Cation exchange concomitant effects

In operation, metal ions (M ) in solution are preferentially bound to the insoluble matrix with the concomitant release of protons or another cation (M). The toxic metal ion (M ) is effectively held within the matrix. The most common examples of cation exchange are water-softening resins. Hard water (containing Ca ) can be treated with an ion-exchange matrix containing sodium ions. The sodium ions are exchanged with the calcium ions, with the resultant removal of calcium from solution (see Figure 14.3). 

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