Article pubs.acs.org/jced
Extractive Separation of Benzylformic Acid with Phosphoric Acid Tributyl Ester in CCl4, Decanol, Kerosene, Toluene, and Xylene at 298 K Kanti Kumar Athankar,† Kailas L. Wasewar,*,† Mahesh N. Varma,† Diwakar Z. Shende,† and Hasan Uslu‡ †
Advance Separation and Analytical Laboratory (ASAL), Department of Chemical Engineering, Visvesvaraya National Institute of Technology (VNIT), Nagpur, Maharashtra 440010, India ‡ Engineering and Architecture Faculty, Department of Chemical Engineering, Beykent University, Ayazagi Koyu, Istanbul 34433, Turkey ABSTRACT: An equilibrium isotherm of benzylformic acid with phosphoric acid tributyl ester in carbon tetrachloride, decanol, kerosene, toluene, and xylene at 298 K has been studied. The equilibrium data are discussed in terms of partition coefficient (P), dimerization constant (D), overall equilibrium complexation constant (E), and loading factor (ϕ). Moreover, the distribution coefficient (KD) and extraction efficiency (η%) with phosphoric acid tributyl ester in CCl4 is 0.199 to 52.1 and 16.6 to 98.1; in decanol, 5.66 to 45.9 and 85 to 97.9; in kerosene, 0.03 to 73.2 and 2.9 to 98.7; in toluene, 0.381 to 70.3 and 27.6 to 98.6; and in xylene, 0.322 to 57.7 and 24.3 to 98.3, respectively. The extraction efficiency of benzylformic acid was found to be more than 95 % with all these diluents. Loading factor ϕ < 0.5 was observed and it indicates that only 1:1 benzylformic acid−phosphoric acid tributyl ester complex in above said diluents were formed. Furthermore, the values of overall equilibrium complexation are determined with the relative basicity model using experimental result.
1. INTRODUCTION Benzylformic acid (BFA) has a prominent pharmaceutical significance and its derivatives can be used as a therapeutic agent for the treatment of cancer. Kim et al. have produced benzylformic acid by fermentation of soybean along with B. Licheniformis.1,2 It is found in essential oil (e.g., neroli, rose oil) and in many fruits. It can also used as a flavouring and perfumery ingredient. Due to its medicinal functionality and various applications in chemical and its allied industries, it is required to maximize the production of benzylformic acid. In the fermentation process, purity of the product and efficiency of the medium is the major problem. Over the last three decades, solvent extraction is one of the prominent techniques for the separation of carboxylic acids. L−L extraction can be employed in downstream separation and also in combination with fermentation.3 Alternate processes has been reported for the recovery of acid, which include precipitation with calcium hydroxide, usages of ion exchange resins, electrodylasis, distillation, and so forth.4−9 Some of the methods are either complicated, yield low quantities of product, have low purity, cause disposal and environmental problems, or are costly, which at the end makes about 50 % of the total cost spent on separation and purification.10,11 In lieu of all these, distillation can be used to separate water based products, but in the case of carboxylic acids, it can be deformed at high temperature.12 Research has been carried out on the probable use of some groups of extractants (such as alcohols, acetates, ketones, etc.) for the latter process; long chain alcohols were found to be © 2015 American Chemical Society
suitable for this purpose, and their liquid−liquid equilibrium data were also determined.13,14 Also, the equilibrium condition between the organic and aqueous solutions was found to be a very important aspect of the liquid to liquid extraction process and variables most generally considered for the process are physical properties (density, viscosity, polarity, etc.), chemical properties (distribution coefficient, selectivity, etc.), availability, and cost.15−17 It has been observed that very few literatures are reported on reactive extraction of benzylformic acid as shown in Table 1. In this consideration and various application of benzylformic acid in the pharmaceutical, food, perfume, and other industries, it is necessary to recover this acid from aqueous solution. In this work, extraction of benzylformic acid from aqueous solution with phosphoric acid tributyl ester in polar and nonpolar diluents have been studied and the results were reported in terms of distribution coefficient, partition coefficient, dimerization constant, extraction efficiency, overall equilibrium constant, and loading factor. Furthermore, the experimental results were presented by relative basicity approach. The equilibrium results can be used for the designing of liquid−liquid extraction system in continuous mode for recovery of benzylformic acid with phosphoric acid tributyl ester in carbon tetrachloride, kerosene, decanol, toluene, and xylene. Received: September 22, 2014 Accepted: February 12, 2015 Published: February 25, 2015 1014
DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
Article
Table 1. Reactive Extraction of Benzylformic Acid with Tri-n-Butyl Phosphate in Different Diluents range
diluent
η
KD
extractant
(mol·L−1)
TBP (mol·L−1)
0.005 to 0.099
benzene
0.734 1.464 0.734 1.464 0.734 1.464 0.734 1.464 0.734 1.464 0.734 1.464
hexanol rice bran oil 0.005 to 0.099
castor oil soybean oil sunflower oil
Eαβ
reference
37.64 14.80 59.82 21.53 20.57 6.75 23.2 15.1 28.1 18.0 19.5 15.7
18
(%) 25.75 20.95 41.21 30.58 14.0 9.55 15.75 21.38 19.2 25.41 13.36 22.28
95.55 94.13 97.45 96.36 91.01 87.68 91.86 93.98 93.68 94.58 91.33 93.91
19
Table 2. Various Physicochemical Properties of Diluents Chosen in Extraction of Benzylformic Acida diluents
MW
MS
BP K
carbon tetrachloride decanol kerosene toluene xylene
ρ
Swater
MP K
kg·m
μ
RI −3
ε
ET
log(P)
DM
cP
D
15382
CCl4
349.87
250.23
insoluble
1586
1.4601
0
2.24
NA
2.64
0
15828 170 9214 10617
CH3(CH2)9OH NA C6H5CH3 C6H4(CH3)2
503.15 420.15 383.75 411.1 to 415.1
280.15 200.15 180.15 225.15
0.37 g/100 mL insoluble 0.053 g/100 mL immiscible
829 817 865 865
1.4295 1.443 1.497 1.4958
8.925 NA 0.590 0.9
8.1 1.8 2.379 2.27
48.1 NA 33.9 NA
4.23 NA 2.69 3.15
1.68 NA 0.36 0
MW, molecular weight; MS, molecular structure; BP, boiling point; MP, melting point; Swater, solubility in water at 298 K; ρ, density of pure liquid; RI, refractive index; μ, viscosity; ε, dielectric constant; ET, transmission energy; log(P), water partition coefficient; DM, dipole moment; NA, not available. a
2. MATERIALS AND EXPERIMENTAL PROCEDURE 2.1. Materials. Phosphoric acid tributyl ester (PATBE) (molar mass, 15 382 kg·mol−1; chemical formula, C12H27O4P; density, 975 kg·m−3 at 298 K) was used as an extractant with carbon tetrachloride, decanol, toluene, kerosene, and xylene. Benzylformic acid (molar mass, 13615 kg·mol−1; chemical formula, C8H8O2; density, 1080 kg·cm−3; solubility in water, 15 kg·m−3). The maximum absorption of BFA in UV range (λmax) was observed to be 215 nm. Physicochemical properties of diluents used in present study are shown in Table 2. The chemicals used in present work were procured from Merck, India, with more than 0.98 mass fraction purity whereas BFA was purchased from Acros Organics, India, and kerosene from the local market. All the chemicals were used without any further purification. 2.2. Experimental Procedure. An organic solution was prepared by dissolving phosphoric acid tributyl ester in the range of 7.53 × 10−4 to 1.51 × 10−3 mol·kg−1 in carbon tetrachloride, decanol, kerosene, toluene, and xylene. Aqueous solution of benzylformic acid was prepared (5.0 × 10−6 to 9.90 × 10−5) mol·kg−1 in deionized water without pH adjustment. Equal volumes of aqueous and organic solutions (15 mL) were shaken in temperature controlled water bath shaker (REMI make RSB 12 Mumbai, India) at 298 K to attain equilibrium. Post extraction benzylformic acid concentration of aqueous solution was determined by HPLC using C-18 column.18,19 The pH of aqueous solution before and after extraction was measured by Lab India pH meter Mumbai, India. All experiments and analysis was done in triplicates under identical conditions and the average value of the parameters was reported. The maximum experimental error was observed below ± 2 %.
Figure 1. Physical equilibria of benzylformic acid with different diluents.
Table 3. Partition Coefficient and Dimerization Constant of Benzylformic Acid at T = 298 Ka 2 C̅ HA = P . C HA + D. C HA
R2
carbon tetrachloride
2 C̅ HA = 0.115C HA + 70341C HA
0.998
decanol
2 C̅ HA = 8.008C HA + 20447C HA
0.991
kerosene
2 C̅ HA = 0.006C HA + 6597C HA
0.999
toluene
2 C̅ HA = 0.257C HA + 75560C HA
0.999
xylene
2 C̅ HA = 0.175C HA + 56848C HA
0.999
diluents
a
1015
Standard uncertainties u are u(T) = ± 1 K. DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
Article
2.3. Uncertainty Analysis. In this paper, experimental uncertainty was calculated as per the National Institute of Standard and Technology (NIST) protocols.20 Few experiments were performed in triplicate and the reliability of replicated experiments was found within ± 2 % having confidence interval 95 %. Standard uncertainty was evaluated to be ± 0.001 by using following eq
3. RESULTS AND DISCUSSION The extraction equilibria of benzylformic acid with diluents referred as physical extraction, whereas blending of extractant− diluent is known as reactive extraction. The physical extraction equilibria with carbon tetrachloride, decanol, kerosene, toluene, and xylene were (see Figure 1) discussed in the next section. 3.1. Dimerization and Partition Coefficient. The acid can be extracted in diluents due to the ion−ion interaction. Weak diluents viz. aliphatic and aromatic hydrocarbons involve the dimerization of acid owing of poor solvation characteristics. Whereas, polar diluents involve ion pair or hydrogen bonding and dimerization is not predicted. Therefore, the presence of acid in aqueous solution results in low pH of the solution.
N
∑i = 1 (xi − x ̅ )2
u(x) =
N−1
(1)
where xi = values of experimental observations, x̅ = mean of three observations, and N = number of observations. For further calculations, average of the replicated data was used.
Table 4. Reactive Extraction of Benzylformic Acid with Phosphoric Acid in Carbon Tetrachloride at T = 298 Ka C̅ PATBE −1
mol·kg 0
7.53 × 10−04
1.51 × 10−03
a
CHA mol·kg
C̅ HA −1
3.8 × 10−06 6.4 × 10−06 1 × 10−05 1.38 × 10−05 1.84 × 10−05 2.7 × 10−05 4.26 × 10−07 6.38 × 10−07 8.51 × 10−07 1.06 × 10−06 1.49 × 10−06 2.55 × 10−06 4.26 × 10−07 6.38 × 10−07 8.51 × 10−07 1.06 × 10−06 1.28 × 10−06 1.70 × 10−06
mol·kg 7.55 2.26 6.29 1.02 1.99 4.53 3.12 6.38 1.31 1.97 3.31 6.58 4.17 8.54 1.75 2.64 4.44 8.88
× × × × × × × × × × × × × × × × × ×
KD
η%
ϕ
0.199 0.354 0.629 0.738 1.080 1.677 7.3 10.0 15.3 18.5 22.2 25.8 9.8 13.4 20.5 24.8 34.8 52.1
16.6 26.1 38.6 42.5 51.9 62.6 88.0 90.9 93.9 94.9 95.7 96.3 90.7 93.0 95.4 96.1 97.2 98.1
0 0 0 0 0 0 0.004 0.008 0.017 0.026 0.044 0.087 0.003 0.006 0.012 0.018 0.030 0.059
Eexp
Erbm
RMSE
2.3 × 1004
2.30 × 1004
0.125
1.78 × 1004
1.78 × 1004
0.022
Eexp
Erbm
RMSE
3.62 × 1004
3.61 × 1004
0.157
1.95 × 1004
1.94 × 1004
0.318
−1
10−07 10−06 10−06 10−05 10−05 10−05 10−06 10−06 10−05 10−05 10−05 10−05 10−06 10−06 10−05 10−05 10−05 10−05
Standard uncertainties u are u(T) = ± 1 K, u(CHA) = ± 0.001 mol·kg−1.
Table 5. Reactive Extraction of Benzylformic Acid with Phosphoric Acid in Decanol at T = 298 Ka C̅ PATBE
CHA
C̅ HA
mol·kg−1
mol·kg−1
mol·kg−1
0
7.53 × 10−04
1.51 × 10−03
a
4.00 1.00 1.40 2.00 2.80 5.40 3.79 6.38 8.96 1.20 1.85 2.99 4.58 6.57 7.77 9.36 1.29 2.23
× × × × × × × × × × × × × × × × × ×
10−07 10−06 10−06 10−06 10−06 10−06 10−07 10−07 10−07 10−06 10−06 10−06 10−07 10−07 10−07 10−07 10−06 10−06
2.89 5.66 1.17 1.76 2.97 5.89 5.38 1.09 2.23 3.36 5.61 1.12 4.81 9.90 2.04 3.08 5.16 1.02
× × × × × × × × × × × × × × × × × ×
10−06 10−06 10−05 10−05 10−05 10−05 10−06 10−05 10−05 10−05 10−05 10−04 10−06 10−06 10−05 10−05 10−05 10−04
KD
η%
ϕ
7.232 5.660 8.355 8.804 10.601 10.901 14.2 17.1 24.8 28.1 30.3 37.4 10.5 15.1 26.2 32.9 39.8 45.9
87.9 85.0 89.3 89.8 91.4 91.6 93.4 94.5 96.1 96.6 96.8 97.4 91.3 93.8 96.3 97.0 97.6 97.9
0 0 0 0 0 0 0.007 0.014 0.030 0.045 0.075 0.149 0.003 0.007 0.014 0.020 0.034 0.068
Standard uncertainties u are u(T) = ± 1 K, u(CHA) = ± 0.001 mol·kg−1. 1016
DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
Article
Table 6. Reactive Extraction of Benzylformic Acid with Phosphoric Acid in Kerosene at T = 298 Ka C̅ PATBE
CHA
C̅ HA
mol·kg−1
mol·kg−1
mol·kg−1
0
7.53 × 10−04
1.51 × 10−03
a
4.77 9.13 1.68 2.39 3.57 6.00 4.05 6.07 8.10 1.01 1.21 1.62 4.05 6.07 8.10 1.01 1.21 1.42
× × × × × × × × × × × × × × × × × ×
10−06 10−06 10−05 10−05 10−05 10−05 10−07 10−07 10−07 10−06 10−06 10−06 10−07 10−07 10−07 10−06 10−06 10−06
1.44 5.48 2.01 3.86 9.00 2.46 5.45 1.11 2.28 3.44 5.79 1.16 4.89 9.99 2.04 3.08 5.19 1.04
× × × × × × × × × × × × × × × × × ×
10−07 10−07 10−06 10−06 10−06 10−05 10−06 10−05 10−05 10−05 10−05 10−04 10−06 10−06 10−05 10−05 10−05 10−04
KD
η%
ϕ
0.030 0.060 0.120 0.162 0.252 0.409 13.5 18.4 28.1 34.0 47.7 71.4 12.1 16.4 25.2 30.5 42.7 73.2
2.9 5.7 10.7 13.9 20.1 29.1 93.1 94.8 96.6 97.1 97.9 98.6 92.3 94.3 96.2 96.8 97.7 98.7
0 0 0 0 0 0 0.007 0.015 0.030 0.046 0.077 0.154 0.003 0.007 0.014 0.020 0.034 0.069
Eexp
Erbm
RMSE
5.15 × 1004
5.07 × 1004
1.722
2.31 × 1004
2.25 × 1004
1.382
Eexp
Erbm
RMSE
4.01 × 1004
3.94 × 1004
1.673
2.21 × 1004
2.17 × 1004
1.225
Standard uncertainties u are u(T) = ± 1 K, u(CHA) = ± 0.001 mol·kg−1.
Table 7. Reactive Extraction of Benzylformic Acid with Phosphoric Acid in Toluene at T = 298 Ka C̅ PATBE −1
mol·kg 0
7.53 × 10−04
1.51 × 10−03
a
CHA mol·kg 3.11 5.25 7.98 1.07 1.46 2.26 4.17 6.25 1.04 1.25 1.67 1.88 4.17 6.25 8.33 1.04 1.25 1.46
× × × × × × × × × × × × × × × × × ×
C̅ HA −1
10−06 10−06 10−06 10−05 10−05 10−05 10−07 10−07 10−06 10−06 10−06 10−06 10−07 10−07 10−07 10−06 10−06 10−06
mol·kg 1.19 2.99 7.56 1.21 2.23 4.81 5.16 1.06 2.13 3.24 5.44 1.09 4.82 9.85 2.01 3.04 5.12 1.03
× × × × × × × × × × × × × × × × × ×
KD
η%
ϕ
0.381 0.568 0.948 1.134 1.526 2.130 12.4 16.9 20.5 25.9 32.7 58.3 11.6 15.8 24.2 29.2 41.0 70.3
27.6 36.2 48.7 53.1 60.4 68.0 92.5 94.4 95.3 96.3 97.0 98.3 92.0 94.0 96.0 96.7 97.6 98.6
0 0 0 0 0 0 0.007 0.014 0.028 0.043 0.072 0.145 0.003 0.007 0.013 0.020 0.034 0.068
−1
10−06 10−06 10−06 10−05 10−05 10−05 10−06 10−05 10−05 10−05 10−05 10−04 10−06 10−06 10−05 10−05 10−05 10−04
Standard uncertainties u are u(T) = ± 1 K, u(CHA) = ± 0.001 mol·kg−1.
3.2. Distribution Coefficient. All forms of acid (ionized and un-ionized) can be extracted by phosphoric acid tributyl ester in organic solution. Distribution coefficient for ionized benzylformic acid can be expressed as
At pH > pKa (4.31) of acid, it is present in ionized form, whereas at pH < pKa, the presence of acid in dimerized form is accounted by dimerization constant represented as the concentration of dimerized acid in organic solution to concentration of total acid in organic solution. The dimerization constant D and partition coefficient P can be calculated by using following correlation as21 C̅ HA = P . C HA + D.
2 C HA
KD(A−) =
(2)
C̅ PATE:A− C HA + C A−
(3)
where over bar stand for concentration of species in organic solution. For extraction of un-ionized acid molecules, distribution coefficient can be written as
where CHA is the concentration of unextracted benzylformic acid concentration in aqueous solution and over bar indicates concentration of benzylformic acid in organic solution at equilibrium. Partition coefficient and dimerization constant values are tabulated in Table 3.
KD(HA) = 1017
C̅ PATE:HA C HA + C A−
(4) DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
Article
Table 8. Reactive Extraction of Benzylformic Acid with Phosphoric Acid in Xylene at T = 298 Ka C̅ PATBE
CHA
C̅ HA
mol·kg−1
mol·kg−1
mol·kg−1
0
7.53 × 10−04
1.51 × 10−03
a
3.31 5.84 9.14 1.25 1.69 2.63 3.94 5.91 7.87 9.84 1.38 2.36 5.91 7.87 9.84 1.18 1.38 1.77
× × × × × × × × × × × × × × × × × ×
10−06 10−06 10−06 10−05 10−05 10−05 10−07 10−07 10−07 10−07 10−06 10−06 10−07 10−07 10−07 10−06 10−06 10−06
1.06 2.62 6.83 1.10 2.08 4.57 5.17 1.06 2.16 3.26 5.46 1.09 4.63 9.68 2.00 3.03 5.11 1.02
× × × × × × × × × × × × × × × × × ×
10−06 10−06 10−06 10−05 10−05 10−05 10−06 10−05 10−05 10−05 10−05 10−04 10−06 10−06 10−05 10−05 10−05 10−04
KD
η%
ϕ
0.322 0.449 0.747 0.886 1.229 1.742 13.1 17.9 27.4 33.1 39.6 45.9 7.8 12.3 20.3 25.6 37.1 57.7
24.3 31.0 42.7 47.0 55.1 63.5 92.9 94.7 96.5 97.1 97.5 97.9 88.7 92.5 95.3 96.2 97.4 98.3
0 0 0 0 0 0 0.007 0.014 0.029 0.043 0.073 0.144 0.003 0.006 0.013 0.020 0.034 0.068
Eexp
Erbm
RMSE
4.22 × 1004
4.22 × 1004
0.170
1.85 × 1004
1.86 × 1004
0.098
Standard uncertainties u are u(T) = ± 1 K, u(CHA) = ± 0.001 mol·kg−1.
Therefore, eq 5 represents the overall distribution coefficient KD = KD(A−) + KD(HA)
(5)
Phosphoric acid tributyl ester was used as an extractant in the range of (7.53 × 10−4 to 1.51 × 10−3) mol·kg−1 for the benzylformic acid concentrations of (5.0 × 10−6 to 9.90 × 10 −5) mol·kg −1 . The equilibrium data for distribution coefficient of benzylformic acid were tabulated in Tables 4 to 8. In physical extraction, (see Figure 2) average distribution coefficient of benzylformic acid extracted with these diluents was found in following orders: decanol > toluene > xylene > CCl4 > kerosene. Maximum and minimum KD value was found for decanol and kerosene respectively due to their corresponding polarities. Due to greater hydrophobic nature as compare to toluene (reflected in solubility data Table 2) xylene showed less interaction with the polar acidic group of benzylformic acid, which consequently result lower KD value between the two diluents whereas in chemical extraction, the distribution coefficient value has been observed as 7.3 to 52.1 for CCl4, 14.2 to 45.9 for decanol, 13.5 to 73.2 for kerosene, 12.4 to 70.3 for toluene, and 13.1 to 57.7 for xylene, respectively. Athankar et al.19 has been reported the KD value of α-toluic acid using tri-n-butyl phosphate (20 to 40 % volume fraction) in castor oil, soybean oil, and sunflower oil. 3.3. Extraction Efficiency. Extraction efficiency is the ratio of concentration of benzylformic acid in organic solution to the initial concentration in aqueous solution it can be expressed as η% =
C HAo − C HA × 100 C HAo
Figure 2. Distribution coefficient of benzylformic acid with phosphoric acid tributyl ester (7.53 × 10−4 to 1.51 × 10−3 mol·kg−1) in five different diluents.
(CH3CH2CH2CH2) free. Available sites of extractant interact with nonpolar part of diluents due to this reason ion pair formation between (PO) and carboxylic group of benzylformic acid molecule can be favored the nonpolar diluents for higher extraction. The results of present study were compared with reactive extraction of other carboxylic acids viz. propionic acid,22−25 caproic acid,26−28 picolinic acid,29,30 nicotinic acic,30 pyruvic acid,31 with phosphoric acid tributyl ester in various diluents (Table 9), and it has been found that benzylformic acid has the highest distribution coefficient and extraction efficiency. 3.4. Equilibrium Complexation Constant. At the interphase of aqueous and organic solution, the extraction equilibria of un-ionized molecule of benzylformic acid with phosphoric acid tributyl ester can be represented as32−34
(6)
Increasing the concentration of benzylformic acid favors the extraction efficiency with all diluents. In physical extraction, it has been observed that decanol favors the extraction in the range of 87.9 % to 91.6 %, 27.6 % to 68 % for toluene, 24.3 % to 63.5 % for xylene, 16.6 % to 62.6 % for CCl4, and 2.9 % to 29.1 % for kerosene. Although in chemical extraction, it is vice versa, it may be due to fact that the presence of phosphoric acid tributyl ester dissolved in these diluents has only nonpolar sites
E
C HA + PATBE ↔ C̅ HA:PATBE
(7)
where E is the overall equilibrium complexation constant 1018
DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
Article
Table 9. Reactive Extraction of Other Carboxylic Acid with Tri-n-Butyl Phosphate acid
range
diluent
−1
0.05 to 0.4
hexane
benzene
toluene
heptane
petroleum ether
paraffin liquid
propionic acid
0.05 to 0.4
petroleum ether
propionic acid
0.05 to 0.4
MIBK
propionic acid
0.2 to 0.4
petroleum ether
n-heptane
toluene
0.005 to 0.057
benzene toluene
caproic acid
0.005 to 0.057
xylene MIBK
caproic acid
0.005 to 0.057
η
2.26 2.68 3.77 2.35 1.558 1.65 1.87 2.44 0.87 1.47 2.503 3.315 2.168 1.15 2.47 3.15 0.901 1.72 2.53 3.35 0.688 1.266 1.92 2.43 0.76 1.351 1.903 2.34 0.523 1.138 2.408 0.759 1.353 1.906 2.34 2.42 2.91 0.740 1.303 1.911 2.380 0.616 1.260 1.899 2.524 0.863 2.484 2.478 3.349 30.28 21.26 18.06 21.3 17.61 23.98 10.77 14.38 6.95 5.29
69.13 72.63 78.68 67.12 60.71 62.16 64.55 71 46.25 50.84 71.32 76.75 68.30 53.19 70.86 75.82 47.3 63.175 71.69 77 40.51 55.64 65.69 70.43 43.02 57.41 65.40 69.87 33.99 53.06 70.49 43.03 57.41 65.40 69.87 70.57 74.30 42.53 56.58 65.65 70.41 38.12 55.75 65.51 71.62 46.32 71.30 71.25 77.01 96.35 93.03 92.75 93.5 90.013 93.35 90.65 90.88 72.76 80.6
TBP (mol·L ) n-butyl acetate
1-dodecanol
caproic acid
KD
−1
(mol·L ) propionic acid
extractant
hexanol
0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.65 0.37 0.74 1.10 1.65 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.37 0.74 1.10 1.65 0.732 1.464 0.732 1.464 0.732 1.464 0.732 1.464 0.732 1.464
1019
Eαβ
reference
(%) 4.34
22
2.18
2.39
2.79
2.75
2.03
2.12
1.7
23
24 1.658
25
1.715
2.261
43.5
26
14.9 27
9.91 3.69
28
DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
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Table 9. continued acid
range
diluent
extractant
−1
(mol·L )
sunflower oil
castor oil
picolinic acid
0.01 to 0.25
soybean oil
nicotinic acid
0.01 to 0.25
soybean oil
pyruvic acid
0.1 to 0.5
n-heptane
toluene
MIBK
benzylformic acid
0.005 to 0.099
CCl4 1-decanol kerosene toluene xylene
E=
E=
(8)
C̅ PATBE:HA(K a + [H ]) [H+]([HA] + [A−])C̅ PATBE
KD =
Ka (K a + [H+])
29
30
31
0.482
0.578
35.4 20.1 31.6 18.9 44.1 22.3 36.3 21.6 38.4 18.1
C̅ PATBE:HA = E(1 − β)C̅ PATBE C HA + C A−
KD(HA) (1 − β)
(10)
present study
(12)
= E . C̅ PATBE
(13)
If the ionized part of benzylformic acid is deserted, that is, β = 0, then the distribution coefficient and overall equilibrium complexation constant of un-ionized benzylformic acid molecule can be calculated using eq 14
where Ka is the ionization constant of the benzylformic acid. Ionized part of benzylformic acid is represents the following equation β=
22.64 4.25 23.25 10.45 0.205 0.132 0.120 0.112 0.172 0.043 0.106 0.242 0.163 0.138 0.120 0.019 0.022 0.024 0.369
(9)
KD(HA) C̅ PATBE(1 − β)
92.15 85.1 91.5 90.91 11.09 14.94 19.27 23.01 10.17 5.59 17.25 26.03 9.82 16.26 20.36 1.41 3.15 5.07 18.63 12.047 23.44 37.52 51.35 12.15 21 29.96 42.48 52.35 31.69 40.55 45.77 52.4 57.58 95.28 95.5 95.1 95.38 95.76 95.73 95.15 95.63 95.63 94.48
reference
Rearranging eq 9, we get
C̅ HA:PATBE C HA . C̅ PATBE +
E=
15.81 6.09 16.19 14.93 0.135 0.188 0.278 0.313 0.135 0.061 0.231 0.346 0.114 0.199 0.260 0.0143 0.0326 0.0536 0.077 0.138 0.315 0.618 1.068 0.140 0.270 0.554 0.754 1.116 0.475 0.687 0.853 1.114 1.378 24.26 28.43 21.73 26.8 31.38 29.91 24.66 30.45 26.28 25.51
Eαβ
(%)
0.732 1.464 0.732 1.464 0.732 1.464 2.196 2.928 0.732 1.464 2.196 2.928 0.732 1.464 2.196 0.732 1.464 2.196 0.366 0.733 1.099 1.831 2.564 0.366 0.733 1.099 1.831 2.564 0.366 0.733 1.099 1.831 2.564 0.732 1.646 0.732 1.646 0.732 1.646 0.732 1.646 0.732 1.646
decanol 0.01 to 0.25
η
TBP (mol·L ) octanol
picolinic acid
KD
−1
log KD = log E + log(C̅ PATBE)
(11) 1020
(14) DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
Article
3.6. Relative Basicity Approach. Relative basicity approach relates the 1:1 equilibrium complex constant with relative basicity, which governs by the following equation19,28−30,37 log E = [ω1(pKb − pK a) + log(ω2P)]
where pKb is the relative basicity of the extractant mixture to hydrochloric acid, exclude solute nature. If the basicity of the extractant mixture is relative to the solute, this relative basicity of the extractant can represent all of the nature of the solute, diluents, and extractant. Overall equilibrium complexation constant values (E) are the excellent fit with the relative basicity model predicted value as shown in Figure 3. Hence, it can be used to illustrate the reactive extraction of benzylformic acid with phosphoric acid tributyl ester in various diluents. Relative basicity constants parameters are presented in Table 10. Root mean square error method was used to calculate the deviation for experimental and relative basicity model predicted value using eq 17.
Figure 3. Experimental overall equilibrium complexation constant against Erbm.
n
RMSE =
Table 10. Relative Basicity Model Parameters diluent
ω1
log(ω2P)
carbon tetrachloride
−0.426 −0.539 −0.326 −0.472 −0.528 −0.528 −0.503 −0.526 −0.423 −0.638
5.087 5.260 5.244 5.275 5.730 5.330 5.444 5.417 5.457 5.450
decanol kerosene toluene xylene
C̅ HAtotal C̅ PATBEtotal
∑i = 1 (Eexp − Erbm)2 N−1
(17)
where E and Erbm are the experimental and model predicted overall equilibrium complexation contestant values, respectively. N is the number of experimental data. The RMSE values for all diluents was found to in the range of 0.125 to 0.022 for CCl4, 0.157 to 0.318 for decanol, 1.722 to 1.382 for kerosene, 1.673 to 1.225 for toluene, and 0.170 to 0.098 for xylene, which are acceptable.
4. CONCLUSION Reactive extraction of benzylformic acid was investigated using with phosphoric acid tributyl ester in carbon tetrachloride, decanol, kerosene, toluene, and xylene. The results are presented in terms of various physical and chemical extraction equilibrium parameters. Physical extractions were found to be inadequate along with very low distribution coefficient values. The average KD values were observed as kerosene = 0.172 < CCl4 = 0.779 < xylene = 0.896 < toluene = 1.115 < decanol = 8.592. Moreover, in chemical extraction a significant enhancement of KD values was observed for all diluents. The extraction efficiency of benzylformic acid was found to be ∼ 98 % with all diluents. Furthermore, loading factor ϕ ≥ 0.5 was observed it indicates that only 1:1 benzylformic acid-phosphoric acid tributyl ester complex in above said diluents were formed. Overall equilibrium complexation constant E were obtained as 2.3 × 104 to 1.78 × 104 in carbon tetrachloride; 3.62 × 104 to 1.95 × 104 in decanol; 5.15 × 104 to 2.31 × 104 in kerosene; 4.01 × 104 to 2.21 × 104 in toluene; 4.22 × 104 to 1.85 × 104 in xylene for (7.53 × 10−4 to 1.51 × 10−3) mol·kg−1 with phosphoric acid tributyl ester, respectively. Besides, relative basicity model has been applied to experimental result with R2 = 0.999.
The plot of logKD in opposition with log(C̅ PATBE) gives a straight line with the intercept of logE, from which overall equilibrium complexation constant can be obtained. The E values for phosphoric acid tributyl ester concentration (7.53 × 10−4 to 1.51 × 10−3) mol·kg−1 were tabulated in Tables 4 to 8. Gaidhani et al.35 reported equilibrium complexation constant for reactive extraction of phenylacetic acid with alamine-336 in kerosene 0.2702 m3·kmol−1 and MIBK 0.0301 m3·kmol−1. 3.5. Loading Factor. The maximum capacity of organic solution (PATBE + diluents) can be occupied with benzylformic acid is expressed as the loading ratio36 ϕ=
(16)
(15)
Loading factor values were revealed in Tables 4 to 8 and found to be less than 0.5, and also, it was inversely proportional to the phosphoric acid tributyl ester concentration (7.53 × 10−4 to 1.51 × 10−3) mol·kg−1. The acid−extractant complexes with more than one acid molecule per extractant molecule are known as overloading phenomenon. In this study, overloading was not found at any concentration of phosphoric acid tributyl ester, that is, only 1:1 complex were formed. The first molecule of benzylformic acid attaches with the phosphoric acid tributyl ester to form an ion pair and the hydroxyl group of another acid molecule carboxyl unite a hydrogen bond by the conjugated CO of the carboxyl group of the first acid to from an acid− extractant complex.32
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AUTHOR INFORMATION
Corresponding Author
*E-mail: k_wasewar@rediffmail.com;
[email protected]. in. Telephone: +91-712-280-1561. Fax: +91-712-280-1565. Notes
The authors declare no competing financial interest. Additional author e-mails:kanti.kumar@rediffmail.com,
[email protected],
[email protected],
[email protected]. 1021
DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
Journal of Chemical & Engineering Data
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Article
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NOMENCLATURE CHA=Concentration of benzylformic acid in aqueous solution, mol·kg−1 C̅ HA=Concentration of benzylformic acid in organic solution, mol·kg−1 C̅ PATBE=Phosphoric acid tributyl ester concentration in organic phase, mol·kg−1 D=Dimerization coefficient E=Overall equilibrium complexation constant, kg·mol−1 Ka=Dissociation constant KD=Distribution coefficient of physical extraction N=Number of observation P=Partition coefficient pKb=Relative basicity of phosphoric acid tributyl ester xi=Experimental observations u=Uncertainty magnitude
GREEK WORDS
η=Extraction efficiency ϕ=Loading factor ω1 and ω2=Relative basicity model constants
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DOI: 10.1021/je500943m J. Chem. Eng. Data 2015, 60, 1014−1022
