Download - Water Academy Ion Exchange
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Ion Exchange 101
Donna DeFlavis
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ContentIntroduction to Ion Exchange What is IX? Types of resins Applications Manufacturing
Chemical and Physical Characteristics Particle Size Ionic Form Total Exchange Capacity Water retention Capacity Mechanical Stability Thermal and Oxidative Stability
Dynamic Properties IX reactions IX kinetics Selectivity Regenerability Operating capacity
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Introduction to Ion Exchange
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Introduction
What is IX?
Types of resins
Applications
Manufacturing
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What is IX?-Definition of ion exchange
Ion exchange is the reversible exchange of ions between a solid and a liquid in which there is no substantial change in the structure of the solid.
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Exhaustion Regeneration
Cation resin bead
H+
H+
H+
H+
H+
H+
H+
Na+ Na+
Na+Cation resin bead
H+
H+
H+
H+
H+
H+
H+
Na+
Na+
Na+
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Type of Resins-Resin Polymer structure
Composition Polystyrene (85% of all resins) Polyacrylate (10%) Phenol-formaldehyde
Crosslinking We introduce cross-linking to our copolymers in the form of divinyl
benzene abbreviated as DVB. The amount of DVB determines the level of cross-linking which is in
effect the tightness or looseness of the finished ion exchange resin. Production of the copolymer is very important as it determines many of
the physical properties of the final product such as bead size and bead strength.
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Types of Resin-Polymer matrix
Gel resins Continuous polymer with low pore size 5-15 Translucent Good regeneration/ highest capacity
Macroporous resins
Void volumes with large pore size 50-200 Opaque Good bead strength/organic removal
Gel matrix Macroporous matrixGel matrix
Macroporous matrix
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Types of resins-functional groups
Cation Exchange Resins Strong Acid (SAC) Weak Acid (WAC)
Anion Exchange Resins Strong Base (SBA)
Type 1 Type 2
Weak Base (WBA) other special chemical groups, such as chelating resins
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Strong Acid Cation (SAC) Exchange Resin
Removes: Na+, Ca2+Mg2+, Fe2+ etc.
SO3- H+
SO3-
Removes:Cations present with alkalinity
High total exchange capacityHigh chemical efficiency
CO
O-H+
Weak Acid Cation (WAC)Exchange Resin
Types of resins-Cation exchange resin
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Type 1 anion exchange resin
Type 2 anion exchange resin
High Chemical Stability High Silica Removal
Remove: Cl-, SO42-, HCO3-, HSiO3-, etc
N+ CH3 CH3
OH-CH3
N+ CH3
CH3
CH2 CH2 OHOH-
Lower basicity than Type 1 High Operating Capacity/ regeneration Lower Silica Removal than Type 1 Sensitive to temperature
Types of resins-Strong base anion exchange resin
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N:CH3
CH3
HCl Only Removes Acids: HCl, H2SO4, Formic acid, etc.
High Operating Capacity High Regeneration Efficiency Good for organics removal
Types of resins-Weak base anion exchange resin (WBA)
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Applications
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WATER TREATMENTIndustrial water softeningIndustrial water demineralizationCondensate polishingUltra-pure water production
FOOD & PHARMACEUTICAL APPLICATIONSSugar juice treatmentBrewery, Fruit juicesPharmaceutical
CHEMICAL INDUSTRY POLLUTION CONTROLElectroplating Nitrate removalHydrometallurgy Heavy metals removalCatalysis Cl-solvent removal
Waste waterNUCLEAR INDUSTRY
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Manufacturing steps
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DRYINGSIEVING
SULFONATIONHYDRATION
CHLOROMETHYLATIONAMINATION
WASHINGDEWATERINGPACKAGING
CO-POLYMERIZATIONCation Anion
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MONOMERSSTYRENE
DIVINYLBENZENECATALYSTS
WATER + STABILISER
CONTROLTEMPERATURE
STIRRING
HEATING
(POROGENIC CHEM.)
SUSPENSION MEDIUM
Polymerization (Gaussian Beads)
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Jetting Polymerization (Uniform Beads)
Dynamic formulation of the dropletsResin beads are jettedBead size is uniform
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Chemical and Physical Characteristics
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Content
Particle Size Characterization Uniformity Coefficient
Mean Size
Ionic Form of resin
Total Exchange Capacity
Water Retention Capacity (%)
Mechanical stability
Thermal and oxidative stability
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Particle Size
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Conventional (Gausssian) resins typically 0.3-1.2 mm bead size rangeUPS resin typically ~0.6mm (600 m)
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900600300 m
Number of beads
1200
Uniform(Marathon/Monosphere/Amberjet)
Gaussian(Dowex/Amberlite)
Particle Size-Uniformity Coefficient
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How do you Measure Uniformity?
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screen size passing 90%Uniformity Coefficient (UC) = -------------------------------
screen size passing 40%
0 200 400 600 800 1000 1200 1400
Bead Size, microns
Volu
me
Perc
ent 40%
90%
UC = 1010 m / 650 m = 1.6
0 200 400 600 800 1000 1200 1400
Bead Size, microns
Volu
me
Perc
ent 40%
90%
UC = 580 m / 540 m = 1.07
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Type of Resins-Bead uniformity
AMBERJET, MARATHON, MONOSPHEREVery uniform UC* 1.1 to 1.2
Highest performance Mandatory for AMBERPACK & packed bed systems requesting NO FINES Very useful in mixed beds (no need for interface) DOWEX UPCORE for UPCORE plants & designs Block reverse flow and co-flow systems
Specially graded resins UC* 1.1 to 1.5
RF for AMBERPACK & other Reverse Flow systems SB, LB for STRATABED , Layered Bed units
AMBERLITE, DOWEXGaussian UC* 1.3 to 1.8
For co-flow systems
*UC = Uniformity Coefficient
Number of beads
900600300 m1200
Uniform
Gaussian
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Other particle size definitions
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A = Effective Size = 90% volume of beads retainedB = Volume Median Diameter = 50% volume of beads passed
Bead diameter
Vol. (%)
0 A
90%
B
50%
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INDUCES A CHANGEIN VOLUME
STRONG ACID CATION RESIN STRONG BASE ANION RESIN
GEL Na to H + 7% Cl to OH + 15-20%MACRO Na to H + 5% Cl to OH + 10-12%
WEAK ACID CATION RESIN WEAK BASE ANION RESIN
MACRO H to Ca + 15% FB to HCl + 20-35%MACRO H to Na + 60% GEL H to Na + 90%
Ionic form-Change of resin volume
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Total exchange capacity
Defined as theoretical total exchangeable ions from the resin
Expressed,
either volume unit : eq/l wet
or weight unit : eq/kg dry
With reference to a specified ionic form
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Total exchange capacity
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CATION EXCHANGE RESINS STRONG ACID WEAK ACIDGEL MACRO GEL MACRO
EQ/L (Na) 2.00 1.85 2.35 2.65EQ/L (H) 1.85 1.75 4.40 4.20EQ/KG (Na) 4.50 4.50 - -EQ/KG (H) 5.00 4.90 9.00 9.00
ANION EXCHANGE RESINS STRONG BASE WEAK BASEGEL MACRO MACRO
EQ/L (Cl) 1.40 1.15 1.05EQ/L (OH) 1.15 1.00 1.40EQ/KG (Cl) 3.90 4.00 3.80EQ/KG (OH) 4.20 4.30 4.40
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Water Retention Capacity (WRC)-Ion Exchange Resins Hold Water
After functional charges are added: resins become hydrophilic, absorbing water (40-60%
water) functional charges are repelled from one another,
causing resin swelling the presence of water is critical for transport of ions into
and out of the resin bead
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Water retention capacity vs. ionic form
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STRONG ACID CATION EXCHANGE RESINS
H FORM Na/NH4 FORM
GEL TYPE 8% DVB 50-55% 44-48%
GEL TYPE 10% DVB 46-50% 38-43%
MACROPOROUS TYPE 50-55% 44-50%
STRONG BASE ANION EXCHANGE RESINS
OH FORM Cl FORM
GEL TYPE 55-65% 43-48%
MACROPOROUS TYPE 65-72% 56-64%
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Water Retention Capacity (WRC)-WRC vs. degree of cross-linkage
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Mechanical Stability
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Pressure on: The resin bed surface The resin beads
Shear forces exerted by one bead on another during: Backwashing Resin transfer Air cleaning/mixing
Shrink and swell stress exerted on a bed during: Loading/regeneration Resin cleaning Cross-regeneration (mixed
beds)
FRIABILITY (Crush)
ATTRITION
OSMOTIC SHOCK
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CATIONS: Can operate up to 150C (300F) in the Na form. Degrade through loss of sulfonate functional group at >120C in the H
form. Cation resin stability dependent on pH: cleavage of carbon-sulfur bond
increases at lower pH: up to 120 C in the H form.
ANIONS: Degrade through conversion of strong base groups into weak base
groups. Type 2 also lose ethanol group and form weak base groups (max 35C) Can operate up to 60C (140F) recommended for OH cycle (Type 1). Anion resin stability dependent on pH: cleavage of carbon-nitrogen bond
increases at higher pH.
Thermal Stability
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Strong acid cation 150 C in Na form 120 C in H+ form
Weak base anion and strong base anion type I 80 - 100 C in loaded form 50 - 60 C in regenerated form
Strong base anion type II 35 C in regenerated form
Thermal Stability
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Strong acid cation Structure more sensitive than active group Loss of crosslinking, increase of water content Lower volume capacity, density and mechanical stability
Strong base anion Active group more sensitive than structure Loss of TVC
Weak base anion Loss of active groups Increase of rinse requirements: formation of COOH
Oxidative Stability
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Following levels of free chlorine can be tolerated
Weakly acidic cation exchanger < 0.5 ppm
Strong acid cation exchanger gel < 0.20 ppm
Weakly basic anion exchanger < 0.05 ppm
Strong base anion exchanger < 0.05 ppm
Oxidative Stability
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Dynamic properties
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Content
IX reactions
IX kinetics
Selectivity
Regenerability
Operating capacity
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Splits salts/neutralize bases:
R-H + Na+Cl R-Na+ + HCl
In the neutral (sodium) form, they can be used for softening:
2R-Na + Ca2+Cl2 R2-Ca + 2 Na+Cl
Ion exchange reactions-Strong acid cations
Strong Acid Cation
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High capacity for alkaline earth metals associated with alkalinity:
2R-H + Ca2+(HCO3)2 R2-Ca2+ + 2CO2 + 2H2O
No significant salt splitting occurs with neutral salts, due to equilibrium with HCl:
R-H + Na+Cl R-Na+ + HCl
However, if resin is neutral (Na form), softening can be performed:
2R-Na + Ca2+Cl2 R2-Ca2+ + 2NaCl
Weak Acid Cation
Ion exchange reactions-Weak acid cations
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Weak base anion resins are capable of adsorbing strong acids onto the electron pair on the free amine group:
R-N: + H+Cl- R-N: HCl
Weak Base Anion
Ion exchange reactions-Weak base anions
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Splits salts/neutralize acids:
R-OH + NaCl- R-Cl- + NaOH
2R-OH + H2SO4 R2-SO4 + 2H2O
R-OH + HSiO3- R-HSiO3 + OH-
In the neutral (chloride) form, they can be used for nitrate or anionic metal complex removal:
R-Cl + NaNO3 R-NO3 + NaCl
Strong Base Anion Type 1
Ion exchange reactions-Strong base anions
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Kinetic Rate governs the speed of ion exchange Selectivity governs the preference for a particular ion In some applications, speed of ion exchange is critical
Kinetics: Rate of Ion Exchange
Ion exchange resin kinetics
A+
SOLUTION
LIQUID FILM
RESIN BEAD
R
( boundary layer )
H+
A+A+
H+H+
The diffusion rate is a function of:
In the resin: 1/R2In the film : 1/RIn the solution : not influenced
by bead size
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Selectivity Increases with Increasing Charge Al3+ > Ca2+ > Na+
SO42- > Cl
Selectivity Increases with Atomic Number (Size) Ba2+ > Sr2+ > Ca2+ > Mg2+
Br- > Cl- > F-
Ion exchange selectivity
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Resin selectivity creates chromatographic exhaustion:
loosely held ions travel quickly
tightly held ions travel slowly
moving ionic wave fronts are established
Ca2+
Mg2+
Na+
H+
Ion exchange selectivity
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ION VALENCE DEGREE OF CROSS-LINKAGE
MONOVALENT IONS 4% DVB 8% DVB 16% DVBH 1.0 1.0 1.0Li 0.90 0.85 0.7Na 1.3 1.5 1.9NH4 1.6 1.95 2.5K 1.75 2.5 3.3Cs 2.0 2.7 3.4Ag 6.0 7.6 17.0
DIVALENT IONSMn 2.2 2.35 2.7Mg 2.4 2.5 2.8Zn 2.6 2.7 3.0Cu 2.7 2.9 3.6Ca 3.4 3.9 5.8Pb 5.4 7.5 14.5Ba 6.15 8.7 16.5
Strong acid cation exchange resins-Resins selectivity coefficient
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TYPE 1 TYPE 2
OH 1.0 1.0
FLUORIDE 1.6 0.3ACETATE 3.2 0.5BICARBONATE 6.0 1.2CHLORIDE 22 2.3BISULFITE 27 3NITRATE 65 8CITRATE 220 23SALICYLATE 450 65LIGNOSULFONATE >500 75
Strong base anion exchange resins-Resins selectivity coefficient
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Resin operating capacity and total capacity
0102030405060708090
100
0 50 100 150 200 250Feed water passed
Ioni
c le
akag
e (a
s %
of f
eed) A B
Inlet feed concentration
Total capacity = A + B
Ionic leakage Ionic breakthrough
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Operating vs. total capacity-Typical figures
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0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Typi
cal c
apac
ity (e
q/l)
Total capacity (area A+B)Operating capacity (area A)
Comparison of Operating and Total Capacity
Weak cation
Strong cation
Weak anion
Stronganion type 1
Stronganion type 2
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Regenerability
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Stoichiometric ratio = [2/1.3] x 100 = 154%
%100 added Regenerant
(eq/l) achievedcapacity Resin efficiencyon Regenerati = [1.3/2] x 100 = 65%
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Factors affecting regenerability and operating capacity
Regenerant level: High amount of regenerant gives higher operating capacity.
Matrix cross-linking: High DVB content slows ion diffusion due to tight matrix structure and gives lower regenerability and operating capacity. Macroporous worse than gel.
Ionic form: High selectivity ions (e.g. calcium) more difficult to regenerate off the resin, so operating capacity lower.
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Effect of matrix structure on performance
Total capacity Selectivity Physical stability Chemical stability
Water retention Swelling Kinetics Regenerability/Operating capacity Organic desorption abilityIF % DVB
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