Separation of Protocatechuic Acid Using Di-(2-ethylhexyl)phosphoric

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

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Separation of Protocatechuic Acid Using Di-(2-ethylhexyl)phosphoric Acid in Isobutyl Acetate, Toluene, and Petroleum Ether Fiona Mary Antony and Kailas Wasewar* Advance Separation and Analytical Laboratory (ASAL), Department of Chemical Engineering, Visvesvaraya National Institute of Technology (VNIT), Nagpur 440010, India ABSTRACT: Protocatechuic acid has potential pharmacological significance, like antioxidant, antibacterial, and anticancer activity. The extraction of carboxylic acids from dilute aqueous phase is a topic of current interest to researchers. The present equilibrium study deals with the reactive extraction of protocatechuic acid from an aqueous solution by using di-(2-ethylhexyl)phosphoric acid (D2EHPA) in diluents, such as isobutyl acetate (IBA), toluene, and petroleum ether at isothermal conditions (298 ± 1 K). The physical extraction of protocatechuic acid with pure diluents is also carried out. The difference between the physical extraction and the reactive extraction was studied. The effects of acid concentration (0.001− 0.01 mol·kg−1), extractant concentration (0.3445−3.1010 mol· kg−1), and type of diluent on the recovery of protocatechuic acid from aqueous solution were determined. KD values were obtained in the ranges of 1.14−4.03, 0.12−0.67, and 0.08−0.48 for D2EHPA in isobutyl acetate, toluene, and petroleum ether, respectively. A maximum KD was obtained as 4.03 using 3.101 mol·kg−1 D2EHPA (in IBA), while 80.11% of the initial protocatechuic acid was extracted. The D2EHPA−IBA system was found to provide the highest distribution coefficient of the three diluents tested. The extraction equilibrium complexation constant, KE, was obtained in the ranges of 5.56−1.17, 0.82−0.20, and 0.49−0.14 for D2EHPA in isobutyl acetate, toluene, and petroleum ether, respectively. The feasibility of the extraction process was evaluated by calculating the minimum solvent to feed ratio and the number of theoretical stages of the extraction column. The number of theoretical stages for the D2EHPA−IBA system was calculated to be 3, and it was 1 for the D2EHPA− toluene and D2EHPA−petroleum ether systems. cardiovascular, and neuro-degenerative diseases.10 Apart from pharmacological uses, PCA is used in synthesizing polymers and plastics. An electrode made of a composite polymer of PCA and an aniline was found to function with a good electrochemical activity.11 The direct extraction of PCA from plant secondary metabolites is difficult. Thus, biosynthesis of PCA is considered more economical and is gaining importance. PCA can be obtained from fermentation broth by several species of Bacillus, including Bacillus cereus, Bacillus anthracis from siderophore,12,13 and Bacillus thuringiensis.14 There are reports of PCA production by recombinant microorganisms from sugar.15 The traditional method used for recovery of carboxylic acids is based on precipitation of the insoluble calcium salt of carboxylic acids with Ca(OH)2 or CaCO3 followed by reacidification with H2SO4, but this method offers several disadvantages, like handling large amounts of solid and slurry, and the production of equal amounts of calcium sulfate waste.16 Another process is liquid−liquid extraction with conventional solvents, such as ether, but is considered unfeasible for the

1. INTRODUCTION The recovery of carboxylic acid from aqueous solutions and fermentation broth has always been a topic of interest for researchers. Carboxylic acids are usually produced either from petroleum-based feedstocks through chemical synthesis or from fermentation broths. Protocatechuic acid (PCA) (C7H6O4, 3,4dihydroxybenzoic acid) is one of the most important carboxylic acids, existing in fruits, edible plants, and vegetables.1 It is a main metabolite of complex polyphenols, especially anthocyanins, which are converted to PCA and also abundantly formed and absorbed in the large intestine because of microbial metabolization.2,3 It is found in many food plants, such as Olea europaea (olives), Hibiscus sabdariffa (roselle), Eucommia ulmoides (du-zhong), Citrus microcarpa Bunge (calamondin), and Vitis vinifera (white wine grapes).4 PCA is also a biologically active component found in some medicinal plants, which are mainly used in natural medicine, such as sudan Mallow (H. sabdariffa L.),5,6 Japanese ginkgo (Ginkgo biloba), and St. John’s wort (Hypericum perforatum L.).7 The pharmacological properties of PCA reported to date include antioxidant,8 anti-inflammatory, antihyperglycemia, antiapoptosis/proapoptosis, antiaging, anticancer,9 antifibrotic, antiviral, and antimicrobial activities.4 Recently, PCA has been recognized for the prevention of some chronic-degenerative, © XXXX American Chemical Society

Received: September 6, 2017 Accepted: February 16, 2018

A

DOI: 10.1021/acs.jced.7b00797 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

recovery of most carboxylic acids due to the low activity coefficient of the acid in the aqueous phase which does not allow for significant transfer of the acid into the solvent.16 Sorption is also an effective technique for carboxylic acid separation, but the limited capacity for the carboxylic acid on the solid surface is a disadvantage.17 Another method proposed as a substitute for the recovery of carboxylic acids is membrane processes, such as electrodialysis, nanofiltration, and reverse osmosis; however, these methods are still in the early stages of development.18,19 Several techniques for the recovery of PCA have been in practice, namely adsorption,20 microbial degradation,21 ultrafiltration,22 and O3/UV or H2O2/UV.23 But these methods face some demerits, such as being less selective, ineffective for dilute solutions, energy intensive, and time consuming, and often generating toxic byproducts. For the recovery of carboxylic acids from dilute fermentation broths, reactive extraction is found to be an effective method.24−26 It offers several advantages over conventional techniques, like the acid can be re-extracted and the solvent can be reused, better control of pH in the bioreactor, better recovery of acid with higher product purity, reduction of downstream processing load and recovery cost, reactants that are relatively immiscible, etc. In reactive extraction, the reversible reaction between the acid molecule in the aqueous phase and the extractant in the organic phase results in the formation of the acid−extractant complex. It has been successfully used for the separation of phenylacetic acid,27−29 tartaric acid,30 gallic acid,31−33 nicotinic acid,34 benzoic acid,35 cupric acid,36−38 itaconic acid,39 propionic acid,40−42 acrylic acid,43,44 levulinic acid,45 and lactic acid.46 Despite the massive commercial importance of PCA, no work has been found on the reactive extraction of PCA from aqueous streams or fermentation broths with the best of literature available. The present study focuses on the reactive extraction of PCA from the aqueous phase using di-(2ethylhexyl)phosphoric acid (D2EHPA) as an extractant using diluents, isobutyl acetate, toluene, and petroleum ether. D2EHPA is an organo-phosphorus compound with the formula (C8H17O)2PO2H. D2EHPA is one of the most widely used and characterized extractants in the chemical, hydrometallurgical, and nuclear processing industries.47 A few studies on reactive extraction of various chemicals using D2EHPA are listed in Table 1. The results of reactive extraction of PCA are discussed in terms of the distribution coefficient, extraction efficiency, loading ratio, and extraction equilibrium complexation constant.

Table 1. Studies Involving Reactive Extraction with D2EHPA extracted species lactic acid L-valine

uranium rosmarinic acid

pantothenic acid

nicotinic acid

vanadium indium gadolinium nickel, zinc aminophenol calcium, magnesium zinc, copper

ammonia

diluent

ref

diethylbenzene kerosene solvent naphtha 1-octanol dodecane n-heptane n-butyl acetate dichloromethane 1-octanol n-heptane n-butyl acetate dichloromethane n-heptane n-butyl acetate dichloromethane n-heptane isoparaffin 22/25 exxsol D100 exxsol D100 hexane 2-octanol kerosene exxsol D80 toluene chloroform carbon tetrachloride benzene cyclohexane n-hexane xylene toluene n-heptane kerosene

48 49

50 51

52

53

54 55 56 57 58 59 60

61

An equal volume of the aqueous and organic phase was taken in a 100 mL Erlenmeyer flask and shaken for 5 h in an orbital shaking incubator (REMI S-24BL, Mumbai, India) to attain equilibrium. Five hours was sufficient to reach the equilibrium.62 Further phase separation was done by centrifugation (REMI R-4C, Mumbai, India) for 5 min at 4000 rpm. The aqueous phase obtained was used for pH (measured by CyberScan pH2100, Eutech Instruments) and concentration analysis. The equilibrium concentration of the aqueous phase PCA was analyzed by an UV/vis spectrophotometer (Shimadzu 1800, Japan) at 260 nm. The concentration of PCA in the organic phase at equilibrium was determined by component mass balance with the following assumptions: (i) both the organic and aqueous phases had the same volume, (ii) the solubility of water in the organic phase was neglected, and (iii) the solubility of extractant and diluents in water was neglected. Reproducing a few sets of experiments under identical conditions proved that the error was less than 2%. The random measurements for the volume of the aqueous and organic phases were taken to check the water co-extraction, and it was found to be negligible. The initial pH of PCA in aqueous solution was low (98%. The diluents, isobutyl acetate (IBA), toluene, and petroleum ether, were of reagent grade and used without any further pretreatment. PCA (purity >98%) was obtained from Avra. Physicochemical properties and other details of chemicals used are summarized in Table 2. Deionized water was used to prepare the aqueous solution of PCA. The experiments were carried out at room temperature (25 °C, 298 K) and atmospheric pressure (101.325 kPa). The aqueous phase of PCA was prepared in the concentration range of 0.001−0.01 mol·kg−1, as this is the maximum possible concentration in fermentation.15 The proportion of extractant D2EHPA in diluents, isobutyl acetate, toluene, and petroleum ether, was varied from 10 to 50% by volume, which constituted the organic phase. B



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Table 2. Physical Characteristics of Chemicals Used in the Study molar mass (kg kmol−1)

chemical

molecular formula

protocatechuic acid

154.12

C7H6O4

di-(2-ethylhexyl)phosphorc acid isobutyl acetate

322.42

C16H35O4P

116.16

C6H12O2

toluene petroleum ether (60−80)

92.14

C6H5−CH3

purity (mass fraction)

purification method

Avra Synthesis Pvt. Ltd., India Spectrochem, India

99-50-3

0.98

none

298-07-7

0.98

none

Avra Synthesis Pvt. Ltd., India SDFCL, India Rankem, India

110-19-0

0.98

none

108-88-3 8032-32-4

0.995

none none

extractable (pKA = 4.48). The relation/trend of natural pH for various concentrations of PCA is shown in Figure 1. pH = 3.95 − 0.222 ln mPCA,0

CAS number

suppliers

KD =

(1)

mPCA,org mPCA,aq

(2)

The degree of extraction (%E) at equilibrium can be calculated from the expression as shown in the following equation

where mPCA,0 is the initial concentration of PCA in an aqueous stream in mol·kg−1.

E=

KD × 100 1 + KD

(3)

Uncertainty may be observed in experimentations due to instrumental error or random variation. The deviation from the average value of the observation was used as experimental error. The experimental uncertainty was determined as u(a) =

1 N−1

N

∑ (xi − x ̅ )2 (4)

i=1

where xi is the experimental observation, x̅ is sample mean of two observations, and N is the number of observations. Figure 1. pH for various initial concentrations of PCA (mol·kg−1).

3. RESULTS AND DISCUSSION 3.1. Physical Extraction. Experiments for the extraction of PCA were performed using pure diluents, IBA, toluene, and petroleum ether. The results of the physical extractions in terms of distribution coefficient, extraction efficiency, partition coefficient, and dimerization constant are summarized in Table 3. The distribution coefficient (KD) was found in the ranges of 1.04−1.87, 0.08−0.19, and 0.07−0.16 with IBA,

The experimental value of the distribution ratio, KD, in molar concentration scale expressed in terms of the total concentrations of the acid in all its possible forms in the aqueous (mPCA,aq) and the organic (mPCA,org) phases is given by

Table 3. Distribution Coefficient, KD, and Extraction Efficiency, η, Values for the Equilibrium Isotherm (Physical) of Protocatechuic Acid from Aqueous Streams into Diluents at 101.325 kPa and 298 ± 1 Ka diluent isobutyl acetate

toluene

petroleum ether

mPCA,0 (mol·kg−1)b mPCA,aq (mol·kg−1)c mPCA,org (mol·kg−1)d 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01

0.0005 0.0013 0.0020 0.0027 0.0035 0.0009 0.0027 0.0044 0.0060 0.0084 0.0009 0.0027 0.0044 0.0061 0.0086

0.0005 0.0017 0.0030 0.0043 0.0065 8 × 10−5 3 × 10−4 6 × 10−4 1 × 10−3 2 × 10−3 6.9 × 10−5 2.9 × 10−4 5.6 × 10−4 9.0 × 10−4 1.4 × 10−3

KD

avg KD

η%

avg η%

partition coefficient (P)

dimerization coefficient (D)

1.04 1.31 1.50 1.58 1.87 0.08 0.12 0.15 0.16 0.19 0.07 0.11 0.13 0.15 0.16

1.46

51.10 56.67 60.04 61.29 65.13 7.81 10.97 12.96 14.00 15.69 6.90 9.60 11.26 12.86 13.70

58.84

0.9419

146.6

12.29

0.0826

956.8

10.86

0.0724

0.14

0.12

1048

Standard uncertainties, u, are u(T) = 1 K, u(p) = 1 kPa, u(mPCA,0) = 0.001 mol·kg−1, u(mPCA,aq) = 0.001 mol·kg−1, and u(mPCA,org) = 0.001 mol·kg−1. mPCA,0, initial molality of the protocatechuic acid in the aqueous phase. cmPCA,aq, equilibrium molality of the protocatechuic acid in the aqueous phase. dmPCA,org, equilibrium molality of the protocatechuic acid in the organic phase. a b

C



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Table 4. Distribution Coefficient, KD, Extraction Efficiency, η, Loading Ratio, Z, and Equilibrium Complexation Constant, KE, Values for the Chemical Equilibrium of Protocatechuic Acid with Di-(2-ethylhexyl)phosphoric Acid in Isobutyl Acetate at 101.325 kPa and 298 ± 1 Ka,b mD2EHPA,0org (mol·kg−1)c

mPCA,0 (mol·kg−1)d

mPCA,aq (mol·kg−1)e

mPCA,org (mol·kg−1)f

KD

avg KD

η%

avg η%

Z

KE

0.3445

0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01

0.0005 0.0012 0.0019 0.0025 0.0032 0.0004 0.0011 0.0017 0.0022 0.0029 0.0004 0.0010 0.0015 0.0020 0.0026 0.0003 0.0009 0.0014 0.0018 0.0023 0.0003 0.0008 0.0012 0.0015 0.0020

0.0005 0.0018 0.0031 0.0045 0.0068 0.0006 0.0019 0.0033 0.0048 0.0071 0.0006 0.0020 0.0035 0.0050 0.0074 0.0007 0.0021 0.0036 0.0052 0.0077 0.0007 0.0022 0.0038 0.0055 0.0080

1.14 1.42 1.61 1.78 2.14 1.45 1.68 1.92 2.22 2.51 1.78 2.10 2.28 2.56 2.87 2.04 2.37 2.63 2.99 3.44 2.34 2.80 3.15 3.60 4.03

1.62

53.21 58.60 61.66 64.09 68.17 59.21 62.63 65.72 68.93 71.47 64.02 67.70 69.55 71.93 74.16 67.06 70.34 72.44 74.97 77.47 70.06 73.71 75.90 78.24 80.11

61.15

0.0015 0.0051 0.0089 0.0130 0.0198 0.0008 0.0024 0.0042 0.0062 0.0092 0.0005 0.0015 0.0026 0.0038 0.0056 0.0003 0.0010 0.0018 0.0025 0.0037 0.0002 0.0007 0.0012 0.0018 0.0026

5.5661

0.7752

1.3291

2.0674

3.1010

1.95

2.32

2.69

3.18

65.59

69.47

72.46

75.60

2.9311

1.9835

1.5058

1.1794

Standard uncertainties, u, are u(T) = 1 K, u(p) = 1 kPa, u(mPD2EHPA,0) = 0.001 mol·kg−1, u(mPCA,0) = 0.001 mol·kg−1, u(mPCA,aq) = 0.001 mol·kg−1, and u(mPCA,org) = 0.001 mol·kg−1. bSolvent: di-(2-ethylhexyl)phosphoric acid + isobutyl acetate. cmD2EHPA,0org, initial molality of D2EHPA in the organic phase. dmPCA,0, initial molality of the protocatechuic acid in the aqueous phase. emPCA,aq, equilibrium molality of the protocatechuic acid in the aqueous phase. fmPCA,org, equilibrium molality of the protocatechuic acid in the organic phase.

a

in IBA, toluene, and petroleum ether was obtained as 0.9419, 0.0826, and 0.0724, respectively. Furthermore, the dimerization coefficient was estimated as 146.6, 956.8, and 1048 for IBA, toluene, and petroleum ether, respectively. Solute−solute interactive forces act intensely as compared to solute−solvent interactions, which lead to dimer formation. It can be observed that the values of P and D are inversely related. Due to ion-pair interactions in the case of esters, they have higher P values and lower D values in comparison to those of aliphatic and aromatic hydrocarbons. The distribution coefficient and extraction efficiency of PCA in diluents without D2EHPA (physical extraction) were found to follow the trend as IBA > toluene > petroleum ether. Further, higher KD values are observed for diluents having less dimerization. 3.2. Reactive Extraction. The results of physical extraction showed that organic diluents alone were not sufficient for the efficient recovery of PCA. Therefore, the recovery of PCA was also carried out with an extractant, D2EHPA (0.3445−3.1010 mol·kg−1) dissolved in different diluents. Five different initial concentrations of the acid (0.001−0.01 mol·kg−1) were considered for study. Extraction with diluents helped in controlling the viscosity and density of the solvent phase. The chemical equilibrium results are presented in Tables 4, 5, and 6. An improvement in the extraction efficiency in terms of KD was observed when D2EHPA was used with diluents as compared to that of pure diluent alone. The extraction efficiency increases from 65.13 to 80.11% for IBA + D2EHPA, 15.69 to 40.25% for toluene + D2EHPA, and 13.7

toluene, and petroleum ether, respectively, for PCA concentrations in the range of 0.001−0.01 mol·kg−1. The trend of the overall distribution coefficient was observed as IBA > toluene > petroleum ether. The average extraction efficiency is approximately 58.84% in IBA, 12.29% in toluene, and 10.86% in petroleum ether. Thus, the distribution coefficient was found to be increased with the acid concentration, which may be due to the higher driving force to accommodate the acid in the organic phase, and also may be due to the emaciation of the bond between the acid and water molecules as acid molecules become more available in the aqueous phase.63 The two main factors affecting the extractability of the carboxylic acid in physical extraction are the extent of hydration of the acid and the energy of the bond to the water molecule.64,65 The probable reason for the low values of distribution coefficients ( toluene (KD = 0.22− 0.52) > petroleum ether (KD = 0.13−0.38). Under the same D2EHPA concentrations in different diluents, efficiencies were found to be increased in the order IBA > toluene > petroleum ether. For D2EHPA (0.3445−3.101 mol·kg−1) in IBA, the average extraction was found between 61.15 and 75.6%, whereas the corresponding values in the case of toluene are in the range of 17.72−33.77%, and for petroleum ether from 11.7 to 27.44%. The maximum extraction efficiency was reached as 80.11% with IBA at the highest extractant concentration level. D2EHPA can react with PCA, resulting in the formation of an ion-pair complex which exhibits a certain polarity. The stronger solubility vs the complex is exhibited with diluents of greater polarity. IBA provided the most favorable soluble conditions for the complexes, so the highest KD values were obtained. At all D2EHPA concentrations, KD < 1 suggests that the D2EHPA−petroleum ether system is a poor solvent system for extraction of PCA. Thus, it can be concluded, on the basis of the overall extraction efficiency, that IBA is a better solvent for the reactive extraction of PCA using D2EHPA.

to 32.5% for petroleum ether + D2EHPA systems for an initial acid concentration of 0.01 mol·kg−1 and at a D2EHPA concentration of 1.513 mol·kg−1 compared to that of physical extraction. The extraction equilibrium isotherms for PCA extraction by D2EHPA in IBA, toluene, and petroleum ether are shown in Figures 2, 3, and 4, respectively. 3.3. Effect of the Initial Concentration of PCA. At a constant D2EHPA concentration, with an increase in acid concentration from 0.001 to 0.01 mol·L−1, the distribution coefficient (KD) and efficiency (η%) were found to be increased for all diluents. With 0.01 mol·kg−1 PCA, KD values were observed in the range of 2.14−4.3 (IBA), 0.32−0.67 (toluene), and 0.19−0.48 (petroleum ether) for extractant concentrations of 0.3445−3.101 mol·kg−1. The variation of extraction efficiency (%) and KD with an initial acid concentration for all diluents at 3.1010 mol·kg−1 D2EHPA is shown in Figures 5 and 6. From Tables 4−6, it is observed that KD increased with an increase in the initial concentration of PCA, and the trend was observed for all D2EHPA levels. This phenomenon has been previously reported for other extractant−acid systems.63,67 The higher KD (4.03 for IBA at 3.101 mol·kg−1 D2EHPA) was obtained at a higher concentration of PCA (0.01 mol·kg−1), signifying the advantage of the addition of the reactive component, D2EHPA, which can successfully extract acid from aqueous streams. The highest recovery efficiency (80.11% in IBA, 40.25% in toluene, and 32.5% in petroleum ether) was obtained with 3.101 mol·kg−1 D2EHPA and 0.01 mol·kg−1 protocatechuic acid. E



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Table 6. Distribution Coefficient, KD, Extraction Efficiency, η, Loading Ratio, Z, and Equilibrium Complexation Constant, KE, Values for the Chemical Equilibrium of Protocatechuic Acid with Di-(2-ethylhexyl)phosphoric Acid in Petroleum Ether at 101.325 kPa and 298 ± 1 Ka,b mD2EHPA,0org (mol·kg−1)c

mPCA,0 (mol·kg−1)d

mPCA,aq mol·kg−1)e

mPCA,org (mol·kg−1f

KD

avg KD

η%

avg η%

Z

KE

0.3445

0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01

0.0009 0.0028 0.0043 0.0060 0.0084 0.0009 0.0026 0.0042 0.0058 0.0081 0.0009 0.0025 0.0040 0.0055 0.0078 0.0008 0.0024 0.0039 0.0053 0.0075 0.0008 0.0022 0.0035 0.0049 0.0068

0.0001 0.0002 0.0007 0.0010 0.0016 0.0001 0.0004 0.0008 0.0012 0.0019 0.0001 0.0005 0.0010 0.0015 0.0022 0.0002 0.0006 0.0011 0.0017 0.0025 0.0002 0.0008 0.0015 0.0021 0.0033

0.08 0.09 0.15 0.16 0.19 0.12 0.17 0.20 0.21 0.23 0.17 0.22 0.25 0.28 0.29 0.19 0.25 0.28 0.32 0.34 0.24 0.35 0.41 0.43 0.48

0.13

7.30 8.13 13.28 14.01 15.79 11.05 14.67 16.96 17.29 18.58 14.76 18.13 19.88 21.57 22.20 16.26 20.30 22.08 24.39 25.28 19.34 26.03 29.02 30.29 32.50

11.70

0.0002 0.0007 0.0019 0.0028 0.0046 0.0001 0.0006 0.0011 0.0016 0.0024 0.0001 0.0004 0.0007 0.0011 0.0017 0.0001 0.0003 0.0005 0.0008 0.0012 0.0001 0.0003 0.0005 0.0007 0.0010

0.4947

0.7752

1.3291

2.0674

3.1010

0.19

0.24

0.28

0.38

15.71

19.31

21.66

27.44

0.2793

0.2059

0.1553

0.145

Standard uncertainties, u, are u(T) = 1 K, u(p) = 1 kPa, u(mPD2EHPA,0) = 0.001 mol·kg−1, u(mPCA,0) = 0.001 mol·kg−1, u(mPCA,aq) = 0.001 mol·kg−1, and u(mPCA,org) = 0.001 mol·kg−1. bSolvent: di-(2-ethylhexyl)phosphoric acid + petroleum ether. cmD2EHPA,0org, initial molality of D2EHPA in the organic phase. dmPCA,0, initial molality of the protocatechuic acid in the aqueous phase. emPCA,aq, equilibrium molality of the protocatechuic acid in the aqueous phase. fmPCA,org, equilibrium molality of the protocatechuic acid in the organic phase.

a

Figure 3. Equilibrium isotherms for reactive extraction of PCA (0.001−0.01 mol·kg−1) with D2EHPA (0.3445−3.101 mol·kg−1) in toluene.

Figure 2. Equilibrium isotherms for reactive extraction of PCA (0.001−0.01 mol·kg−1) with D2EHPA (0.3445−3.101 mol·kg−1) in IBA at 298 K.

D2EHPA (0.3445−3.101 mol·kg−1) dissolved in diluents are shown in Figures 8 and 9. It was found that the percentage extraction depends significantly on the concentration of D2EHPA; increasing the D2EHPA concentration in the organic phase increases the equilibrium concentration of the acid in the organic phase and, hence, gives the higher distribution. Higher KD values were obtained under higher D2EHPA concentrations, which can be associated with the movement of the extraction equilibrium toward the direction of formation of the complexes. Similar trends were observed for reactive extraction of L-valine using D2EHPA,49 pantothenic acid using D2EHPA,52 and nicotinic acid using D2EHPA.62 The tendency continued with the increase in extractant

3.5. Effect of Extractant Concentration. D2EHPA concentration has an important effect on the KD values for the reactive extraction of PCA, as shown in Figure 7. The maximum removal of PCA is 80.11% with D2EHPA (3.101 mol·kg−1) + IBA, 40.25% with D2EHPA (3.101 mol·kg−1) + toluene, and 32.5% with D2EHPA (3.101 mol·kg−1) + petroleum ether at 0.01 mol·kg−1 of the PCA initial concentration. The average distribution coefficients were acquired as 1.62−3.18, 0.22−0.52, and 0.13−0.38 with D2EHPA at 0.3445−3.101 mol·kg−1 in IBA, toluene, and petroleum ether, respectively. Plots between the average percentage extraction efficiency and average KD against F



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Figure 4. Equilibrium isotherms for reactive extraction of PCA (0.001−0.01 mol·kg−1) with D2EHPA (0.3445−3.101 mol·kg−1) in petroleum ether at 298 K.

Figure 5. Effect of the initial acid concentration (0.001−0.01 mol· kg−1) on efficiency (%) for reactive extraction of PCA using D2EHPA (3.101 mol·kg−1) in different diluents (IBA, toluene, and petroleum ether) at 298 K.

Figure 7. Variation of KD with D2EHPA (mol·kg−1) concentrations for initial concentration of PCA (0.001−0.01 mol·kg−1) in (a) IBA, (b) toluene, and (c) petroleum ether.

Figure 6. Effect of the initial acid concentration (0.001−0.01 mol· kg−1) on KD for reactive extraction of PCA using D2EHPA (3.101 mol·kg−1) in different diluents (IBA, toluene, and petroleum ether) at 298 K.

concentration, and the highest KD values were obtained as 4.03 (IBA), 0.67 (toluene), and 0.48 (petroleum ether) with the highest D2EHPA concentration (3.101 mol·kg−1) studied. Generally, in the reactive extraction method, the association and dissolving capacity of the complex formed increases with an increase in the extractant concentration. The results suggested PCA could be effectively extracted with a high concentration of D2EHPA,66 which helps the extraction complex to dissolve easily in the organic phase. However, some factors, i.e., the density, viscosity, surface properties, and loading capacity of the organic phase, should also be considered. 3.6. Loading Factor and Complex Formation. Reactive extraction represents a reaction between the acid (solute) and extractant molecule at the interface of the aqueous and organic phase, where transfers of acid molecules take place by the

Figure 8. Effect of D2EHPA concentration (0.3445−3.101 mol·kg−1) on the average extraction efficiency (η%) for reactive extraction of PCA in different diluents (IBA, toluene, and petroleum ether) at 298 K.

diffusion and solubilization mechanism. The extraction of PCA by using D2EHPA dissolved in diluents at equilibrium can be described by the theory of Mass Action Law. In the Mass Action Law model, activities of the aqueous and organic phase species are assumed to be proportional to the respective concentration of the species, and the equilibrium constant takes G



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Figure 10 shows the plot of Z/(1 − Z) versus mPCA,aq for the extraction of PCA using D2EHPA in different diluents. A linear

Figure 9. Effect of D2EHPA concentration (0.3445−3.101 mol·kg−1) on the average distribution coefficient (KD) for reactive extraction of PCA in different diluents (IBA, toluene, and petroleum ether) at 298 K. Figure 10. Plot of Z/(1 − Z) versus [CPCA]aq (mol·kg−1) for estimation of the 1:1 PCA−D2EHPA equilibrium complexation constant (KE) for [CD2EHPA] = 3.101 (mol·kg−1) in diluents (IBA, toluene, and petroleum ether) at 298 K.

care of the constant of proportionality or the non-idealities associated with the reactive system. In reactive extraction, the reaction between D2EHPA and PCA resulting in the complex formation in the organic phase can be expressed as KE

mPCA + mD2EHPA ↔ mPCA mD2EHPA

relationship was obtained with an intercept of zero, and the slope of the straight line represents the equilibrium complexation constant, KE. KE for the 1:1 complex of PCA and D2EHPA at 298 K for the extraction of acid in the entire concentration ranges of D2EHPA (0.3445−3.101 mol·kg−1) and acid (0.001−0.0001 mol·kg−1) is given in Tables 4−6. The values of KE for PCA in different diluents with D2EHPA follos the order IBA (5.5661−1.1794) > toluene (0.8205−0.2003) > petroleum ether (0.4947−0.145). The higher loading ratios were obtained at 0.3445 mol·kg−1 of D2EHPA in all the diluents, and therefore higher loading may be expected at higher acid concentrations, that is, at lower pH values. For PCA, the IBA system showed values of KE higher than those of the toluene and petroleum ether systems, indicating that IBA has a greater ability to solvate the complex than the other solvents. 3.7. Calculation of the Minimum S/F, Number of Stages. For analyzing the feasibility of the extraction process of PCA using D2EHPA, the minimal S/F ratio required for the recovery of PCA and the minimal number of stages required for counter-current extraction were determined.

(6)

where KE is the extraction equilibrium complexation constant, and it can be expressed using the law of mass action as KE = [mPCA mD2EHPA ]org /[mPCA ]aq [mD2EHPA ]org

(7)

where mPCA and mD2EHPA are the concentrations of PCA and D2EHPA, respectively. The subscripts aq and org represent the concentration in the aqueous and organic phase, respectively. The degree of extraction is defined as the ratio of the acid concentration in the extracted phase to the initial acid concentration in aqueous solution by assuming no change in volume at equilibrium. The extent to which the organic phase (extractant and diluents) may be loaded with acid is expressed by the loading ratio, Z (ratio of the total acid concentration in the organic phase to the total D2EHPA concentration) mPCA,org z= mD2EHPA,0 org (8)

x − xout ⎛S⎞ ⎜ ⎟ = in ⎝ F ⎠min KDx in − yin

where mD2EHPA,0org is the initial concentration of D2EHPA in the organic phase. If the organic phase is not highly concentrated by acid, i.e., at very low loading ratios (Z < 0.5), the 1:1 complex of acid and D2EHPA is formed. A plot of Z/(1 − Z) versus mPCA,aq yields a straight line with a slope of the complexation constant (KE)

(10)

where xin and xout are the concentrations in the feed and the raffinate, respectively, and yin is the initial PCA concentration in the extract phase. In the developed model, (S/F)min depends on the initial concentration of acid, and as a rule of thumb for an extraction process with a finite number of extraction stages, (S/ F)act corresponds to 1.5 times the minimum S/F ratio.68 The number of theoretical stages (NTS) for a counter-current extraction process was found using the modified Kremser equation with the extraction factor, Ex, as

Z = KEmPCA,aq (9) 1−Z The loading factor values were in the range of 0.0015− 0.0198, 0.0003−0.007, and 0.0002−0.0046 with IBA, toluene, and petroleum ether, respectively (at 0.3445 mol·kg −1 D2EHPA). It was observed that the loading ratio decreases with an increase in the D2EHPA concentration for all concentrations of PCA in different diluents, and higher loadings were obtained at a lower concentration of D2EHPA and a higher PCA concentration. The stoichiometry of the overall extraction reaction is based on the loading ratio in the organic phase. It was observed that Z < 0.5 for all concentrations of D2EHPA and PCA, which indicates no overloading and formation of only the 1:1 complex of PCA.

NTS =

⎡⎛ x − y / K ⎞ ln⎢⎜ x in − yin / KD ⎟(1 − 1/Ex ) + ⎣⎝ out in D ⎠ ln Ex

1⎤ Ex ⎥ ⎦

(11)

S (12) F In this study, the maximum distribution and the recovery of the acid were obtained by using 3.101 mol·kg−1 D2EHPA in diluents at a temperature of 298 K, and these values were used Ex = KD

H



Article

Table 7. Minimum Solvent-to-Feed (S/F) Ratio and Number of Theoretical Stages (NTS) for the Recovery of Protocatechuic Acida diluent IBA

toluene

petroleum ether

a

xin

xout

KD

(S/F)min

(S/F)act

EX

NTS

0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01 0.001 0.003 0.005 0.007 0.01

0.0003 0.0008 0.0012 0.0015 0.0020 0.0008 0.0020 0.0032 0.0044 0.0060 0.0008 0.0022 0.0035 0.0049 0.0068

2.3400 2.8036 3.1501 3.5957 4.0277 0.3045 0.4748 0.5533 0.5989 0.6736 0.2398 0.3520 0.4088 0.4344 0.4815

0.2994 0.2629 0.2410 0.2176 0.1989 0.7666 0.6781 0.6438 0.6254 0.5975 0.8066 0.7397 0.7098 0.6971 0.6750

0.4491 0.3944 0.3614 0.3264 0.2984 1.1499 1.0171 0.9567 0.9381 0.8963 1.2099 1.1095 1.0647 1.0457 1.0125

1.0509 1.1056 1.1386 1.1736 1.2017 0.3501 0.4829 0.5343 0.5619 0.6038 0.2901 0.3905 0.4353 0.4543 0.4875

2.1625 2.3634 2.5008 2.6643 2.8108 0.7935 0.9755 1.0502 1.0916 1.1566 0.7141 0.8476 0.9088 0.9351 0.9821

Standard uncertainties, u, are u(xout) = 0.001 mol·kg−1. ship of phenolic acids and derivatives. Protocatechuic acid alkyl esters. J. Agric. Food Chem. 2010, 58, 6986−6993. (2) Kay, C. D.; Mazza, G. J.; Holub, B. J. Anthocyanins exist in the circulation primarily as metabolites in adult men. J. Nutr. 2005, 135, 2582−2588. (3) Vitaglione, P.; Donnarumma, G.; Napolitano, A.; Galvano, F.; Gallo, A.; Scalfi, L.; Fogliano, V. Protocatechuic acid is the major human metabolite of cyanidin-glucosides. J. Nutr. 2007, 137, 2043− 2048. (4) Semaming, Y.; Pannengpetch, P.; Chattipakorn, S. C.; Chattipakorn, N. Pharmacological Properties of Protocatechuic Acid and Its Potential Roles as Complementary Medicine. Evid Based Complement Alternat Med. 2015, 2015, 1−11. (5) Tseng, T. H.; Hsu, J. D.; Lo, M. H.; Chu, C. Y.; Chou, F. P.; Huang, C. L.; Wang, C. J. Inhibitory effect of hibiscus protocatechuic acid on tumor promotion in mouse skin. Cancer Lett. 1998, 126, 199− 207. (6) Ali, B. H.; Al Wabel, N.; Blunden, G. Phytochemical, pharmacological and toxicological aspects of Hibiscus sabdariffa L.: a review. Phytother. Res. 2005, 19, 369−375. (7) Ellnain-Wojtaszek, M. Phenolic acids from Ginkgo biloba L. Part II. Quantitative analysis of free and liberated by hydrolysis phenolic acids. Acta Polym. Pharm. 1997, 54, 229−232. (8) Li, X.; Wang, X.; Chen, D.; Chen, S. Antioxidant Activity and Mechanism of Protocatechuic Acid in vitro. Funct. food health dis. 2011, 7, 232−244. (9) Kakkar, S.; Bais, S. A review on protocatechuic acid and its pharmacological potential. ISRN Pharmacol 2014, 2014, 1. (10) Masella, R.; Santangelo, C.; D’Archivio, M.; LiVolti, G.; Giovannini, C.; Galvano, F. Protocatechuic acid and human disease prevention: biological activities and molecular mechanisms. Curr. Med. Chem. 2012, 19, 2901−2917. (11) Sun, J. J.; Zhou, D. M.; Fang, H. Q.; Chen, H. Y. The electrochemical copolymerization of 3,4-dihydroxybenzoic acid and aniline at microdisk gold electrode and its amperometric determination for ascorbic acid. Talanta 1998, 45, 851−856. (12) Wilson, M. K.; Abergel, R. J.; Raymond, K. N.; Arceneaux, J. E.; Byers, B. R. Siderophores of Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis. Biochem. Biophys. Res. Commun. 2006, 348, 320−325. (13) Garner, B. L.; Arceneaux, J. E. L.; Byers, B. R. Temperature control of a 3,4-dihydroxybenzoate (protocatechuate)-based siderophore in Bacillus anthracis. Curr. Microbiol. 2004, 49, 89−94. (14) Williams, K. M.; Martin, W. E.; Smith, J.; Williams, B. S.; Garner, B. L. Production of protocatechuic acid in Bacillus thuringiensis ATCC33679. Int. J. Mol. Sci. 2012, 13, 3765−3772.

to calculate the minimum S/F ratio and NTS. The values of NTS showed that at maximum, approximately 3 theoretical stages would be sufficient to achieve the desired extraction efficiency of PCA in a continuous extraction column. The values of S/F and NTS are given in Table 7 for each of the diluents for the concentration of extractant, which yields the maximum value of KD.

4. CONCLUSION The equilibrium study on the reactive extraction of PCA using D2EHPA in diluents, IBA, toluene, and petroleum ether, was performed. The results of reactive extraction are presented in terms of various physical and chemical extraction equilibrium parameters. A loading factor of less than 0.5 was observed, implying the formation of only the 1:1 PCA−D2EHPA complex in IBA, toluene, and petroleum ether. Significant improvement in extraction of PCA was observed by reactive extraction using D2EHPA. The isobutyl acetate was found to be the most effective solvent with a maximum distribution value of 4.03. Almost more than 80% of the extraction was observed with D2EHPA in diluent IBA. The highest KE value was obtained for D2EHPA in IBA and was in the range of 5.56− 1.17. The KD, E%, and KE values obtained were in the order of IBA > toluene > petroleum ether. The overall equilibrium complexation constants (KE) for the reactive extraction of PCA in D2EHPA were estimated. The number of theoretical stages (NTS) for counter-current extraction was found to be 3 using the modified Kremser equation.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: k_wasewar@rediffmail.com; Tel.: +91-712-2801561; Fax: +91-712-2223969. ORCID

Kailas Wasewar: 0000-0001-7453-6308 Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Reis, B.; Martins, M.; Barreto, B.; Milhazes, N.; Garrido, E. M.; Silva, P.l.; Garrido, J.; Borges, F. Structure-property-activity relationI



Article

(15) Okai, N.; Miyoshi, T.; Takeshima, Y.; Kuwahara, H.; Ogino, C.; Kondo, A. Production of protocatechuic acid by Corynebacterium glutamicum expressing chorismate-pyruvate lyase from Escherichia coli. Appl. Microbiol. Biotechnol. 2016, 100, 135−145. (16) Hong, Y. K.; Hong, W. H.; Han, D. H. Application of Reactive Extraction to Recovery of Carboxylic Acids. Biotechnol. Bioprocess Eng. 2001, 6, 386−394. (17) Tung, L. A.; King, C. J. Sorption and extraction of lactic and succinic acids at pH > pKa1. 1. Factors Governing Equilibria. Ind. Eng. Chem. Res. 1994, 33, 3217−3223. (18) Lee, E. G.; Moon, S. H.; Chang, Y. K.; Yoo, I.-K.; Chang, H. N. Lactic acid recovery using two-stage electrodialysis and its modelling. J. Membr. Sci. 1998, 145, 53−66. (19) Kim, Y. H.; Moon, S. H. Lactic acid recovery from fermentation broth using one-stage electrodialysis. J. Chem. Technol. Biotechnol. 2001, 76, 169−178. (20) Sarma, J.; Mahiuddin, S. Specific ion effect on the point of zero charge of α-alumina and on the adsorption of 3, 4-dihydroxybenzoic acid onto α-alumina surface. Colloids Surf., A 2014, 457, 419−424. (21) Buchan, A.; Collier, L. S.; Neidle, E. L.; Moran, M. A. Key aromatic-ring cleaving enzyme, protocatechuate 3,4-dioxygenase, in the ecologically important marine Roseobacter lineage. Appl. Environ. Microbiol. 2000, 66, 4662−4672. (22) Galanakis, C. M.; Tornberg, E.; Gekas, V. Clarification of highadded value products from olive mill wastewater. J. Food Eng. 2010, 99, 190−197. (23) Benitez, F. J.; Beltran-Heredia, J.; Acero, J. L.; Gonzalez, T. Degradation of protocatechuic acid by two advanced oxidation processes: Ozone/UV radiation and H2O2/UV radiation. Water Res. 1996, 30, 1597−1604. (24) Wennersten, R. Extraction of carboxylic acid from fermentation broth in using solution of tertiary amine. J. Chem. Technol. Biotechnol., Biotechnol. 1983, 33, 85−94. (25) Hartl, J.; Marr, R. Extraction processes for bioproduct separation. Sep. Sci. Technol. 1993, 28, 805−819. (26) Cascaval, D.; Galaction, A. I. New separation techniques on bioseparations 1. Reactive extraction. Hem. Ind. 2004, 58, 375−386. (27) Athankar, K. K.; Wasewar, K. L.; Varma, M. N.; Shende, D. Z. Separation of phenylacetic acid using tri-n-butyl phosphate in hexanol: Equilibrium and kinetics. Sep. Sci. Technol. 2017, 52, 2696−2703. (28) Athankar, K. K.; Varma, M. N.; Shende, D. Z.; Yoo, C. K.; Wasewar, K. L. Reactive Extraction of Phenylacetic Acid with Tri-nbutyl Phosphate in Benzene, Hexanol, and Rice Bran Oil at 298 K. J. Chem. Eng. Data 2013, 58, 3240−3248. (29) Athankar, K. K.; Wasewar, K. L.; Varma, M. N.; Shende, D. Z.; Uslu, H. Extractive Separation of Benzylformic Acid with Phosphoric Acid Tributyl Ester in CCl4, Decanol, Kerosene, Toluene, and Xyleneat 298 K. J. Chem. Eng. Data 2015, 60, 1014−1022. (30) Sharma, H.; Singh, K.; Wasewar, K. L.; Athankar, K. L. L(+)tartaric Acid Separations Using Aliquat 336 in n-Heptane, Kerosene, and 1-Octanol at 300 ± 1 K. J. Chem. Eng. Data 2017, 62, 4047−4063. (31) Rewatkar, K.; Shende, D. Z.; Wasewar, K. L. Reactive Separation of Gallic Acid: Experimentation and Optimization Using Response Surface Methodology and Artificial Neural Network. Chem. Biochem. Eng. Q. 2017, 31, 33−46. (32) Athankar, K. K.; Wasewar, K. L.; Varma, M. N.; Shende, D. Z. Reactive extraction of gallic acid with tri-n-caprylylamine. New J. Chem. 2016, 40, 2413−2417. (33) Rewatkar, K.; Shende, D. Z.; Wasewar, K. L. Effect of Temperature on Reactive Extraction of Gallic Acid Using Tri-n-butyl Phosphate, Tri-n-octylamine and Aliquat 336. J. Chem. Eng. Data 2016, 61, 3217−3224. (34) Waghmare, M. D.; Wasewar, K. L.; Sonawane, S. S.; Shende, D. Z. Reactive Extraction of Picolinic Acid and Nicotinic Acid by NaturalNon-Toxic Solvent. Sep. Purif. Technol. 2013, 120, 296−303. (35) Datta, D.; Kumar, S.; Wasewar, K. L. Reactive Extraction of Benzoic Acid and Pyridine −3-Carboxylic Acid using Organophosphoric and Aminic Extractant Dissolved in Binary Diluent Mixtures. J. Chem. Eng. Data 2011, 56, 3367−3375.

(36) Wasewar, K. L.; Shende, D. Z. Equilibrium for the Reactive Extraction of Caproic Acid Using Tri-n-Butyl Phosphate in MethylIsobutyl Ketone and Xylene. J. Chem. Eng. Data 2011, 56, 3318−3322. (37) Wasewar, K. L.; Shende, D. Z. Reactive Extraction of Caproic Acid Using Tri-n-Butyl Phosphate in Hexanol, Octanol, and Decanol. J. Chem. Eng. Data 2011, 56, 288−297. (38) Wasewar, K. L.; Shende, D. Z. Extraction of Caproic Acid Using Tri-n-Butyl Phosphate in Benzene and Toluene at 301 K. J. Chem. Eng. Data 2010, 55, 4121−4125. (39) Wasewar, K. L.; Shende, D. Z.; Keshav, A. Reactive Extraction of itaconic acid using Aliquat 336 in various diluents. Ind. Eng. Chem. Res. 2011, 50, 1003−1011. (40) Keshav, A.; Wasewar, K. L.; Chand, S. Reactive Extraction of Propionic Acid Using Tri-n-Octylamine. Chem. Eng. Commun. 2009, 197, 606−626. (41) Keshav, A.; Chand, S.; Wasewar, K. L. Equilibrium Studies for Extraction of Propionic Acid Using Tri-n-Butyl Phosphate in DifferentSolvents. J. Chem. Eng. Data 2008, 53, 1424−1430. (42) Keshav, A.; Wasewar, K. L. Back Extraction of propionic acid from loaded organic phase. Chem. Eng. Sci. 2010, 65, 2751−2757. (43) Keshav, A.; Wasewar, K. L.; Chand, S. Reactive extraction of acrylic acid using Tri-n-Butyl Phosphate in DifferentSolvents. J. Chem. Eng. Data 2009, 54, 1782−1786. (44) Sharma, H.; Singh, K.; Wasewar, K. L.; Athankar, K. K. L(+)tartaric Acid Separations Using Aliquat 336 in n-Heptane,Kerosene, and 1-Octanol at 300 ± 1 K. J. Chem. Eng. Data 2017, 62, 4047−4063. (45) Uslu, H.; Kirbaslar, S. I.; Wasewar, K. L. Reactive Extraction of Levulinic Acid by Amberlite LA-2 Extractant. J. Chem. Eng. Data 2009, 54, 712−718. (46) Wasewar, K. L.; Heesink, A. B. M.; Versteeg, G. F.; Pangarkar, V. G. Equilibria and Kinetics for Back Extraction of Lactic Acid using Trimethylamine. Chem. Eng. Sci. 2004, 59, 2315−2320. (47) Koekemoer, L. R.; Badenhorst, M. J. G.; Everson, R. C. Determination of Viscosity and Density of Di-(2-ethylhexyl) Phosphoric Acid + Aliphatic Kerosene. J. Chem. Eng. Data 2005, 50, 587−590. (48) Kochetkov, K. A.; Belikov, V. M. Russ. Chem. Rev. 1987, 56, 1045. (49) Bai, H.; Guo, K.; Chen, X.; Chang, Z.; Li, D. Reactive extraction of L-valine with di(2-ethylhexyl)phosphate acid. J. Chem. Technol. Biotechnol. 2016, 91, 3096−3102. (50) Gadgil, O. D.; Dalvi, V. H.; Shenoy, K. T.; Rao, H.; Ghosh, S. K.; Joshi, J. B. Kinetics of extraction of uranium from phosphoric acid by D2EHPA−TBP and D2EHPA−TOPO systems using constant interfacial area stirred cell. Chem. Eng. Sci. 2014, 110, 169−184. (51) Poştaru, M.; Kloetzer, L.; Galaction, A. I.; Blaga, A. C.; Caşcaval, D. Comparative study on rosmarinic acid separation by reactive extraction with Amberlite LA-2 and D2EHPA 2. kinetics of the interfacial reactions. Environ. Engineer. Manag. J. 2014, 13, 1473−1482. (52) Poştaru, M.; Bompa, A. S.; Galaction, A. I.; Blaga, A. C.; Caşcaval, D. Comparative Study on Pantothenic Acid Separation by Reactive Extraction with Tri-n-octylamine and Di-(2-ethylhexyl) Phosphoric Acid. Chem. Biochem. Eng. Q. 2016, 30, 81−92. (53) Caşcaval, D.; Blaga, A. C.; Cămăruţ, M.; Galaction, A. I. Comparative Study on Reactive Extraction of Nicotinic Acid with Amberlite LA-2 and D2EHPA. Sep. Sci. Technol. 2007, 42, 389−401. (54) Hu, G.; Chen, D.; Wang, L.; Liu, J. C.; Zhao, H.; Liu, Y.; Qi, T.; Zhang, C.; Yu, P. Extraction of vanadium from chloride solution with high concentration of iron by solvent extraction using D2EHPA. Sep. Purif. Technol. 2014, 125, 59−65. (55) Fortes, M. C. B.; Martins, A. H.; Benedetto, J. S. Indium recovery from acidic aqueous solutions by solvent extraction with D2EHPA: a statistical approach to the experimental design. Braz. J. Chem. Eng. 2003, 20, 121−128. (56) Morais, C. A.; Mansur, M. B. Solvent extraction of gadolinium (III) from hydrochloric acid solutions with cationic extractants D2EHPA and Ionquest 801. Trans. Inst. Min. Metall., Sect. C 2014, 123, 61−66. J



Article

(57) Gharabaghi, M.; Irannajad, M.; Azadmehr, A. R. Separation of nickel and zinc ions in a synthetic acidic solution by solvent extraction using d2ehpa and cyanex 272. Physicochem. Probl. Miner. Process. 2013, 49, 233−242. (58) Cui, J. H.; Li, D. L. Reactive Extraction of o-Aminophenol with Di(2-ethylhexyl)phosphoric Acid in Different Diluents. J. Chem. Eng. Data 2007, 52, 671−675. (59) Guimares, A. S.; Mansur, M. B. Selective solvent extraction of calcium and magnesium from concentrate nickel solution using mixtures of cyanex 272 and D2EHPA. International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering 2016, 10, 515−518. (60) Singh, R. K.; Dhadke, P. M. Extraction and separation studies of zinc(II) and copper(II) with D2EHPA and PC-88A from perchlorate media. J. Serb. Chem. Soc. 2002, 67, 41−51. (61) Zhu, X.; Chai, W.; Liu, W.; Zhang, W.; Zhou, Z.; Ren, Z. Extraction of ammonia fromsolutions with D2EHPA in three diluents: extraction equilibria and modelling. J. Chem. Technol. Biotechnol. 2017, 92, 133−139. (62) Caşcaval, D.; Blaga, A. C.; Cămăruţ, M.; Galaction, A. I. Comparative Study on Reactive Extraction of Nicotinic Acid with Amberlite LA-2 and D2EHPA. Sep. Sci. Technol. 2007, 42, 389−401. (63) Kojima, T.; Fukutomi, H. Extraction Equilibria of Hydrochloric Acid by Trioctylamine in Low-Polar Organic Solvents. Bull. Chem. Soc. Jpn. 1987, 60, 1309−1320. (64) Kumar, S.; Uslu, H.; Datta, D.; Rarotra, S.; Rajput, K. Investigation of Extraction of 4 Oxopentanoic Acid by N,N Dioctyloctan-1-amine in Six Different Diluents: Equilibrium Study. J. Chem. Eng. Data 2015, 60, 1447−1453. (65) Athankar, K. K.; Varma, M. N.; Shende, D. Z.; Yoo, C. K.; Wasewar, K. L. Reactive Extraction of Phenylacetic Acid with Tri n butyl Phosphate in Benzene, Hexanol, and Rice Bran Oil at 298 K. J. Chem. Eng. Data 2013, 58, 3240−3248. (66) Kertes, A. S.; King, C. J. Extraction chemistry of Fermentation Product Carboxylic Acids. Biotechnol. Bioeng. 1986, 28, 269−282. (67) Athankar, K. K.; Wasewar, K. L.; Varma, M. N.; Shende, D. Z. Reactive Separation of Benzeneacetic Acid with Tri−n−caprylyl Amine: Equilibrium and Modeling. J. Chem. Eng. Data 2016, 61, 2335−2345. (68) King, C. J. Separation Processes, 2nd ed.; McGraw-Hill: NewYork, 1980.

K


Separation of Protocatechuic Acid Using Di-(2-ethylhexyl)phosphoric

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