Synthetic Ion Exchangers:

Virtually the field of ion exchange has been dominated by organic ion exchange resins. An almost unlimited variety of resins with different compositions and degrees of cross linking can be prepared. The resins consist of an elastic 3D network of hydrocarbons that carry fixed ionic groups. A charge of the group is balanced through mobile counter ions. As a matter of fact, these resins are cross-linked polyelectrolytes. Within a cation exchanger, the matrix carries ionic groups like

- SO₃^-, - COO^-, - PO₃^3-

and in an anion exchanger, it carries groups like as

-NH₃⁺,  >NH₂  , > N⁺

An ion exchange resin particle is one single macromolecule. A chemical, thermal and mechanical stability and the ion exchange behaviour of the resin depend chiefly on the structure and the degree of cross-linking of the matrix and on the nature and the number of fixed ionic groups. A degree of cross-linking denotes the mesh width of the matrix which in turn affects the swelling of the resin and the mobilities of the counter ions. This last affects the rate of ion exchange and other processes and the electrical conductivity. It should be clear in which ion exchange resins do not have unlimited chemical and thermal stability. The general causes of resin degradation are thermal and chemical deterioration. A primary of commercial ion exchange resins are stable in all general solvents except within the presence of strong oxidizing and reducing agents. They could commonly withstand temperatures slightly higher than 100ºC.

As pointed out previous in which the ion exchange behaviour of the resin is majorly determined through the fixed ionic groups. A number of groups denote the ion exchange capacity. The chemical nature of groups to a great extent affects the ion exchange equilibria. One of the significant factors is the acid and base strength of the group. This could be describes through taking a few examples. The groups COO^- are ionized just at high pH and at low pH; they merge along with H⁺ creating the undissociated COOH. Therefore, they no longer act as fixed charges. Instead, strong acid groups such as SO -remain ionized even at low pH. Same, weak base group NH ⁺ lose a proton, forming an uncharged NH₂ while pH is high and strong base groups like as -N(CH₃)₃⁺  remain ionized even at high pH. Therefore, the operative capacity of weak acid and weak base exchanges is more pH dependent.