Reactive Extraction of Gallic Acid Using Aminic and Phosphoric

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Reactive Extraction of Gallic Acid using Aminic and Phosphoric Extractants Dissolved in Different Diluents: Effect of Solvent’s Polarity and Column Design SHITANSHU PANDEY, and Sushil Kumar Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b05110 • Publication Date (Web): 03 Feb 2018 Downloaded from http://pubs.acs.org on February 4, 2018

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Industrial & Engineering Chemistry Research

Reactive Extraction of Gallic Acid using Aminic and Phosphoric Extractants Dissolved in Different Diluents: Effect of Solvent’s Polarity and Column Design Shitanshu Pandey♦, Sushil Kumar♦*

♦

Department of Chemical Engineering, Motilal Nehru National Institute of Technology (MNNIT) Allahabad – 211 004 (UP) India. *

Corresponding Author

Email: [email protected]

ABSTRACT The current study is focused on the reactive extraction of gallic acid from aqueous solution using tri-n-octylamine (TOA) and tri-n-butyl phosphate (TBP) as extractants dissolved in four different diluents (4-methylpentan-2-one, kerosene, octane-1-ol and decane) at 298 ±1 K and 101.325 ±1 kPa. A mathematical model for mass action law is used for estimation of equilibrium parameters and stoichiometric coefficients. The extraction results were interpreted as distribution coefficient (KD) and degree of extraction (E). The solvent’s ability to extract acid is observed as MIBK > 1 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

octane-1-ol > n-decane > kerosene and MIBK > n-decane ≥ kerosene > octane-1-ol with TOA and TBP, respectively. On basis of extraction capabilities, TOA with active diluents and TBP with inactive diluents are found suitable for recovery of gallic acid from aqueous solution/ fermentation broth. The feasibility of the extraction process for a counter current reactive liquid extraction column is assessed by calculating design parameters of rotating disc contactor (RDC) such as column diameter (DT), number of theoretical stages (NTS), height equivalent to theoretical stage (HETS ) and height of extraction column (H) for recovery of gallic acid. Keywords: Gallic Acid, Reactive Extraction, Equilibria, Column Design, Solvent Polarity.

1. INTRODUCTION 3, 4, 5-trihydroxy benzoic acid (Figure 1) also called Gallic acid, is a chemical with industrial importance and widely used in food, pharmaceutical, pigment and cosmetic industries. Its antioxidant, anti-fungal, anti-inflammatory and antiviral abilities attract a considerable interest of researchers in view of its recovery from industrial downstream processes. Gallic acid is usually present in plants and beverages such as oak bark, walnuts, apples, blueberries, olive, tea, wine etc1-3. Gallic acid is commercially produced by microbial fermentation4-7 as well as extraction from tea processing and olive processing mill wastewater8,9 . It is found found in its natural sources from under detectable level to 8.87 mg/ml.9,10

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Figure 1. Molecular structure of 3, 4, 5-trihydroxy benzoic acid (Gallic acid) Gallic acid production has been reported from myrabolan, tara, sumac and Chinese tannins. Removal of gallic acid from the industrial waste streams and fermentation broth is an economical issue. Extensive literature is available on the reactive extraction of different carboxylic acids from aqueous streams but limited studies on the gallic acid recovery have done. Nowadays, liquid–liquid extraction is a separation technique to isolate and concentrate valuable components from an aqueous solution by using organic solvents11-14. In the intensification of this process reactive liquid extraction is often applied to enhance the separation efficiency. Reactive extraction finds its application in separation, purification or enrichment of the product in the mining industries, environmental applications, recovery of organic & inorganic acids, organic chemical intermediates and pharmaceuticals15. The reactive extraction has potential to recover organic acids from their dilute aqueous medium or fermentation broth16-19. This method has been known for the advantages like effective separation, regeneration of solvent, pH control, better recovery of solute with high product purity and decrease in recovery cost20-22. In the reactive extraction, the extractant molecule reacts with the solute molecule and formed solute-extractant complex in the organic phase which makes it different from the traditional extraction process. Extractants are generally viscous organic liquids, thus improvement in their physical properties like interfacial surface area, surface tension and viscosity is needed. Diluents play a vital role to achieve these appropriate properties and also provide a higher solubility of extractants by specific solvation in which acid:extractant complexes are formed23. Often polar diluents are more favorable than non-polar or low polarity diluents. Reactive extraction depends on the interactions between extractant and acid, diluent and acid, and diluent & extractant. The solvation of the whole extractant-acid complex is based on dipole-dipole interaction and has 3 ACS Paragon Plus Environment


been found to play an important role in the neutralization reaction between acid and extractant, which is promoted by increasing the polarity of the diluent24-26. Long chain aliphatic amines (trin-octylamine, tri-dodecylamine, amberlite LA-2 etc.) and organophosphoric solvents (tri-n-butyl phosphate, trioctyl phosphine oxide, etc.) are proposed as appropriate extractants for the reactive extraction of organic acids27-30. These extractants are generally used with polar/ non-polar diluents which have the major effect on the extent of extraction. The most efficient diluents are used in the extraction due to their best solvation property for the acid-extractant complexes formed31,32. Solvent polarity is one of the most important characteristics in solvating an acidextractant complex during the extraction. Solvent extraction columns are widely used in chemical, petrochemical, hydrometallurgical and nuclear processes. The main apparatus used for solvent extraction is mixer-settler or mixersettler cascades but the main disadvantages are their large footprint, which is mainly determined by the settling zone and multiple pumps and piping requirements. By comparison, solvent extraction columns provide a high number of theoretical stages at high throughputs, requiring only a small footprint and low capital costs. Despite their advantages, solvent extraction columns are not widely employed due to their sophisticated layout and scale-up. Uncertainties mainly arise from the complex interactions of the liquid phases such as back and forward mixing and a changing droplet size distribution by coalescence and breakage. These phenomena finally have an impact on the operation limits and the efficiency of the column. Hence, in the field of solvent extraction design, a scale-up from mini-plant columns to industrially sized columns has become an important feature. For the improved and reliable design of solvent extraction columns, standardized lab-scale cells are developed that allow monitoring of single droplet behavior.


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Mini-plant column experiments could capture pilot-scale effects, especially during long duration runs33,34. The objective of the present study is to analyze the effect of two extractants [tri-n-octylamine (TOA), an amine based extractant and a phosphorus bonded oxygen donor extractant, tri-n-butyl phosphate (TBP)] dissolved in four different categories of organic solvents (ketone, alcohol, aliphatic and aromatic hydrocarbon) and to produce the reactive extraction data at equilibrium for the process intensification of gallic acid recovery from fermentation broth and process wastewater. The diluents/ solvents like 4-methylpentan-2-one (MIBK), kerosene, octan-1-ol and decane are used with reactive or chemical extraction to investigate their solvation ability and to improve the extractive efficiency of TBP and TOA. Also, the effects of diluent polarity, initial acid concentration, and composition of extractants on the distribution of acid are deliberated. Mass action law is applied to derive an equilibrium model, and this model is used to determine the equilibrium extraction constants (KE) and stoichiometry of reaction (the number of extractant molecules per acid molecule, n). Also, an approach is made to design extraction column for present study on the reactive extraction of gallic acid.

2. EXPERIMENTAL WORK 2.1. Materials and Method The chemicals used for the experimental process are listed in Table 1 with their physical properties. All the chemicals were used without any further purification. Aqueous solutions (0.0029 kmol.m-3 to 0.0588 kmol.m-3) were prepared from stock solution of gallic acid (0.0588 kmol.m-3) by serial dilutions with Milli-Q deionized water. The different organic solutions for 5 ACS Paragon Plus Environment


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extraction of gallic acid from aqueous solutions ,were prepared by dissolving TOA in the range of 0.2287–0.9151 kmol.m-3 and TBP in the range of 0.3652– 1.4609 kmol.m-3 with four different diluents/ solvents i.e. methylisobutyl ketone (MIBK, dipole moment µ = 2.69 D, dielectric constant ε = 13.1), kerosene (dipole moment µ = 0.06 D, dielectric constant ε = 1.8), 1-octanol (dipole moment µ = 1.68 D, dielectric constant ε = 10.3) and n-decane (dipole moment µ = 0.07 D, dielectric constant ε = 1.95). Equal volume (20 mL) of each phase (i.e. aqueous solutions and organic solutions) was taken in the conical flask of 100 mL and shaken at 120 ±5 rpm for 6 hours in a temperature controlled reciprocating water shaker bath (Albatech LSB-0305) at a constant temperature of 298 ±1K and pressure 101.325 ±1 kPa, for Equilibrium. After attaining equilibrium, the mixture was kept in a separating funnel of 60 mL for 2 h at 298 ±1K for clear separation of phases. after phase separation, the aqueous solution was analyzed to determine the concentration of gallic acid at equilibrium by UV-vis-spectrophotometer (Shimadzu UV-3600 Plus) at maximum absorption wavelength of gallic acid, λmax= 261nm. This λmax value for gallic acid was determined experimentally by scanning of different dilutions of gallic acid. Water coextraction in the organic phase by extractants/ solvents is found insignificant (0.5% v/v)35. Therefore, the change in the volume of each phase was neglected in the calculation of distribution coefficient and degree of extraction. Table 1. List of chemicals used for the experimental purpose with their physical properties, purchased from and purity Role

Chemical

Solute

Gallic Acid

Extactant

Tri-n-butyl Phosphate

IUPAC Name 3,4,5Trihydroxybenzoic acid Tri-n-Butyl Phosphate

Density Viscosity MW 3 (cP at (kg/kmol) (kg/m ) 298 K) 170.12

1700

-----

266.32

970

3.39


Make SigmaAldrich, USA Alfa Aesar, Great Britain

Purity (%w) ≥98 ≥98

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(TBP)

Extactant

Trioctylamine (TOA)

N,N-Dioctyloctan1-Amine

353.67

810

7.86

Spectrochem Pvt. Ltd., India

≥98

Solvent

Methyl Isobutyl Ketone (MIBK)

4-Methylpentan-2one

100.16

802

0.58

Spectrochem Pvt. Ltd. India

≥99

Solvent

n-Decane

Decane

142.29

730

0.838

Solvent

1-Octanol

Octane-1-ol

130.23

824

7.360

Solvent

Kerosene

---------

170.00

800

1.640

2.2.

Spectrochem Pvt. Ltd. India SRL Pvt. Ltd., India Spectrochem Pvt. Ltd. India

≥99 ≥99 ≥98

Theory

The separation of gallic acid by the extractants dissolved in different diluents, can be presented by an interfacial reaction taking place between m molecules of gallic acid (HGA) and n molecules of extractant (T) to form various acid-extractant complexes. The interaction between acid and extractant with apparent equilibrium constant (KE) is given by Eq. (2).

KE mHGA + nT ←→ ( HGA) m (T ) n

(1)

With an expression of equilibrium constant as follows:

KE =

( HGA) m (T ) n

(2)

n

[HGA]m + [T ]

The distribution coefficient can be determined experimentally by Eq. (3).



KD =

C HGA CHGA

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(3)

̅ Where, HGA and HGA are the total gallic acid concentration in the organic and aqueous phase, respectively. Assuming negligible physical extraction of gallic acid with diluents/ solvents used then the total ̅ amount of acid present in the organic phase (HGA ) will be extracted by the extractant. Therefore, over all distribution coefficient, as shown in Eq. (3), can be represented as Eq. (4).

KD =

C HGA m[( HGA) m (T ) n ] = CHGA CHGA

(4)

Acid also dissociates at equilibrium in the aqueous phase and the reaction is written as Eq. (5) with the dissociation constant (Ka).

HGA ← → H + + GA−

;

Ka =

[ H + ][GA− ] [ HGA]

(5)

The gallic acid concentration in the aqueous phase CHGA is the total concentration of undissociated ([HGA]) and dissociated concentration ([GA–]) of gallic acid and can be expressed by Eq. (6).

 K  CHGA = [ HGA] + [GA− ] = [ HGA] 1 + a+   [H ] 

(6)

Substituting the value of [() ( ) ] from Eq. (2) and CHGA from Eq. (6) in Eq. (4), Eq. (7) is derived.


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 K  K D  1 + a+   [H ]  KE = m −1 mCHGA [T ]n

m

(7)

The free extractant concentration, [

] in the organic phase at equilibrium is represented as:

[T ] = [T ]o − n[( HGA)m (T )n ] = [T ]o − K D

nCHGA m

(8)

Where, [

]o is initial extractant concentration.

The value of [

] from Eq. (8) is substituted in Eq. (7) which results in Eq. (9). n

m −1 nCHGA  CHGA  K D = mK E  [T ]o − K D  m m    Ka  1 + [ H + ]   

(9)

Now, for the estimation of equilibrium constant (KE) and the number of extractant molecules per acid molecule (n), the theoretical equation (9) is to be solved. For dilute solution, an assumption

of [

]o >> n[ () m n ] may be used to find the values of KE and n for m=1. Rearranging Eq. (9)

≈ [ ]

, Eq. (10) is obtained. for m=1 and [ ]

 K  log KD + log 1 + a+  = log K E + n log[T ]o  [H ]  A plot of log D + log 1 +

a

[]

(10)

versus log[

] yielded a straight line with a slope of n and

an intercept of logKE. For same volume ratio of aqueous and organic phases, the degree of extraction (E) is defined by Eq. (11).



E=

KD ×100 1 + KD

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(11)

3. RESULT AND DISCUSSION 3.1.

Effect of Extractant Type

It is obvious from the cited literature for several carboxylic acids that the use of any diluent alone for the recovery purpose was not sufficient for the commercial recovery of product from aqueous solution20,21,31. Therefore, the addition of an extractant in the solvent phase is meaningful and will also boost the efficiency. In the present study, trioctylamine (TOA), an amine based extractant and tri-n-butyl phosphate (TBP), a phosphorus bonded oxygen donor extractant are tested for their extraction efficiency for the recovery of gallic acid (pKa,= 4.4) from aqueous solution and the results are compared. The formation of acid-extractant complex is shown in Figure 2(a) and 2(b). The range of concentration for gallic acid is taken 0.0029 kmol.m-3 to 0.0588 kmol.m-3 as found in wastewater effluent/ downstream processes. Extractants, TOA (0.2287–0.9151 kmol.m-3) and TBP (0.3652–1.4609 kmol.m-3) are used in four diluents (4methylpentan-2-one, octane-1-ol, kerosene and decane) to enhance the recovery of gallic acid from wastewater stream and fermentation broths. It is observed that TOA is found to be more effective one with MIBK and 1-octanol (active diluents) rather than TBP with same diluents. TOA has shown the maximum extraction efficiency at its minimum concentration (0.2287 kmol.m-3); on the other hand TBP with kerosene and decane (inert diluents) has shown better extraction capability on compared to TOA.


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2(a)

2(b) Figure 2. Reactive extraction of gallic acid with extractants (a) TOA, (b) TBP 11 ACS Paragon Plus Environment


3.2.

Effect of acid/ extractant concentration

The results for chemical extraction of gallic acid are obtained using extractants, TOA (0.2287 kmol.m-3–0.9151 kmol.m-3) and TBP (0.3652 kmol.m-3–1.4609 kmol.m-3) dissolved in four different diluents. These extractant concentrations are imposed on five different initial gallic acid concentrations in the range of 0.0029 kmol.m-3–0.0588 kmol.m-3. The extraction equilibrium results for TOA and TBP as extractants are presented in Tables 2–5 and Tables 6–9, respectively. Significantvariations in KD values depending upon acid and extractant concentration, are found to be 0.95–12.61 for MIBK, 0.41–11.86 for 1-octanol, 0.06–6.95 for kerosene, 0.01–8.88 for decane using TOA as extractant and 0.08–24.56 for MIBK, 1.3–9.33 for 1-octanol, 0.25–21.18 for kerosene, 0.44–21.35 for decane using TBP as extractant, shown in Tables 2–9. Extraction efficiency E and distribution coefficient KD are found to increase with an increase in gallic acid concentration using TOA in MIBK and 1-octanol (polar diluents), at all TOA concentrations (Tables 2–3). Acid concentration shows an inverse effect with TOA in kerosene and decane (non-polar diluents), as extraction yield decreases with increase in acid concentration (Table 4–5). Active/ polar diluents not only take part in extraction but also facilitate the complex formation between TOA and acid. On other hand, TBP in all four diluents shows an increment in extraction yield with an increase in gallic acid concentration (Tables 6–9). In experimental domain, the minimum concentration of TOA (0.2287 kmol.m-3) dissolved in MIBK caused a high recovery of gallic acid (E = 92.65%, KD = 12.61) at the initial gallic acid concentration 0.0588 kmol.m-3 while on increasing TOA concentration in MIBK caused a decrease in extraction yield for all concentrations of gallic acid (Table 2). It may be due to the polarity and hydrogen bonding ability with acid-amine complex of MIBK decreases with 12 ACS Paragon Plus Environment

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increase in TOA concentration. TOA dissolved in 1-octanol also provides a considerable extraction yield (E = 92.23%) at its maximum concentration (0.9151 kmol.m-3) at a gallic acid concentration, CHGA,in=0.0588 kmol.m-3. Since, only undissociated acid can be extracted by hydrogen bonding, when TOA is dissolved in kerosene and Decane, no consequential extraction yield observed and maximum extraction yield (E = 87.41% and 89.8% respectively) is found only at lowest concentration of gallic acid (0.0029 kmol.m-3) and highest concentration of TOA (0.9151 kmol.m-3) (Table 4–5 ). It is because of inactive (non-polar) diluents with aminic extractants can only provide large interface for acid-TOA complex formation but cannot plays any role in H-bonding and ion pair formation. The extraction enhancement caused by increasing concentration of TBP in different diluents is clearly observed for all acid levels (Tables 6–10). Among all four diluents, the maximum extraction yield is E = 96.09% for MIBK, E = 95.53% for decane, E = 95.49% for kerosene and E = 90.32% for 1-octanol with maximum TBP concentration (1.4609 kmol.m-3) at gallic acid concentration (0.0588 kmol.m-3). Here active diluents (MIBK and 1-octanol) play a supporting role in acid-TBP complex formation by H-bonding and ion pair. TBP has higher viscosity (3.39 cP), therefore, in inactive diluents (kerosene and decane) a less viscous medium facilitates TBP molecules to interact with each other and disrupt head-to-tail structure of their filaments and produce a greater number of nodes for solute (gallic acid) interaction36. The equilibrium data shows that TOA with the lowest concentration (0.2287 kmol.m-3) dissolved in MIBK or 1-octanol can be selected for the recovery of gallic acid from aqueous water stream/ fermentation broth. Also, TBP with higher concentration (1.4609 kmol.m-3) in any less viscous diluent, kerosene/ decane, may be a better choice for gallic acid extraction since the extraction yield is found greater than 90% for all four diluents. 13 ACS Paragon Plus Environment


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Table 2. Equilibrium extraction results of Gallic acid from aqueous solution using TOA in MIBK at 298 ±1K

"]o CHGA,in [! -3 kmol.m kmol.m-3

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

E (%)

pH (--)

0.0029

0.2287 0.4575 0.6862 0.9151

0.00067 0.00105 0.00132 0.00151

0.00227 0.00189 0.00162 0.00143

3.39 1.8 1.23 0.95

77.21 64.29 55.1 48.64

3.79 3.69 3.64 3.61

0.0118

0.2287 0.4575 0.6862 0.9151

0.0022 0.00317 0.00385 0.00439

0.00956 0.00859 0.00791 0.00737

4.35 2.71 2.05 1.68

81.29 73.04 67.26 62.67

3.53 3.45 3.41 3.38

0.0294

0.2287 0.4575 0.6862 0.9151

0.0026 0.00386 0.00482 0.00562

0.02679 0.02553 0.02457 0.02377

10.3 6.61 5.1 4.23

91.15 86.87 83.6 80.88

3.49 3.41 3.36 3.32

0.0471

0.2287 0.4575 0.6862 0.9151

0.00351 0.00496 0.00596 0.00683

0.04352 0.04207 0.04107 0.0402

12.4 8.48 6.89 5.89

92.54 89.45 87.33 85.48

3.43 3.35 3.31 3.28

0.0588

0.2287 0.4575 0.6862 0.9151

0.00432 0.00571 0.00672 0.00752

0.05446 0.05307 0.05206 0.05126

12.61 9.29 7.75 6.82

92.65 90.29 88.57 87.21

3.38 3.32 3.29 3.26

Table 3. Equilibrium extraction results of Gallic acid from aqueous solution using TOA in 1Octanol at 298 ±1K

"]o CHGA,in [! -3 kmol.m kmol.m-3 0.0029

0.2287 0.4575 0.6862

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

0.00208 0.00179 0.00161

0.00086 0.00115 0.00133

0.41 0.64 0.83


E (%)

pH (--)

29.25 3.54 39.12 3.57 45.24 3.6

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0.9151

0.00147

0.00147

1

50

3.62

0.0118

0.2287 0.4575 0.6862 0.9151

0.0047 0.00355 0.00297 0.0026

0.00706 0.00821 0.00879 0.00916

1.5 2.31 2.96 3.52

60.03 69.81 74.74 77.89

3.36 3.42 3.46 3.49

0.0294

0.2287 0.4575 0.6862 0.9151

0.00897 0.00628 0.00511 0.00431

0.02042 0.02311 0.02428 0.02508

2.28 3.68 4.75 5.82

69.48 3.22 78.63 3.3 82.61 3.35 85.34 3.38

0.0471

0.2287 0.4575 0.6862 0.9151

0.00957 0.00641 0.00511 0.00381

0.03746 0.04062 0.04192 0.04322

3.91 79.65 3.21 6.34 86.37 3.3 8.2 89.13 3.35 11.34 91.9 3.41

0.0588

0.2287 0.4575 0.6862 0.9151

0.01042 0.00785 0.00598 0.00457

0.04836 0.05093 0.05280 0.05421

4.64 6.49 8.83 11.86

82.27 86.65 89.83 92.23

3.19 3.25 3.31 3.37

Table 4. Equilibrium extraction results of Gallic acid from aqueous solution using TOA in Kerosene at 298 ±1K

"]o [! kmol.m-3

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

E (%)

pH (--)

0.0029

0.2287 0.4575 0.6862 0.9151

0.00105 0.00075 0.00051 0.00037

0.00189 0.00219 0.00243 0.00257

1.8 2.92 4.76 6.95

64.29 74.49 82.65 87.41

3.69 3.76 3.85 3.92

0.0118

0.2287 0.4575 0.6862 0.9151

0.0076 0.00649 0.00527 0.00219

0.00416 0.00527 0.00649 0.00957

0.55 0.81 1.23 4.37

35.37 44.81 55.19 81.38

3.26 3.29 3.34 3.53

0.0294

0.2287 0.4575 0.6862 0.9151

0.02684 0.0257 0.02136 0.01692

0.00255 0.00369 0.00803 0.01247

0.1 0.14 0.38 0.74

8.68 12.56 27.32 42.43

2.99 2.99 3.03 3.09

0.0471

0.2287 0.4575

0.04395 0.04054

0.00308 0.00649

0.07 0.16

6.41 2.83 13.64 2.85

CHGA,in kmol.m-3



0.0588

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0.6862 0.9151

0.03335 0.02766

0.01368 0.01937

0.41 0.7

28.99 2.89 41.2 2.93

0.2287 0.4575 0.6862 0.9151

0.05545 0.05393 0.04665 0.03768

0.00333 0.00485 0.01213 0.0211

0.06 0.09 0.26 0.56

5.51 7.91 20.82 35.91

2.88 2.88 2.91 2.96

Table 5. Equilibrium extraction results of Gallic acid from aqueous solution using TOA in Decane at 298 ±1K

CHGA,in kmol.m-3

" HGA "]o CHGA # [! -3 -3 kmol.m kmol.m kmol.m-3

KD (--)

E (%)

pH (--) 3.71 3.83 3.91 3.96

0.0029

0.2287 0.4575 0.6862 0.9151

0.00096 0.00054 0.00038 0.0003

0.00198 0.0024 0.00256 0.00264

2.06 4.44 6.74 8.8

67.35 81.63 87.07 89.8

0.0118

0.2287 0.4575 0.6862 0.9151

0.00862 0.00652 0.00392 0.00295

0.00314 0.00524 0.00784 0.00881

0.36 0.8 2 2.99

26.7 3.23 44.56 3.29 66.67 3.4 74.91 3.46

0.0294

0.2287 0.4575 0.6862 0.9151

0.02812 0.02499 0.02103 0.01772

0.00127 0.0044 0.00836 0.01167

0.05 0.18 0.4 0.66

4.32 2.98 14.97 3 28.45 3.04 39.71 3.08

0.0471

0.2287 0.4575 0.6862 0.9151

0.04633 0.04258 0.03772 0.03084

0.0007 0.00445 0.00931 0.01619

0.02 0.1 0.25 0.52

1.49 9.46 19.8 34.42

2.87 2.88 2.91 2.96

0.0588

0.2287 0.4575 0.6862 0.9151

0.05848 0.05612 0.05139 0.04488

0.0003 0.00266 0.00739 0.0139

0.01 0.05 0.14 0.31

0.51 4.53 12.57 23.65

2.82 2.82 2.84 2.87


Page 17 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 6. Equilibrium extraction results of Gallic acid from aqueous solution using TBP in MIBK at 298 ±1K

"]o [! kmol.m-3

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

0.0029

0.3652 0.7305 1.0957 1.4609

0.00163 0.00136 0.00112 0.00102

0.00131 0.00158 0.00182 0.00192

0.8 1.16 1.63 1.88

44.56 3.59 53.74 3.63 61.9 3.67 65.31 3.7

0.0118

0.3652 0.7305 1.0957 1.4609

0.00334 0.00234 0.0016 0.0012

0.00842 0.00942 0.01016 0.01056

2.52 4.03 6.35 8.8

71.6 3.44 80.1 3.51 86.39 3.6 89.8 3.66

0.0294

0.3652 0.7305 1.0957 1.4609

0.00588 0.00366 0.00223 0.00164

0.02351 0.02573 0.02716 0.02775

4 7.03 12.18 16.92

79.99 87.55 92.41 94.42

3.31 3.42 3.53 3.59

0.0471

0.3652 0.7305 1.0957 1.4609

0.00874 0.0054 0.00338 0.00211

0.03829 0.04163 0.04365 0.04492

4.38 7.71 12.91 21.29

81.42 88.52 92.81 95.51

3.23 3.33 3.44 3.54

0.0588

0.3652 0.7305 1.0957 1.4609

0.01087 0.00668 0.00411 0.0023

0.04791 0.0521 0.05467 0.05648

4.41 7.8 13.3 24.56

81.51 88.64 93.01 96.09

3.18 3.29 3.39 3.52

CHGA,in kmol.m-3

E (%)

pH (--)

Table 7. Equilibrium extraction results of Gallic acid from aqueous solution using TBP in 1Octanol at 298 ±1K

CHGA,in kmol.m-3 0.0029

"]o [! kmol.m-3

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

0.3652 0.7305 1.0957

0.00128 0.00115 0.00102

0.00166 0.00179 0.00192

1.3 1.56 1.88


E (%)

pH (--)

56.46 3.65 60.88 3.67 65.31 3.7


Page 18 of 37

1.4609

0.00088

0.00206

2.34

70.07 3.73

0.0118

0.3652 0.7305 1.0957 1.4609

0.00365 0.00294 0.00214 0.0016

0.00811 0.00882 0.00962 0.01016

2.22 3 4.5 6.35

68.96 3.42 75 3.47 81.8 3.53 86.39 3.6

0.0294

0.3652 0.7305 1.0957 1.4609

0.00836 0.00589 0.00437 0.00315

0.02103 0.0235 0.02502 0.02624

2.52 3.99 5.73 8.33

71.55 79.96 85.13 89.28

0.0471

0.3652 0.7305 1.0957 1.4609

0.01283 0.0089 0.00636 0.00476

0.0342 0.03813 0.04067 0.04227

2.67 4.28 6.39 8.88

72.72 3.15 81.08 3.22 86.48 3.3 89.88 3.36

0.0588

0.3652 0.7305 1.0957 1.4609

0.01531 0.01074 0.0077 0.00569

0.04347 0.04804 0.05108 0.05309

2.84 4.47 6.63 9.33

73.95 81.73 86.9 90.32

3.24 3.31 3.38 3.45

3.11 3.18 3.26 3.32

Table 8. Equilibrium extraction results of Gallic acid from aqueous solution using TBP in Kerosene at 298 ±1K

"]o [! kmol.m-3

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

0.0029

0.3652 0.7305 1.0957 1.4609

0.00235 0.00143 0.0008 0.00063

0.00059 0.00151 0.00214 0.00231

0.25 1.06 2.68 3.67

20.07 3.51 51.36 3.62 72.79 3.75 78.57 3.8

0.0118

0.3652 0.7305 1.0957 1.4609

0.00751 0.00462 0.00142 0.00094

0.00425 0.00714 0.01034 0.01082

0.57 1.55 7.28 11.51

36.14 60.71 87.93 92.01

3.26 3.37 3.62 3.71

0.0294

0.3652 0.7305 1.0957 1.4609

0.01814 0.00868 0.00289 0.00202

0.01125 0.02071 0.0265 0.02737

0.62 2.39 9.17 13.55

38.28 70.47 90.17 93.13

3.07 3.23 3.47 3.55

CHGA,in kmol.m-3


E (%)

pH (--)

Page 19 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.0471

0.3652 0.7305 1.0957 1.4609

0.02818 0.01344 0.00428 0.00273

0.01885 0.03359 0.04275 0.0443

0.67 40.08 2.97 2.5 71.42 3.14 9.99 90.9 3.38 16.23 94.2 3.48

0.0588

0.3652 0.7305 1.0957 1.4609

0.03395 0.01582 0.00517 0.00265

0.02483 0.04296 0.05361 0.05613

0.73 42.24 2.93 2.72 73.09 3.1 10.37 91.2 3.34 21.18 95.49 3.49

Table 9. Equilibrium extraction results of Gallic acid from aqueous solution using TBP in Decane at 298 ±1K

"]o [! kmol.m-3

CHGA kmol.m-3

" HGA # kmol.m-3

KD (--)

E (%)

pH (--)

0.0029

0.3652 0.7305 1.0957 1.4609

0.00204 0.0017 0.00092 0.00076

0.0009 0.00124 0.00202 0.00218

0.44 0.73 2.2 2.87

30.61 42.18 68.71 74.15

3.54 3.58 3.72 3.76

0.0118

0.3652 0.7305 1.0957 1.4609

0.00766 0.006 0.00168 0.00106

0.0041 0.00576 0.01008 0.0107

0.54 0.96 6.00 10.09

34.86 48.98 85.71 90.99

3.26 3.31 3.59 3.69

0.0294

0.3652 0.7305 1.0957 1.4609

0.01882 0.01001 0.0029 0.00164

0.01057 0.01938 0.02649 0.02775

0.56 1.94 9.13 16.92

35.96 3.06 65.94 3.2 90.13 3.47 94.42 3.59

0.0471

0.3652 0.7305 1.0957 1.4609

0.02947 0.01519 0.00432 0.00267

0.01756 0.03184 0.04271 0.04436

0.6 37.34 2.96 2.1 67.7 3.11 9.89 90.81 3.38 16.61 94.32 3.49

0.0588

0.3652 0.7305 1.0957 1.4609

0.03511 0.01651 0.00516 0.00263

0.02367 0.04227 0.05362 0.05615

0.67 2.56 10.39 21.35

CHGA,in kmol.m-3


40.27 71.91 91.22 95.53

2.93 3.09 3.34 3.49


3.3.

Stoichiometry of Acid-Extractant Complex

Number of extractant molecules reacting with one acid molecule (n) and reaction equilibrium constant (KE) are calculated using mass action law equations. According to Eq. (17), a plot of

log D + log 1 +

a

[]

versus log[

]o yields a straight line with a slope of n and an

intercept of log KE. This graphical representation is used to estimate the values of KE and n for different extraction systems [for TOA Fig. 3 (a) –3(d) and for TBP Fig. 4(a) –4(d)]. The values of n and KE are presented in Tables 10 and 11 for different initial gallic acid concentrations. The

graphical method is used with an assumption of [

]o >> n[ () m n ] in the extraction of gallic acid which is applicable at a very dilute aqueous solution of acid compared to extractant concentration.

1.2

1.0

log Kd + log(1+Ka/[H])

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 37

0.8 TOA-MIBK Gallic Acid -3 Conc. (kmol.m ) 0.00294 0.01176 0.02939 0.04703 0.05878

0.6

0.4

0.2

0.0 -0.7

-0.6

-0.5

-0.4

-0.3

-0.2

log [T]0

3(a)


-0.1

0.0

Page 21 of 37

1.2


1.0 0.8 TOA-Octanol

0.6 Gallic Acid Conc. (kmol.m-3) 0.00294 0.01176 0.02939 0.04703 0.05878

0.4 0.2 0.0 -0.2 -0.4 -0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

log [T]0

3(b)

1.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.5

TOA-Kerosene Gallic Acid -3 Conc. (kmol.m y1 ) 0.00294 y2 0.01176 y3 0.02939 y4 0.04703 y5 0.05878

0.0

-0.5

-1.0

-1.5 -0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

log [T]0

3(c)


0.0


1.0

0.5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 37

TOA-Decane

0.0

Gallic Acid Conc. (kmol.m-3) 0.00294 0.01176 0.02939 0.04703 0.05878

-0.5

-1.0

-1.5

-2.0 -0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

log [T]0

3(d)

Figure 3. Determination of KE and n using TOA (0.2287–0.9151 kmol.m-3) dissolved in (a) MIBK, (b) 1-octanol, (c) Kerosene (d) Decane for Gallic acid reactive extraction ; – linear fit lines

Table 10. Number of TOA molecules reacting with one acid molecule (n), equilibrium constant (KE) and coefficient of determination (R2) in 1-octanol at 298 ±1K

CHGA,in kmol.m-3

n

KE

R2

Extractant

Diluent

TOA

MIBK

0.0029 0.0118 0.0294 0.0471 0.0588

0.966 0.711 0.666 0.557 0.459

1.01 1.728 4.323 6.024 7.024

0.99 0.98 0.99 0.99 0.99

TOA

1-Octanol

0.0029 0.0118 0.0294 0.0471 0.0588

0.661 0.636 0.693 0.767 0.681

1.235 4.189 6.772 12.658 12.831

0.99 0.96 0.98 0.99 0.97


Page 23 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOA

Kerosene

0.0029 0.0118 0.0294 0.0471 0.0588

1.036 1.355 1.442 1.596 1.68

9.219 3.418 0.696 0.512 0.469

0.99 0.92 0.94 0.94 0.99

TOA

Decane

0.0029 0.0118 0.0294 0.0471 0.0588

1.143 1.592 1.878 2.341 2.466

13.463 3.69 0.827 0.645 0.376

0.96 0.99 0.99 0.98 0.99

The stoichiometry of the acid-extractant complex formed in reactive extraction is analyzed by estimation of n, i.e. number of extractant molecules per acid molecule. n values are obtained in the range of 0.459–0.966 for TOA in MIBK, 0.636–0.767 for TOA in 1-Octanol, 1.036–1.68 for TOA in kerosene, 1.143–2.466 for TOA in decane (Table 10), 0.669–1.238 for TBP in MIBK, 0.434–0.880 for TBP in 1-octanol, 2.077–2.517 for TBP in kerosene and 1.484–2.598 for TBP in decane (Table 11). The n values nearly equal to one (n ≈ 1) promoting the 1:1 acid-extractant complex, less than one shows 1:1 acid-extractant complex with some effect of acid-diluent interaction, through physical extraction. Value of n greater than one (n > 1) promoting the 1:2 and 1:3 acid-extractant complex formation (Figure 2) as in case of non-polar diluents n-decane, kerosene. Using the equilibrium data, the KE values obtained for the extractant- gallic acid complex formations are in the range of 1.01–7.024for TOA in MIBK, 1.235–12.831 for TOA in 1-Octanol, 0.469–9.219 for TOA in kerosene, 0.376–13.463 for TOA in decane (Table 10), 1.762–14.632 for TBP in MIBK, 2.266–6.79 for TBP in 1-octanol, 2.361–8.373 for TBP in kerosene and 1.932–8.22 for TBP in decane (Table 11). In all the tested extractants with different diluents, TOA (tertiary amine) in MIBK is found to be a good solvating agent for gallic acid-extractant complexation reaction taking place at the aqueous-organic interface. 23 ACS Paragon Plus Environment


1.6


1.4 1.2 TBP-MIBK

1.0

Gallic Acid y1 -3) Conc. (kmol.m y2 0.00294 y3 0.01176 y4 0.02939 y5 0.04703 0.05878

0.8 0.6 0.4 0.2 0.0 -0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

log [T]0

4(a)

1.0 0.9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 37

0.8

TBP-Octanol Gallic Acid -3 Conc. (kmol.m y1 ) 0.00294 y2 0.01176 y3 0.02939 y4 y5 0.04703 0.05878

0.7 0.6 0.5 0.4 0.3 0.2 -0.5

-0.4

-0.3

-0.2

-0.1

0.0

log [T]0

4(b) 24 ACS Paragon Plus Environment

0.1

0.2

Page 25 of 37

1.5


1.0 TBP-Kerosene Gallic Acid y1 -3 Conc. (kmol.m ) y2 0.00294 y3 0.01176 y4 0.02939 y5 0.04703 0.05878

0.5

0.0

-0.5

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

log [T]0

4(c)

1.6 1.4 1.2


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1.0

TBP-Decane

0.8

Gallic Acid y1-3) Conc. (kmol.m 0.00294y2 0.01176y3 0.02939y4 0.04703y5 0.05878

0.6 0.4 0.2 0.0 -0.2 -0.4 -0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

log [T]0

4(d)

Figure 4. Determination of KE and n using TBP (0.3652–1.4609 kmol.m-3) dissolved in (a) MIBK, (b) 1-octanol, (c) Kerosene (d) Decane for Gallic acid reactive extraction ; – linear fit lines



Page 26 of 37

Table 11. Number of TBP molecules reacting with one acid molecule (n), equilibrium constant (KE) and coefficient of determination (R2) in 1-octanol at 298 ±1K

CHGA,in kmol.m-3

n

KE

R2

MIBK

0.0029 0.0118 0.0294 0.0471 0.0588

0.669 0.94 0.95 1.159 1.238

1.762 6.817 12.328 13.81 14.632

0.99 0.99 0.99 0.98 0.98

TBP

1-Octanol

0.0029 0.0118 0.0294 0.0471 0.0588

0.434 0.775 0.866 0.868 0.88

2.266 4.944 6.133 6.531 6.79

0.97 0.97 0.99 0.99 0.99

TBP

Kerosene

0.0029 0.0118 0.0294 0.0471 0.0588

2.077 2.346 2.376 2.429 2.517

2.361 5.47 6.669 7.323 8.373

0.99 0.98 0.99 0.99 0.99

TBP

Decane

0.0029 0.0118 0.0294 0.0471 0.0588

1.484 2.298 2.398 2.539 2.591

1.932 4.34 6.841 7.003 8.22

0.96 0.95 0.99 0.99 0.99

Extractant

Diluent

TBP

3.4. Estimation of Extraction Column Design Parameters (RDC or Kühni column) The feasibility of the extraction process is assessed for maximum recovery of gallic acid with different extractant-diluent system by calculating minimum solvent to feed ratio ($/&)min , actual solvent to feed ratio ($/&)Act , flooding velocity (Vf50, assuming 50%), Column Diameter (DT), the number of theoretical stages (NTS), height equivalent to theoretical stage (HETS) and height of extraction column (H). Minimum solvent to feed ratio is calculated by Eq. (20). 26 ACS Paragon Plus Environment

Page 27 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


xin − xout S   =  F  min K D xin − yin

(20)

Where xin and xout are the gallic acid concentrations in the feed and the raffinate respectively, and yin is the initial acid concentration in the extract phase. For an extraction process with a finite number of extraction stages, the ($/&)Act is 1.5 times to

($/&)min .37 For a counter current extraction process the theoretical stages are found using the modified Kremser equation as given in Eq. (21) with the extraction factor (ξ) from Eq. (22).

  yin   xin − KD  1 ln  (1 − 1 ) +   ξ ξ y  xout − in K   D     NTS = ln ξ

ξ = KD

(21)

S F

(22)

Table 12. Minimum Solvent-to-Feed (S/F) ratio, 50% Flooding Velocity (Vf50), Column Diameter (DT), Number of Theoretical Stages (NTS), Height Equivalent to Theoretical Stage (HETS ) and height of extraction column (H) for TOA in polar diluents and TBP in non-polar diluents

Extractant TOA

TBP

(' /()Act

Column Design Vf50 DT (m/h) (m)

Diluent

(' KDmax F (-) (kg/h) /()min

MIBK

12.61

100

0.073

0.11

37.71

0.062

4.61

0.195

0.899

1-Octanol

11.86

100

0.081

0.122

38.12

0.062

4.38

0.212

0.929

Kerosene

21.18

100

0.045

0.068

43.86

0.056

5.51

0.195

1.080


NTS HETS

H (m)


n-Decane

21.35

100

0.045

0.068

55.31

Page 28 of 37

0.05

5.46

0.185

1.010

As found in experimental results, TOA in polar diluent (MIBK and 1-octanol) and TBP with non-polar diluent (Kerosene and Decane) perform well for extraction of gallic acid from aqueous solutions. Hence, column design parameters are estimated for TOA–MIBK, TOA–1-octanol, TBP–Kerosene and TBP–n-Decane systems for rotating disc contractor (RDC) or Kühni column with feed flow rate (F) of 100 kg/h, assuming 50% flooding velocity the extraction (Table 12) according to the guidelines provided by Stichlmair37, 38.

4. CONCLUSIONS In the present study, the reaction equilibrium data (KD, E and KE) and stoichiometric coefficient (n) are calculated for reactive extraction of gallic acid from aqueous solution/ fermentation broth using an amine based extractant TOA and a phosphorus bonded oxygen donor extractant TBP, in combination with different diluents (polar and non-polar) systems. The TOA and TBP in different diluents are compared on their extraction capabilities for the recovery of gallic acid from aqueous solutions. The solvent’s ability to extract gallic acid is observed as MIBK > octane-1-ol > n-decane > kerosene and MIBK > n-decane ≈ kerosene > octane-1-ol and with TOA and TBP respectively. TOA (0.2287 kmol.m-3) and TBP (1.461 kmol.m-3) dissolved in polar/ active diluents, MIBK showed the maximum extraction capabilities (%E = 92.65 and 96.09, respectively) at gallic acid concentration, 0.0588 kmol.m-3.The stoichiometric coefficient, n values between 0.45 to 2.5 promoted the formation of different type of acid:extractant complex (1:1, 1:2 and 1:3) for different extractant-diluent system. For a counter current liquid- liquid extraction process in rotating disc contactor (RDC) or Kühni column, the values of minimum solvent to feed ratio ($/&)min , actual solvent to feed ratio ($/&)Act , flooding velocity (Vf50), 28 ACS Paragon Plus Environment

Page 29 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Column Diameter (DT), the number of theoretical stages (NTS), height equivalent to theoretical stage (HETS ) and height of extraction column (H) are estimated for TOA in MIBK and 1octanol, and TBP in kerosene and n-decane .

AUTHOR INFORMATION Corresponding Author Dr. Sushil Kumar Department of Chemical Engineering, Motilal Nehru National Institute of Tehnology (MNNIT) Allahabad – 211 004 (UP) India. *

Email: [email protected]

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT Authors would like to thank the Department of Chemical Engineering, Motilal Nehru National Institute of Technology, Allahabad, India to provide the necessary laboratory and infrastructure facility to carry out the experiment.



ABBREVIATIONS TOA

Tri-n-octylamine

TBP

Tri-n-butyl Phosphate

MIBK

Methylisobutyl Ketone

µ

Dipole moment

ε

Dielectric constant

KD

Distribution coefficient

E

Extraction Efficiency, Extraction Yield

n

Number of extractant molecules

m

Number of acid molecules

KE

Reaction equilibrium constant

λmax

Maximum absorption wavelength

HGA

Acid in aqueous phase

HGA

Acid in organic phase

[HGA]

Undissociated acid concentration in aqueous phase

] [HGA

Undissociated acid concentration in organic phase

[H+]

Hydrogen ion concentration, proton concentration

Ka

Acid dissociation constant 30 ACS Paragon Plus Environment

Page 30 of 37

Page 31 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


HGA

Toatl acid concentration in aqueous phase

HGA,in

Initial acid concentration in aqueous phase

HGA

Toatl acid concentration in organic phase

[) ]

Dissociated acid concentration in aqueous phase

[ ]

Extractant concentration in organic phase

o

[ ]

Initial extractant concentration

() m ( )n Acid-extractant complex with m molecules of acid and n molecules of extractant Log P

Hydrophilicity constant

R2

Regression coefficient

F

min

F

Act

S

S

Minimum Solvent-to-Feed Ratio

Actual Solvent-to-Feed Ratio

NTS

Number of Theoretical Stages

ξ

Extraction factor

xin

Concentration of acid in the feed

xout

Concentrations of acid in the raffinate phase

yin

Initial acid concentration in the extract phase



RDC

Rotating Disc Contactor

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Reactive Extraction of Gallic Acid Using Aminic and Phosphoric

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