Resin Processes, based on ionic exchange resins, are widely used for industrial water treatments
Resin processes are based on ionic exchange resins, i.e. insoluble organic substances able to exchange their ions with other ions having the same load and contained in the solution in which they are immersed.
The resins have a certain number of radicals available for the exchange process; once these have been used, the exchange ceases. It is possible, however, to reconstitute the radicals by means of a chemical process called regeneration.
The most common resin treatments for industrial water are:
- Softening: consists in elimination of the temporary hardness (Ca and Mg bicarbonates) and permanent hardness (calcium and magnesium ions).
- Decarbonation: consists in total or partial elimination of the temporary hardness constituted by the alkaline earth bicarbonates (Ca and Mg).
- Demineralization: consists in elimination of the salinity of the water (Ca, Mg, Na, K salts).
- Adsorption: the adsorbent resins adsorb polar organic molecules, reversibly and selectively “capturing” them inside the pores of the filtering medium (resin).
- Nitrogen removal: the ions typically removed from the polluted flows are the NH4+ ammonium ion and the NO3– nitrate ion. The substituting ion varies depending on the solution used for regeneration of the resin, i.e. according to which ions are on the active sites of the resin.