Solvent extraction, and use

As we will also show, polymers built on hydrophobic polyols and isocyanates are appropriate for the extraction of hydrophobic pollutants. The intent of most polyurethane research is to develop polymers of sufficient strength to meet the requirements of a particular application, for example, designing a polymer to extract an aromatic hydrocarbon from the air. As we begin to develop applications, we will use the principles of solvent extraction and use specific polyols matched to extractants. 

And there was another problem how much acrylamide you detect depends on the way you analyse for it. In fact there was no foolproof way of measuring it, as the pages of the leading journal Analyst were to prove. One method based on slow solvent extraction, and used in Sweden, gave levels of acrylamide seven times high that the more general method based on rapid extraction. One batch of potato crisps had more than... 

Butadiene Separation. Solvent extraction is used in the separation of butadiene (qv) [106-99-0] from other C-4 hydrocarbons in the manufacture of synthetic mbber. The butadiene is produced by catalytic dehydrogenation of butylene and the Hquid product is then extracted using an aqueous cuprammonium acetate solution with which the butadiene reacts to form a complex. Butadiene is then recovered by stripping from the extract. Distillation is a competing process. 

Synthetic Fuel. Solvent extraction has many appHcations in synthetic fuel technology such as the extraction of the Athabasca tar sands (qv) and Irish peat using / -pentane [109-66-0] (238) and a process for treating coal (qv) using a solvent under hydrogen (qv) (239). In the latter case, coal reacts with a minimum amount of hydrogen so that the solvent extracts valuable feedstock components before the soHd residue is burned. Solvent extraction is used in coal Hquefaction processes (240) and synthetic fuel refining (see Coal conversion processes Fuels, synthetic). 

Miscellaneous Pharmaceutical Processes. Solvent extraction is used for the preparation of many products that ate either isolated from naturally occurring materials or purified during synthesis. Among these are sulfa dmgs, methaqualone [72-44-6] phenobarbital [50-06-6] antihistamines, cortisone [53-06-5] estrogens and other hormones (qv), and reserpine [50-55-5] and alkaloids (qv). Common solvents for these appHcations are chloroform, isoamyl alcohol, diethyl ether, and methylene chloride. Distribution coefficient data for dmg species are important for the design of solvent extraction procedures. These can be determined with a laboratory continuous extraction system (AKUEVE) (244). 

The purification of the galHum salt solutions is carried out by solvent extraction and/or by ion exchange. The most effective extractants are dialkyl-phosphates in sulfate medium and ethers, ketones (qv), alcohols, and trialkyl-phosphates in chloride medium. Electrorefining, ie, anodic dissolution and simultaneous cathodic deposition, is also used to purify metallic galHum. 

Another solvent extraction scheme uses the mixed anhydrous chlorides from a chlorination process as the feed (28). The chlorides, which are mostly of niobium, tantalum, and iron, are dissolved in an organic phase and are extracted with 12 Ai hydrochloric acid. The best separation occurs from a mixture of MIBK and diisobutyl ketone (DIBK). The tantalum transfers to the hydrochloric acid leaving the niobium and iron, the DIBK enhancing the separation factor in the organic phase. Niobium and iron are stripped with hot 14—20 wt % H2SO4 which is boiled to precipitate niobic acid, leaving the iron in solution. 

Solvent Treatment. Solvent processes can be divided into two main categories, solvent extraction and solvent dewaxing. The solvent used in the extraction processes include propane and cresyHc acid, 2,2 -dichlorodiethyl ether, phenol (qv), furfural, sulfur dioxide, benzene, and nitrobenzene. In the dewaxing process (28), the principal solvents are benzene, methyl ethyl ketone, methyl isobutyl ketone, propane, petroleum naphtha, ethylene dichloride, methylene chloride, sulfur dioxide, and iV-methylpyrroHdinone. 

The principle of solvent extraction in refining is as follows when a dilute aqueous metal solution is contacted with a suitable extractant, often an amine or oxime, dissolved in a water-immiscible organic solvent, the metal ion is complexed by the extractant and becomes preferentially soluble in the organic phase. The organic and aqueous phases are then separated. By adding another aqueous component, the metal ions can be stripped back into the aqueous phase and hence recovered. Upon the identification of suitable extractants, and using a multistage process, solvent extraction can be used to extract individual metals from a mixture. 

The actual solvent extraction processes used, including the specific extractants and the order in which the components are separated, vary from refinery to refinery. However, a typical scheme is shown in Figure 3 (12). 

Recovery of Uranium from Leach Solutions. The uranium can be recovered from leach solutions using a variety of approaches including ion exchange (qv), solvent extraction, and chemical precipitation. The most common methods in practice are ion exchange and solvent extraction to purify and concentrate the uranium prior to final product precipitation. 

Rice-Bran Wax. Rice-bran wax [8016-60-2] is extracted from cmde rice-bran oil. It can be degummed, the fatty acid content reduced by solvent extraction, and bleached. The wax is primarily composed of esters of lignoceric acid (43 wt %), behenic acid (16 wt %), and 22 02 alcohols (28 wt %). Rice-bran wax may be used in some food apphcations under the regulations described in 21 CFR 172.890. 

Polyethers are usually found in both the filtrate and the mycelial fraction, but in high yielding fermentations they are mosdy in the mycelium because of their low water-solubiUty (162). The high lipophilicity of both the free acid and the salt forms of the polyether antibiotics lends these compounds to efficient organic solvent extraction and chromatography (qv) on adsorbents such as siUca gel and alumina. Many of the production procedures utilize the separation of the mycelium followed by extraction using solvents such as methanol or acetone. A number of the polyethers can be readily crystallized, either as the free acid or as the sodium or potassium salt, after only minimal purification. 

Pharmaceuticals. Pharmaceuticals account for 6% of the Hquid-phase activated carbon consumption (74). Many antibiotics, vitarnins, and steroids are isolated from fermentation broths by adsorption onto carbon foUowed by solvent extraction and distillation (82). Other uses in pharmaceutical production include process water purification and removal of impurities from intravenous solutions prior to packaging (83). 

A predictive macromolecular network decomposition model for coal conversion based on results of analytical measurements has been developed called the functional group, depolymerization, vaporization, cross-linking (EG-DVC) model (77). Data are obtained on weight loss on heating (thermogravimetry) and analysis of the evolved species by Eourier transform infrared spectrometry. Separate experimental data on solvent sweUing, solvent extraction, and Gieseler plastometry are also used in the model. 

Scraped-surface exchangers are particularly suitable for heat transfer with crystalhzation, heat transfer with severe folding of surfaces, heat transfer with solvent extraction, and heat transfer of high-viscosity fluids. They are extensively used in paraffin-wax plants and in petrochemical plants for ciystallization. 

From hen egg white. Purified by solvent extraction and chromatography on alumina. Suspended in distilled water and kept frozen until used [Lee and Hunt J Am Chem Soc 106 7411 1984, Singleton et al. J Am Oil Chem Soc 42 53 7965]. For purification of commercial egg lecithin see Pangborn [J Biol Chem 188 471 7957]. 

Ley et al. reported oxidation of alcohols catalyzed by an ammonium perruthenate catalyst dissolved in [NEtJBr and [EMIM][PFg] [60]. Oxygen or N-methylmorpholine N-oxide is used as the oxidant and the authors describe easy product recovery by solvent extraction and mention the possibility of reusing the ionic catalyst solution. 

The primary sources of toluene and xylenes are reformates from catalytic reforming units, gasoline from catcracking, and pyrolysis gasoline from steam reforming of naphtha and gas oils. As mentioned earlier, solvent extraction is used to separate these aromatics from the reformate mixture. 

Liquid solvents are used to extract either desirable or undesirable compounds from a liquid mixture. Solvent extraction processes use a liquid solvent that has a high solvolytic power for certain compounds in the feed mixture. For example, ethylene glycol has a greater affinity for aromatic hydrocarbons and extracts them preferentially from a reformate mixture (a liquid paraffinic and aromatic product from catalytic reforming). The raffinate, which is mainly paraffins, is freed from traces of ethylene glycol by distillation. Other solvents that could be used for this purpose are liquid sulfur dioxide and sulfolane (tetramethylene sulfone). 

Solvent extraction may also be used to reduce asphaltenes and metals from heavy fractions and residues before using them in catalytic cracking. The organic solvent separates the resids into demetallized oil with lower metal and asphaltene content than the feed, and asphalt with high metal content. Figure 3-2 shows the IFP deasphalting process and Table 3-2 shows the analysis of feed before and after solvent treatment. Solvent extraction is used extensively in the petroleum refining industry. Each process uses its selective solvent, but, the basic principle is the same as above. 

The residues from the vacuum distillation can also be refined to provide very viscous lubricants. The residues from paraflmic base oils are generally solvent extracted and dewaxed. The main use of these products (bright stocks) is as blending components for heavy lubricants. Thus residues from naphthenic base oils, which are also used as blending components for heavy lubricants, are normally not extracted. 

Multi-element analyses involving solvent extraction and high performance liquid chromatography (HPLC) have also been described. The extracts, containing metal-chelate complexes with sulphur-containing reagents, such as dithizone and diethyldithiocarbamate, were used directly for determination of the metals by HPLC.14... 

The procedure followed entails the removal of gross interferences by solvent extraction, and the selective extraction and concentration of the trace metal by use of a chelating agent. The alloy used should not contain more than 0.1 g of copper in the sample weighed out. 

Testing is undertaken by several methods, including chloroform extraction and use of a sulfonphthalein dye (absorbance of yellow-colored complex using bromophenol blue and bromocresol green) or the use of eosin (sodium tetrabromofluorescein) solution in acetone and tetrachloroethane solvent. After shaking with a citric acid buffer and eosin addition, upon standing the lower layer turns pink if filmer is present. Subsequent titration with Manoxol OT (sodium dioctyl sulfosuccinate) quantifies the filmer, with loss of the pink color indicating the end point. 

An overview is presented of plutonium process chemistry at Rocky Flats and of research in progress to improve plutonium processing operations or to develop new processes. Both pyrochemical and aqueous methods are used to process plutonium metal scrap, oxide, and other residues. The pyrochemical processes currently in production include electrorefining, fluorination, hydriding, molten salt extraction, calcination, and reduction operations. Aqueous processing and waste treatment methods involve nitric acid dissolution, ion exchange, solvent extraction, and precipitation techniques. 

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