Cation-exchange resin, example

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. 

Ion exchange, in which cation and/or anion resins are used to replace undesirable anionic species in liquid solutions with nonhazardous ions. For example, cation-exchange resins may contain nonhazardous, mobile, positive ions (e g., sodium, hydrogen) which are attached to immobile acid groups (e.g., sulfonic or carboxylic). Similarly, anion-exchange resins may include nonhazardous, mobile, negative ions (e.g., hydroxyl or chloride) attached to immobile basic ions (e.g., amine). These resins can be used to eliminate various species from wastewater, such as dissolved metals, sulfides, cyanides, amines, phenols, and halides. 

Catalysts for hydrogenation can be also supported on ion exchange resins. For example, rhodium(III) chloride, attached to a 3-carboxy-butenolic acid/DVB cation exchange resin with... 

However, this method possesses several disadvantages such as long reaction time and complicated work-up procedure. For example, in the case of Sc(OTf)3-catalyzed reaction, the treatment required 72 h to get completed at the ambient temperature. After that a pure product was isolated from the reaction mixture by the capture of the solid phase by using strongly acidic cation exchange resin, followed by washing of the solvent and final treatment of resin with 2 M methanolic ammonia. 

Ion exchange is used to purify water. Deionized water is prepared by passing water through an anion-exchange resin in its OH- form and a cation-exchange resin in its H form. Suppose, for example, that Cu(N03)2 is present in the solution. The cation-exchange resin binds Cu2+ and replaces it with 2H+. The anion-exchange resin binds N03 and replaces it with OH-. The eluate is pure water ... 

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