Salt splitting capacity

Acrylic This resin is manufactured from a copolymer of acrylic or methacrylic acid with divinylbenzene (Figure 4.10). The result is a weak acid ion-exchange resin with -COOH groups that have very little salt splitting capacity, but are very effective in removing Ca2+ and similar ions under alkaline conditions. 

Resin lonogenic groups Total capacity (meq/g) Salt-splitting capacity (meq/g) Loss in capacity on heating with water (%) Ref. 

Salt splitting capacity is a value sometimes used to describe the strongly functional component only of a resin s total capacity. The term is usually reserved for strongly basic anion exchangers where it is identical to the value for strong base capacity or for weakly acidic cation exchange resins in which case it is a measure of the usually low capacity for the exchange of neutral cations. 

Demineralization by SAC(H)/SBA(OH) Removes virtually all TDS, including carbon dioxide and silica. The TDS in treated water is normally below 2 to 4 ppm. Conductivity is below 10 to 15 pS/cm, but this depends on the degree of sodium slip from the cation. Any slip is converted to sodium hydroxide in the anion unit (salt splitting), causing a sharp increase in conductivity and increased silica solubility. The lack of a degasser drains the anion unit capacity and requires increased caustic for regeneration. 

Weak base resins are like weak acid resins, in that the degree of ionization is strongly influenced by pH. Consequently, weak base resins exhibit minimum exchange capacity above a pH of 7.0. These resins merely sorb strong acids they caimot split salts. 

The capacity to form phosphonium salts decreases when negatively charged substituents are introduced at the silicon atom. Thus, with F3Si—PH2, only a slight tendency to form adducts and to split the Si—P bond is observed (9). Silylphosphanes with a PH2 group like... 

Weak base anion resins Just like for weak acid resins, the operation of weak base anion resins is greatly affected by pH. They exhibit their maximum exchange capacity in the pH range up to 7.0. They hardly adsorb any strong acids they cannot split salts. 

The synthesis of weak acid cation resins has been described above. The ability of this type of resin to split neutral salts is very limited. The resin has the greatest affinity for alkaline earth metal ions in the presence of alkalinity. Only limited capacities for the alkali metals are obtained when alkalinity other than hydroxide is present. Effective use is limited to solutions above pH 4.0. 

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