Article pubs.acs.org/jced
Reactive Extraction of (E)‑Butenedioic Acid (Fumaric Acid) by Nontoxic Diluents Hasan Uslu,*,‡ Ayşegül Gemici,† Aslı Gök,† and Ş. Iṡ mail Kırbaşlar† Chemical Engineering Department, Engineering Faculty, Iṡ tanbul University, 34320 Avcılar, Iṡ tanbul, Turkey Chemical Engineering Department, Engineering & Architecture Faculty, Beykent University, Ayazağa, Iṡ tanbul, Turkey
† ‡
ABSTRACT: In this work, the equilibrium distribution of (E)butenedioic acid (fumaric acid) between water and tridodecylamine (TDDA) or tributylamine (TBA) was carried out at 298 K. The organic phase was prepared using both TDDA and TBA in three nontoxic diluents (canola oil, sesame oil, and almond oil). The batch equilibrium experimental data are presented by calculation of the loading factor (Z), extraction efficiency (E), and distribution coefficient (KD). The highest extraction efficiencies of 92.59 % and 92.50 % with values of KD equal to 12.50 and 12.40 were obtained with 0.789 mol·kg−1 TDDA in canola oil and 2.080 mol·kg−1 TBA in canola oil. The extraction abilities of TDDA and TBA in different nontoxic natural diluents in terms of KD and E were found to be in the order of canola oil > almond oil > sesame oil. Partition coefficients (P = 0.3819, 0.4739, and 0.7535) and dimerization constants (D = 83.64, 50.28, and 43.51) were calculated according to physical extraction for sesame oil, almond oil, and canola oil, respectively.
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INTRODUCTION (E)-Butenedioic acid, which is also called fumaric acid, is a fourcarbon dicarboxylic acid. It is a white crystalline compound. Currently, fumaric acid is synthesized chemically from maleic anhydride. However, as petroleum prices are increasing day by day, maleic anhydride as a petroleum derivative has increased in price as well. This situation has caused a search for new ways to produce fumaric acid, such as fermentation.1 Recently, three strains of the fungus Rhizopus oryzae were screened to produce fumaric acid using untreated and treated corn distillers’ dried grains.2 Microbial production has even been discussed using the bacterial strain Lactobacillus.3 Fumaric acid has many uses in industrial applications, such as the production of synthetic resins, alkyd resins, paper resins, plasticizers, biodegradable polymers, succinic acid, maleic acid, etc.4 Therefore, it is important to purify fumaric acid for use in the above-mentioned applications. Liquid−liquid extraction is a prominent, energy efficient, environmentally friendly, and economical process for the separation of carboxylic acids from the downstream of chemical industry (pharmaceutical, petroleum, food processing, tanning, etc.) and fermentation broth.5−10 Organophosphorus-bonded (tri-n-butyl phosphate) and long-chain aliphatic amine (tri-noctylamine) extractants are reactive extractants and more effective than conventional extractants.11,12 The use of a reactive extractant in a liquid−liquid extraction process is termed reactive extraction. In reactive extraction, the extractant and acid molecules form a complex in the organic phase, thereby allowing more acid to be extracted from the aqueous © 2014 American Chemical Society
phase. In the reactive extraction process, a nonreactive extractant is used as a diluent to decrease the viscosity and enhance the surface properties of the reactive extractant.12 There are very limited studies about extraction of carboxylic acids from aqueous solutions using nontoxic diluents such as rice bran oil, sunflower oil, soybean oil, and sesame oil. Keshav et al.13 studied the extraction of citric acid from aqueous media using the reactive extractant tri-n-octylamine (TOA). The nontoxic natural diluents rice bran oil, sunflower oil, soybean oil, and sesame oil were used to dilute TOA. TOA was found to be an effective extractant for the removal of acid, providing distribution coefficients (KD) as high as 18.51 [extraction efficiency (E) = 95 %], 16.28 (E = 94 %), 15.09 (E = 94 %), and 12.82 (E = 93 %) when used with rice bran oil, sesame oil, soybean oil, and sunflower oil, respectively. Overall extraction constants for TOA + rice bran oil, or sunflower oil, or soybean oil, or sesame oil were determined as (35.48, 29.79, 33.79, and 37.64) mol·kg−1, respectively. Harrington and Hossain14 used sunflower oil as the solvent for recovery of lactic acid from aqueous solution. Organic solutions consisting of Aliquat 336, TOA, and tributyl phosphate (TBP) mixed with sunflower oil (as the solvent) were prepared for equilibrium studies. The optimum extraction parameters were determined as a function pH (range 4.0 to 6.5). The highest extraction was reached with an organic phase consisting of a mixture of 15 wt % TOA and Received: July 8, 2014 Accepted: September 23, 2014 Published: October 3, 2014 3767
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Table 1. Physical Properties of the Chemicals Used in This Study MW
density
chemical
IUPAC name
kg·kmol−1
kg·m−3
supplier
(wt %)
purity pKa
fumaric acid tridodecylamine (TDDA) tributylamine (TBA)
(E)-butenedioic acid N,N-didodecyldodecan-1-amine N,N-dibutyl-1-butanamine
116.07 521.99 185.36
1635 823 778
Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich
> 99 > 97 > 98.5
3.03, 4.44 − −
Figure 1. Plots of KD,diluent vs [H2A]aq for physical extraction of fumaric acid using natural diluents:▲, canola oil; ■, almond oil; ◆, sesame oil.
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MATERIALS AND METHODS Materials. The properties of the chemicals used in this study are presented in Table 1. The nontoxic natural solvents sesame oil, almond oil, and canola oil are commercial. All of the chemicals were used without any pretreatment. Ultrahighpurity water from a Millipore Milli-Q3 water system was used for the experiments. Experiments. Five different organic phase concentrations were prepared by adding diluents to TBA or TDDA in ratios of (50, 60, 70, 80, and 90) vol %. The concentrations were (0.157, 0.315, 0.473, 0.631, and 0.789) mol·kg−1 for TDDA and (0.418, 0.851, 1.255, 1.674, and 2.080) mol·kg−1 for TBA. The aqueous phase was prepared as 0.054 mol·kg−1 fumaric acid because of its highest solubility in water at 298 K. To perform the equilibrium experiments, mixtures of equal volumes (15 mL) of the aqueous and organic phases were shaken for 12 h at 298 K in a constant-temperature shaking bath and then allowed to settle for 2 h. Preliminary studies showed that this was a sufficient time to reach the equilibrium. Experiments were performed in duplicate. Final concentrations of fumaric acid in the aqueous phase were determined by acid−base titration using sodium hydroxide (0.1 N), which was standardized with 0.1 N HCl as the titrant and 3,3-bis(4-hydroxyphenyl)isobenzofuran-1(3H)-one (phenolphthalein) as the indicator. The relative uncertainty in the titration method was found not to exceed ± 3 %. The extracted acid concentration in the organic phase was calculated by considering complete mass balance.
15 % Aliquat 336 dissolved in 35 wt % TBP and 35 % sunflower oil. They reported that lactic acid was recovered from the organic phase by using 0.5 M aqueous sodium carbonate, with 90 % of it being obtained within a time of 4 h. Waghmare et al.15 used sunflower oil and castor oil as nontoxic solvents for extraction of picolinic acid by TBP, and the distribution coefficients and extraction efficiencies were compared. KD changed from 0.0066 to 0.664 for sunflower oil and from 0.0099 to 0.94 for castor oil, while E was changed from 0.65 % to 42.9 % for sunflower oil and from 0.9 % to 74.6 % for castor oil. They reported that loading factors < 0.5 were found. Athankar et al.16 focused on extraction of phenylacetic acid from aqueous media because of its wide usage in the production of β-lactam antibiotics. Rice bran oil was chosen as well as benzene and hexan-1-ol for dilution of TBP. The equilibrium of reactive extraction of phenylacetic acid was presented in light of the mass action law model. Waghmare et al.17 investigated the extractability of both picolinic acid and nicotinic acid from fermentation broth. Soybean oil was selected as the nontoxic solvent to dilute TBP, and comparative results were presented in terms of distribution coefficients and extraction efficiencies. KD increased from 0.01 to 0.374 for picolinic acid and from 0.0073 to 0.0752 for nicotinic acid. E increased from 0.9 % to 27.22 % for picolinic acid and from 0.72 % to 6.99 % for nicotinic acid. The extraction of fumaric acid by amine-based extractants such as tridodecylamine (TDDA) and tributylamine (TBA) with nontoxic natural diluents was the aim of the present work. To date, no previous work on the reactive extraction of fumaric acid using natural nontoxic diluents such as sesame oil, almond oil, and canola oil is available.
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RESULTS AND DISCUSSION Physical Extraction. In this section, the results obtained for the extraction equilibrium of fumaric acid from aqueous solutions with a single nontoxic natural diluent (sesame oil, 3768
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0.3819 and 83.64, 0.4739 and 5028, and 0.7535 and 43.51, respectively. Chemical Extraction. Reactive extraction is described as a reaction between undissociated acid molecules R′(COOH)n (n = 1 for monoprotic acids, n = 2 for diprotic acids, etc.) in the aqueous phase and amine molecules (R3N) in the organic phase, which in general form can be written as follows:
almond oil, or canola oil) are presented. Two factors were taken into account to show the influence of the pure diluents on the extraction of acid: (1) partial dissociation of the acid in the aqueous phase and (2) dimerization in the organic phase. The physical extraction of carboxylic acids with pure diluents is described using the distribution coefficient (KD,diluent). For low concentrations of acids (as used in the study), Kertes and King7 presented a correlation of KD,diluent in terms of the dimerization constant (D = [(H2A)2]/[H2A]2) and the partition coefficient (P = [H2A]org/[H2A]aq), as shown in eq 1: KD,diluent = P + 2DP 2[H 2A]aq
m[R′(COOH)n ]aq + p(R3N)org ⇄ {[R′(COOH)n ]m · (R3N)p }org
(1)
Here the extractability of fumaric acid (a dicarboxylic acid, H2A) from aqueous solution was studied. Replacing the symbol R′(COOH)2 with H2A allows eq 2 to be written more compactly as follows:
Plots of KD,diluent versus [H2A]aq were drawn using linear fitting in Excel 2010 (Figure 1), and the values of P and 2DP2 were obtained from the intercepts and slopes, respectively. To estimate the parameters, the χ2 minimization or “weighted least-squares” method was used, in which the goal is to minimize the sum of the squares of the deviations between the theoretical curve and the experimental points for a range of independent variables. The values of P and D obtained for extraction of fumaric acid using the natural diluents are presented in Table 2 and shown in Figure 1.
(H 2A)aq + p(R3N)org ⇄ [H 2A·(R3N)p ]org
diluent sesame oil
almond oil
canola oil
[H2A]aq
[H2A]org
−1
−1
−1
mol·kg 0.01 0.02 0.03 0.04 0.05 0.01 0.02 0.03 0.04 0.05 0.01 0.02 0.03 0.04 0.05
mol·kg
0.0064 0.0120 0.0171 0.0211 0.0248 0.0061 0.0116 0.0166 0.0207 0.0243 0.0049 0.0092 0.0128 0.0159 0.0184
mol·kg
0.0036 0.0080 0.0129 0.0189 0.0252 0.0039 0.0084 0.0134 0.0193 0.0257 0.0051 0.0108 0.0172 0.0241 0.0316
E
D
%
P
kg·mol−1
36.00 40.00 43.00 47.25 50.40 39.00 42.00 44.67 48.25 51.40 51.00 54.00 57.33 60.25 63.20
0.3819
83.64
(H 2A)aq ⇄ (HA−)aq + H+
K a1 =
(4)
[HA−]aq ·[H+] [H 2A]aq −
0.4739
(5) +
where [H2A]aq, [HA ]aq, and [H ] are the concentrations of undissociated fumaric acid, singly dissociated fumaric acid, and hydrogen ion in the aqueous phase. [H2A]aq can be found as
50.28
[H 2A]aq = [H 2A]tot,aq − [HA−]aq 0.7535
(3)
In eq 3, the value of m from eq 2 has been set equal to 1, so p denotes the number of amine molecules that react per molecule of acid. The reactive extraction of fumaric acid can be explained with two different mechanisms depending on the pH because fumaric acid is a dicarboxylic acid, as explained by Kloetzer et al.18 At low pH values, one must consider the first dissociation constant of fumaric acid (Ka1) and the corresponding dissociation reaction:
Table 2. Results for Physical Extaction of Fumaric Acid by Single Diluents at T = 298.15 Ka [H2A]init
(2)
(6)
where [H2A]tot,aq is the total concentration of all forms of the acid in the aqueous phase. Combining eqs 5 and eq 6 gives
43.51
[H 2A]aq =
[H 2A]tot,aq 1+
a
[H2A]init is the initial acid concentration in the aqueous phase, [H2A]aq is the concentration of acid in the aqueous phase after extraction, [H2A]org is the concentration of acid in the organic phase after extraction, D is the dimerization constant, and P is the partition coefficient.
K a1 [H+]
(7)
The extraction equilibrium constant (KE) can be written according to eq 3 as follows: KE =
[H 2A·(R3N)p ]org p [H 2A]aq · [R3N]org
(8)
The distribution coefficient (KD) is defined as the ratio of the concentration of the acid in the organic phase to that in the aqueous phase (i.e. KD = [H2A·(R3N)p]org/[H2A]tot,aq). Combining eqs 7 and 8 gives the following expression for KD:
The physical extraction experiments of fumaric acid were studied using three different nontoxic natural diluents: sesame oil, almond oil, and canola oil. Figure 2 shows equilibrium isotherms for physical extraction of fumaric acid. At the beginning, a linear relationship for the equilibrium of fumaric acid between the organic and aqueous phases was determined until an initial acid concentration of 0.02 mol·kg−1. Above this concentration, a parabolic relationship was observed for the three diluents. At higher concentrations, some deviation from Henry’s law (nonideal behavior) was observed. The partition coefficients (P) and dimerization constants (D) for fumaric acid in sesame oil, almond oil, and canola oil were determined as
KD =
p KE·[R3N]org
(1 +
K a1 [H+]
)
(9)
Equation 9 can be converted to logarithmic form: ⎛ K a1 ⎞ ln KD + ln⎜1 + ⎟ = ln KE + p ·ln[R3N]org ⎝ [H+] ⎠ 3769
(10)
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Figure 2. Equilibrium isotherms for physical extraction fumaric acid. Symbols:
▲
for canola oil; ■ for almond oil; ◆ for sesame oil.
Table 3. Experimental Results for the Extraction of Fumaric Acid by TDDA in Nontoxic Natural Diluents at T = 298.15 Ka [R3N] diluent
mol·kg
canola oil
mol·kg
0.157 0.315 0.473 0.631 0.789 0.157 0.315 0.473 0.631 0.789 0.157 0.315 0.473 0.631 0.789
almond oil
sesame oil
E
[H2A]org
−1
−1
0.037 0.040 0.044 0.047 0.050 0.038 0.040 0.045 0.048 0.050 0.039 0.041 0.043 0.046 0.049
pH(aq)
KD
Z
%
KE
p
3.776 3.843 3.907 3.955 3.972 3.721 3.786 3.896 4.045 4.110 3.787 3.810 3.980 3.985 4.110
2.47 3.08 4.89 6.71 12.50 2.37 2.86 5.00 8.00 10.00 2.60 3.15 4.30 6.57 9.80
0.236 0.127 0.093 0.074 0.063 0.242 0.127 0.095 0.076 0.063 0.248 0.130 0.091 0.073 0.062
71.15 75.47 83.02 87.03 92.59 70.37 74.07 83.33 88.89 90.91 72.22 75.92 81.13 86.79 90.74
6.73·102
0.98
4.80·102
0.89
4.58·102
0.86
a
[R3N] is the initial amine concentration in the organic phase, [H2A]org is the concentration of acid in the organic phase after extraction, KE is the thermodynamic extraction equilibrium constant, and p is the number of amine molecules per acid molecule.
If the reactive extraction is carried out at pH > pKa2, the second dissociation constant of fumaric acid must be taken into account: 2−
(H 2A)aq ⇄ (A )aq + 2H K a2 =
+
KD =
(12)
(13)
K a2 [H+]2
(15)
(16)
At both low pH and high pH, the values of the extraction equilibrium constant (KE) and the number of aminic extractant molecules per acid molecule (p) can be calculated from the intercepts and slopes, respectively, of plots of {ln KD + ln(1 + Ka1/[H+])} versus ln[R3N]org (at low pH) and {ln KD + ln(1 + Ka2/[H+]2)} versus ln[R3N]org (at high pH). Tables 3 and 4 present KE and p values for extraction of fumaric acid by both TDDA and TBA in natural diluents. As shown in Tables 3 and 4, the KE values changed from (4.58·102 to 6.73·102) kg·mol−1 for TDDA and from (2.03·102 to 4.48·102) kg·mol−1 for TBA. The values of p in canola oil, almond oil, and sesame oil were calculated as 0.98, 0.89, and 0.86, respectively, for TDDA and
[H 2A]tot,aq 1+
)
⎛ K a2 ⎞ ln KD + ln⎜1 + ⎟ = ln KE + p ·ln[R3N]org ⎝ [H+]2 ⎠
Combining eqs 12 and 13 gives [H 2A]aq =
K a2 [H+]2
Similarly, eq 15 can be represented in logarithmic form:
Under these conditions, the concentration of undissociated acid in the aqueous phase is given by [H 2A]aq = [H 2A]tot,aq − [A2 −]aq
(1 +
(11)
[A2 −]aq ·[H+]2 [H 2A]aq
p KE·[R3N]org
(14)
In the same way as for the low-pH conditions, the following expression for the distribution coefficient (KD) is obtained: 3770
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Table 4. Experimental Results for the Extraction of Fumaric Acid by TBA in Nontoxic Natural Diluents at T = 298.15 Ka diluent canola oil
almond oil
sesame oil
[R3N]
[H2A]org
mol·kg−1
mol·kg−1
0.418 0.851 1.255 1.674 2.080 0.418 0.851 1.255 1.674 2.080 0.418 0.851 1.255 1.674 2.080
0.039 0.042 0.045 0.046 0.050 0.038 0.041 0.044 0.046 0.049 0.033 0.039 0.042 0.045 0.048
KD
pH(aq) 6.742 6.858 6.969 6.987 6.994 6.796 6.850 6.871 6.903 6.932 6.472 6.782 6.877 6.922 6.984
Z
2.60 3.50 5.00 5.75 12.40 2.37 3.15 4.40 5.75 9.80 1.57 2.60 3.82 5.62 8.00
E/%
0.248 0.133 0.095 0.073 0.063 0.242 0.130 0.093 0.073 0.062 0.210 0.124 0.088 0.071 0.061
72.22 77.77 83.33 85.18 92.50 70.37 75.92 81.48 85.18 90.74 61.11 72.22 79.24 84.90 88.88
KE
p 2
4.48·10
0.93
2.11·102
0.84
2.03·102
0.81
a
[R3N] is the initial amine concentration in the organic phase, [H2A]org is the concentration of acid in the organic phase after extraction, KE is the thermodynamic extraction equilibrium constant, and p is the number of amine molecules per acid molecule.
Figure 3. Reaction between fumaric acid and TDDA or TBA to form the 1:1 acid·amine complex.
obtained: canola oil (12.50) > almond oil (10.00) > sesame oil (9.80) in TDDA and canola oil (12.40) > almond oil (9.80) > sesame oil (8.00) in TBA. The maximum extraction efficiencies of fumaric acid were 92.59 % and 92.50 % using canola oil at 0.759 mol·kg−1 TDDA and 2.080 mol·kg−1 TBA, respectively. Increasing in the amine concentration results in a regular increase in the extraction efficiency. When the extraction efficiencies of physical extraction and chemical extraction were compared, the extraction efficiency increased approximately from 63 % to 93 % for canola oil, from 51 % to % 91 for almond oil, and from 50 % to 90 % for sesame oil. These efficiencies may be raised by using reactive extractants. Further extra benefits of natural nontoxic diluents may be gained by using canola oil, almond oil, and sesame oil.
0.93, 0.84, and 0.81, respectively, for TBA. These values show that one amine molecule reacts with each acid molecule to form the complex. This situation also can be explained by the loading factor (Z), which expresses the extent to which the organic phase (extractant and diluents) may be loaded with acid. Z is defined as the ratio of the total acid concentration in the organic phase at equilibrium to the total initial extractant concentration in the extract phase: Z=
[H 2A]org [R3N]
(17)
It can clearly be observed from Tables 3 and 4 that the loading factor values for all of the natural diluents were lower than 0.5. The Z values were in the range from 0.062 to 0.248 for TDDA and 0.061 to 0.248 for TBA. Overloading (Z > 1) was not observed. This suggests that the complex form contains one amine molecule and one acid molecule (1:1) for both extractants. Figure 3 presents the reaction between fumaric acid and TDDA or TBA to give the complex. Barrow and Yerger19 presented an acid·amine complex structure. They proposed that the proton (H+) in the −COOH group of the carboxylic acid molecule interacts directly with the amine to form an ion pair and hence the 1:1 acid·amine complex. The results of extraction of fumaric acid by TDDA and TBA dissolved in the natural nontoxic diluents canola oil, almond oil, and sesame oil in terms of distribution coefficient and extraction efficiency are tabulated in Tables 3 and 4. The extraction power of (TDDA + diluent) and (TBA + diluent) mixtures changes with increasing initial concentration of amine in the organic phase. When the distribution coefficients (KD) of the diluents were compared, the following orders were
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CONCLUSION The extractability of fumaric acid by amine extractants (TDDA and TBA) dissolved in natural nontoxic diluents (canola oil, almond oil, and sesame oil) were investigated. Physical and chemical extraction were compared in terms of extraction efficiency. The extraction equilibrium was taken to be a result of the formation of 1:1 acid·amine complexes. The thermodynamic extraction constants KE were obtained from a graphical method. The maximum synergistic extraction efficiency (E) was determined as 92.59 % with TDDA in canola oil.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest. 3771
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REFERENCES
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