Solvent extraction from water

The octanol/water partition coefficient is the log of solubility of the solvent in water relative to that in octanol. This coefficient is used to estimate biological effects of solvents. It can also be used to estimate the potential usefulness of a solvent extraction from water by... 

In Example 1 the solute, acetone, contains a ketone carbonyl group which is a hydrogen acceptor, i.e., solute class 5 according to Table 15-4. This solute is to be extracted from water with chloroform solvent which contains a hydrogen donor group, i.e., solvent class 4. The solute class 5 and solvent class 4 interaction in Table 15-4 is shown to give a negative deviation from Raonlt s law. 

These acids are less stable, less soluble and less acidic than the corresponding sulfonic acids. The common impurities are the respective sulfonyl chlorides from which they have been prepared, and the thiolsulfonates (neutral) and sulfonic acids into which they decompose. The first two of these can be removed by solvent extraction from an alkaline solution of the acid. On acidification of an alkaline solution, the sulfinic acid crystallises out leaving the sulfonic acid behind. The lower molecular weight members are isolated as their metal (e.g. ferric) salts, but the higher members can be crystallised from water (made slightly acidic), or alcohol. 

Law and Goerlitz in 1970 reported the effective removal of co-extractives from water using microcolumns of these three adsorbents for the analysis of chlorinated pesticides. The development of polystyrene resins such as XAD increased the ability to concentrate pesticide residues from water. Large volumes of sample water could be passed through an XAD resin and the pesticide would adsorb on the resin. Elution of the pesticide by an organic solvent such as methanol and subsequent cleanup by the adsorbent materials became the industry standard. 

Water samples are acidified and extracted with solvent (Kawamura and Kaplan 1983 Muir et al. 1981). Clean-up steps may be used (Kawamura and Kaplan 1983). Methylene chloride is often used as the extracting solvent, and it may interfere with the nitrogen-phosphorus detector. In this case, a solvent-exchange step is used (Muir et al. 1981). Analysis by GC/NPD or GC/MS provides specificity (Kawamura and Kaplan 1983 Muir et al. 1981). Accuracy is acceptable (>80%), but precision has not been reported. Detection limits were not reported, but are estimated to be 0.05-0.1 pg/L (Muir et al. 1981). Detection limits at the low ppt level (ng/L) were achieved by concentrating organophosphate esters on XAD-2 resin. The analytes were solvent extracted from the resin and analyzed by GC/NPD and GC/MS. Recovery was acceptable (>70%) and precision was good (<10% RSD) (LeBel et al. 1981). 

Acid hydrolysis of the polysaccharide portion of wood will release lignin but also causes major condensation reactions in the product(2l). These reactions can be minimized by using 41 wt. percent hydrochloric acid in place of other mineral acids but some condensation reactions still occur(22). This is not an effective method by which to obtain unaltered lignin. On the other hand, lignin can be solvent extracted from wood at temperature of 175°C using solvent mixtures such as 50/50 by volume water/1,4-dioxacyclohexane(23) Changes in lignin under these conditions appear to be minor. 

The development of more benign alternatives to cyanide for gold-leaching (see Section 9.17.3.1) such as thiourea, thiocyanate, or thiosulfate, which form stable complexes in water has prompted research to identify suitable solvent extractants from these media. Cyanex 301, 302, 272, Ionquest 801, LIX 26, MEHPA, DEHPA, Alamine 300 (Table 5) have been evaluated as extractants for gold or silver from acidic thiourea solutions.347 Whilst the efficacy of Cyanex 301 and 302 was unaffected by the presence of thiourea in the aqueous feed, the loading of the other extractants is severely depressed. Formation of solvated complexes of gold and of an inner-sphere complex of silver has been proposed.347... 

In order to extract from water a dissolved reaction product, or one which is not sufficiently solid or crystalline to be removed by filtration, or else to separate a substance from insoluble material which accompanies it, it is taken up in a suitable solvent. Ether is most commonly used for this purpose. Thus, for example, the distillate from a steam distillation is treated in this way unless it spontaneously separates into two layers. 

Study of the eflSciency of packed columns in liquid-liquid extraction has shown that spontaneous interfacial turbulence or emulsification can increase mass-transfer rates by as much as three times when, for example, acetone is extracted from water to an organic solvent (84, 85). Another factor which may be important for flow over packing has been studied by Ratcliff and Reid (86). In the transfer of benzene into water, studied with a laminar spherical film of water flowing over a single sphere immersed in benzene, they found that in experiments where the interface was clean... 

Anhydrous Hydrogen Chloride is a colorless gas, which on liquefaction gives colorless (or si yellowish) fuming, strongly corrosive liquid mw 36.47, sp gr of gas at 0° 1.268 (Air) fr p -114.3° bp -111° (Lange) bp -84.8° sol in w, ale, eth benz. It can be prepd by furnace combstn pf hydrogen, methane or water-gas, in chlorine or by solvent extraction from hydrochloric acid (aqueous HC1). 

To summarize this example, we have shown how a team of researchers might be led to polyurethane as an extraction solvent for aqueous-based pollutants. The polymer has attributes that can provide for additional benefits as weU-including cost, surface area, and flow-through characteristics. This specific example deals with extraction from water, but many of the same arguments could have been applied to extractions from gases. 

Chlorophyll. Chemically pure chlorophyll is difficult to prepare, since it occurs mixed with other colored substances such as carotenoids. Commercially it is solvent extracted from the dried leaves of various plants such as broccoli or spinach. Chlorophyll is water-iosoluble. It has none of the characteristics of a dye in that it has no aflinity for the usual libers such as cotton or wool. Chlorophyll is properly classified as a pigment tCI Natural Green 3 Cl 75810), As such. It finds use lor coloring soaps, waxes, inks. fats, or nils. Chlorophyll is an ester composed of an acidic pint, chlorophyllin, esterilied by an aliphatic alcohol known as phylol. Hydrolysis of chlorophyll using sodium hydroxide produces the moderately water-soluble sodium salts of chlorophyllin. phytol. and methanol. The magnesium in chlorophyllin may be replaced by copper. The sodium copper chlorophyllin salt is heat-stable, and is ideal for coloring foods where heat is involved, such as in canning. 

The flavour and modern phytopharmaceutical industries have made big changes to the traditional pharmaceutical extraction processes. Whereas ethanol was really the only significant solvent apart from water used by the traditional pharmaceutical extractors, solvents such as hexane and acetone have been used by flavour companies to make soft-extract oleoresins for natural flavour components. Sub- and supercritical carbon dioxide and also some fluorohydrocarbons are now used to produce some very high-quality extracts. Modern concentration and drying processes such as reverse osmosis, spray-drying and freeze-drying... 

A related test method (ASTM D-5368) describes the standard procedures for gravimetricafly determining the total nonvolatile and semivolatile organic content of solvent extracts from soils or solid wastes. As written, the test method is used after a solvent extract is obtained from a soil or solid waste. For these methods to be applicable, the extraction solvent must have a boiling point less than that of water at ambient pressure. Again, the total solvent extractable content (TSEC) of a soil, sediment, sludge, or solid waste depends on the solvent and method used for the extraction. 

Shaking. Pollutants are generally extracted from water samples, and in some cases soil samples, by shaking with an appropriate solvent or solvent combination. Mechanical shakers are used to handle several water or soil samples at once. These devices allow the analyst to conduct long-term extractions (e.g., 24 h) if required. Two or more shakings normally are required for complete removal (i.e., >98%) of the toxicant from the sample matrix. 

Competitive (seven-metal) solvent extraction experiments (water/chloroform) and related bulk membrane transport (water/chloroform/water) experiments have been performed in which each of the four tri-branched ligands as well as their single ring analogues were employed as the extractant/ionophore in the respective chloroform phases [37], In both sets of experiments the aqueous source phases contained an equimolar mixture of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Ag(I) and Pb(II) nitrates and were buffered at pH 4.9. For membrane transport the aqueous receiving phase was buffered at pH 3 under these conditions any transport will be driven by the back transfer of protons. Under the conditions employed, the results from the solvent extraction and the bulk membrane transport experiments clearly paralleled each other -for each ligand system high extraction/transport selectivity for Ag(I) was observed over the other six metal ions present in the respective source phases. 

Organic Extraction GLC solvent column from water details Detector Comments LD Ref... 

In general, to extract lignans from plants, the first step is to apply polar solvents to different parts of the plants involved. The resulting extracts are then dissolved in water and re-extracted with nonpolar solvents. Extracts from Taxus species are obtained in a similar manner to this [1,3,10]. 

Willis (W12, W14) reported the determination of lead in urine. Lead was chelated with ammonium pyrrolidine dithiocarbamate and extracted into methyl-n-amyl ketone. Urine samples of 50 ml had to be extracted into 1.5 ml of the solvent to obtain sufficient concentration of the metal. Differences in the efficiency of extraction from water and urine at various pH values were noted. The availability of a reliable and simple method such as the one described will be welcomed by medical laboratories, but unfortunately the limited sensitivity requiring large original samples makes the method less applicable for the determination of lead in blood. 

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