Cation exchange treatments

In one paper [51] examining cation-exchanger treatment of water a mbcture of equal amounts of strong- and weak-acid ion exchangers was employed. 

In both of the preceding instances, it is recommended that the cation exchange treatment is applied to approximately 10-20% of the total volume of the wine. The treated wine is then mixed into the rest. It is also advisable to cold-stabilize the wine prior to ion exchange treatment to enhance protection from tartrate precipitation. 

Cation exchange treatments in must and wine are authorized in some countries. When used for stabilizing tartaric precipitation, these treatments acidify the resulting product but in normal treatment conditions, the pH is not lowered by more than 0.2. Eliminating potassium by electrolysis (Volume 2, Section 12.5) also causes a slight decrease in pH. 

Table 9.1 Surface tension values and parameters for a group of clay minerals, each saturated with a specific cation (Norris, 1993 Norris et al., 1993). The heading Nat refers to the clay with no cation exchange treatment. Amm refers to an exchange with the ammonium cation. All values are in units of mJ/w measured at 2CPC. The values listed under are the calculated...

After cation exchange treatment to replace cations with H2O sample (150 mL) is adjusted to pH 2, applied to the column, and rinsed with 0.01 M HCl. After elution of inorganic salts (detected by conductivity), organic ions are eluted with 75 25 CH3CN/O.IM HCl. 

Deamidation of soy and other seed meal proteins by hydrolysis of the amide bond, and minimization of the hydrolysis of peptide bonds, improves functional properties of these products. For example, treatment of soy protein with dilute (0.05 A/) HCl, with or without a cation-exchange resin (Dowex 50) as a catalyst (133), with anions such as bicarbonate, phosphate, or chloride at pH 8.0 (134), or with peptide glutaminase at pH 7.0 (135), improved solubiHty, whipabiHty, water binding, and emulsifying properties. 

In the recovery of cadmium from fumes evolved in the Imperial Smelting process for the treatment of lead—zinc concentrates, cadmium is separated from arsenic using a cation-exchange resin such as Zeocarb 225 or Ambedite 120 (14,15). Cadmium is absorbed on the resin and eluted with a brine solution. The cadmium may then be recovered direcdy by galvanic precipitation. 

Cation exchange resin. Conditioned before use by successive washing with water, EtOH and water, and taken through two H -Na -H cycles by successive treatment with M NaOH, water and M HCl then washed with water until neutral. 

Regenerant The solution used to restore the activity of an ion exchanger. Acids are employed to restore a cation exchanger to its hydrogen form brine solutions may be used to convert the cation exchanger to the sodium form. The anion exchanger may be rejuvenated by treatment with an alkaline solution. 

Weakly acidic cation exchangers (e.g. polymethylacrylic acid resins). These resins (Zerolit 226, Amberlite 50, etc.) are usually supplied in the hydrogen form. They are readily changed into the sodium form by treatment with 1M sodium hydroxide an increase in volume of 80-100 per cent may be expected. The swelling is reversible and does not appear to cause any damage to the bead structure. Below a pH of about 3.5, the hydrogen form exists almost entirely in the little ionised carboxylic acid form. Exchange with metal ions will occur in solution only when these are associated in solution with anions of weak acids, i.e. pH values above about 4. 

Sodium 4-pyridinesulfonate has been obtained from the oxidation of 4 pyndinethiol with hydrogen peroxide in sodium hydroxide solution,15 and from the reaction of 4-chloropyridme with aqueous sodium sulfite16 The salt has been converted to the free acid by treatment with a cation-exchange resin 1011 or with sulfuric acid.11... 

Also, nylon-6 waste may be hydrolyzed in the presence of an aqueous alkali metal hydroxide or acid5 to produce an alkali metal or acid salt of 6-aminocaproic acid (ACA). The reaction of nylon-6 waste with dilute hydrochloric acid is rapid at 90- 100°C. The reaction mixture is poured into water to form a dilute aqueous solution of the ACA salt. Filtration is used to remove undissolved impurities such as pigments, additives, and fillers followed by treatment of the acid solution with a strong cation exchange resin. A sulfonic acid cationic exchanger absorbs ACA salt and pure ACA is eluted with ammonium hydroxide to form a dilute aqueous solution. Pure ACA is obtained by crystallization of die solution. 

Recovery of phenylalanine from aqueous solutions by cation-exchange resins has been reported by Carta and co-workers (Borst et al., 1997). It might be possible to improve the efficiency of resin treatment by raising the operating temperature, to, say, 65 °C. 

One notable result is the treatment of 2-hydroxy cyclic ether analog, 2-deoxy-D-ribose with aniline in water catalyzed by InCl3 to afford the novel tricyclic tetrahydroquinoline compounds (Eq. 12.60). The reaction can also be catalyzed by recoverable cation-exchange resin instead of indium chloride.132 By using a stoichiometric amount of indium metal, a domino reaction of nitroarenes with 2,3-dihydrofuran generates the same products. 133... 

Tyree and Bynum [132] described an ion chromatographic method for the determination of nitrate and phosphate in seawater. The pre-treatment comprised vigorous mixing of the sample with a silver-based cation-exchange resin, followed by filtration to remove the precipitated silver salt. 

---