Neutral cation exchange solutions

Extraction with Neutral Cation Exchange Solutions 215... 

Griffin and Albaugh [102] describe a procedure whereby the neutral AOS product is converted to the parent acids by cation exchange and then titrated potentiometrically. A dilute aqueous solution of AOS is passed through cationic ion exchange resin in acid form. The acids are eluted with small portions of water and titrated potentiometrically using tetrabutylammonium hydroxide solution in a solvent mixture of 70 30 benzene/methanol. It is probable that the benzene can be replaced with toluene for safety reasons or that ASTM titration solvent (ASTM D664 toluene/propan-2-ol/water) can be used. 

Reactions with clay minerals can neutralize both low-pH and high-pH solutions. Neutralization of acids occurs when hydrogen ions replace Al, Mg, and Fe. In alkaline solutions, neutralization is more complex and may involve cation exchange, clay dissolution, and reaction of cations with hydroxide ions to form new minerals called zeolites.39... 

FIGURE 4.6 Schematic view of the equilibria between sample, ion-selective membrane, and inner filling solution for three important classes of solvent polymeric ion-selective membranes. Top electrically neutral carrier (L) and lipophilic cation exchanger (R ) center charged carrier (L-) and anion exchanger (R+) and bottom cation exchanger (R-). 

The lonsiv ion exchange resins are extraction technologies used to separate radionuclides from alkaline wastewater in the presence of competing cations. These resins include lonsiv IE-910 and lonsiv IE-911, which are manufactured using a new class of crystalline silicotitanates (CSTs) invented by researchers from Sandia National Laboratory (SNL) and Texas A M University. CSTs demonstrate high distribution coefficients in acidic, neutral, and alkaline solutions with high concentrations of competitive ions such as sodium and potassium. The affinity of CSTs for strontium in neutral or alkaline wastes is also high. 

The step 1 product (20-30 mg) was suspended in 10ml20%KOH/water/methanol/ dimethyl sulfoxide (DMSO), 5 4 1, respectively, and then heated to 80°C for 3 hours. The homogeneous solution was neutralized to pH 7 with 10% nitric acid and then passed through a cation exchange column containing AG 50W X8 and washed with methanol and water. The eluted material was then lyophilized to yield 24.8 mg of product isolated as a brown solid. 

The mixed lanthanide (III) ions (Ln3+) can be absorbed from solution at the top of a column of a cation-exchange resin RSOsNa (Section 14.4) and then selectively eluted from it, that is, swept down the column in bands by a stream of a solution of a substance that competes with the Ln3+ for sites in the resin. An acidic tribasic chelating agent H3X (usually citric acid/sodium citrate buffer) is used so that, as in reaction 17.16, the tendency for a specific Ln3+ to form neutral LnX and so escape the electrostatic... 

An interesting variant of cationic-resin capture has recently been reported wherein a strongly acidic cation exchange resin mediated sequential amine deprotection and resin capture (Scheme 6).78 Protected aminoalco-hols were reacted with an excess of isocyanates to form /V-BOC-amine carbamates in solution phase. Methanol was subsequently added to quench excess isocyanates as the neutral methyl carbamate byproducts. Sulfonic acid resin 51 was then used to affect amine-BOC group deprotection and resin capture of the deprotected amines. Washing of the resin bed and release (ammonia/methanol) afforded purified amine carbamate products. 

Evaluations of an integrated adsorption system were also conducted. In this system, by varying the pH conditions, the dissolved organics (model compounds) are separated into fractions by isolation onto Amberlite XAD-8, AG MP-50 cation-exchange resin, and graphitized carbon black. The procedure is based on the separation of organic solutes into hydrophobic and hydrophilic neutral, acidic, and basic fractions. 

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