Ionic extraction

The ionic extractants are those chemicals that carry within an ion pair a labile cation or anion, which will exchange with the appropriate metal species in the aqueous phase. Their role may be regarded as a form of liquid ion exchange. Several commercially available amines belong to this class, are shown in Figure 17. 

Functionalised polymers have been used to covalently or ionically extract unpleasantly smelling and / or toxic molecules from a solution. o A classic example is given in Figure 13.3. 

The LCPs retain 70% of their notched Izod impact values down to a temperature of about —270°C (—450°F). They are also resistant to bleaches, chlorinated organic solvents and alcohols. They have extremely low gas-permeation rates compared to commercial packaging films. Their ionic extractables are well below those needed for corrosion-free environments for integrated circuit chip apphcations. The... 

Fig, 11. Cathodic corrosion rate of aluminum increases with the contents of ionic extracts from molding compounds into water... 

Semiconductor devices are particularly sensitive to ions, and the levels of ionic extractables in electronics packaging materials are becoming more important as devices become increasingly smaller. Again, as is illustrated in Table 7.11, some LCPs, owing to the use of high-purity monomers and small amounts of catalyst, exhibit very low levels of ionic extractables. This relative purity also has positive implications for the employment of LCPs in many other application areas. 

In total, seven PILs based on five organic superbases and two p-diketones, illustrated in Fig. 3.4, were investigated as ionic extractants for La and Ba " solvent extractions in the aprotic IL [C4mim][NTf2] [91]. The La and Ba ... 

Different types of other coal liquefaction processes have been also developed to convert coals to liqnid hydrocarbon fnels. These include high-temperature solvent extraction processes in which no catalyst is added. The solvent is usually a hydroaromatic hydrogen donor, whereas molecnlar hydrogen is added as a secondary source of hydrogen. Similar but catalytic liquefaction processes use zinc chloride and other catalysts, usually under forceful conditions (375-425°C, 100-200 atm). In our own research, superacidic HF-BFo-induced hydroliquefaction of coals, which involves depolymerization-ionic hydrogenation, was found to be highly effective at relatively modest temperatnres (150-170°C). 

Metal carboxylates are ionic and when the molecular weight isn t too high the sodium and potassium salts of carboxylic acids are soluble m water Carboxylic acids therefore may be extracted from ether solutions into aqueous sodium or potassium hydroxide... 

Their basicity provides a means by which amines may be separated from neutral organic compounds A mixture containing an amine is dissolved m diethyl ether and shaken with dilute hydrochloric acid to convert the amine to an ammonium salt The ammonium salt being ionic dissolves m the aqueous phase which is separated from the ether layer Adding sodium hydroxide to the aqueous layer converts the ammonium salt back to the free amine which is then removed from the aqueous phase by extraction with a fresh portion of ether... 

However, the quantity of Pa produced in this manner is much less than the amount (more than 100 g) that has been isolated from the natural source. The methods for the recovery of protactinium include coprecipitation, solvent extraction, ion exchange, and volatility procedures. AH of these, however, are rendered difficult by the extreme tendency of protactinium(V) to form polymeric coUoidal particles composed of ionic species. These caimot be removed from aqueous media by solvent extraction losses may occur by adsorption to containers and protactinium may be adsorbed by any precipitate present. 

Separation Processes. The product of ore digestion contains the rare earths in the same ratio as that in which they were originally present in the ore, with few exceptions, because of the similarity in chemical properties. The various processes for separating individual rare earth from naturally occurring rare-earth mixtures essentially utilize small differences in acidity resulting from the decrease in ionic radius from lanthanum to lutetium. The acidity differences influence the solubiUties of salts, the hydrolysis of cations, and the formation of complex species so as to allow separation by fractional crystallization, fractional precipitation, ion exchange, and solvent extraction. In addition, the existence of tetravalent and divalent species for cerium and europium, respectively, is useful because the chemical behavior of these ions is markedly different from that of the trivalent species. 

Fig. 2. Ultracentrifugal pattern for the water-extractable proteins of defatted soybean meal in pH 7.6, 0.5 ionic strength buffer. Numbers above peaks are approximate sedimentation coefficients in Svedberg units, S. Molecular weight ranges for the fractions are 2S, 8,000—50,000 7S, 100,000—180,000 IIS, 300,000—350,000 and 15S, 600,000—700,000 (9). The 15S fraction is a dimer of the IIS protein (10).

Zirconium and hafnium have very similar chemical properties, exhibit the same valences, and have similar ionic radii, ie, 0.074 mm for, 0.075 mm for (see Hafniumand hafnium compounds). Because of these similarities, their separation was difficult (37—40). Today, the separation of zirconium and hafnium by multistage counter-current Hquid—Hquid extraction is routine (41) (see Extraction, liquid—liquid). 

Isolation. Isolation procedures rely primarily on solubiHty, adsorption, and ionic characteristics of the P-lactam antibiotic to separate it from the large number of other components present in the fermentation mixture. The penicillins ate monobasic catboxyHc acids which lend themselves to solvent extraction techniques (154). Pencillin V, because of its improved acid stabiHty over other penicillins, can be precipitated dkecdy from broth filtrates by addition of dilute sulfuric acid (154,156). The separation process for cephalosporin C is more complex because the amphoteric nature of cephalosporin C precludes dkect extraction into organic solvents. This antibiotic is isolated through the use of a combination of ion-exchange and precipitation procedures (157). The use of neutral, macroporous resins such as XAD-2 or XAD-4, allows for a more rapid elimination of impurities in the initial steps of the isolation (158). The isolation procedure for cephamycin C also involves a series of ion exchange treatments (103). 

Further Preparative Reactions. When pulps are to be used in the production of materials that do not retain the original fiber stmcture, such as rayon or ceUulose acetate film, the lignin, hemiceUulose, and other components must be reduced to the lowest possible concentrations. A surfactant (ionic or nonionic) is often added during a hot, weakly alkaline extraction step after chlorination. Another approach, sometimes used in addition to the surfactant step, is to treat the pulp with 6—10% NaOH after most of the oxidative bleaching is finished. This treatment removes most of the hemiceUulose. In most purification plants the final stage includes use of sulfuric acid chelators are optional. 

Recent publications indicate the cloud-point extraction by phases of nonionic surfactant as an effective procedure for preconcentrating and separation of metal ions, organic pollutants and biologically active compounds. The effectiveness of the cloud-point extraction is due to its high selectivity and the possibility to obtain high coefficients of absolute preconcentrating while analyzing small volumes of the sample. Besides, the cloud-point extraction with non-ionic surfactants insures the low-cost, simple and accurate analytic procedures. 

THE USE OF PROTONIC EQUILIBRIUM OF DIMERIC RHODAMINE 6G ON EXTRACTION OF IONIC ASSOCIATIONS... 

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