Double-solvent extraction

Duosol Process. The Duosol process developed by the Max B. Miller Co. (28) is an outstanding example of commercial adoption of a double solvent extraction process. Patents (27) for this process date from May 1933 and cover numerous aspects of the problem including a variety of paraffinic solvents (ethane, propane, butane, petroleum ether) and naphthenic solvents (wood tar acids, cresols, creosote, and phenol). Present commercial application utilizes propane and Selecto (a mixture of phenol and cresylic acid, normally ranging in composition from 20 to 80% phenol). 

If the compound is present at a low concentration in the presence of many interfering compounds, cleanup and concentration steps become necessary [8]. Solvent extraction procedures are used often for sample preparation for drugs and many other small molecules in the chromatographic technique. Solid-phase methods are very popular because of the wide choice of the packing material. Sample extraction methods have two other main advantages in CE, namely sample concentration and elimination of both sample ions and proteins. Double-solvent extraction is very useful for elec-trokinetic injection, especially for basic compounds. It eliminates variability due to matrix effects in electro-kinetic injection. 

Nuclear Waste. NRC defines high level radioactive waste to include (/) irradiated (spent) reactor fuel (2) Hquid waste resulting from the operation of the first cycle solvent extraction system, and the concentrated wastes from subsequent extraction cycles, in a faciHty for reprocessing irradiated reactor fuel and (3) soHds into which such Hquid wastes have been converted. Approximately 23,000 metric tons of spent nuclear fuel has been stored at commercial nuclear reactors as of 1991. This amount is expected to double by the year 2001. 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

Fig. 18 Free energy profiles for the solvent extraction of copper, where L is Acorga P50. The profile shows the free energy of a site on the liquid/liquid interface. All higher-order rate constants are reduced to first-order rate constants by using the concentrations of reactants in either phase. The free energy lost in each cycle can be seen from the difference between 0 and the 10%, 50% and 80% extraction lines on the right of the diagram. The double-headed arrows indicate the rate-limiting free energy difference.

Encinar JR, Rodriguez-Gonzalez P, Fernandez JR, Alonso JIG, Diez S, Bayona JM, Sanz-Medel A. Evaluation of accelerated solvent extraction for butyltin speciation in PACS-2 CRM using double-spike isotope dilution-GC/ICPMS. Anal. Chem. 2002 74 5237-5242. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

Increases in yield of naval stores are brought about by chemical treatment of the exposed wood, especially with paraquat herbicides (dipyridyl compounds). This treatment stimulates extensive oleoresin formation and diffusion into the wood, extending to the pith of the tree and several feet above the treatment level. As much as 40 percent oleoresin content in the wood has been produced. Such treatment could double naval stores production, for both gum and sulfate processes. It also has the potential of providing a new type of wood naval stores by solvent extraction prior to kraft pulping, or a combination of both methods. 

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