Solutions, solvent stripping

Inversion ofMon cjueous Polymers. Many polymers such as polyurethanes, polyesters, polypropylene, epoxy resins (qv), and siHcones that cannot be made via emulsion polymerization are converted into latices. Such polymers are dissolved in solvent and inverted via emulsification, foUowed by solvent stripping (80). SoHd polymers are milled with long-chain fatty acids and diluted in weak alkaH solutions until dispersion occurs (81). Such latices usually have lower polymer concentrations after the solvent has been removed. For commercial uses the latex soHds are increased by techniques such as creaming. 

Recovery of the solvent, sometimes by chemical means but more often by distillation, is almost always required, and the recoveiy system ordinarily is considered an integral part of the absorption-system process design. A more efficient solvent-stripping operation normally will result in a less costly absorber because of a smaller concentration of residual dissolved solute in the regenerated solvent however, this may increase the overall cost of solvent recoveiy. A more detailed discussion of these and other economic considerations is presented later in this section. 

The products of the solvent extraction process are tantalum strip solution, niobium strip solution and raffinate - liquid wastes containing impurities and residual acids. 

The mass spectra of mixtures are often too complex to be interpreted unambiguously, thus favouring the separation of the components of mixtures before examination by mass spectrometry. Nevertheless, direct polymer/additive mixture analysis has been reported [22,23], which is greatly aided by tandem MS. Coupling of mass spectrometry and a flowing liquid stream involves vaporisation and solvent stripping before introduction of the solute into an ion source for gas-phase ionisation (Section 1.33.2). Widespread LC-MS interfaces are thermospray (TSP), continuous-flow fast atom bombardment (CF-FAB), electrospray (ESP), etc. Also, supercritical fluids have been linked to mass spectrometry (SFE-MS, SFC-MS). A mass spectrometer may have more than one inlet (total inlet systems). 

One obvious procedural refinement would be to precoat the catalyst on the Teflon tape. This would allow low loadings to be delivered by length as opposed to mass measurements, or the tedious preparation of standard solutions. Accordingly, strips of tape were added to a solution of 16-Rf6 in CFaCeFii. The solvent was removed under an inert gas stream to give a yel-... 

Although there is no specific method of conditioning, a rule of thumb is to treat the freshly prepared solvent with a solution similar to that used in the test work. This may require several contacts with the aqueous solution, with stripping between contacts if a metal is extracted. 

The most popular method used is a dynamic method, the saturation method. In this technique, the non-volatile, heavy solid solute is loaded into a saturator, or a battery of two or more saturators connected in series, and remains there as a stationary phase during the experiment. In most cases the saturator is in the form of a packed column. At constant pressure, a steady stream of supercritical fluid (solvent) passes through a preheater, where it reaches the desired system temperature. Then this fluid is continuously fed to the bottom of the saturator, and the solute is stripped from the stationary heavy phase in the column. The supercritical fluid saturated with the solute leaves the saturator at the top. 

A solution of 2.1 g 2,5-dimethoxy-4-(methylthio)benzaldehyde in 7,5 mL nitromethane was treated with 0.45 g anhydrous ammonium acetate and held at steam bath temperature for 6 h. The deep red solution was stripped of solvent to give a residue that spontaneously crystallized. This was ground up under 12 mL MeOH, filtered, and washed with MeOH to yield, after air-drying, 1.7 g of 2,5-dimethoxy-4-methylthio-B-nitrostyrene as orange solids. Recrystallization from EtOHprovided rust-orange colored crystals with a mp of 165.5-166 °C. Anal. (C,, H13N04S) C,H,N S calcd, 12.56 found, 11.96. 

Delmau, L.H., Bonnesen, P.V., Moyer, B.A. 2004. A solution to stripping problems caused by organophilic anion impurities in crown-ether based solvent extraction systems A case study of cesium removal from radioactive wastes. Hydrometallurgy 72 (1-2) 9-19. 

Although solvent samples have been observed for approximately one year without any solids formation, work was completed to define a new solvent composition that was thermodynamically stable with respect to solids formation and to expand the operating temperature with respect to third-phase formation.109 Chemical and physical data as a function of solvent component concentrations were collected. The data included BC6 solubility cesium distribution ratio under extraction, scrub, and strip conditions flowsheet robustness temperature range of third-phase formation dispersion numbers for the solvent against waste simulant, scrub and strip acids, and sodium hydroxide wash solutions solvent density viscosity and surface and interfacial tension. These data were mapped against a set of predefined performance criteria. The composition of 0.007 M BC6, 0.75 M l-(2,2,3,3-tetrafluoropropoxy)-3-(4-.sw-butylphenoxy)-2-propanol, and 0.003 M TOA in the diluent Isopar L provided the best match between the measured properties and the performance criteria. 

Delmau, L. H., Bonnesen, P. V., and Moyer, B. A. A Solution to Stripping Problems Caused by Organophilic Anion Impurities in Crown-Ether Based Solvent Extraction Systems, A Case Study of Cesium Removal from Radioactive Wastes, Hydrometallurgy 72(1,2) (2004), 9-19. 

II). trans-m-Bromocinnamic acid (14.8 g), ethanol (173 ml) and concentrated sulfuric acid (0.4 ml) were combined and heated at reflux for 15 hours. About 150 ml of the ethanol was distilled off, and the remaining solution was poured into ice/water (140 ml). The cold mixture was made strongly alkaline with 40% sodium hydroxide and extracted with methylene chloride (4x60 ml). The combined methylene chloride extract was dried over anhydrous potassium carbonate. The potassium carbonate was removed by filtration and the solvent stripped off under reduced pressure. trans-ethyl-3-Bromocinnamate, was obtained as a partially solidified oil. (IR spectrum was consistent with this compound). 

Type of plant Feed gas Solutes Solvent Commercial purpose Stripping practice... 

SYNTHESIS A suspension of 10 g tryptamine base in 10 g butyl formate was held at reflux for 24 h. The resulting clear solution was stripped of volatiles under vacuum, and the residue partitioned between dilute HC1 and CH2CI2, and the aqueous phase extracted twice with additional CH2CI2. The pooled organic extracts were washed once with dilute aqueous HC1, once with dilute aqueous NaOH, and the solvent removed under vacuum to give a black oil. This was distilled at the KugelRohr to give 9.05 g (11%) of... 

Scandium, thorium and the rare earths The metals are present as nitrates in dilute nitric acid solution. The solvent is 2-methyltetrahydroxyfuran (tetrahydrosylvan) containing 5 per cent (v/v) water and 10 per cent (v/v) nitric acid (d. 1 42). The mixture is spotted upon paper and dried thoroughly in the air. The relative humidity inside the extraction vessel is maintained at 80 per cent by means of a saturated solution of ammonium chloride. After the solvent has diffused about 15 cm down the solvent strip, it is allowed to evaporate, and the strip is placed for about 10 minutes in an atmosphere of ammonia vapour. The paper chromatogram is then sprayed with an alcoholic solution of alizarin and finally with 2m acetic acid. The following results are obtained. 

Tests for Identification of Some Synthetic Dyes. Two very simple reactions can confirm the presence of synthetic dyes. In the solvent stripping test, if the ammonia solution is heavily stained and it becomes irreversibly colorless upon the addition of zinc dust even at room temperature, the presence of an azo dye with sulfo group or groups is indicated (an acid or direct dye) (36, 37). The color of the solution in concentrated sulfuric acid can also be an important indication for identifying synthetic dyes. In this test, a few drops of concentrated sulfuric acid are dripped on a small sample of the dyeing, and the color of the sulfuric acid is observed after a few minutes. Intensive magenta red, red-violet, violet, blue, and green solutions indicate the presence of synthetic dyes (36, 37). 

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