Separations of citric acid

When the distribution coefficient for the desired solute from aqueous solutions into even the best of solvents is unfavourable it may become attractive to superimpose reaction. Consider the. separation of citric acid from aqueous solutions, for which physical extraction is unattractive. Here we can use a bulky tertiary amine, e.g. tri-2-ethylhexylamine, which has a very low solubility in water, and dissolve it in a suitable, water-insoluble solvent this will... 

Citric acid (Ruthven, 1997). In the separation of citric acid from fermentation liquors the Sorbex process can be used. In the conventional process neutralization is carried out with lime followed by acidification with sulphuric acid to produce calcium sulphate as waste. The Sorbex technology avoids lime and sulphuric acid wastage and calcium sulphate disposal. 

Kulprathipanja, S. (1988) Separation of citric acid from fermentation broth with neutral polymeric adsorbent. U.S. Patent 4720579. 

Separation of citric acid from fermentation broth Separation of lactic acid from fermentation broth Production of acetone, butanol, and ethanol (ABE) from potato wastes Separation of long-chain unsaturated fatty acids... 

Basu R and Sirkar KK. Hollow fiber contained liquid membrane separation of citric acid. AIChE J, 1991 37(3) 383-393. 

Today, most bipolar ion exchange membranes are industrially used in continuous ion exchange reactions across the membrane by the use of H+ and OH-generated from the bipolar ion exchange membrane. Examples include separation of gluconic acid from gluconate,28 production of amino acids from amino acid salts,29 separation of citric acid from citrate,101 ion exchange of soybean protein,102 and conversion of lactate into lactic acid.82... 

Kesner. L. and Muntwyler, E. Separation of Citric Acid Cycle and Related Compounds by Partition Column Chromatography," in Methods in Enzymology, Vol. I3. M. Lowenstein, ed.) Academic Press, New York, 1969, p. 415. 

Rathore, H. S., Kumari, K., and Agrawal, M. (1985). Quantitative separation of citric acid from trichloroacetic acid on plates coated with calcium sulfate containing zinc oxide. J. Liq. Chromatogr. 8 1299-1317. 

Riley, R. T., and Mix, M. X. (1980). Thin-layer separation of citric acid cycle intermediates, lactic acid, and the amino acid taurine. J. Chromatogr. 189 286-288. 

Alcock, N.W. (1969), Separation of citric acid cycle and related compounds by gas chromatography. In Methods in Enzymology, vol. XIII (ed. J.M. Lowenstein), Academic Press, London and New York. 

Lime-Sulfuric. Recovery of citric acid by calcium salt precipitation is shown in Figure 3. Although the chemistry is straightforward, the engineering principles, separation techniques, and unit operations employed result in a complex commercial process. The fermentation broth, which has been separated from the insoluble biomass, is treated with a calcium hydroxide (lime) slurry to precipitate calcium citrate. After sufficient reaction time, the calcium citrate slurry is filtered and the filter cake washed free of soluble impurities. The clean calcium citrate cake is reslurried and acidified with sulfuric acid, converting the calcium citrate to soluble citric acid and insoluble calcium sulfate. Both the calcium citrate and calcium sulfate reactions are generally performed in agitated reaction vessels made of 316 stainless steel and filtered on commercially available filtration equipment. 

Fig. 1 Separation of carboxylic acids (schematic representation). Citric acid (1), lactic acid (2), phthalic acid (3), sebacinic acid (4), salicylic acid (5), mixture (M).

The copper complex is very stable at neutral pH, but it fades very rapidly in the presence of hydrogen ions. Other complex formers such as tartaric acid or citric acid and thiourea interfere with the reaction and, therefore, should not be included in mobile phases used for the separation of amino acids [3]. 

There is increasing interest in the use of specific sensor or biosensor detection systems with the FIA technique (Galensa, 1998). Tsafack et al. (2000) described an electrochemiluminescence-based fibre optic biosensor for choline with flow-injection analysis and Su et al. (1998) reported a flow-injection determination of sulphite in wines and fruit juices using a bulk acoustic wave impedance sensor coupled to a membrane separation technique. Prodromidis et al. (1997) also coupled a biosensor with an FIA system for analysis of citric acid in juices, fruits and sports beverages and Okawa et al. (1998) reported a procedure for the simultaneous determination of ascorbic acid and glucose in soft drinks with an electrochemical filter/biosensor FIA system. 

Figure 4.7 Anion exchange separation of carboxylic acids in red wine. Column, Shodex C811, 100 cm x 7.6 mm i.d. eluent, 3 mM perchloric acid flow rate, 0.9 ml min-1 temperature, 60 °C detection, reaction detection using chloro-phenol red at 430 nm. Peaks 1, citric acid 2, tartaric acid 3, malic acid 4, succinic acid 5, lactic acid 6, formic acid and 1, acetic acid.

FIGURE 2 Separation of 15 acids used as pharmaceuticai sait-forming agents, peak assignment i. Hydrochioric, 2. Nitric, 3. Suifuric, 4. Tartaric, 5. Maiic, 6. Citric, 7. Succinic, 8. Acetic, 9. Lactic, iO. Phosphate, i i. Propionic, i2. Butyric, i3. Pentanoic, i4. Hexanoic, and iS. Octanoic (taken from reference 2 i. With permission.). 

I 6 Aspects of Mechanisms, Processes, and Requirements for Zeolite Separation Table 6.2 Analysis of citric acid product by adsorption. 

The specificity tests depend on the type and purpose of the method. If a specific method is being validated, an interference study should be undertaken. In the case above of the analysis of citric acid and sodium citrate, all other ingredients except microcrystalline cellulose and carboxymethyl cellulose sodium should be chromatographed separately. The known impurities related to memetasone furoate, if available, should be injected as well as the diluting solvent. Interference from filters is required. For nonspecific methods, specificity studies must be determined on a case-by-case basis. For example, the determination of molar ratio of citric acid and sodium citrate by pH in Nasonex should be designed to exclude any other contribution of acidity from other ingredients. 

Citrates (like tartrates) in solution change silver of amnmnio-silver nitrate into metallic silver. Calcium citrate, due to its solubility characteristics. is of importance in the separation and recovery of citric acid. Calcium ciiraic plus dilute H.SOj yields citric acid plus calcium sulfate, and the latter may he separated by filtration. Citric acid may be obtained by evaporation of Ihc filtrate. 

ED appears to be an inefficient method to recover free citric acid because of its low electric conductivity (Novalic et al., 1995). As it is converted into the monovalent (at pH ca. 3), divalent (at pH ca. 5), or trivalent (at pH about 7) citrate anion, there is a significant increase in the electric conductivity (%), the latter increasing from 0.95 to 2.18 and to 3.9 S/m, respectively, in the case of an aqueous solution containing 50 kg/m3 of citric acid equivalent (Moresi and Sappino, 1998). By increasing the pH from 3 to 7, e reduced about eight times, the solute flux (JB) practically doubled, while the overall water transport (/w) increased 3-4 times. The latter partly counterbalanced the greater effectiveness of the electrodialytic concentration of citric acid at pH 7 with respect to that at pH 3. Table XV presents a summary of the effect of current density ( j) on the main performance indicators of the electrodialytic recovery of the monovalent, divalent, or trivalent ionic fractions of citric acid (Moresi and Sappino, 1998). All the mean values or empirical correlations of the earlier indicators were useful to evaluate the economic feasibility of this separation technique (Moresi and Sappino, 2000). 

Novalic, S., Okwor, J., and Klaus, D.K. 1996. The characteristic of citric acid separation using electrodialysis with bipolar membranes. Desalination 105, 277-282. 

Tetrahydrofuran (3.2 ml) and S-(+)-3-chloro-l,2-propanediol (0.299 ml, 3.58 mmol, 1.19 eq) are mixed. The mixture of THF (3.2 ml) and S-(+)-3-chloro-1,2-propanediol (0.299 ml, 3.58 mmol, 1.19 eq) is cooled to -16°C and potassium t-butoxide (3.2 ml, 1.0 M) in THF (3.2 mmol, 1.07 eq) is added at less than -10°C. The resulting slurry is stirred at -14-0°C for 1 hour. Then added to the lithium anion mixture while maintaining both mixtures at 0°C, then rinsed in with THF (2 ml). The resultant slurry is stirred at 20-23°C for 2 hour and then cooled to 6°C and a mixture of citric acid monohydrate (0.4459 g, 2.122 mmol, 0.705 eq) in water (10 ml) is added. The resultant liquid phases are separated and the lower aqueous phase is washed with ethyl acetate (12 ml). The organic layers are combined and solvent is removed under reduced pressure until a net weight of 9.73 g remains. Heptane (10 ml) and water (5 ml) are added and solvent is removed 4-nitrobenzenesulfonyl chloride y reduced pressure until a total volume of 5 ml remains. The precipitated product is collected by vacuum filtration and washed with water (7 ml). The solids are dried in a stream of nitrogen to give (R)-[N-3-(3-fluoro-4-(4-morpholinylphenyl)-2-oxo-5-oxazolidinyl]methanol. 

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