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Lactic acid extraction in systems containing organic amines Igor Yu. Fleitlikh, Boris N. Kuznetsov, Lidya Nikiforova, Natalya A. Grigorieva, and Natalya Beregovtsova Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b01112 • Publication Date (Web): 19 Jan 2018 Downloaded from http://pubs.acs.org on January 19, 2018

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Industrial & Engineering Chemistry Research

Lactic acid extraction in systems containing organic amines Igor Yu. Fleitlikh, Boris N. Kuznetsov, Lidya K. Nikiforova, Natalya A. Grigorieva*, Natalya G. Beregovtsova Institute of Chemistry and Chemical Technology SB RAS, Federal Research Center “Krasnoyarsk Science Center SB RAS”; Academgorodok, 50/24, 660036; Krasnoyarsk, Russia

e-mail: [email protected] Abstract A new high-performance system for lactic acid (HL) extraction from glucose-containing solutions is proposed. Trialkylbenzylammonium sulfate (C7–C9 fraction) with P-tertbutyl phenol in a diluent is used as the extractant. The maximum extraction region for HL is found to be at pH = 5.0–7.0, which coincides with the range of optimal pH values for glucose conversion to lactic acid. In 5 extraction stages, at an organic to aqueous phase ratio of 1:1, the acid recovery is 96.7%. HL stripping is carried out with 2.0–3.0 M NaOH solutions which achieves a significant increase in HL concentration. The stripping process in alkaline medium is easy (not less than 93.45% in one stage) due to the formation of trialkylbenzylammonium phenolate in the organic phase. Regeneration and conversion of the extractant to the SO4-form (TABAS) are carried out by treating the organic phase with sulfuric acid.

Keywords: lactic acid, solvent extraction, trialkylbenzylammonium sulfate Introduction Lactic acid (HL) is an important food acid and is widely used in the food, pharmaceutical and textile industries. Recently, it is of interest as a raw material for the synthesis of biodegradable polymers. The existing acid production processes are based on the precipitation of calcium lactate using quenched lime or calcium carbonate from biomass fermentation solutions. The solution, containing 11–14% of calcium lactate, is evaporated to a concentration of 27–30%, cooled to a temperature of 25–30 °C and kept in crystallizers for 36–48 hours. From the mother liquor, lactate crystals are separated by centrifugation.1 The disadvantages of this method are the process discontinuity and the long crystallization time. Furthermore, the crystals formed are of different sizes as a result of which they are poorly washed from the mother liquor.

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2 Solvent extraction processes provide alternatives to the precipitation processes. A number of oxygen extractants have been studied,2–5 including tributyl phosphate (TBP),2,3 trioctylphosphine oxide (TOPO)2,4 and crown ethers.5 The degree of HL extraction with TBP from enzymatic solutions was low. The extent of extraction with TOPO was slightly higher than with TBP, but it was close to zero at pH> 5.0, which is optimal for the fermentation process. The use of a crown ether (octol) allows the extraction to take place over a rather wide pH range of 1– 6. Unfortunately, the practical realization of this method is difficult, mainly because of the high cost of crown ethers. Data on lactic acid extraction from solutions using organic tertiary amines (R3N) are available in the literature.2,

6–11

It was recommended to carry out the HL extraction from the

technological solutions with a mixture of trioctylamine (TOA) and TBP6,7 and to carry out stripping of the acid with sodium carbonate, in the first case, and with water, in the second case. To recover lactic acid, Kyuchoukov and Yankov used trioctylamine solutions mixed with decane and decanol followed by the stripping of the acid with ammonium bicarbonate.8 According to published information,9 HL extraction from a multicomponent aqueous solution is carried out at pH 2.0-2.2 with a solution of TOA in octane with the addition of octanol, then HL stripping is carried out with a sodium hydroxide solution. The re-extract was then treated with the solution of polynonylnaphthalene sulfonic acid in octane to convert sodium lactate to the free lactic acid form. For HL extraction from the fermentation solution, other extractants, apart from TOA, were tested, in particular, LIX 7950 (guanidine derivative) and tetradodecyl-bis-N-oxide.10

The

highest distribution coefficients (D) were observed for TOA. The extraction of acid with LIX 7950 and the N-oxide was negligible. The high degree of HL extraction with TOA was achieved at a pH below 4.5, but thereafter fell rapidly as the pH value increased to ≈ 6.0, which is the optimum value for the fermentation process. This is a major and significant disadvantage of all extraction systems with TOA.2 The extraction capacity of secondary amines was higher than that of tertiary amines: dioctylamine > TOA,2 Amberlite LA-2 > tridodetcylamine (TDA).11

Moreover, secondary

amines showed a high extraction capacity at pH ≥ 6.0. The problem with the use of secondary amines is the considerable increasing of the aqueous phase pH value (up to 3) after extraction2 that may significantly reduce the extraction. In addition, secondary amines have a high toxicity for the bacteria in the fermentation solution.4 Besides secondary and tertiary amines for the purpose of lactic acid extraction a number of investigations using quaternary ammonium salts have been conducted.2, 12–15 It was shown that trioctylmethyl ammonium chloride (Aliquat 336)12 and trioctylmethyl ammonium ACS Paragon Plus Environment

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3 carbonate13 can extract HL over a wide pH range. Experimental results showed that the carbonate form is more effective than Aliquat 336 in its classical chloride form. The efficiency of monocarboxylic acid extraction using trioctylammonium di(2ethylhexyl)phosphate in toluene decreases in the following order: caproic > butyric > propionic > formic > acetic > lactic.14 The presence of a hydroxide group in the lactic acid molecule significantly increases its hydrophilicity and, consequently, significantly decreases its extractability.11

An investigation of HL extraction with binary extracting agents based on

trioctylmethylammonium showed the following order of extraction capacity: p-tertbutylphenolate

>>

caprylate

>

dialkylphosphinate

>

dialkylmonothiophosphinate

dialkylphosphate > dinonylnaphthalene sulfonate > dialkyldithiophosphinate.

>

15

A successful combination of the extraction and fermentation process has been presented.2 The lactic acid was recovered from the fermentation solution by extraction with trioctylmethyl ammonium chloride (TOMAC) in oleyl alcohol in the pH range of 5.5–6.5. The degree of acid recovery (ε) reaches 30%. Acid stripping is carried out using sodium chloride which simultaneously regenerates the extractant to the Cl-form. The raffinate and the extractant are recycled. When the glucose concentration reaches the initial value, the refined solution is returned to the fermentation process and the regenerated extractant is recycled to the extraction stage. From the above it follows that the most effective extractants for lactic acid recovery from fermentation solutions are quaternary ammonium salts. However, known extractants,

for

example, Aliquat 336 or TOMAC, do not allow extraction of lactic acid from the fermentation solution with high efficiency in the optimum region pH = 5.0–7.0. The aim of the present study was to search for new effective extraction systems based on quaternary ammonium salts and the development of a process for the efficient extraction of lactic acid extraction from solutions within the pH range 5.0–7.0 and also its stripping. Commercially available reagents, like the quaternary ammonium salts in the mixture with a p-alkylphenol were used as the extractants.

2. EXPERIMENTAL 2.1. Reagents The extractants were as follows:1. A technical mixture of primary amines (R1)(R2)(R3)CNH2 (ΣC=18-24) – Primene 81-JMT® (80 wt.%, Rohm and Haas,USA). Before extraction, the extractant of a required concentration was converted to the sulfate form by treatment with a stoichiometric amount of sulfuric acid. ACS Paragon Plus Environment


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4 2. Trialkylbenzylammonium chloride (TABAC, R4NCl®, [(С7-С9)3СН2С6Н5N]Cl), the content of С7-С9 fraction was 70%, produced by Institute “Gidrozvetmet”, Novosibirsk, Russia. 3. HPh – p-tert-butylphenol (p-С(СН3)3С6Н4ОН), 85 wt.%, %, produced by N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Novosibirsk, Russia. 4. Trialkylbenzylammonium phenolate (R4NPh). This was produced by the reaction between R4NCl and p-tert-butylphenol in an organic solvent after two pretreatments with 1.5 M NaOH (O:A = 1:1). 5. Trialkyl benzyl ammonium sulfate (TABAS, [(С7-С9)3СН2С6Н5N]2SO4). The extractant was prepared by treating trialkyl benzyl ammonium phenolate (R4NPh) with a stoichiometric amount of sulfuric acid. The neutral reagents used as additives were tributyl phosphate (TBP) (Joint-stock Company Chimprom, Volgograd, Russia) and trialkylphosphine oxide (TAPO) – Cyanex 923® (93 wt.%, Cytec, Canada). Octanol of chemically pure grade was used as a modifier. Nonane, de-aromatized kerosene (C10H22, TС 38-101-454-74) and toluene of pure grade were used as diluents, providing a high compatibility of extractable compounds and extractants in the organic phase. Lactic acid, 40% (by mass), of pure grade (GOST 490-79) was used for the extraction studies. Mineral salts, glucose and acids used were of chemically pure or analytical grades. 2.2. Experimental Procedure The liquid–liquid extraction testwork was carried out by mechanical mixing of the phases in test-tubes or in separatory funnels. When necessary, the pH value of the aqueous solution was adjusted with solutions of NaOH and sulfuric acid of appropriate concentrations. In some cases, to

change

pH

a

mixture

of

trialkylbenzylammonium

sulfate

[(R4N)2SO4]

and

trialkylbenzylammonium phenolate (R4NPh) was used. The extraction experiments were carried at 22–25°C, at an aqueous to organic phase ratio of 1:1, while the duration of the extraction and stripping tests was 1 h. Changes to these parameters are marked in the text. The pH values of the initial and equilibrium aqueous phases were determined by potentiometric titration with a glass electrode using a pH meter, Akvilon pH-410. The concentration of lactic acid was determined in the aqueous phase. The concentration of the lactic acid in the organic phase was calculated as the difference between its concentration in the initial solution and its concentration in the aqueous phase after extraction. Sometimes stripping with 0.1 M HClO4 solution was carried out.


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5 The lactic acid concentrations in the aqueous phase were determined by HPLC, using a “Milichrom A-02” microcolumn liquid chromatograph (ZAO EcoNova, Novosibirsk, Russia) with a short column (2x75 mm) ProntoSil-120-5-C18 AQ and UV detection. As the mobile phase A - [4M LiClO4–0,2M H3PO4]:deionized water = 5:95; mobile phase B - acetonitrile of an HPLC grade – 1% were used at a flow rate of the eluent of 100 µL/min. The column temperature was 35.0 ± 0.3°С. Detection was performed at 210, 220 nm. The volume of the injected sample was 4 µL. HL was identified at a retention time of 3 min and spectral ratios for the HL peak of S220/S210. For quantitative determination of lactic acid, the device was calibrated with standard aqueous solutions of HL in the concentration range of the samples under study. Each concentration of the standard solution was analyzed six times. Each sample of the aqueous HL solution was analyzed three times under identical conditions and the average value of three measurements has been taken. The results obtained were reproducible to within ± 5%.

3. RESULTS AND DISCUSSION 3.1. The extraction of lactic acid with Primene 81-JMT®and trialkylbenzylammonium chloride (TABAC)

The influence of the pH value of the equilibrium aqueous phase on the degree of lactic acid extraction from glucose solutions (ε,%) with Primene -JMT® (1) and TABAC (2) are presented in Figure 1. It is seen that the pH dependence for both curves is extreme. For Primene JMT® it can be assumed that the ascending part of curve 1, in analogy with trioctylamine, can be explained by the extraction of undissociated molecules of HL with formation of ion pairs RNH3+L− .

16

The descending part of the curve, at relatively high pH values of > 6.0, is clearly

associated with amine deprotonation and, accordingly, loss of extraction ability. For TABAC,12 in the initial part of curve 2, the extraction of undissociated and dissociated forms of the acid takes place. In the latter case, the chloride ion of the extractant is exchanged for lactate due to the ion exchange mechanism. The descending part of curve 2, cannot be explained by the drop (deterioration) in lactic acid extraction by a reduction in the extraction of undissociated molecules of HL, as has been reported,12 because, at pH ≥ 5.0, lactic acid in molecular form in the aqueous phase is absent and is present mainly in the form of lactate ions (≥ 94.0%) (HL pKa = 3.83).17 Reduction in the extraction at pH values > 5.0, apparently is due to the formation of lactic acid micelles in the aqueous phase, thus preventing extraction.18 As can be seen from



6 Figure 1,

Primene JMT® extracts HL more poorly than TABAC and the degree of acid

extraction does not exceed 38%. It was noted above that the presence of the lactic acid hydroxide groups significantly reduces its extractability. It has been suggested that the introduction to the organic phase containing TABAC, of TBP or trialkylphosphine oxides can increase lactic acid extraction due to the interaction of HL with TBP or TAPO through hydrogen bond formation e.g. OH ... O = P. However the results show that the introduction of these additives into the organic phase containing 0.45 M TABAC in toluene did not increase the acid extraction. So when the concentration of the additives rises from 0.0 to 0.8 M, the acid recovery reached 40.0–42.8 for TBP and 35.5–42.8% for TAPO (pH = 6.8–7.0) (Figure 2).

3.2. Extraction of lactic acid with a mixture of trialkylbenzylammonium sulfate (TABAS) and p-tert-butylphenol (HPh)

Figure 3 illustrates the dependence of equilibrium aqueous phase pH on lactic acid extraction with HPh (curves 1 and 2). For comparison, the similar dependence for TABAC is included in the figure (curve 3). From the results presented in the figure, one can see that the character of all the curves is the same. Thus extraction of HL with TABAS, as well as with TABAC, increases (curves 1, 2) at pH5 the extraction of the dissociated form of HL (L-) occurs predominately by an anion exchange mechanism. A decrease in the HL extraction for pH values > 5.0 is similar to the behavior of other monocarboxylic acids with binary extractants and corresponds to the basic laws of binary extraction.14 It is probably associated with lactic acid micelle formation in the aqueous phase. Figure 3 shows that lactic acid extraction with TABAS is more effective than extraction with TABAC. It is known that the sulfates of organic amines can be solvated by different proton donor compounds, for example, high molecular weight alcohols. The formation of a stable solvate of TOA sulfate with n-octanol has been reported.19 It can be assumed that TABAS forms the same compounds with molecules of

alkylphenol – (R4N)2SO4·2HPh. Accordingly, the extracted

lactate ion is also solvated by phenol (R4NL·HPh) and HL present in the aqueous phase,14 mostly, in the anion form. Taking this into account, the extraction process occurs by an anion exchange mechanism at pH > 5.0, which can be expressed by equation 1: (R4N)2SO4·2НPh(о) + 2L-(aq) ↔ 2R4NL·НPh(о) + [SO4]2-(aq)


(1)

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7 Figure 4 shows the isotherm of lactic acid extraction with a mixture of TABAS and HPh. From the results presented in the figure, one can see, that acid recovery reaches 96.7% after five extraction steps. The remaining HL in the raffinate is not a lost because the raffinate is returned to the fermentation cycle. It is obvious that in real systems during fermentation the range of lactic acid concentrations can vary over a relatively wide range. For example, according to published information,4 the glucose and lactic acid concentrations ranged from 0.11 to 0.55 and from 0 to 0.66 M, respectively. The change in the concentration of lactic acid upwards or downwards is not critical. At the same time, the extractant flow will increase or decrease. At a given extractant concentration, the organic phase flow and the number of extraction stages can be determined using the extraction isotherm and an operating line20 (similar to the procedure in Fig. 4).

3.3. Stripping of lactic acid

The process of lactic acid stripping with sodium hydroxide solutions was investigated for the organic-phase systems containing alkylphenols (HPh) (Eq. 2). The presence of HPh in the organic phase significantly simplifies lactic acid stripping due to the formation of a new compound in the organic phase i.e. phenolate trialkylbenzylammonium (R4NPh) and shifts the equilibrium (2) to the right.

R4NL·НPh(о) + NaОН(aq) ↔ R4NPh(о) + NaL (aq) + Н2О

(2)

Table 1. Dependence of the stripping of lactic acid on the concentration of NaOH Extractant: 0.225 M solution of (R4N)2SO4 + 0.45 M HPh in kerosene + 10% n-octanol. The content of lactic acid in the organic phase: 26.75 g /L. Re-extractant: sodium hydroxide solutions of different concentrations

№

СNaOH, M

СHL(о), g/L

СHL(aq), g/L

Stripping degree, *ε, %

1 2 3 4 5

0.0 0.5 1.0 2.0 3.0

24.48 1.75 0.95 0.75 0.67

2.27 25.0 25.8 26.0 26.1

8.5 93.45 96.4 97.2 97.5

* The standard deviation (sx) for the stripping degree values (ε,%) is 0.8%. **DHL = СHL(о),g/L/СHL(aq) ACS Paragon Plus Environment

HL distribution coefficient, **DHL 10,78 0,07 0,036 0,028 0,025


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8 Table 2. Isotherm for lactic acid stripping with sodium hydroxide Extractant: 0.225 M solution of (R4N)2SO4 + 0.45 M HPh in kerosene + 10% n-octanol. The content of lactic acid in the organic phase: 26.75 g/L. Re-extractant: 2.5 M NaOH solution

№

О:Aq

СHL(о), g/L

СHL(aq), g/L

1 2 3 4

1:1 2:1 3:1 4:1

1.15 1.58 1.62

26.75 51.2 75.5 98.75

Stripping degree, ε, % 100 95.7 94.1 93.9

DHL 0.022 0.021 0.016

According to Eq. 2, when stripping the lactic acid, 1 mole of alkali is consumed per mole of extractant. As can be seen from Tables 1 and 2, the stripping of HL with NaOH solutions proceeds very efficiently. Thus, when O:A = 1: 1, already at an alkali concentration of 0.5 M (10% excess over stoichiometry), the degree of stripping in one stage is 93.45% (Table 1, No. 2). An increase in the NaOH concentration results in a small increase in stripping. Low acid distribution coefficients (DHL = 0.025–0.07) allow it to be concentrated in the strip liquor by a factor of 15–40 (the concentration limit is the inverse of DHL, i.e., 1/DHL20). As seen from Table 2, a suitably high concentration of the acid in the strip liquor can be achieved. Obviously, the stripping conditions are not optimal and the production of more concentrated solutions is possible. Based on the data obtained, it is possible to carry out stripping at O:A = 5–6:1 and an alkali concentration of 2.5–3.0 M. Direct use of trialkylbenzylammonium phenolate for HL extraction is not useful, because in this case, the pH value increases significantly, resulting in a decrease in extraction (Table 3). To maintain optimum and stable pH values (5.0–7.0) in the extraction step, the organic phase must be regenerated. For this purpose, it was treated with sulfuric acid solution after stripping. Thus the extractant is converted into the sulfate form, (R4N)2SO4, and the phenolate ion is converted into phenol (HPh) (Eq. 3):

2 R4NPh(о) + H2SO4(aq) ↔ (R4N)2SO4·2НPh(о)

(3)

Table 3. Influence of the extractant composition on equilibrium (final) pH and extraction of lactic acid

Organic phase: 0.45 M solution of [(R4N)2SO4·2НPh+R4NPh] in nonane + 10% n-octanol. Aqueous phase: 0.3 M lactic acid + 0.5 M of glucose; pH(initial) = 5.5


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9 №

R4NPh, %

(R4N)2SO4·2НPh, %

pH(eq.)

1 2 3 4 5 6 7

0.0 20 35 40 60 80 100

100 80 65 60 40 20 0.0

3.5 4.1 5.05 6.7 8.2 9.56 10.45

Extraction degree; ε,% 52.5 62.7 64.7 59.3 56.3 34.8 23.5

The obtained results (Table 3) show that it is necessary to convert not more than 60–65% of the extractant into the sulfate form (№ 3, 4). The regenerated extractant is returned to the extraction cycle.

3.4. Practical implications for lactic acid extraction with mixtures of tetraalkylammonium sulfate and alkyl phenol

The results of these experiments allow recommendions for HL extraction and concentration from the fermentation solution through the following sequence of operations: – five steps of acid extraction with mixtures of tetra-alkylammonium sulfate and alkyl phenol at pH 5.0–7.0 (O:A = 1:1); – 1–2 stages of impurities removal from the extract with water at pH = 5.0–6.0; – 1–2 stages of acid stripping with sodium hydroxide solution at О:A = 5–6:1 at concentrations of 2.5–3.0 M; – 1 regeneration stage of the extractant into the SO4- form with sulfuric acid solution. The specific process parameters, obviously, should be defined for each solution separately. The process flow diagram for lactic acid extraction from fermentation broth is presented in Figure 5. The use of the extractant in the sulfate form leads to the accumulation of sulfate ions in the aqueous solution (Eq.1). This does not diminish the lactic acid extraction, unlike, for example, chloride ion, since the sulfate ion is much more poorly extracted, than chloride.[1] In contrast to the chloride ion, the sulfate ion can be simply removed from the solution using known methods, for example, adding calcium carbonate to precipitate gypsum. In this study, the toxicity of the dissolved extractant towards the microbes that produce lactic acid was not considered. However, purification of the raffinate from organic impurities must be carried out.1 A cation exchange resin2 or an active charcoal20 could be used for this purpose. Such testwork should be carried out on the proposed extraction system, but these studies are outside the scope of this paper. ACS Paragon Plus Environment


10 CONCLUSIONS

The extraction of HL from glucose-containing solutions with Primene 81-JMT, TABAC and mixture of TABAS, HPh in nonane (kerosene) with n-octanol was studied. HL extraction decreased in the following order: TABAS + HPh > TABAC > Primene 81-JMT. For TABAS+HPh the region of maximum HL extraction was observed at pH 5.0–7.0, which coincides with the range of optimal pH values of glucose conversion to lactic acid. HL stripping was carried out in NaOH solutions which gave significant concentration of the HL. The ease of stripping was due to the formation of trialkylbenzylammonium phenolate (R4NPh) in the organic phase, after the extractant was treated with alkali. Regeneration of the extractant and its conversion into the SO4–form (TABAS) was carried out by treating the organic phase with sulfuric acid solutions. As a result of the research, a new high-efficiency extraction system based on a mixture of TABAS and HPh for the recovery of lactic acid has been developed. The technology developed in this work is free from the drawbacks inherent in the traditional precipitation methods used for lactic acid recovery, such as process discontinuity, long crystallization time, the difficulty in washing the mother liquor from the crystals so formed, etc.1 There is no doubt that the new extraction system has advantages over such extractants as TBP,3,4 TAPO3 and TOA,6,7 since these extractants recover HL only in the acidic range and are completely inefficient when pH = 5.0–7.0, i.e. in the range of the optimal pH for a solution resulted from glucose conversion into lactic acid. The proposed mixture (TABAS and HPh) also has advantages over such a widely known extractant as trioctylmethyl ammonium chloride (Aliquat 336). This extractant has proved to be well suited for the recovery of lactic acid from fermentation broth at a pH of 5.5– 6.0 (the degree of lactic acid extraction in one stage was about 30%),2 but it is significantly poorer than the proposed mixture of the extractants, for which lactic acid recovery in the same pH range was 62.5–64.5% (Fig. 4, curve 3). It should be added that the analogue of Aliquat 336, trialkylbenzylammonium chloride (TABAC), also has poorer characteristics as the degree of lactic acid extraction in one stage did not exceed 38% (Fig. 3, curve 1). The positive results on the recovery of lactic acid from the fermentation broth using trioctylmethyl ammonium chloride2 suggest that the extraction system based on trialkylbenzyl ammonium sulfate could be used more efficiently to extract lactic acid from the real fermentation broth. This system includes the effective extraction for HL and its following stripping.

Notes ACS Paragon Plus Environment

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11 The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was financially supported by Project № V.46.1.2 of Russian Academy of Sciences.

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Stripping

from Loaded Organic Phase. Ind. Eng. Chem. Res., 2010, 49 (17), 8238- 8243. (9) Kuvaeva Z.I, Kovalchuk I.V., Vodopiyanov L.A. A method of lactic acid extraction from water. 2014, Certificate of Authorship, BY No. 17968 C1. (10) Krzyzaniak A., Boelo Schuur B., de Haan A. Extractant screening for bio-based recovery of carboxylic acids. Proceedings of the 19th International Solvent Extraction Conference, ISEC'2011, 2011, 3–7 October, Santiago, Chile, p.152 (on CD, chapter 6, no.152, 1–7). (11) Bayazit S.S., Uslu H., Đnci I. Comparison of the Efficiencies of Amine Extractants on Lactic Acid with Different Organic Solvents. J. Chem. Eng. Data 2011, 56 (4), 750 – 756.



12 (12) Kyuchoukov G., Yankov D., Albet J., Molinier J. Mechanism of Lactic Acid Extraction with Quaternary Ammonium Chloride (Aliquat 336). Ind. Eng. Chem. Res. 2005, 44 (15), 5733–5739. (13) Kyuchoukov G., Marinova М., Albet J., Molinier J. New Method for the Extraction of Lactic Acid by Means of a Modified Extractant (Aliquat 336). Ind. Eng. Chem. Res. 2004, 43 (5), 1179–1184. (14) Zahodyaeva Y.A., Voshkin A.A., Belova V.V., Khol'kin A.I. Extraction of monocarboxylic acid with di(2-ethylhexyl)phosphate trioctylmethylammonium. Chemical Technology 2010, 10, P.605-611. (15) Y.A. Zahodyaeva, Voshkin A.A., Belova V.V., Khol'kin A.I. Extraction of monocarboxylic acids with binary extracting agents based on amines and quaternary ammonium salts. Chemical Technology 2010, 7, 407-411. (16) Yankov D., Molinier J., Albet J., Malmary G., Kyuchoukov G. Lactic acid extraction from aqueous solutions with tri –n-octyl amine dissolved in decanol and dodecane. Biochem. Eng. J. 2004, V.21.p.63-71. (17) Lurie Y.Y. Handbook of Analytical Chemistry. Moscow, 1979. (18) Voyutsky S.S. Course of Colloid Chemistry. Moscow, 1976. (19) Schmidt V.S. Extraction with amines. Moscow, 1980. (20) Gindin L.M. Extraction processes and their application. Nauka, Moscow, Russia, 1984, 144. (21) Tymoshenko M.N., Klimenko N.A. Application of active coals in the wastewater treatment technologies. Chemistry and technology of water 1990, V.12, (8), 727-738.


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Page 13 of 16 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


13

40

εHL, %

2

30

1 20

10

pH 0

0

2

4

6

8

10

12

Figure 1. Influence of the equilibrium aqueous phase pH on the degree of lactic acid extraction with Primene -JMT® (1) and TABAC (2). Organic phase: 1. 0.4 М Primene -JMT® in SO4-form in nonane + 10% n-octanol; 2. 0.45 М TABAC in nonane + 10% n-octanol. Aqueous phase: 1, 2 – 0.29 M lactic acid + 0.5 M glucose.

44

εHL, %

42

40

1

38

2 36

CX, M

34 0.0

0.2

0.4

0.6

0.8

1.0

Figure 2. Effect of additives on lactic acid extraction with TABAC in toluene: (1) TBP and (2) TAPO. Organic phase: Cx is the additive concentration; 1. 0.45 M TABAC + TBP; 2. 0.45 M TABAC + TAPO. Aqueous phase: 1, 2 – 0.31 M lactic acid + 0.5 M glucose; pH(initial) = 5.6; pH(eq.) = 6.93–7.0; 2. pH(eq.) = 6.1–7.05.



Page 14 of 16

14

70

εHL, %

60 50

2

40

1

30

3

20 10

pH

0 0

2

4

6

8

10

12

Figure 3. Influence of the equilibrium aqueous phase pH on lactic acid extraction with quaternary ammonium salts: Organic phase: 1. 0.15 M (R4N)2SO4 + 0.3 M HPh in nonane + 10% n-octanol; 2. 0.225 M (R4N)2SO4 + 0.45 M HPh in nonane + 10% n-octanol. 3. 0.45 M TABAC in nonane + 10% n-octanol. Aqueous phase:1, 2 – 0.31 M lactic acid + 0.5 M glucose; pH(initial) = 5.6; 3. 0.29 M lactic acid + 0.5 M glucose; pH(initial) = 5.65.

35

CHL(org), g/l

30 25 20 15 10 5

CHL(aq), g/l 0 0

5

10

15

20

25

30

35

Figure 4. Lactic acid extraction isotherm. Organic phase: 0.225 M (R4N)2SO4 + 0.45 M HPh in kerosene + 10% n-octanol. Aqueous phase: 27.75 g/l lactic acid + 0.5 M of glucose; pH(initial) = 5.5; pH(eq.) = 5.8–6.3; O:Aq ≠ const


Page 15 of 16 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


15

Extractant (R4N)2SO4 + НPh

Initial fermentation solution

Lactic acid extraction Extract

Н2О

Raffinat to fermentation

Washing of impurities from the extract

Extract

NaOH solution

Lactic acid stripping

Extractant

H2SO4 solution

Wash Liquor

Reextract to lactic acid recovery

Extractant regeneration

Regenerated extractant

Figure 5. Schematic flowsheet for lactic acid extraction from a fermentation solution with mixtures of (R4N)2SO4 and HPh in the diluent.



16

(R4N)2SO4·2HPh(о) + 2L-(aq) ↔ 2R4NL· HPh(о) + [SO4]2-(aq) - 0.225 M (R4N)2SO4 + 0.45 M HPh

70

- 0.15 M (R4N)2SO4 + 0.3 M HPh 60

- 0.45 M R4NCl

50

εlactic acid,%

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

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40 30 20 10 0

3.5

5.0

6.51

8.0

Highlight


9.5

pH

Figure - American Chemical Society

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