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INTRODUCTION to ION EXCHANGE Part 1

INTRODUCTION to ION EXCHANGE Part 1. ION EXCHANGE RESINS. Introduction to Ion Exchange. Structure and activity of resins Matrix Functional group Cross-linking Classification Ion exchange resin properties Capacity Particle size Moisture Ion exchange reactions Selectivity

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INTRODUCTION to ION EXCHANGE Part 1

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  1. INTRODUCTION to ION EXCHANGEPart 1 ION EXCHANGE RESINS

  2. Introduction to Ion Exchange • Structure and activity of resins • Matrix • Functional group • Cross-linking • Classification • Ion exchange resin properties • Capacity • Particle size • Moisture • Ion exchange reactions • Selectivity • Column operation • Mode of regeneration

  3. Structure • Structure of Ion Exchange Resins • An ion exchanger consists of the polymer matrix and the functional groups that interact with the ions • Polymer matrix: • Polystyrene (85% of all resins) • Polyacrylate (10%) • Phenol-formaldehyde • Functional groups: • Cation-exchange • Anion-exchange • Chelating groups

  4. Polystyrene H C H H C C H H C C C C H H C H Simplified representation of styrene Styrene monomer Linear polystyrene

  5. Cross-Linking DVB links linear chains of polystyrene to obtain 3-dimensional stability Styrene Divinylbenzene (DVB) Cross-linked polystyrene

  6. Gel structure • Cross_linking is evenly distributed in the matrix • Pseudo-crystalline structure • Pores = mesh of the matrix • Natural porosity • Even pore size (a few Å) • Gel resin is transparent

  7. Macroporosity • Artificial porosity is created with a porogen or phase extender • The porogen doesn't participate in the polymerisation • It just takes room in the system • It is washed away once the polymerisation is complete • It leaves voids in the structure = macropores • Macroporous resins are opaque

  8. Sulphonation SO3H SO3H SO3H SO3H Non-reactive polystyrene Sulphonated polystyrene = strongly acidic cation exchange resin (SAC) H2SO4 Sulphonic group Amberjet 1200 H, Amberlite IR120 H

  9. Chloromethylation CH2Cl CH2Cl CH2Cl CH2Cl Anion exchange resins : Activation is a2-step process Chloromethylated polystyrene (not an ion exchanger !) Cl is covalent, not ionic CH3- O - CH2Cl Chloromethyl ether

  10. Amination CH3 CH3 - N CH3 Cl + CH3 CH2 CH3 N CH2Cl CH3 This Cl is ionic = Strongly basic anion exchange resin (SBA) Called Type 1 + Trimethyl amine Quaternary ammonium Amberlite IRA 402 Cl, Amberjet 4200 Cl

  11. Other amines CH3 CH3 N CH3 CH2Cl H N CH2 CH2 OH CH3 CH3 - CH3 Cl + N CH2 CH2 CH3 N CH3 CH2CH2OH Dimethyl ethanol amine Dimethyl amine + H+ Cl- SBA type 2 WBA Amberjet 4600 Cl Amberlite IRA96

  12. Basicity CH3 CH3 CH3 OH- OH- + + N CH2 CH3 CH2 CH3 CH2 N N CH3 CH3 CH2 CH2 OH SBA type 1 SBA type 2 WBA Resins shown in their regenerated form IRA402 IRA410 IRA96 Decreasing basicity

  13. Weakly Acidic Resins CH2 CH2 CH2 H CH2 CH CH CH C CN CN CN CN H CH2 CH2 CH2 CH2 C CH CH CH COOCH3 COOCH3 COOCH3 COOCH3 There are two routes to produce the acrylic matrix:  Acrylonitrile  Methyl acrylate Both are crosslinked, with DVB or other cross-linkers

  14. Hydrolysis CH2 CH2 CH2 CH CH CH CN CN CN CH2 CH2 CH2 CH CH CH COOH COOH COOH CH2 CH2 CH2 CH CH CH COOCH3 COOCH3 COOCH3 H2SO4 NaOH Polycarboxylic acid = Weakly acidic cation exchange resin (WAC) Amberlite IRC86

  15. Summary O CH3 _ + R CH2 N R C H CH3 O CH3 - Cl + R CH2 N CH3 R SO3- H+ CH3 WAC WBA Amberlite IRC86 Amberlite IRA96 SAC SBA Amberjet 1200 H Amberjet 4200 Cl

  16. Acrylic anion resins H CH2 CH2 CH2 CH2 C CH CH CH COOCH3 COOCH3 COOCH3 COOCH3 Same polymerisation as WAC ! Polymerisation + Amidation + Dimethylaminopropylamine WBA Amberlite IRA67

  17. Weak and strong acrylic resins CH2 CH2 CH CH CH3Cl CH CH CH3 Cl- C C CH3 or (CH3)2SO4 NHCH2CH2N NHCH2CH2N+-CH3 O O CH3 CH3 Quaternisation SBA WBA Amberlite IRA458 Cl Amberlite IRA67

  18. Secondary cross-linking CH2 CH2 CH2 CH2 CH CH CH CH CH2 Cl CH2 H CH CH CH2 CH2 CH CH CH2 CH2 +HCl

  19. Tertiary cross-linking CH2 CH2 CH2 CH2 CH CH CH CH CH2 Cl CH2 Cl- CH3 CH3 N N+ CH3 CH3 CH2 CH2 CH CH CH CH CH2 CH2 CH2 CH2

  20. Cross-linking and porosity High Operating capacity Mobility of ions (kinetics) Resistance to oxidation Difference in ionic affinity Low DVB High

  21. Other typesof ion-exchange resin CH3 • Thiol -SH • Aminodiacetic acid -CH2N(CH2COOH)2 • Aminophosphonicacid -CH2NHCH2CH2PO3H • N-Methylglucamine -CH2N-(CHOH)4CH2OH

  22. Examples of special resins CH2 CH2 CH2 COOH O CH2 CH2 N N SH P CH2 COOH OH H OH Thiol Aminophosphonic Aminodiacetic Duolite GT73 Duolite C467 Amberlite IRC748

  23. Properties: capacity DEFINITIONS Total capacity : quantity of active groups = total quantity of exchangeable ions Operatingcapacity : quantity of ions really exchangedduring onecycle

  24. Properties : moisture holding 100 90 80 70 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 16 18 20 Moisture content % H2O % cross-linking (DVB) Gel type sulphonic polystyrene resins

  25. Particle size of standard resins 0 < 315 315 - 400 400 - 500 500 - 630 630 - 800 800 - 1000 1000 - 1250 > 1250 Gaussian distribution Number of beads between sieves Particle size range in µm

  26. Particle size definitions % Volume passing through sieve 99.9 99 90 60 50 Mean Diameter (d50) 40 10 Effective size (d10) 1 d10 d60 0.1 0.2 0.3 0.4 0.6 0.8 1.2 mm Gaussian-logarithmic plot U.C.= d60/ d10 On graph: d10 = 0.48 mm d50 = 0.74 mm d60 = 0.78 mm UC = 1.62

  27. SAC exchange R - SO-3H+ + NaCl R - SO-3Na+ + HCl 2 R - SO-3H+ + Ca(HCO3)2 (R - SO-3)2Ca++ + H2CO3 2 R - SO-3Na+ + CaCl2 (R - SO-3)2Ca++ + 2 NaCl (Softening)

  28. WAC exchange 2 R - COOH + Ca(HCO3)2 (R - COO-)2Ca++ + 2 H2CO3 R - COOH + CaCl2 No reaction ! R - COOH + NaHCO3 R - COO-Na+ + H2CO3 R - COOH + NaOH R - COO-Na+ + H2O CO2 +H2 O (Neutralisation : possible only with macroporous resins) WAC resins (H+) work only with alkalinity

  29. SBA exchange R - N+R’3OH- + NaCl R - N+R’3Cl- + NaOH R - N+R’3OH- + CO2 R - N+R’3HCO-3 R - N+R’3OH- + SiO2 R - N+R’3HSiO-3 Neutral salt Strong acid R - N+R’3OH- + HCl R - N+R’3Cl- + H2O Irreversible ! CO2 = weak acid SiO2 = very weak acid

  30. WBA exchange R - NR’2 + NaCl No reaction ! R - NR’2 + CO2No reaction except with acrylics R - NR’2 + SiO2No reaction Neutral salt Strong acid R - NR’2 + HCl R - N+HR’2Cl-(or R - NR’2.HCl) Only strong acids can be exchanged because the weak base needs a proton CO2 = weak acid SiO2 = very weak acid

  31. Selectivity In general (dilute solutions) Trivalent > Divalent > Monovalent ions Sulphonic (SAC) resins Ba > Pb > Sr > Ca > Ni > Cu > Mg Ag >> Cs > K > NH4 > Na > H > Li Quaternary Ammonium (SBA) SO4 > CrO4 > NO3 > CH3COO > I > Br > Cl > F > OH Amberjet 1200 Amberjet 4200

  32. Selectivity scales SAC Amberjet1200 SAC resin, 8% DVB Monovalent Selectivity H 1.0 Li 0.85 Na 1.5 NH4 1.9 K 2.5 Cs 2.7 Cu 5.3 Ag 7.6 SAC resin, 8% DVB Divalent Selectivity Mn 2.3 Mg 2.5 Fe 2.6 Zn 2.7 Cu 2.9 Ca 3.9 Sr 4.9 Pb 7.5 Ba 8.7

  33. Selectivity scales SBA Quaternary ammonium resin Ion Type 1 Type 2 OH 1.0 1.0 F 1.6 0.3 HCO3 6.0 1.2 Cl 22 2.3 NO2 24 3 CN 28 3 NO3 65 8 HSO4 85 15 I 175 17 Benzenesulphonate 600 75 Amberjet 4200 Amberjet 4600 Note : this is only typical : Different SBA resins have different affinity scales

  34. Selectivity cont. Note on crosslinking Resins with higher X-linking (higher DVB) have a higher affinity scale SAC % DVB Na/H affinity 4 1.3 8 1.5 12 1.7 16 1.9 Note for SBA resins Different active groups may change the order of affinities (e.g. Nitrate-specific resin)

  35. Selectivity cont. Carboxylic (WAC) resins H >> Ca > Mg >> Na Note 1 : At pH < 5, WAC resins are in the -COOH form, very little dissociated. They can be used only in neutral or alkaline solutions. Note 2 : Ba and Sr are not well removed by a WAC resin Weakly Basic resins (amines, usually tertiary) They remove only Strong Acids from solution, e.g. HCl, H2SO4. They can operate only in acidic solutions. Note on Acrylic WBA resins They remove also carbonic acid (CO2), to a great extent. IRC86 IRA96 IRA67

  36. Column operation Fluid to be treated (Influent) Total capacity 2.1 eq/l resin Resin bed 1 Bed volume (BV) Treated fluid (Effluent)

  37. Operating capacity Exhausted resin Bed Depth Reaction zone 0 100 Regenerated resin Exhaustion, %

  38. Cycle end point Operating capacity 1.3 eq/l resin Exhausted resin Reaction zone 0 100 Regenerated resin Exhaustion, % Leakage

  39. Co-flow regeneration Liquid to be treated Regenerant Eluate (spent regenerant) Leakage

  40. Counter-flow regeneration Liquid to be treated Eluate (spent regenerant) Clean polishing zone Regenerant

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