Comparison of Extractability of Oxalic Acid from Dilute Aqueous

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Comparison of Extractability of Oxalic Acid from Dilute Aqueous Solutions Using Dioctylamine and Trioctylphosphine Oxide ̇ Erdem Hasret,† Ş ah Ismail Kırbaşlar,† and Hasan Uslu*,‡,§ †

Istanbul University-Cerrahpasa, Engineering Faculty, Chemical Engineering Department, Avcılar, 34320 Istanbul, Turkey Istanbul Aydın University, Engineering Faculty, Food Engineering Department, Kücu̧ ̈kçekmece, 34295 Istanbul, Turkey § Chemical and Materials Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia Downloaded via UNIV OF TEXAS AT DALLAS on March 10, 2019 at 18:28:17 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

ABSTRACT: In this investigation, the reactive extraction of oxalic acid from its dilute solutions using trioctylphosphine oxide (TOPO) or dioctylamine (DOA) mixed with several solvents was studied to examine the most proper extractant mixture. The organic-phase combinations were prepared by merging either TOPO or DOA with n-octane, 1-butanol, 1-decanol, methyl isobutyl ketone (MIBK), diisobutyl ketone (DIBK), and diethyl sebacate (DES), respectively. The distribution coefficient, loading factor, and the extraction yield data were calculated for the interpretation of the results. It is found that in comparison with the physical extraction experiments performed with pure solvents oxalic acid extraction from aqueous solutions can be improved significantly by introducing TOPO or DOA to the extractant composition. According to the results, the maximum oxalic acid extraction is obtained with an extraction efficiency of 98.74% and a distribution coefficient of 78.125 if 1.652 mol·kg−1 of DOA dissolved in MIBK is used as the extractant mixture. It can be inferred that using DOA instead of TOPO gives better results for the oxalic acid extraction; however, an aggregate formation was observed with this extractant leading to the problems in the back extraction step of oxalic acid.

1. INTRODUCTION

The reactive extraction technique that relies on the chemical interaction between the solute and extractant molecule is an encouraging separation method due to the product formation with high purity, high selectivity, and efficient pH control of the fermentation media, low secondary product formation, and low energy consumption6 since many investigations were performed for the purification of organic acids from aqueous solutions via reactive extraction.7−13 In these studies, several parameters have been observed such as initial acid concentration, the effect of the diluents, the effect of the pH, etc. on the extraction process. In this study, experiments were implemented to examine the extraction of oxalic acid using TOPO and DOA diluted with various diluents in order to find the most favorable extractant combination to separate acid from aqueous solutions. DOA is picked as an extractant due to the lack of work for the recovery of oxalic acid using this amine. Although some studies have been made for the separation of oxalic acid using phosphorbonded extractants, studies involving comparison of the extractability of oxalic acid using TOPO and DOA are missing in the literature.

Carboxylic acids are organic acids containing a functional carboxylic group that is expressed as a hydroxyl group attached to a carbonyl group symbolized with −COOH. These acids are essential since they are broadly used in pharmaceutical and chemical industries as an additive or a raw material.1 Oxalic acid is one of the carboxylic acids containing two carboxylic groups classified as dicarboxylic acid. It is consumed in many industries as a precipitating substance in metal processing, a rust remover for metal treatment, a purifying substance in the pharmaceutical industry, a bleaching substance in textile industry, etc.2 Recently, either the chemical synthesis or fermentation route is utilized for the industrial production of the carboxylic acids. However, with the increase in oil price and the consumer demand to the natural products, the manufacturing of these acids from renewable resources through biological processes has been gaining interest.3 The challenge in the synthesis of carboxylic acid via the fermentation route is the separation of these products from the dilute fermentation environment and also the presence of byproducts in the media.4 Thus, various separation techniques have been studied for the purification of these acids from the fermentation media including precipitation, electrodialysis, adsorption, ultrafiltration, extraction, distillation, etc.5 © XXXX American Chemical Society

Received: December 3, 2018 Accepted: February 26, 2019

A

DOI: 10.1021/acs.jced.8b01155 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Properties of the Chemicals chemical

IUPAC name

MW (kg·kmol−1)

density (kg·m−3)

supplier

purity (% w)

CAS #

1-butanol 1-decanol methyl isobutyl ketone diisobutyl ketone diethyl sabecate n-octane tri-n-octylphosphine oxide dioctylamine oxalic acid

butan-1-ol decan-1-ol 4-methylpentan-2-one 2,6-dimethylheptan-4-one 1,10-diethyl decanedioate octane 1-dioctylphosphoryloctane N-octyloctan-1-amine ethanedioic acid

74 158.29 100 142.23 258.35 114 386.64 241.46 90.04

810 840 801 806 963 703 831 790 1900

Merck Merck Merck Merck Aldrich Merck Acros Acros Acros

≥99.5 ≥99 ≥99 ≥96 ≥98 ≥99 ≥99 ≥99 ≥98

71-36-3 112-30-1 108-10-1 108-83-8 110-40-7 111-65-9 78-50-2 1120-48-5 144-62-7

Table 2. Oxalic Acid Extraction Results with the TOPO + Diluent System at T = 293.15 K and P = 101.3 kPaa,b acid

solvent

CB,(org) (mol·kg−1)

CA,aq (mol·kg−1)

CA,org (mol·kg−1)

KD

Z

E%

oxalic acid

1-butanol

oxalic acid

1-decanol

oxalic acid

DES

oxalic acid

MIBK

oxalic acid

n-octane

oxalic acid

DIBK

0.240 0.519 0.884 1.391 2.072 0 0.233 0.518 0.888 1.376 2.069 0 0.230 0.516 0.885 1.380 2.078 0 0.229 0.518 0.887 1.380 2.060 0 0.232 0.523 0.889 1.381 2.068 0 0.235 0.517 0.888 1.378 2.067 0

0.544 0.539 0.519 0.477 0.464 0.538 0.846 0.820 0.727 0.627 0.491 0.883 0.848 0.682 0.613 0.471 0.377 0.941 0.711 0.504 0.495 0.416 0.316 0.878 0.877 0.716 0.646 0.505 0.434 0.943 0.797 0.697 0.590 0.493 0.385 0.952

0.422 0.427 0.447 0.489 0.502 0.428 0.120 0.146 0.239 0.339 0.475 0.083 0.118 0.284 0.353 0.495 0.589 0.025 0.255 0.462 0.471 0.550 0.650 0.088 0.089 0.250 0.320 0.461 0.532 0.023 0.169 0.269 0.376 0.473 0.581 0.014

0.776 0.791 0.862 1.024 1.084 0.797 0.141 0.178 0.328 0.541 0.967 0.094 0.139 0.417 0.575 1.051 1.559 0.026 0.359 0.917 0.951 1.323 2.053 0.1 0.102 0.350 0.495 0.913 1.227 0.025 0.212 0.385 0.637 0.960 1.511 0.014

1.761 0.822 0.506 0.351 0.242 0 0.514 0.282 0.269 0.246 0.229 0 0.513 0.551 0.399 0.359 0.283 0 1.115 0.892 0.531 0.399 0.315 0 0.386 0.478 0.360 0.334 0.257 0 0.72 0.519 0.423 0.343 0.281 0

43.69 44.15 46.31 50.59 52.02 44.34 12.39 15.11 24.71 35.10 49.16 8.61 12.23 29.44 36.53 51.23 60.92 2.56 26.41 47.84 48.75 56.95 67.24 9.12 9.25 25.91 33.11 47.72 55.10 2.42 17.51 27.80 38.93 48.97 60.18 1.42

a

CB,(org) is the organic-phase extractant concentration; CA,aq is the acid concentration in the aqueous phase; CA,org is the acid concentration in the organic phase; KD is the distribution coefficient; Z is the loading factor; and E is the extraction efficiency. bStandard uncertainties u are u(CB,(org)) = 0.001 mol·kg−1, u(CA,aq) = 0.001 mol·kg−1, u(CA,org) = 0.01 mol·kg−1, u(T) =0.01 K, u(P) = 0.1 kPa.

2. EXPERIMENTAL SECTION

mixed with six different solvents (n-octane, 1-butanol, 1decanol, MIBK, DIBK, DES) having different chemical structures to attain the most appropriate extractant composition. The prepared oxalic acid solution and extractant solution were merged in an erlenmeyer flask and were agitated at 150 rpm in a temperature-controlled shaker at 25 °C for 2 h. Then the resulted mixture was held 2 h to achieve a complete segregation of the phases. The concentration of the residual

2.1. Materials. The properties of the chemicals under investigation are shown in Table 1. All chemicals are consumed without further treatment. 2.2. Methods. Oxalic acid solution was prepared using distilled water with a concentration of 0.966 mol·kg−1. TOPO (C24H51OP) and DOA (CH3(CH2)7NH(CH2)7CH3) were B



Article

Table 3. Oxalic Acid Extraction Results with the DOA + Diluent System at T = 293.15 K and P = 101.3 kPaa,b acid

solvent

CB,(org) (mol·kg−1)

CA,aq (mol·kg−1)

CA,org (mol·kg−1)

KD

Z

E%

oxalic acid

1-butanol

oxalic acid

1-decanol

oxalic acid

DES

oxalic acid

MIBK

oxalic acid

n-octane

oxalic acid

DIBK

0.362 0.662 0.994 1.327 1.668 0 0.359 0.656 0.970 1.243 1.625 0 0.329 0.669 1.003 1.338 1.665 0 0.345 0.683 1.013 1.329 1.652 0 0.317 0.663 0.985 1.321 1.638 0 0.345 0.678 0.972 1.345 1.707 0

0.418 0.157 0.023 0.019 0.016 0.538 0.555 0.446 0.179 0.141 0.130 0.883 0.619 0.405 0.415 0.249 0.126 0.941 0.231 0.093 0.020 0.015 0.012 0.878 0.731 0.673 0.309 0.157 0.095 0.943 0.624 0.338 0.333 0.202 0.013 0.952

0.548 0.809 0.943 0.947 0.950 0.428 0.411 0.520 0.787 0.825 0.836 0.083 0.347 0.561 0.551 0.717 0.840 0.025 0.735 0.873 0.946 0.951 0.954 0.088 0.235 0.293 0.657 0.809 0.871 0.023 0.342 0.628 0.633 0.764 0.953 0.014

1.312 5.164 41.095 50.691 58.322 0.797 0.740 1.164 4.400 5.832 6.448 0.094 0.562 1.383 1.328 2.884 6.641 0.026 3.174 9.418 48.041 61.896 78.125 0.100 0.322 0.435 2.127 5.147 9.217 0.025 0.547 1.855 1.899 3.786 76.193 0.014

1.555 1.212 0.950 0.714 0.569 0 1.178 0.792 0.812 0.669 0.515 0 1.026 0.838 0.549 0.537 0.504 0 2.142 1.260 0.943 0.716 0.577 0 0.742 0.435 0.667 0.613 0.535 0 1.020 0.940 0.645 0.564 0.559 0

56.75 83.78 97.62 98.07 98.31 44.34 42.52 53.80 81.48 85.36 86.57 8.61 35.97 58.04 57.05 74.26 86.91 2.56 76.04 90.40 97.96 98.41 98.74 9.12 24.33 30.31 68.03 83.73 90.21 2.42 35.36 64.97 65.50 79.11 98.70 1.42

a

CB,(org) is the organic-phase extractant concentration; CA,aq is the acid concentration in the aqueous phase; CA,org is the acid concentration in the organic phase; KD is the distribution coefficient; Z is the loading factor; and E is the extraction efficiency. bStandard uncertainties u are u(CB,(org)) = 0.001 mol·kg−1, u(CA,aq) = 0.001 mol·kg−1, u(CA,org) = 0.01 mol·kg−1, u(T) = 0.01 K, u(P) = 0.1 kPa.

acid in the aqueous phase after the extraction process was found by titrating with sodium hydroxide in the presence of phenolphthalein indicator. The results were evaluated using the distribution coefficient, loading factor, and the extraction yield data. Karl Fischer was used for solubility of the diluents to determined water after extraction. The distribution coefficient (KD), extraction yield (E %), and the loading factor (Z) values can be calculated using the following equations:14 KD = CA(org)/CA(aq)

(1)

E% = (1 − (CA(aq)/CAo)) × 100

(2)

Z = CA(org)/C B(org)

(3)

CB(org): The extractant concentration in the organic phase. CAo: The initial acid concentration in the aqueous phase.

3. RESULTS AND DISCUSSIONS 3.1. Physical Extraction Results. The physical extraction experiments were implemented by using pure solvents in order to observe the effect of introducing either DOA or TOPO to the extractant composition and to compare the physical extraction and reactive extraction results. Six different solvents having distinct chemical structure including 1-butanol, 1decanol, DES, MIBK, DIBK, and n-octane were used without further purification. The results given in Table 2 and Table 3 also can be seen from Figure 1. It can be inferred from the results that the extraction of oxalic acid from its dilute aqueous solutions using only pure solvents is an inefficient route for the recovery of this acid since the maximum extraction efficiency value was obtained using butanol as 44.34%. The affinity of oxalic acid to the water may lead to the low distribution coefficient values. Thus, the

CA(org): The acid concentration in the organic phase after the extraction. CA(aq): The acid concentration in the aqueous phase after the extraction. C



Article

DOA/Diluent System (KD): MIBK > DIBK > 1-Butanol > n-Octane > 1-Decanol > DES In the reactive extraction experiments using amines, the dissolution of the formed complex in the organic phase is a critical step for the yield of the extraction operation. Since MIBK is polar and also has a functional group that favors the interaction with the formed complex, the distribution coefficients attained using the combination of either DOA or TOPO dissolved in MIBK exhibit higher values with respect to the other solvents involved. Although the results reveal that DOA is an efficient extractant for the recovery of oxalic acid, the formation of dense aggregates using this amine occurred with almost all the specimens performed in this study. When TOPO was used in the organic phase instead of DOA, the formation of aggregates was not observed. This situation leads to the difficulties in the separation step of the acid from the formed complex, causing the extraction process to become unfeasible. Some researchers have also encountered the same issue in several investigations, and they describe this state as the third phase or aggregate formation.15,16 The formed complex is insoluble, and it is difficult to back extract the acid from the formed structure. Despite having high extraction capacities using DOA, the occurrence of dense aggregates favors the use of TOPO because of the problems encountered in the recovery of the acid. It can be seen from the distribution coefficient results that merging DOA or TOPO with several solvents instead of using pure solvents considerably improves the extraction process, and in comparison with the results obtained from physical extraction, reactive extraction is a far better separation technique for the purification of oxalic acid from dilute solutions. 3.2.2. Loading Factor. Loading factor is an essential parameter because the rise in the amine concentration might lead to a probable side effect of the microorganisms in the extractive fermentation. However, for the extraction efficiency there must be a balance between distribution factor and loading factor since our goal is to extract the maximum amount with the minimum extractant consumption considering the cost of the process. In Figure 3(a) and Figure 3(b) the change in loading ratio values with respect to the TOPO and DOA concentration is shown, respectively.

Figure 1. Physical extraction results of oxalic acid.

necessity of the investigation of various extractant combinations was revealed for the oxalic acid extraction, and reactive extraction experiments were performed in order to enhance the physical extraction process adding either DOA or TOPO to the extractant composition. 3.2. Reactive Extraction Results. 3.2.1. Distribution Coefficient. The reactive extraction results performed by using DOA or TOPO dissolved in six different solvents are revealed in Table 2 and Table 3. The distribution of oxalic acid between the phases described with the KD value is illustrated in Figure 2(a) and Figure 2(b). It is obvious from Figure 2a and Figure 2b that for reactive extraction experiments implemented using both TOPO and DOA the distribution coefficient values increase with the rise in the initial TOPO or DOA quantity. According to the results, maximum extracted oxalic acid (KD: 78.125) was obtained if an extractant combination of 1.652 mol·kg−1 of DOA diluted with MIBK was used with respect to the other solvents considered in this study. Also, maximum extracted oxalic acid (KD: 2.053) was attained with 2.06 mol·kg−1 of TOPO dissolved in MIBK if TOPO instead of DOA is used in the organic phase. However, a dense aggregate formation was observed in the experiments performed with DOA leading to the difficulties in the phase separation step. The distribution coefficient values for the extraction of oxalic acid using different solvents were found in the following order: TOPO/Diluent System (KD): MIBK > DES > DIBK > n-Octane > 1-Butanol > 1-Decanol

Figure 2. Distribution coefficient change with increasing extractant concentration: (a)TOPO and (b) DOA. ⧫, Butanol; ×, DES; ■, Dekanol; -, DIBK; +, Octane; *, MIBK. D



Article

Figure 3. Loading factor change with increasing extractant concentration: (a) TOPO and (b) DOA. ⧫, Butanol; ×, DES; ■, Dekanol; -, DIBK; +, Octane; *, MIBK.

Figure 4. Extraction efficiency change with increasing extractant concentration: (a) TOPO and (b) DOA. ⧫, Butanol; ×, DES; ■, Dekanol; -, DIBK; +, Octane; *, MIBK.

MIBK is a polar diluent and has a reactive functional group that enhances the extraction capability of the formed acid− amine complex. The results reveal that the increase in the initial amount of TOPO or DOA in the organic phase significantly enhances the extraction yield of the process.

Overloading resembles the formation of complexes having more than one acid for each extractant molecule. The results show us that overloading occurred with butanol and MIBK in the vicinity of 0.229 and 0.24 mol·kg−1 of TOPO, and except for n-octane, overloading is observed with 0.329 and 0.362 mol·kg−1 of DOA regardless of the type of solvent. In these cases, there is more than one amine per complex. However, in this study it can be clearly seen that the loading factors with all diluents decrease with the rise in DOA or TOPO concentration, and they become lower than unity in higher concentrations; so, overloading has not occurred. The same results (Z > 1, low concentrations) are also revealed in different studies in the literature.17,18 3.2.3. Extraction Yield. Examining the extraction efficiency data reveals that the yield of the extraction of oxalic acid with TOPO changes between 9.25% and 67.24% with respect to the solvents used, and the maximum oxalic acid extraction can be obtained using TOPO (2.06 mol·kg−1) dissolved in MIBK as 67.24%. Also extraction yield of oxalic acid with DOA varies in the range of 24.33%−98.74%, and the maximum oxalic acid extraction can be obtained using DOA (1.652 mol·kg−1) dissolved in MIBK as 98.74%. The extraction efficiency data of the processes are illustrated in Figure 4(a) and Figure 4(b), respectively. It is known that polar diluents improve the extraction ability of the extractant by ensuring extra solvating power, allowing the formation of higher levels of acid−extractant complexes.

4. CONCLUSIONS In this investigation, we show the extractability of oxalic acid using DOA or TOPO diluted with six distinct solvents (MIBK, DIBK, DES, 1-butanol, 1-decanol, n-octane) having different chemical structures. Furthermore, physical extraction experiments with pure solvents were implemented in order to compare the influence of the DOA or TOPO addition to the extraction media. The results were evaluated using extraction efficiency, distribution coefficient, and loading factor data. It was concluded that introducing DOA or TOPO to the process remarkably improved the extraction yield of oxalic acid from its aqueous solutions, and thus pure solvents alone are not convenient for the extraction processes. The rise in the yield of the extraction with mixed extractant can result from the formation of a complex. Despite having the same issues in the purification stage, an amine-based extractant DOA gives remarkably better results with respect to the phosphorus-based extractant TOPO for the extraction operations of oxalic acid. The maximum oxalic acid extraction is obtained with an extraction efficiency of 98.74% and a distribution coefficient of 78.125 if 1.652 mol·kg−1 of E



Article

(12) Hong, Y. K.; Hong, W. H. Reactive extraction of succinic acid with tripropylamine (TPA) in various diluents. Bioprocess Biosyst. Eng. 2000, 22, 281−284. (13) Qin, W.; Cao, Y.; Luo, X.; Liu, G.; Dai, Y. Extraction mechanism and behaviour of oxalic acid by Trioctylamine. Sep. Purif. Technol. 2001, 24, 419−426. ̇ (14) Bayazit, S. S.; Uslu, H.; Inci, I.̇ Comparison of the efficiencies of amine extractants on lactic acid with different organic solvents. J. Chem. Eng. Data 2011, 56, 750−756. (15) Kurzrock, T.; Weuster-Botz, D. New reactive extraction systems for separation of bio-succinic acid. Bioprocess Biosyst. Eng. 2011, 34, 779−787. (16) Hong, Y. K.; Hong, W. I.̇ Influence of chain length of tertiary amines on extractability and chemical interactions in reactive extraction of succunic acid. Korean J. Chem. Eng. 2004, 21, 488−493. (17) Tuyun, A. F.; Uslu, H. Reactive extraction of cyclic polyhydroxy carboxylic acid using trioctylamine (TOA) in different diluents. J. Chem. Eng. Data 2012, 57, 2143−2146. ̇ (18) Aşcı̧ , S.; Inci, I.̇ Extraction equilibria of propionic acid from aqueous solutions by Amberlite LA-2 in diluent solvents. Chem. Eng. J. 2009, 155, 784−788.

DOA dissolved in MIBK is used as the extractant mixture. The rise in the initial amount of both DOA and TOPO in the extractant combination improves the extraction yield and distribution coefficient of the extraction process. It can be inferred from the results that oxalic acid extraction can be improved remarkably by using phosphorus or aminebased extractants such as DOA or TOPO and especially a DOA/MIBK combination to give better results with respect to the other solvents involved in this study. Although having some problems in the purification process such as aggregate formation, the use of this solution is recommended if the problems in the back extraction step of oxalic acid are resolved.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Hasan Uslu: 0000-0002-4985-7246 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS

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REFERENCES

This work was supported by Scientific Research Project Coordination Unit of Istanbul University. Project number: 22274.

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Comparison of Extractability of Oxalic Acid from Dilute Aqueous

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