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Greetings

MD. AKMOL HOSSAINID: 20121207048

Department Of Applied Chemistry & Chemical Engineering

Session: 2012-2013

BSMRSTU

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Principles of Ion-Exchange process

Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex

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Ion ExchangeIon 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 on a 1:1 charge basis. For example:

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Applications of ion exchange in water & wastewater

• Ca, Mg (hardness removal) exchange with Na or H.• Fe, Mn removal from groundwater.• Recovery of valuable waste products Ag, Au, U• Demineralization (exchange all cations for H all anions for OH)• Removal of NO3, NH4, PO4 (nutrient removal).

In Addition - purification, separation, and decontamination of aqueous and other ion-containing solutions

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Ion Exchangers (types)

Natural• Proteins, • Soils, • Lignin, • Coal, • Metal oxides, • Aluminosilicates (zeolites)

(NaOAl2O3.4SiO2).

Synthetic• zeolite gels and • Most common -polymeric resins

(macroreticular, large pores).

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Ion Exchange Resin

Higher molecular weight & cross linked polymer Contain exchangeable Cation & Anion

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Polymeric resins are made in 3-D networks by cross-linking hydrocarbon chains. The resulting resin is insoluble, inert and relatively rigid. Ionic functional groups are attached to this framework.

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These resins are generally manufactured by polymerizing neutral organic molecules such as sytrene (to form polystrene) and then cross-linked with divinyl benzene (DVB). Functional groups are then added according to the intended use. For example the resin can be sulfonated by adding sulfuric acid to get the structure shown above.

Divinylbenzene:

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sjhgfhdghhvghvjhgfhv

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Cation exchange Resin,contains -COO-, - SO (negative group by covalent bond)Neutralized by equivalent amount of free Cation (By Ionic bond) Salt of solution contact with Resin & Cation exchange between solution and resin

(Res-SO3-)M+ + M’+

(aq) ↔ (Res-SO3-) M’+ + M+X-

(aq)

Anion exchange Resin, Contains -R3N+ in it’s molecular structure (positive group by covalent bond) Neutralized by equivalent amount of free anion (By Ionic bond) Salt of solution contact with Resin then anion exchange between solution

and resin

(Res-NR3+)X- + M+ Y-

(aq) ↔ (Res-NR3+)Y- + M+X-

(aq)

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Principle Actions of Cation exchangerCation exchanger are generally denotes (Res-A-)B+

Where, Res is hydrocarbon structure A- is anion part B+ is exchangeable cation

(Res.A-)B+ + C+ (solution) ↔ (Res.A-)C+ + B+ (solution)

(Res-SO3-)Na+ + Ca+ +

(solution) ↔ (Res-SO3-) Ca + + + Na+ (solution)

Sodium sulfonated styrene resin

• Always reversible reaction

Na are separated in solution

Ca are barge into the rtesin

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Similarly Resin of hydrogen condition in neutral salt solution

(Res.SO3-)H+ + Na+ Cl-

(solution) ↔ (Res.SO3-) Na+ + H2O (solution)

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Principle Actions of Anion exchangerAnion exchanger are generally denotes (Res-B+)A-

Where, Res is hydrocarbon structure

A- is anion part

B+ is exchangeable cation

(Res. B+) A-+ D- (solution) ↔ (Res. B+) D- + A- (solution)

2(Res.NMe3+)Cl- + SO4- -

(solution) ↔ (Res. NMe3+)2 SO4- - + 2 Cl- (solution)

Quartarnary amonium resin

Anion wants to barge into resin

Question & Answering Section

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