H RR OHCaSO4Ca RR SO4HOHH RR OHNaClNa RR ClHOHWATER TREATMENT PROCESSESDOE-HDBK-1015/2-93Principles of Water TreatmentCH-04Rev. 0Page 14Ion Exchange Summary (Cont.)Resin beads are long-chain cross-linked polymers that contain sitesoccupied by exchangeable ions. The general order of affinity serves as auseful guide in understanding many ion exchange processes. Cation andanion resins are named according to the identity of the ion occupying theexchange sites, such as hydrogen, hydroxyl, and chloride. Mixed-bedresins are used to remove both cations and anions.The effectiveness of any ion exchanger is directly related to the relativeaffinities between a resin and different ions. In order of decreasingstrength, the relative affinities between a cation resin and various cationsare:Ba > Sr > Ca > Co > Ni > Cu > Mg > Be+2+2+2+2+2 +2 +2+2Ag > Cs > Rb > K NH > Na > H > Li++++++++Similarly, the relative affinities of the anion resin for various anions are:SO> I > NO > Br > HSO > Cl > OH > HCO > F 4333-2--------The higher the relative affinity the more effective the ion exchanger. Thiseffectiveness is expressed by the Decontamination Factor.The reaction for removal of NaCl and CaSO by a mixed-bed ion4exchanger such as one containing HOH resin is as follows:
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