Wetting time, solvent extraction

After the three solvent extractions, 50 mL of wet resin from each method was placed in separate columns and eluted three times with 1 bed volume of methylene chloride a 20-min contact time between elutions was used. The third elution was collected and concentrated to 1 mL. A homologous series of normal hydrocarbons from C7 to C26 were added as internal standards. Two and one-half microliters of each concentrate was injected onto a 60-m X 0.32-mm i.d., DB-1 fused-silica GC capillary column (J W Scientific). 

An especially intriraing use of liquid-membrane technology, reported for the first time recently by Fox and Hayworth et al.," is the recovery of uranium from wet process phosphoric acid (WPPA). In the manufacture of fertilizer fiom phosphate rock, the acid is solubilized by treatment with sulfuric acid. In addition to HjP04, this crude leachate can contain up to 0.18 g/L of uranium. Under oxidizing conditions this occurs as the uranate ion, UO . Solvent extraction (SX) processes have been developed to recover die uranium values. One of the most common of these uses a mixture of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and trioctylpbosphine oxide (TOPO) in kerosene solution. The chemistry of solvent extraction is as follows ... 

The solvents were evaporated in vacuo, and the residue was taken up in 80 ml of 3M hydrochloric acid. After addition of 220 ml of water, the insoluble material was filtered off, washed with 100 ml of water and then dried. The insoluble material weighed 9.5 g and was mainly unreacted bromo compound. The filtrate was reacted with 50 ml of 7 M NaOH, extracted three times with methylene chloride (50 m -t 2 x 25 ml portions), dried over potassium carbonate, and then evaporated. The yield of residue was 26.8 g which corresponds to 71.4% of the theoretical yield. This residue was a colorless solidifying oil and was dissolved in 200 ml chloroform. Hydrogen chloride was bubbled in until a sample of the solution tested acidic to wet pH indicator paper. A precipitate was obtained and recovered by filtration. The precipitate was washed with chloroform and dried. The melting point was determined to be from 246 Cto247.5°C. 

Uchiyama [11] applied this method to the determination of fluorescent whitening agents and alkyl benzenesulphonates and also methylene blue active substances in bottom sediment samples taken in a lake. The muds were filtered off with a suction filter and frozen until analyzed. About 20g of wet bottom mud was extracted three times with a methanol-benzene (1 1) mixture. After the solvent was evaporated using a water bath, the residue was dissolved in hot water and this solution used for analysis. Table 10.2 shows the analytical results for methylene blue active substances (MBAS), alkyl benzene-sulphonate (ABS), and fluorescent whitening agent (FWA) in bottom sediments. 

To a well-stirred, warm suspension of 6.0 g LAH in 100 mL anhydrous dioxane, there was added a warm solution of 3.2 g of 5-methoxy-3-indolylglyoxylamide in 100 mL of anhydrous THF. The mixture was held at reflux for 38 h, cooled, and the excess hydride decomposed by the sequential addition of wet dioxane followed by 10 mL 5% aqueous NaOH. The resulting solids were removed by filtration, and extracted several times with boiling dioxane. The filtrate and washings were combined, dried over solid KOH, stripped of solvent under vacuum yielding an oily residue. This was dissolved in 80 mL warm benzene, decolorized with charcoal, and the filtered solution treated with an anhydrous solution of HCI in EtOH until it was acidic. The precipitate that formed weighed, after air drying, 1.1 g (29%) with mp 230-235 °C. This solid was recrystallized from EtOH, which provided the product 5-methoxytryptamine hydrochloride... 

The sulfide 1 (0.75 mmol) is dissolved in dichloromethane (2-3 mL) and adsorbed over silica supported sodium periodate (20%, 1.36 g, 1.28 mmol) that is wetted with 0.3 mL of water by thoroughly mixing on a vortex mixture. The adsorbed powdered material is transferred to a glass test tube and is inserted in an alumina bath (alumina 100 g, mesh 65-325, Fisher scientific bath 5.7 cm diameter) inside the microwave oven. The compound is irradiated for the time specified in the table and the completion of the reaction is monitored by TLC examination. After completion of the reaction, the product is extracted into ethyl acetate (2x15 mL). The removal of solvent at reduced pressure affords crude sulfoxide 2 that contains less than 5% sulfone. The final purification is achieved by column chromatography over silica gel column or a simple crystallization. 

Phase II. Additional crystallization studies revealed that the product could be crystallized from toluene-heptane and acetone-water. The product also exhibited limited solubility in toluene. With this information at hand, both reactions were conducted in toluene as before however, during the work-up, dichloromethane was not added. Instead, aqueous hydrochloric acid was added to neutralize excess triethylamine. Heptane was then added to precipitate the product directly from the reaction mixture. The crude wet product was crystallized from acetone-water with an overall yield of 80%. The color of the product was brown. The advantages of this modification are the elimination of several extraction and back-extraction steps and a reduction in processing time and in solvent consumption. 

Relationships between three extraction parameters—solvent composition, temperature, and particle size—can be determined from simple beaker tests. Raw material ground to the desired particle size is contacted with the chosen solvent at the chosen temperature in a beaker and mixed over time. Thief samples are removed at various time intervals and analyzed for the marker. At the completion of the test, the marc is separated from the extract, dried, and analyzed. (In instances when the phytochemical is heat sensitive, the marc can be analyzed wet and the assay calculated on a dry basis). Based on this information, the amount of marker remaining in the dry marc can be determined after correcting for the marker in the absorbed extract in the wet marc. From these data, the equilibrium relationship defined in Equation 11.1 can be determined, as well as the time it takes to reach maximum extraction. Conditions are changed to give a high equilibrium constant and a short extraction time to reach equilibrium. Based on this information, one can select the appropriate extraction equipment as well as the operating conditions to operate the equipment. 

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