Cation ion exchange resin (ion exchange process) is a reversible chemical reaction between the ionic liquid phase and solid phase ions performed when certain ions in the liquid phase ion-exchange solids more preferences, then will be solid ion exchange adsorption, in order to maintain a neutral aqueous solution, it must release the equivalent solid ion exchange ion back solution. Classification of the cationic resin (1) strong acid cation resin such resins (IONRESIN) contains a large amount of strongly acidic groups such as sulfonic acid group -SO3H, readily dissociate in solution H +, it was strongly acidic. After the resin dissociation, the body contains negatively charged groups, such as SO3-, capable of adsorbing the bonding solution of the other cations. Both reaction of the resin in the H + exchange cations in solution. Seth color can strongly acidic resin dissociation strong, can produce dissociation and ion exchange in acidic or alkaline solution. Resin in use for some time, to be regenerated, that the ion exchange reaction with the chemicals in the opposite direction, so that the resin functional groups to restore the state to use again. As described above with a strong acid cation resin is regenerated, then the adsorbed cation resin discharged, then combined with H + and to restore the original composition. (2) weak acid cation resin, such resins (IONRESIN) containing weakly acidic groups such as carboxyl -COOH, can dissociate the H + in water and acidic. Seth resin color can be dissociated after remaining negatively charged groups, such as R-COO- (R is a hydrocarbon group), can be adsorbed in combination with other cations in solution, resulting in a cation-exchange effect. I.e. such a resin acid dissociable weak, it is difficult to exchange and ion dissociation at low pH, only (e.g. pH5 ~ 14) acts in an alkaline, neutral or slightly acidic solution. Seth colored resin can also be regenerated with acid (easier than the strongly acidic resin regeneration). Cationic resin different ion adsorption capacity of the cation exchange resin to cation adsorption capacity of different strength ranking of cation exchange resin present in the solution of a different cation adsorption capacity of different, in general, to the charged ions of the ion adsorption capacity of the low-cost adsorption capacity; with divalent ions, ion adsorption capacity for large diameter greater than the diameter of the smaller ion adsorption capacity. Common cation adsorption capacity for strength in the following order: Fe3 +> Al3 +> Pb2 +> Ca2 +> Mg2 +> K +> Na +> H +