Ion exchange

Ion exchange

اسلاید 1: Ion Exchange Ion exchange is an adsorption phenomenon where the mechanism of adsorption is electrostatic. Electrostatic forces hold ions to charged functional groups on the surface of the ion exchange resin. The adsorbed ions replace ions that are on the resin surface

اسلاید 2: selectivityIon exchange resins have a certain affinity or preference for ions in aqueous solution.This affinity or preference for a given resin is called selectivity

اسلاید 3: Basis for selectivity - chemical properties: -magnitude of valence -atomic number of the ion-physical properties :-pore size distribution-the type of functional groups on the polymer chains- Radius of hydration

اسلاید 4: Radius of hydration The group of water molecules surrounding each ion is called the radius of hydration and is different for different ions

اسلاید 5: Comparision of ionic, hydrated radii , Molecular Weight, and atomic number for a number of cations

اسلاید 6: Preference of selectivityIn general (dilute solutions)Trivalent > Divalent > Monovalent ions (SAC) resinsBa > Pb > Sr > Ca > Ni > Cu > MgAg >> Cs > K > NH4 > Na > H > Li(SBA) resinsSO4 > CrO4 > NO3 > CH3COO > I > Br > Cl > F > OH

اسلاید 7: Sulfonic cation exchange resin operating on the sodium cycleThe preference for divalent ions over monovalent ions dimishes as the ionic strengh of solution increases.In dilute concentrations calcium will replace sodium on the resin structure.In higher concentration sodium can be found in the resin phase.