Cation exchange resins initiator

Ion-exchange separations can also be made by the use of a polymer with exchangeable anions in this case, the lanthanide or actinide elements must be initially present as complex ions (11,12). The anion-exchange resins Dowex-1 (a copolymer of styrene and divinylben2ene with quaternary ammonium groups) and Amherlite IRA-400 (a quaternary ammonium polystyrene) have been used successfully. The order of elution is often the reverse of that from cationic-exchange resins. 

In order to study further the favorable aspects of in situ acid catalyzed hydrolysis, experiments were performed at different temperatures so as to evaluate the dependence of rate on temperature. Solutions of aldlcarb were passed through a jacketed column around which water at 30, 40, or 50°C was circulating. The ion exchange bed (5 cm x 0.70 cm) contained 2.0 g of Bio-Rad AG MP-50 strong acid cation exchange resin (iT ", 100-200 mesh), and the solution flow rate was approximately 1.0 ml/mln. The percent of Initial aldlcarb remaining at the end of the column for each temperature decreased from 76% at 30 C to 56% at 40 C and 35% at 50°C. Future temperature studies will be done in order to evaluate the practicality of temperature control in a detoxification filter unit. 

Preliminary experiments resulted in the formation of a precipitate due to the presence of inorganic salts when the pH of the test solution was raised to 10 for the first passage through the XAD-8 column to isolate the hydrophobic base fraction. Initially, desalting the solution with a cation-exchange resin (i.e., AG-50-X8, Na+ form) was tried before... 

Thiophenes are known to polymerize on treatment with acidic materials this is probably due to successive protonation and electrophilic substitution. It has been reported (79BCJ1126) that 2-chlorothiophene (80) on treatment with Amberlyst 15 (cation exchange resin) and 100% orthophosphoric acid gives (82) and (84) as major products and (83) as a minor one. The suggested mechanism involves initial protonation to form (81), which subsequently acts as an electrophile (Scheme 13). Related dimerizations have been reported on treatment of benzo[6]thiophene with A1C13 <80JCS(P1)677, 81JCR(S)307>. 

On Day 3, the manipulations conducted on Day 2 are tested. Treatments with zeolite, activated carbon, Amberlite XAD , anion and cation exchange resins are conducted and the toxicity tests initiated. 

Resins with good hydrodynamic properties and sorption capadties for proteins and enzymes have been prepared by the polymerization of acrylic acid or methacrylic acid and a crosslinking monomer such as 1,3,5-triacryloylhexahydrotriazine (TAT) in aqueous acetic acid using a radical initiator. Methacrylic add-TAT copolymer prqjared by using a redox catalyst is useful as a cation-exchange resin for selective and reversible sorption of proteolytic enzymes such as terrilytin. 

Figure 8.26 Schematic diagram of a cation-exchange resin framework with fixed exchange sites prior to and following an exchange reaction (a) initial state prior to exchange reaction with cation B (b) equilibrium state after exchange reaction with cation B. ...

The scope of the Ritter reaction can also be extended by avoiding strong acid as the carbenium ion initiator. In at least one case it is possible to omit this reagent entirely because of the facility of 5 1 reaction. Thus, reflux of r-butyl bromide in acetonitrile or propionitrile for 24 h led to formation of A -f-butylamide products. Less commonly used initiators have included cation exchange resins and clayfen. In this latter case, the clay-supported iron(III) nitrate is believed to give rise to nitrosonium ions, which react with the alkyl halide substrate to produce a carbenium ion. Yields of amide from this technique are generally modest (21-35%). 

The results for the isotopic separation of Na/ Na which were obtained by Knochel and Wilken in the system Dowex 50/aqueous or methanolic solution of cryptands are summarized in Table 13 (explanation for Krl and Kr see Chap. 4.3.1.2). To reach a high total enrichment compared with one equilibrium stage, the batch experiments were carried out as a cascade (Chap. 2.5.2). Then Eq. (20) was used for the calculation of a-values. To determine the isotopic separation factor Mr for the complex formation as well, the Kr-vuIucs were analyzed in the same system without cryptands " .iss) see Chap. 4.3.1.2). In all experiments 30 mg cation exchanger resin (Li - or Cs -form) were equilibrated with a 10M Na -solution where a lithium or cesium salt, which corresponds to the counterion of the resin, was added up to a total cation concentration of 10 M. If one has used a complexing ageftt, the initial cryptand concentration has been established to be 10 M (pH = 8). For most of the systems, the standard deviations given in Table 13 correspond to seven parallel experiments. The measurement of the radionuclides Na and Na was carried out as described in Chap. 4.2.4. 

Figures 3 and 4 show Kd values observed for two macroporous cation exchange resins, Duolite GT-73 and Amberlite IRC-718. The adsorption of plutonium on both resins was relatively weak compared with other adsorbents, especially at the lower initial plutonium concentrations. At initial concentrations of about 1 pCi/L, Kd values for Duolite GT-73 and Amberlite IRC-718 were approximately 200 and 76 ml/g, respectively. Surprisingly, no dependence on pH is apparent at the lower initial plutonium concentrations. More cationic plutonium species should be present at lower pH values and would be more strongly adsorbed on cation exchange resin. This effect is only observed for Duolite GT-73 at the higher initial plutonium concentration, 10 iCi/L. The absence of a pH effect at the lower concentration can be explained by the existence of a small concentration of a stable plutonium species in solution that does not interact with cation resins. Additional evidence supporting this explanation is the fact that about 1.3 to 2.8% of the initial plutonium is not adsorbed on the cation resins in both the batch equilibrium adsorption measurements and the column adsorption experiments discussed later. This small fraction of plutonium is not adsorbed over a...

Non-suppressed ion chromatography employs a conventional liquid chromatographic system with a conductivity detector cell connected directly to the outlet end of an ion-exchange separation column. No suppressor unit is required. The successful development of this method was made possible by three principal innovations (1) the use of an anion- or cation-exchange resin of very low capacity (initially 0.007 to... 

Placement of the mini-column prior to the sample introduction port can also be useful in unsegmented flow analysis, as demonstrated in the flow injection spectrophotometric determination of molybdenum in plant digests [236]. This method relied on the influence of molybdate anions on the rate of iodide oxidation by hydrogen peroxide under acidic conditions, and some potential interfering cations needed to be separated. To this end, a cation-exchange resin mini-column was attached to the central sliding bar of an injector-commutator hence, it could be displaced between two different streams. Initially, the sample solution was pumped... 

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