Extraction from Liquid Solutions

Extraction from Aqueous Solutions Critical Fluid Technologies, Inc. has developed a continuous countercurrent extraction process based on a 0.5-oy 10-m column to extract residual organic solvents such as trichloroethylene, methylene chloride, benzene, and chloroform from industrial wastewater streams. Typical solvents include supercritical CO9 and near-critical propane. The economics of these processes are largely driven by the hydrophihcity of the product, which has a large influence on the distribution coefficient. For example, at 16°C, the partition coefficient between liquid CO9 and water is 0.4 for methanol, 1.8 for /i-butanol, and 31 for /i-heptanol. 

Simethicone is an antigas ingredient in many liquid and solid pharmaceutical preparations, and FTIR is used in quality assurance laboratories to determine whether its concentration is at the specified level. A sample of the product is dispersed in an HC1 solution and the simethicone extracted from this solution with toluene. The toluene solutions are then run on the FTIR using a liquid sampling cell. For the quantitative analysis, a simethicone absorption band that is free from interference from the toluene absorption bands is used in a manner similar to that of the isopropyl alcohol band in Experiment 26. 

BrCsCCH(CH3)OH, np(20 ) -12500 (undistilled), is obtained in ca. 85% yield as a viscous liquid after removal of the E O from the extracts from the solution of KOBr (-0.3 mol), 60% is added dropwise over 30 min 10 a mixture of 0.32 mol (slight excess) of HC=CCH(CH3)OH and 40 ml of water. During this addition, the temperature of the mixture is kept between 5 and 10 C. After an additional 15 min (at 10 C) four extractions with EtjO are carried out. The unwashed organic solutions are dried over MgSO. ... 

Figure 10.6 Effect of 1-alkyl group variation of ionic liquids on efficiency of competitive metal cation extraction from aqueous solutions by DCH18C6 (0.1 M) in [C CjIm][Tf2N], (Reproduced from the American Chemical Society from Luo, H. M., Dai, S., Bonnesen, RV., Anal Chem., 76, 2773-2779, 2004. With permission.)...

Room temperature ionic liquids have potential as extractants in recovery of butyl alcohol from fermentation broth water solubility in ionic liquid and ionic liquid solubility in water are important factors affecting selectivity of butyl alcohol extraction from aqueous solutions (Fadeev and Meagher, 2001). 

Phosphotungstic acid crystallizes from water (in which it is extremely soluble) in very heavy white octahedra. The water solution is not stable toward light but slowly turns blue as a result of reduction. Re-oxidation is easily effected by heating with chlorine water. In spite of its great solubility in water, the acid may be completely extracted from water solution by ether. It forms with ether a dense liquid layer of a complex compound which is insoluble both in ether and in water, so that three liquid layers are formed when the water solution is extracted with an excess of ether. In addition to being very soluble in water and ether, phosphotungstic acid is readily soluble in the lower alcohols and esters. 

The liquids in one extract layer containing the acetic acid extracted from a solution that contains solids had a composition of about 70% acetone, 15% water, and 15% acetic acid (2). The first distillate from this layer contained less than 0.1% acetic acid and thus could be recycled directly to the extractor. The balance of the acetone was stripped from the extract layer in a short column, and the water was distilled azeo-... 

Liquid-liquid extraction this uses two immiscible solvents the desired compound in solution or suspension in one solvent is extracted into the other solvent. For example, covalent organic compounds are extracted from aqueous solution into dichloromethane, leaving the ionic byproducts or reagents in the aqueous phase. 

There are several limitations to liquid-liquid extractions. With extractions from aqueous solutions, the solvents that can be used must be immisicible with water... 

In all the cases of extraction from liquids given above, the solute is distributed between the two solvents in such a manner that a definite ratio (the Distribution coefficient or the Partition coefficient) is maintained between the two concentrations i.e. in the instance under consideration. 

The analysis of liquid and solid samples very often requires some form of solvent extraction to isolate organic constituents. Conventional solvent extraction can be used, and the pH may be adjusted to achieve some selectivity, for example, extracting from acid solution to prevent basic compounds from extracting. More efficient means of extraction are commonly employed today, such as microwave-assisted or accelerated solvent extraction for solid samples (Chapter 19). See... 

Partitioning of solutes between the SCCO2 phase and the polymer phase has been studied for cross-linked PDMS and poly(cyanopropylmethylsiloxane) (PCPMS). It has ben shown that naphthalene, acridine, and 2-naphthol partition preferentially into the polymer phase, but the partition constant drops from 10 -10 below 75 bar to only 1-5 at higher pressures [35,36]. One would anticipate, therefore, that heavy polyaromatic compounds wiU be difficult to extract from liquid polymers with SCCO2. Extraction of lighter compounds is relatively facile [10]. 

The distribution of dissolved substances in two solvent phases is employed on a large scale in the industrial separation of mixtures of substances. Examples are the removal of unsaturated constituents from vegetable oils with furfurol or methanol, the purification of animal and vegetable oils with liquid propane, and the removal of waxes from lubricants with liquid propane or ketones. Penicillin is similarly concentrated with methyl isobutyl ketone, and aqueous glycerol is purified with xylene. Preparative and analytical separations are also performed by liquid-liquid extraction. Inorganic salts can be extracted from aqueous solutions with suitable solvents, such as ethers, ketones, and esters. This method is particularly efficient for metal halides and nitrates, e.g., the separation of uranium compounds from aqueous solutions or the fractional extraction of rare earths. 

Rearson, D. 1983. In Flett, D.S. (ed.). Supported liquid membranes for metal extraction from dilute solutions. Ion Exchange Membranes. Society of Chemical Industry, London, U.K., pp. 55-73. 

Chromatography The derivatives can be analysed by several techniques. Liquid chromatography was used to separate acetylated products following extraction from aqueous solutions with chloroform, evaporation of the solvent and dissolution of the residue in the HPLC mobile phase. Separations were achieved by ODS reversed phase liquid chromatography using acetonitrile/ water as the eluent or with hexane/ethanol (19 1) on normal phase columns (Develosil 60). 

Liquid/liquid extraction is a process that involves mass transfer between two immiscible or partially miscible liquids. The separation from a homogeneous liquid solution occurs by adding a liquid component, insoluble or partially soluble in the solution, the solvent, in which the component to be extracted from the solution, the solute, is preferably soluble. The solute diffuses in the solvent with a characteristic velocity until it reaches the equilibrium concentrations in each of the phases formed. This separation process is based on the distribution of the solute between the two phases and partial miscibility of the liquids. 

Caffeine can be extracted from aqueous solution by solid-phase microextraction (Section 22-4). In this procedure, a fused-silica (Si02) fiber coated with a polymer is dipped into the liquid and solutes from the liquid distribute themselves between the polymer phase and the liquid. Then the fiber is withdrawn from the liquid and heated in the port of a gas chromatograph. Solutes evaporate from the polymer and are carried into the column. Suggest a procedure for the quantitative analysis of caffeine in coffee by using solid-phase microextraction with a Cvcaffeine internal standard. 

Francisco et al. (2013) describe further the properties of these mixtures as solvents and reaction media. They note that their preparation is in most cases much simpler and less ecologically undesirable than ionic liquids, as they are prepared by simply mixing the two components. No changes of covalent bonds are required. They present charts showing the fields in which they have been applied, including electrochemistry, the preparation of novel materials, synthesis, and separation processes. The chief drawback of DESs they mention is that they are too water-soluble to be used in two-phase systems with water, for instance, extraction from aqueous solutions. Their thermal stability at higher temperatures is yet to be studied. 

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