEG) at 308.15 K.

points lie on three sections (A, B, and C) but they belong to the same tie lines. Composition of the conjugate layers is read from the intersections of the tie lines with a binodal curve illustrating the equilibrium between one- and two-phase systems. To obtain the average composition of each sample, as well as to investigate the repeatability, all the measurements were repeated three times in the same condition. The composition analysis deviation in the measurement was less than 2 %.

points characterized by a constant ratio of the remaining two components. For each section, a series of mixtures is prepared which occurs in a two-phase region and differs in the solvent content [70:30 (A), 50:50 (B) and 40:60 (C)]. The solution was stirred for 3 h at constant temperature and left overnight to reach the ternary liquid−liquid equilibrium. As the concentration of solvent was increased, samples were taken from each of the two phases and the refractive indices of each equilibrium phase are measured and the relationship between the refractive index and solvent concentration for a given phase is obtained as shown in Figure 3. Since the composition of equilibrium phases lying on one tie line is constant, arbitrary values of the refractive index (nD) shown in Figure 3 may be chosen in the plot of nD vs (Csolvent) which indicates the curves of the corresponding points determining the solvent content in the phases considered. The

3. RESULTS AND DISCUSSION 3.1. Binary Systems. The experimental solubility data (mg/L) of the phenol + water binary mixtures is plotted in Figure 4. The critical solution temperature for this binary system is 74.0 °C. From Figure 4 it can be seen that the two-phase region of phenol with water ranges between 23 % and 91 %. The temperature 1552



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Figure 7. Binodal curve and tie lines for ternary system (P + W + PEG) at 308.15 K.

Figure 8. Binodal curve and tie lines for ternary system (P + W + DMSO) at 308.15 K.

35 °C was chosen for determining liquid−liquid equilibria for all systems. 3.2. Ternary Systems. 3.2.1. Mutual Solubility. The liquid− liquid equilibria data (mutual solubility data) of the following 10 ternary systems have been studied at 308.15 K. 1. ethylene glycol (EG) + water (W) + phenol (P) 2. diethylene glycol (DEG) + water (W) + phenol (P) 3. poly(ethylene glycol) (PEG) + water (W) + phenol (P) 4. dimethylsulfoxide (DMSO) + water (W) + phenol (P) 5. sulfolane (TMS) + water (W) + phenol (P) 6. ethylene glycol (EG) + water (W) + p-chlorophenol (ClP) 7. diethylene glycol (DEG) + water (W) + p-chlorophenol (ClP) 8. poly(ethylene glycol) (PEG) + water (W) + p-chlorophenol (ClP) 9. dimethylsulfoxide (DMSO) + water (W) + p-chlorophenol (ClP) 10. sulfolane (TMS) + water (W) + p-chlorophenol (ClP)

Mutual solubility curves and mixture compositions for these ternary systems have been plotted on a triangular diagram as shown in Figures 5 to 14. The minimum concentration (in % mass) for the solubility of the phenol over the whole composition range in the mixture (water + phenol + solvent) was found to be 9.970, 48.765, 37.262, 23.432, and 46.955 for EG, DEG, PEG, DMSO, and TMS, respectively, and that for the mixture (water + p-chlorophenol + solvent) it was found to be 23.417, 60.401, 34.019, 35.973, and 57.527 for EG, DEG, PEG, DMSO, and TMS respectively. This reflects the magnitude of the area of the two-phase region. This region increases for the systems (water + phenol + solvent) in the order DEG > TMS > PEG > DMSO > EG, while for the systems (water + p-chlorophenl + solvent) in the order DEG > TMS > DMSO > PEG > EG. In the two sets of data, the order of immiscibility is similar except for interchange of DMSO and PEG. It seems to be that PEG is more interactable 1553



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Figure 9. Binodal curve and tie lines for ternary system (P + W + TMS) at 308.15 K.

Figure 10. Binodal curve and tie lines for ternary system (ClP + W + EG) at 308.15 K.

with phenol than with p-chlorophenol. However, the shape of binodal curve seems to be strongly dependent on the type of solvent used. These results are in contrast with these solvents in their ternary systems containing aromatic and aliphatic hydrocarbon mixtures.24−27 3.2.2. Effect of Temperature. The binodal curve results for the ternary system (phenol + H2O + PEG) at 308.15, 318.15, and 328.15 K are presented in Figure 15 as a representative example of the 10 systems. It can be seen from this figure that the heterogeneous region at temperature 308.15 K is greater than that of the other temperature. This is the reason why we chose the temperature 308.15 K for the investigation of the liquid−liquid equilibrium data for the systems under consideration. 3.2.3. Tie-Line Data. The liquid−liquid equilibrium data (tieline data) indicating the composition of the two phases (solvent-rich

phase and water-rich phase) obtained experimentally for the 10 ternary systems at 308.15 K were plotted on equilateral triangles following the method of Francies28 and presented in Figure 5 to 14. These data for the systems fit well on the binodal curves indicating the accuracy of the experimental tie-line data. The slopes of the tie lines of the systems (phenol + water + solvent) are inclined toward the solvent in the case of three systems only, namely (EG + W +P), (PEG + W + P), and (DMSO +W + P); thus, indicating the separation of phenol from water by extraction with these solvents can be achieved in fewer stages. 3.2.3.1. Tie-Line Correlations. The tie-line data of the 10 ternary mixtures were correlated by Bachman,29 Hand,30 and Othmer and Tobias31 as follows: The first empirical equation describing the distribution of components in the three components two-phase liquid systems was due to Bachman. 1554



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Figure 11. Binodal curve and tie lines for ternary system (ClP + W + DEG) at 308.15 K.

Figure 12. Binodal curve and tie lines for ternary system (ClP + W + PEG) at 308.15 K.

⎛ xS,S ⎞ ⎟⎟ xS,S = a1 + b1⎜⎜ ⎝ x W,W ⎠

⎛ 1 − xP,S ⎞ ⎛ 1 − x W,W ⎞ ⎟⎟ = a3 + b3 log⎜⎜ ⎟⎟ log⎜⎜ ⎝ x P,S ⎠ ⎝ x W,W ⎠

(1)

where xS,S and xW,W are the concentration (mass fraction percent) of components solvent (S) in the solvent-rich phase and water (W) in the water-rich phase, respectively; a1 and b1 are constants. Hand correlated the concentration of the solute in two conjugate solutions by the following equation: ⎞ ⎛ x P,S ⎞ ⎛x ⎟⎟ = a 2 + b2 ·log⎜⎜ P,W ⎟⎟ log⎜⎜ ⎝ xS,S ⎠ ⎝ x W,W ⎠

(3)

where a3 and b3 are constants. The parameters aj and bj (j = 1−10) of eqs 1 to 3 were obtained by using the method of the Maximum Likelihood Principle technique32 starting from the experimental tie-line data. The parameters and the correlation coefficients, Rj, are given in Table 3. Since the data show little scattering from a straight line, they are judged acceptable on an empirical basis, indicating internal consistency of the experimental data. 3.2.4. Distribution Coefficient and Selectivity. Selectivity is the ability of solvent to dissolve one material in preference to another. This is of prime importance, since the greater the selectivity the more easily a desired separation can be made.

(2)

where xP,S and xP,W are the mass fractions of phenol and water in the solvent-rich phase and the water-rich phase, respectively; a2 and b2 are constants. Othmer and Tobias proposed the following correlation: 1555



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Figure 13. Binodal curve and tie lines for ternary system (ClP + W + DMSO) at 308.15 K.

Figure 14. Binodal curve and tie lines for ternary system (ClP + W + TMS) at 308.15 K.

(kW) of the phenol and water, respectively, and the selectivity β of the solvent. The distribution coefficient of phenol and water is given by the formula:

The effectiveness of the solvent for extraction can be expressed in terms of the distribution coefficient of the solute and the selectivity of the solvent. Capacity or solvency means the ability of the solvent to dissolve reasonable amounts of the material to be separated while still maintaining a good selectivity. Solvent capacity has an even greater influence on the extraction process. If the capacity is too low, an excessive amount of solvent is required for a given separation so the capacity determines the rate of circulating solvent and the size of most of the plant equipment. In addition, the operating costs are affected by the heat needed for heating the solvent from extraction to distillation temperature. Most solvents with high capacity have low selectivity and vice versa. So, if the solvent has high capacity and selectivity, it is considered the more ideal solvent (an excellent solvent).33 The effectiveness of the solvent for the extraction of phenol can be expressed in terms of the distribution coefficient (kP) and

kP =

x P,S phenol mass % in solvent layer = phenol mass % in water layer x P,W

(4)

kW =

x W,S water mass % in solvent layer = water mass % in water layer x W,W

(5)

The selectivity β which is a measure of the ability of the solvent for the removal of phenol from the phenol−water solution is expressed in terms of the ratio of phenol mass percent in solventfree solvent layer to phenol mass percent in solvent-free water layer as follows: 1556



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Figure 15. The effect of temperature on liquid−liquid equilibria of P + W + PEG ternary system.

Table 3. Results of the Maximum Likelihood Principle Analysis for the Systems W + Solvents + P or ClP at 308.15 K correlation Bachman solvent

a1

b1

Hand R1

a2

b2

Othmer and Tobais R2

a3

b3

R3

0.992 0.975 0.996 0.990 0.989

0.116 0.243 0.160 0.240 0.321

0.507 0.788 0.606 0.651 0.721

0.989 0.969 0.970 0.965 0.984

0.979 0.976 0.991 0.996 0.988

0.464 0.103 0.157 0.245 0.107

1.190 0.521 0.768 0.915 0.526

0.980 0.933 0.992 0.986 0.979

P + W + Solvent EG DEG PEG DMSO TMS

−0.285 −0.435 −0.416 −0.376 −0.400

0.399 0.466 0.458 0.440 0.450

0.987 0.999 0.997 0.998 0.998

EG DEG PEG DMSO TMS

−0.469 −0.413 −0.415 −0.427 −0.438

0.480 0.461 0.486 0.454 0.473

0.999 0.966 0.999 0.999 0.991

1.540 1.020 0.555 0.476 1.971 1.866 2.507 2.213 1.942 1.543 ClP + W + Solvent 0.650 0.684 0.343 0.416 0.662 0.686 0.422 0.531 0.451 0.503

increases, the value of (ln KP − ln KW) therefore, decreases as the concentration of phenol in one of the phases increases. Selectivity decreases with the increase of concentration of the component to be extracted. The distribution coefficients for phenol or p-chlorophenol between water and solvent indicate that the preference of extraction of phenol lies in the following order: DEG > PEG > TMS > DMSO > EG, while for p-chlorophenol it lies in the following order: DEG > TMS > PEG > DMSO > EG. The selectivity for these two systems follows the same trend TMS > DEG > PEG > DMSO > EG which can be obtained from the selectivity diagram illustrated in Figures 18 and 19 which reveal that TMS and DEG are more selective for phenols in the presence of water. 3.2.5. Plait Point. The plait point is the point on the binodal curve at which the tie lines connect two compositions of the equilibrium phases become extremely short. At this point the two phases in equilibrium become identical in composition. Interpolation of tie lines will lead to estimate the position of the plait point. The plait point composition on the binodal curve was determined from the formula:34

x P,S

phenol mass % in solvent free solvent layer β= = phenol mass % in solvent free water layer

x P,S + x W,S x P,W x P,W + x W,W

(6)

The obtained results of the distribution coefficients and the selectivity are listed in Table 4. The distribution coefficient of phenol and the selectivity of the solvents, as calculated from the experimental tie-line data using eqs 4 to 6 are plotted in Figures 16, 17, 18, and 19 respectively. The selectivity of a solvent as mentioned above is its ability to separate the components of a given mixture. The selectivity depends mainly on the distribution coefficient of phenol (KP) and water (KW) and thus could be defined as the difference between the logarithms of KP and KW. Separation by extraction becomes easier as this value increases. The selectivity of the solvent toward components phenol and water depends on the two factors affecting the distribution coefficient values: the concentration and the temperature, (where temperature is constant in this study, this value is affected only by concentration). As the concentration of the phenol in a heterogeneous ternary system 1557



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Table 4. The Distribution Coefficients and Selectivity for the Systems Solvent + W + P or ClP at 308.15 K KP

KW EG + W + P 0.670 0.244 0.215 0.218 DEG + W + P 0.684 0.318 0.265 0.254 0.248 0.245 0.242 PEG + W + P 0.831 0.521 0.461 0.414 0.362 0.344 0.308 DMSO + W + P 0.902 0.400 0.344 0.338 0.317 TMS + W + P 0.736 0.455 0.413 0.361 0.329 0.322 0.291 EG + W + ClP 0.926 0.410

22.369 13.346 12.994 12.011 5.441 5.588 13.691 22.103 18.994 16.899 10.674 3.977 3.455 4.286 5.483 7.213 7.569 9.722 1.587 3.579 5.154 5.953 6.112 6.460 3.458 4.851 7.388 8.810 10.147 12.074 6.242 10.080

x P,W x W,W

=

x P,S x W,S

=

xP xW

β

KP

24.314 13.928 13.479 12.489

12.861 15.364 16.241 13.164 14.132

6.209 6.020 15.089 23.837 20.584 18.214 11.861

11.769 12.080 35.709 27.514 26.716 25.798 17.780

3.970 2.902 3.636 4.741 6.315 6.651 8.915

7.987 8.914 11.716 14.930 21.351 20.300 21.858

1.551 3.209 4.643 5.247 5.588

18.172 19.958 38.633 38.835 35.583 28.664 23.320

6.699 2.840 3.747 5.917 7.492 8.544 10.883

10.582 6.182 4.336 44.144 52.757 56.582 29.145

6.403 10.344

KW EG + W + ClP 0.246 0.272 0.231 0.229 0.223 DEG + W + ClP 0.357 0.127 0.135 0.132 0.130 0.139 0.143 PEG + W + ClP 0.790 0.260 0.248 0.221 0.212 0.206 0.215 DMSO + W + ClP 0.802 0.360 0.283 0.248 0.226 0.217 0.208 TMS + W + ClP 0.535 0.196 0.178 0.150 0.167 0.172 0.174

β 15.288 16.328 16.936 13.696 14.656 18.200 13.645 41.678 33.065 33.546 31.063 21.762 8.149 9.857 12.778 16.249 23.229 21.885 22.570 20.005 21.416 41.713 43.261 39.976 31.203 25.050 13.753 6.542 4.922 49.352 56.607 60.842 32.008

the method of Treybal with the correlation of Hand requires experimental binodal curve data in addition to the tie-line data. This is why the estimation of the compositions of plait points for the ternary liquid−liquid equilibria (LLE) systems by the two methods are different. In general, the plait points resulting from correlation of the tie lines with the thermodynamic models are not located on the experimentally determined binodal curves. 3.3. Selection of Solvent. The result of an extraction is affected in the first place by the extent of the two-phase area. For the separation of a given mixture, the size of this area is dependent on temperature and the nature of the solvent (in this study the temperature is constant). In this study the slopes of tie lines are steeper in the DEG + water system than the corresponding solvents (see Figures 5 to 14), the plait points are located in the region of mixtures containing more DEG in the case of DEG + water + phenol or p-chlorophenol system. So the separation of P or ClP form W + P or ClP by extraction with DEG can be achieved in fewer stages than the separation of P or ClP by other solvents. On the other hand, the solubility gaps (Figures 5 to 14), of DEG + W + P or

(7)

The simplest methods for the interpolation and correlation of tie lines are those based on the construction of the conjugate line, which can be drawn in many ways.35 These methods are to be preferred since they are quick and reliable, and the position of the plait point is readily found. Values of the plait points of the ternary systems under study are listed in Table 5. Treybal et al.,36 proposed a method for estimating plait points using the coordinate system of Hand. The estimation of the plait points for the ternary systems using Hand’s correlation is also listed in Table 5 for comparison. The experimental method (construction method) is a graphical method which uses a conjugate line to interpolate tie lines and it is helpful for interpolation and limited extrapolation when equilibrium data are scarce. With this method, plait points of several ternary systems are estimated, and it turns out that the results are favorably comparable with the results obtained by the method proposed by Treybal. However, it needs to emphasize that the experimental method uses only tie-line data while 1558



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Figure 16. Distribution of phenol between water and solvent layer at 308.15 K.

Figure 18. Selectivity curves for solvents + water + phenol at 308.15 K.

Figure 19. Selectivity curves for solvents + water + p-chlorophenol at 308.15 K.

Figure 17. Distribution of p-chlorophenol between water and solvent layer at 308.15 K.

efficient solvent for the extraction of P or ClP from their mixtures with water. DEG has the highest distribution coefficient and selectivity when it is compared with the other solvents. Although, TMS has the highest distribution coefficient of the other solvents rather than DEG and highest selectivity, it is unsuitable as solvent, since the differences between the boiling point and density of the TMS and P or ClP are too small and also because of its toxicity. The boiling point and density of DEG differ greatly from those of phenols (see Table 1), and so DEG is a more suitable solvent for extraction of phenol and p-chlorophenol from their mixtures with water. Phenols consist of two parts, an alkyl/aryl group and a hydroxyl group (difunctional compounds; the hydroxyl group and the aromatic ring). The properties of phenols are chiefly due

ClP (heterogeneous region) is larger than those of the heterogeneous region of the other solvents. For an extraction study, the selection of a solvent depends on the solvent power measured by the solute distribution coefficient and also on its selectivity. In the case of recovery of solute from diluent (water), a solvent with the largest possible distribution coefficient and highest selectivity toward phenol or p-chlorophenol is preferred. The distribution coefficient of the systems (solvents + W + P or ClP) increases in the order DEG > PEG > TMS > DMSO > EG or DEG > TMS > DMSO > PEG > EG, respectively, while the selectivity of both systems, respectively, is in the following sequence TMS > DEG > PEG > DMSO > EG. However, comparisons of the solubility gaps (Figures 5 to 14), distribution coefficient (Figures 16 and 17) and selectivity (Figures 18 and 19) show that the DEG solvent is the most 1559



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and electron releasing groups decrease it. In substituted phenols, the presence of electron withdrawing groups such as a chloro group, enhances the acidic strength of the phenol. This effect is more pronounced when such a group is present at the ortho and para positions. It is due to the effective delocalization of the negative charge in the phenoxide ion. Compounds that can form intermolecular hydrogen bonds have higher melting points and boiling points than compounds that cannot, such as p-chlorophenol (44 °C, 220 °C). It forms an intermolecular hydrogen bond between the chloro group and the phenol function which reduces its ability to form intermolecular bonds. While a halogen atom or an electron-withdrawing group increases the acidity (pKa(PhOH) = 9.95), the effect greatly varies with the position. The ortho isomers are usually less acidic than the para isomers because an intermolecular hydrogen bond makes it more difficult to remove the phenolic hydrogen. The para and the meta isomers dissolve well in polar solvents and poorly in nonpolar solvents. This is why PEG is more interactable with phenol than with p-chlorophenol, because of the electron withdrawing inductive effect of chlorine. The selection of a solvent for an extraction study depends on the solvent power measured by the solute distribution coefficient and also on its selectivity. The solvent must be miscible with the separated components. The basic concept of miscibility is “like dissolves like” consisting of hydrogen bonding, polar, and dispersion interaction forces. In considering whether A component will dissolve in a liquid, three possible interactions should be considered. In two-component systems namely A and B, there are three interaction among these two components which are A−A, B−B, and A−B. If A−B interaction is strong or comparable to A−A or B−B associations then two liquid components are likely to be miscible and mixed with each other. The first interaction force between two molecules, which is common for all component pairs, is the instantaneous dipole− induced dipole interaction or dispersion force. When two components are attached together, the partial positive charge of one dipole will attract the partial negative in the neighboring molecule or vice versa. The second interaction force is the permanent dipole and permanent dipole interactions (hydrogen bonding). If two atoms constituting a bond have significantly different electronegativities, the bond will be permanently polar and produce a permanent polar molecule. Generally, this type of interaction force occurs with a hydrogen compound which is attached with oxygen, nitrogen, and the halide group. The last one is the interaction force

Table 5. Composition of the Plait Point for the Ternary Systems Solvents + Water + Phenol or P-Chlorophenol at 308.15 K experimental method solvent

xS

xW

xP(or ClP)

Treybal method xS

xW

xP(or ClP)

0.698 0.712 0.743 0.699

0.067 0.203 0.206 0.159

0.798 0.718 0.814 0.792 0.789 0.648

0.068 0.201 0.147 0.115 0.135 0.231

P + W + Solvent EG DEG PEG DMSO

0.189 0.080 0.070 0.171

0.784 0.718 0.796 0.740

EG DEG PEG DMSO TMS TMS

0.126 0.051 0.028 0.069 0.038 0.126

0.830 0.779 0.899 0.845 0.819 0.657

0.028 0.235 0.202 0.085 0.135 0.051 0.089 0.142 ClP + W + Solvent 0.045 0.134 0.170 0.081 0.073 0.039 0.086 0.093 0.150 0.076 0.216 0.121

to the hydroxyl group. The nature of the alkyl and aryl groups simply modify these properties. The solubility of phenols in water is due to their ability to form intermolecular hydrogen bonds with water molecules. The solubility decreases with an increase in size of alkyl/aryl (hydrophobic) groups. Properties like cohesion (intermolecular force between like molecules) and adhesion (intermolecular force between unlike molecules) are also a result of weak intermolecular forces. The physical properties of phenols are strongly influenced by the hydroxyl group, which permits phenols to form hydrogen bonds with other phenol molecules and with water. Thus, phenols have higher melting points and boiling points and are more soluble in water. The presence of the −OH group in phenols activates the aromatic ring toward electrophilic substitution and directs the incoming group to the ortho and para positions due to a resonance effect. Because of the higher electronegativity of sp hybridized carbon of phenol to which −OH is attached, electron density decreases on oxygen. This increases the polarity of the O−H bond and results in an increase in ionization of phenols. Thus, phenols are polar compounds. The −OH group of phenols makes it possible for them to participate in hydrogen bonding. This contributes to the higher boiling points and greater watersolubility of phenolic compounds Phenols are acidic in nature. In fact, phenols are Brönsted acids; that is, they can donate a proton to a stronger base. Electron withdrawing groups in phenol increase its acidic strength

Table 6. UNIQUAC Parameter Uij (J·mol−1) and RMSD Values for the Systems Solvents + W + P or ClP at 308.15 Ka. solvent

U11

U22

U33

U12

U13

U23

RMSD

5.942 6.642 4.021 3.156

6.524 3.215 1.342 2.308

4.081 4.376 5.442 2.711

2.327 6.272 2.094 3.656 3.946 3.716

4.411 2.627 5.123 1.865 1.311 5.231

9.286 6.314 6.608 6.731 5.061 2.905

P + W + Solvent

a

EG DEG PEG DMSO

3.968 4.393 1.219 5.550

1.497 7.984 9.066 1.427


3.563 6.137 1.783 2.764 3.455 1.504

3.527 7.527 1.021 7.662 9.806 1.151

6.865 1.863 3.658 3.966 2.935 1.864 3.588 1.4129 ClP + W + Solvent 2.953 2.746 2.779 4.581 1.0211 4.301 1.877 1.667 1.258 1.657 4.258 8.834

Note: all U values are multiplied by 103. 1560



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Table 7. NRTL Parameter gij (J mol−1), αij and RMSD Values for the Systems Solvents + W + P or ClP at 308.15 Ka g11

solvent

g22

g33

g12

g13

g23

α12

α13

α23

RMSD

1.110 1.099 1.134 9.211

0.456 0.460 0.460 0.360

0.459 0.425 0.255 0.460

0.431 0.431 0.388 0.429

0.112 0.067 0.073 0.099

1.346 1.140 1.123 1.180 1.159 1.194

0.444 0.446 0.460 0.460 0.457 0.455

0.186 0.403 0.437 0.432 0.409 0.417

0.430 0.437 0.414 0.449 0.425 0.395

0.687 0.093 0.113 0.512 0.169 0.029

P + W + Solvent

a

EG DEG PEG DMSO

2.740 2.430 3.535 4.816

1.729 2.610 0.548 3.775

7.570 1.902 3.288 2.521

6.314 6.299 2.373 4.997


6.558 1.631 2.508 3.368 2.328 3.743

1.016 8.464 3.461 2.660 1.789 1.611

1.404 1.012 2.398 2.568 1.092 3.384

5.537 6.677 8.751 7.098 6.932 2.845

6.969 8.596 7.246 9.104 ClP + W + Solvent 8.045 8.957 6.089 7.966 9.305 9.257

Note: all g values are multiplied by 103.

Table 8. Calculated Tie Lines Using the UNIQUAC Model for Solvents + W + P Systems at 308.15 K solvent-rich layer solvent EG

DEG

PEG

DMSO

TMS

Table 9. Calculated Tie Lines Using the UNIQUAC Model for Solvents + W + ClP systems at 308.15 K

water-rich layer

solvent-rich layer

xS

xW

xP

xS

xW

xP

0.090 0.211 0.119 0.055 0.263 0.465 0.428 0.361 0.289 0.207 0.090 0.021 0.269 0.237 0.187 0.092 0.066 0.030 0.099 0.134 0.083 0.020 0.009 0.163 0.331 0.258 0.180 0.136 0.089 0.018

0.824 0.400 0.360 0.356 0.674 0.335 0.378 0.389 0.396 0.398 0.405 0.923 0.457 0.489 0.536 0.531 0.511 0.540 0.763 0.441 0.468 0.488 0.472 0.824 0.355 0.337 0.371 0.415 0.374 0.330

0.085 0.387 0.520 0.588 0.062 0.199 0.192 0.248 0.313 0.393 0.504 0.540 0.273 0.273 0.276 0.376 0.421 0.29 0.164 0.424 0.447 0.490 0.518 0.011 0.312 0.404 0.448 0.448 0.536 0.651

0.055 0.059 0.043 0.032 0.077 0.231 0.149 0.132 0.097 0.073 0.038 0.015 0.193 0.181 0.166 0.153 0.194 0.123 1.040 1.470 1.250 1.680 1.077 0.112 0.314 0.287 0.247 0.234 0.211 0.098

0.728 0.446 0.471 0.505 0.624 0.359 0.386 0.402 0.431 0.463 0.493 0.772 0.328 0.320 0.321 0.351 0.365 0.376 0.655 0.353 0.368 0.377 0.413 0.635 0.260 0.304 0.350 0.354 0.425 0.599

0.216 0.494 0.485 0.461 0.298 0.409 0.464 0.465 0.470 0.463 0.467 0.211 0.477 0.497 0.512 0.495 0.484 0.500 0.240 0.498 0.506 0.454 0.508 0.252 0.425 0.408 0.401 0.411 0.362 0.301

solvent EG

DEG

PEG

DMSO

TMS

produced by a permanent dipole and induced dipole interactions. This type of interaction force can be found between a hydrocarbon and highly polar components such as HCl, phenols, alcohol component, and carboxylic acid component. The solvent prefers to pair with the component that uses the lowest cohesive energy when compared with the other two pairs. Therefore, it can be concluded that the lower is the mixing energy, the easier it is for the two components to attach together. To find the suitable solvent for a given system, one of the interaction forces between the components in the closed boiling

water-rich layer

xS

xW

xP

xS

xW

xP

0.123 0.206 0.291 0.151 0.098 0.066 0.042 0.423 0.643 0.614 0.511 0.423 0.316 0.153 0.027 0.314 0.376 0.296 0.198 0.097 0.039 0.148 0.528 0.468 0.327 0.228 0.132 0.038 0.290 0.607 0.364 0.558 0.324 0.196 0.082

0.871 0.691 0.701 0.689 0.674 0.661 0.657 0.479 0.151 0.205 0.228 0.250 0.259 0.274 0.903 0.528 0.492 0.466 0.463 0.427 0.371 0.838 0.397 0.354 0.348 0.335 0.316 0.303 0.632 0.169 0.201 0.214 0.254 0.270 0.278

0.005 0.101 0.006 0.158 0.227 0.271 0.299 0.097 0.201 0.180 0.260 0.325 0.424 0.571 0.069 0.157 0.131 0.237 0.338 0.478 0.588 0.012 0.074 0.177 0.324 0.436 0.550 0.658 0.076 0.223 0.434 0.226 0.421 0.533 0.638

0.052 0.0127 0.093 0.071 0.048 0.021 0.009 0.097 0.228 0.153 0.104 0.074 0.060 0.450 0.014 0.135 0.089 0.071 0.057 0.041 0.009 0.100 0.122 0.094 0.071 0.059 0.044 0.030 0.104 0.288 0.169 0.156 0.088 0.054 0.0.38

0.903 0.379 0.252 0.304 0.280 0.293 0.298 0.408 0.307 0.346 0.377 0.391 0.427 0.450 0.809 0.290 0.321 0.338 0.364 0.414 0.529 0.761 0.506 0.517 0.540 0.554 0.592 0.626 0.506 0.317 0.383 0.369 0.468 0.528 0.560

0.044 0.493 0.653 0.624 0.671 0.684 0.692 0.493 0.464 0.499 0.517 0.534 0.11 0.504 0.176 0.574 0.588 0.589 0.578 0.543 0.461 0.138 0.370 0.388 0.388 0.386 0.363 0.343 0.389 0.394 0.447 0.473 0.442 0.416 0.400

point system and solvent has to be estimated. Thus, the external factor contains two effects; that is, the electrostatic stabilization of the ionic form and the donor−acceptor interaction of solvent molecules with the free electron pair of the phenolate oxygen atom. 1561



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Table 10. Calculated Tie Lines Using the NRTL Model for Solvents + W + P Systems at 308.15 K solvent-rich layer solvent EG

DEG

PEG

DMSO

TMS

Table 11. Calculated Tie Lines Using the NRTL Model for Solvents + W + ClP Systems at 308.15 K

water-rich layer

solvent-rich layer

xS

xW

xP

xS

xW

xP

0.127 0.140 0.095 0.059 0.243 0.330 0.282 0.248 0.212 0.171 0.120 0.016 0.163 0.139 0.111 0.073 0.063 0.038 0.089 0.119 0.067 0.019 0.009 0.153 0.273 0.209 0.147 0.125 0.077 0.016

0.613 0.232 0.217 0.232 0.563 0.200 0.201 0.205 0.211 0.220 0.232 0.764 0.276 0.271 0.274 0.259 0.249 0.250 0.658 0.258 0.255 0.264 0.254 0.613 0.207 0.207 0.222 0.227 0.236 0.243

0.259 0.627 0.687 0.708 0.192 0.469 0.516 0.546 0.576 0.608 0.647 0.219 0.560 0.589 0.614 0.666 0.627 0.711 0.252 0.629 0.677 0.715 0.736 0.234 0.518 0.583 0.629 0.646 0.686 0.740

0.037 0.089 0.053 0.030 0.103 0.325 0.226 0.191 0.133 0.088 0.029 0.021 0.320 0.309 0.279 0.192 0.157 0.097 0.116 0.177 0.156 0.177 0.079 0.120 0.381 0.354 0.302 0.254 0.244 0.110

0.946 0.771 0.779 0.776 0.878 0.600 0.728 0.764 0.810 0.837 0.860 0.933 0.543 0.578 0.628 0.719 0.750 0.812 0.732 0.604 0.676 0.696 0.769 0.855 0.444 0.494 0.585 0.646 0.673 0.814

0.016 0.139 0.166 0.192 0.018 0.073 0.045 0.043 0.056 0.073 0.110 0.045 0.136 0.112 0.091 0.088 0.091 0.089 0.151 0.218 0.167 0.126 0.151 0.024 0.173 0.150 0.112 0.098 0.081 0.074

solvent EG

DEG

PEG

DMSO

TMS

The polarity difference between the solvent and phenols should not be too high for effective extraction. A low polarity difference between the solvent and phenols results in attractive forces between the different molecules, and as a result the phenols are preferentially pulled toward the solvent. Indeed the hydrogen bonds system formation and the polarity difference between the solvents and phenols support the above arguments. It is clear from what has been considered that the extent in which mixtures deviate from ideality governs the distribution of a solute (phenol) between two solvents (solvent + water). However, it is then possible to predict the nature of extraction of phenols from the mixture on the basis of their hydrogen bonding potentialities. Because, in the case of our ternary systems using five solvents the main molecular interactions are the hydrogen bond forces. Thus, the ability of extraction depends mainly on the solvent used. Therefore, hydrogen bond molecular interactions are the unique force predominant in the extraction process. It is worthwhile to mention that the liquid−liquid equilibrium in the presence of water is determined by intermolecular forces, predominantly hydrogen bonds. The addition of solvents to a mixture of water + phenols enhances the formation of the hydrogen-bonded system. 3.4. Data Correlation. Thermodynamic models, namely the universal-quasi-chemical (UNIQUAC) equation proposed by Anderson and Prausnitz37 and the nonrandom-two-liquid (NRTL) equation proposed by Renon and Prausnitz38 activity

water-rich layer

xS

xW

xP

xS

xW

xP

0.097 0.170 0.251 0.157 0.122 0.070 0.030 0.436 0.395 0.347 0.310 0.312 0.258 0.201 0.032 0.223 0.200 0.174 0.159 0.130 0.036 0.203 0.244 0.219 0.207 0.205 0.152 0.076 0.329 0.402 0.304 0.317 0.204 0.151 0.113

0.853 0.343 0.231 0.266 0.248 0.270 0.281 0.302 0.076 0.097 0.107 0.113 0.129 0.143 0.743 0.202 0.199 0.185 0.185 0.185 0.203 0.701 0.302 0.265 0.254 0.243 0.249 0.258 0.448 0.101 0.116 0.108 0.145 0.168 0.181

0.048 0.485 0.516 0.576 0.628 0.659 0.687 0.261 0.527 0.554 0.582 0.574 0.612 0.654 0.223 0.574 0.600 0.639 0.654 0.683 0.760 0.095 0.452 0.515 0.539 0.551 0.598 0.665 0.221 0.496 0.579 0.574 0.650 0.680 0.705

0.065 0.154 0.108 0.068 0.038 0.020 0.013 0.141 0.372 0.270 0.172 0.101 0.074 0.034 0.011 0.190 0.168 0.121 0.071 0.031 0.010 0.073 0.265 0.201 0.112 0.065 0.038 0.015 0.212 0.434 0.203 0.270 0.140 0.070 0.028

0.922 0.763 0.765 0.789 0.759 0.719 0.695 0.828 0.619 0.728 0.806 0.865 0.857 0.860 0.983 0.759 0.793 0.580 0.909 0.955 0.966 0.915 0.664 0.690 0.740 0.764 0.752 0.735 0.876 0.531 0.661 0.723 0.819 0.848 0.860

0.011 0.082 0.126 0.142 0.201 0.260 0.291 0.030 0.007 0.001 0.021 0.032 0.068 0.105 0.004 0.051 0.038 0.028 0.018 0.013 0.023 0.010 0.070 0.108 0.146 0.169 0.209 0.249 0.002 0.033 0.135 0.006 0.039 0.080 0.111

coefficient models, were used to correlate the experimental data for the 10 systems studied. The difference between the experimental and calculated mass fractions was minimized by the use of the objective function F: n

F=

i−1

xexp jL (i)

3

2

∑ min ∑ ∑ (xjLexp(i) − xjLcal(i))2 (8)

j=1 L=1

xcal jL (i)

is the experimental mass fraction, is the calculated mass fraction, and n is the number of the experimental tie lines. This objective function is minimized by the values of the parameters sought, using both the UNIQUAC model and NRTL model. Using the method of the Maximum Likelihood Principle technique,32 the values of the six parameters for UNIQUAC model: U11, U22, U33, U12, U13, U23 (J·mol−1) were calculated. The values of the nine parameters for the NRTL model are g11, g22, g33, g12, g13, g23, a12, a13, a23 (J·mol−1). As for the ternary liquid−liquid system, they were calculated by using the procedure proposed by Prausnitz et. al.39 The parameters calculated in this way are listed in Tables 6 and 7. The root-mean-square deviation (RMSD) is also included in the Tables and they are defined as 1562



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Figure 20. Comparison of experimental tie line data with the calculated values using UNIQUAC (■) and NRTL (▲) model for TMS + W + P at 308.15 K. 1/2 ⎞ ⎛ n 3 2 ⎛ exp cal (xjL (i) − xjL (i))2 ⎞ ⎟ ⎜ ⎟ RMSD = 100⎜∑ ∑ ∑ ⎜⎜ ⎟ ⎟⎟ ⎜ i=1 j=1 L=1 ⎝ 6n ⎠ ⎠ ⎝

The binary interaction parameters have been calculated using the method of Maximum Likelihood Principle technique. Of the five solvents used to extract the phenol or p-chlorophenol from wastewater, DEG has the highest selectivity and distribution coefficient and the greatest differences between its boiling point and density and those of phenol or p-chlorophenol. It is therefore an excellent solvent for extracting phenol or p-chlorophenol from wastewater. It was found that an increase in solvent concentration decreased the concentration of phenol in the wastewater. This is expected. At a fixed phenol initial concentration increasing the solvent concentration provided more solvent capacity for phenol and hence the removal is enhanced. This effect was stronger for aqueous wastewater than for refinery wastewater for the same amount of solvent. This is due to the existence of other compounds in the real refinery wastewater that compete with phenol for the amount of solvent, and hence lead to a less amount of phenol removed from the wastewater.

(9)

The agreement between the experimental and the calculated values is measured by the (RMSD). The calculated tie lines data obtained by UNIQUAC and NRTL are listed in Tables 8 to 11 and one of them is presented in Figure 20 as a representative example of the other studied ternary systems. The calculation based on both UNIQUAC model and NRTL model gave a good representation of the tie lines data for the systems studied here. However, the NRTL model fitted to the experimental data is more accurate than the UNIQUAC model, as can be seen from the results shown in Tables 6 and 7. The NRTL correlation gives better RMSD than those from UNIQUAC. It indicates that the liquid−liquid equilibria data are better correlated with NRTL than UNIQUAC models

■

4. CONCLUSIONS A survey of the literature indicates that no liquid−liquid equilibrium data are available for the use of different solvents EG, DEG, PEG, DMSO, and TMS for extraction of phenol or p-chlorophenol from wastewater. Phenol samples are collected from a real petroleum refinery and experimentally prepared aqueous solution wastewater. The effectiveness of selective solvent for a given phenol samples was evaluated. The consistency of experimental tie-lines data for the ternary systems (solvents + W + P or ClP) was confirmed for five solvents using Bachman, Hand, and Othmer-Tobias correlations. The good fit confirms the reliability of the data. The calculation based on both the UNIQUAC model and NRTL model gave a good representation of the tie-line data for the systems (solvents + W + P or ClP). However, the calculated values based on the NRTL model are found to be better than those based on the UNIQUAC model. A relative deviation between experimental and calculated distribution coefficient values of phenols is less than 2 %.

AUTHOR INFORMATION

Corresponding Author

*Tel.: +964 790 2 89 80 18. E-mail: khalid_farhod@ uotechnology.edu.iq. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The author acknowledges Mr. K. M. Ahmed’s efforts for his support and help during the revision of this manuscript.

■

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