Synthetic anion exchangers

Definition A synthetic anion exchanged polymer in which quaternary ammonium groups are attached to a copolymer of styrene and divinylbenzene Properties Wh. to buff-colored fine powd. odorless to si. amine odor insol. in water, ethanol, chloroform, ether, benzene, org. soivs. stable to 150 C... 

Synthetic anion exchange resins have proven to be more satisfactory for tin separations than any other ion exchange medium, and papers reporting the use of a number of different anionic tin complexes on this type of exchanger have been published. In HCl solutions the very extensive data compiled by Kraus and Nelson with Oowex-1 anion exchange resins is well known... 

Figure 9 A synthetic mixture of water-soluble carboxylic acids separated by anion-exchange chromatography. Column 0.3 cm x 300 cm Diaoion CA 08, 16-20 p (Mitsubishi Kasei Kogyo). Eluant 200 mM HC1. Detection reaction with Fe3-benzohy-droxamic acid-dicyclohexy carbodiimide-hydroxylamine perchlorate-triethyl amine with absorbance at 536 nm. Analytes (1) aspartate, (2) gluconate, (3) glucuronate, (4) pyroglutamate, (5) lactate, (6) acetate, (7) tartrate, (8) malate, (9) citrate, (10) succinate, (11) isocitrate, (12) w-butyrate, (13) a-ketoglutarate. (Reprinted with permission from Kasai, Y., Tanimura, T., and Tamura, Z., Anal. Chem., 49, 655, 1977. 1977 Analytical Chemistry).

Elderfield and Greaves [629] have described a method for the mass spectromet-ric isotope dilution analysis of rare earth elements in seawater. In this method, the rare earth elements are concentrated from seawater by coprecipitation with ferric hydroxide and separated from other elements and into groups for analysis by anion exchange [630-635] using mixed solvents. Results for synthetic mixtures and standards show that the method is accurate and precise to 1% and blanks are low (e.g., 1() 12 moles La and 10 14 moles Eu). The method has been applied to the determination of nine rare earth elements in a variety of oceanographic samples. Results for North Atlantic Ocean water below the mixed layer are (in 10 12 mol/kg) 13.0 La, 16.8 Ce, 12.8 Nd, 2.67 Sm, 0.644 Eu, 3.41 Gd, 4.78 Dy, 407 Er, and 3.55 Yb, with enrichment of rare earth elements in deep ocean water by a factor of 2 for the light rare earth elements, and a factor of 1.3 for the heavy rare earth elements. 

Figure 5 Chromatogram of a synthetic mixture of chloride (a), bromide (b), nitrate (c), and sulfate (d) separated on an anion-exchange column. (From Ref. 93, with permission.)...

Several limitations on the synthetic techniques that can be employed are imposed by the need for rapidity and minimization of handling because of the radiation hazard, and the low concentration and small physical quantities of the compounds. Purification steps should be eliminated if possible by optimizing yields. Where purification is unavoidable, simple procedures are employed such as use of anion exchange columns to remove perrhenate (the most common contaminant in the final product). A variety of disposable sample preparation columns are well suited to this purpose and are available containing small quantities of anion or cation exchange materials (0.1 to 0.5 g typically) such as quaternary ammonium-, primary ammonium-, or sulfonate-derivatized silica. Reversed phase columns are also often used (C8 or C18-derivatized silica). The purification is often thus reduced to a simple filtration step which can be performed aseptically. 

The presence of color in many industrial effluent streams is highly undesirable. LDHs have been found to be particiflarly effective at removing various synthetic dyes (Table 1) [158]. For example. Acid Blue 29 could be adsorbed on the surface or enter the interlayer region of the LDH by anion exchange an equilibrium time of 1 h with 99 % dye removal was obtained. Furthermore,... 

This is a process mainly used in power plants for removal of ions by sorption on the surface of a solid matrix. Synthetic cation and/or anion exchange resins are required depending on the pollutants to be removed. It may require pH adjustments. The removal efficiency for inorganic pollutants is as follows ... 

However, there also some disadvantages. Specifically, the limited radiation and thermal stability set limits to the usage of synthetic organic ion-exchange resins. Regarding temperature, 150 °C is the maximum temperature that cation-exchange resins can withstand, whereas 70 °C is the limit for anion-exchange resins. Consequently, hot streams to be treated have to be cooled below these temperatures. 

Weak Base Anion Exchangers. Both styrenic and acrylic copolymers can be converted to weak base anion-exchange resins, but different synthetic routes are necessary. Styrene—DVB copolymers are chloromethylated and aminated in a two-step process. Chloromethyl groups are attached to the aromatic rings (5) by reaction of chloromethyl methyl ether [107-30-2], CH3OCH2Cl, with the copolymer in the presence of a Friedel-Crafts catalyst such as aluminum chloride [7446-70-0], A1C13, iron(III) chloride [7705-08-0]9 FeCl3, or zinc chloride [7646-85-7], ZnC. ... 

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