Ion Exchange 101

Donna DeFlavis

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

Introduction to Ion Exchange

Introduction

What is IX?

Types of resins

Applications

Manufacturing

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.

5

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+

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.

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

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

8

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

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

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)

Applications

12

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

Manufacturing steps

13

DRYINGSIEVING

SULFONATIONHYDRATION

CHLOROMETHYLATIONAMINATION

WASHINGDEWATERINGPACKAGING

CO-POLYMERIZATIONCation Anion

MONOMERSSTYRENE

DIVINYLBENZENECATALYSTS

WATER + STABILISER

CONTROLTEMPERATURE

STIRRING

HEATING

(POROGENIC CHEM.)

SUSPENSION MEDIUM

Polymerization (Gaussian Beads)

Jetting Polymerization (Uniform Beads)

Dynamic formulation of the dropletsResin beads are jettedBead size is uniform

Chemical and Physical Characteristics

Content

Particle Size Characterization Uniformity Coefficient

Mean Size

Ionic Form of resin

Total Exchange Capacity

Water Retention Capacity (%)

Mechanical stability

Thermal and oxidative stability

17

Particle Size

18

Conventional (Gausssian) resins typically 0.3-1.2 mm bead size rangeUPS resin typically ~0.6mm (600 m)

900600300 m

Number of beads

1200

Uniform(Marathon/Monosphere/Amberjet)

Gaussian(Dowex/Amberlite)

Particle Size-Uniformity Coefficient

How do you Measure Uniformity?

20

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

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

Other particle size definitions

22

A = Effective Size = 90% volume of beads retainedB = Volume Median Diameter = 50% volume of beads passed

Bead diameter

Vol. (%)

0 A

90%

B

50%

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

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

24

Total exchange capacity

25

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

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

26

Water retention capacity vs. ionic form

27

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%

Water Retention Capacity (WRC)-WRC vs. degree of cross-linkage

28

Mechanical Stability

29

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

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

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

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

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

Dynamic properties

Content

IX reactions

IX kinetics

Selectivity

Regenerability

Operating capacity

35

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

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

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

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

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

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

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

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

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

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

Operating vs. total capacity-Typical figures

46

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

Regenerability

47

Stoichiometric ratio = [2/1.3] x 100 = 154%

%100 added Regenerant

(eq/l) achievedcapacity Resin efficiencyon Regenerati = [1.3/2] x 100 = 65%

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.

48

Effect of matrix structure on performance

Total capacity Selectivity Physical stability Chemical stability

Water retention Swelling Kinetics Regenerability/Operating capacity Organic desorption abilityIF % DVB

Thank You!

For more information please visit our web site or contact your local Dow representative. http://www.dowwaterandprocess.com/