• • • •

Ion Exchange Resins

General resin information Functional Groups Synthesis Types Structure Resin Data Kinetics Thermodynamics Distribution Radiation effects Ion Specific Resins

7-1

Ion Exchange Resins

• •

Resins Organic or inorganic polymer used to exchange cations or anions from a solution phase General Structure Polymer backbone not involved in bonding Functional group for complexing anion or cation

7-2

•

Resins

Properties Capacity



Amount of exchangeable ions per unit quantity of material

*

Proton exchange capacity (PEC) Selectivity



Cation or anion exchange

* *

Cations are positive ions

*

Anions are negative ions



Some selectivities within group Distribution of metal ion can vary with solution

7-3

• •

Resins

Exchange proceeds on an equivalent basis Charge of the exchange ion must be neutralized



Z=3 must bind with 3 proton exchanging groups Organic Exchange Resins Backbone



Cross linked polymer chain

*

Divinylbenzene, polystyrene

*

Cross linking limits swelling, restricts cavity size

7-4

Organic Resins

Functional group



Functionalize benzene

*

Sulfonated to produce cation exchanger

*

Chlorinated to produce anion exchanger

7-5

7-6

7-7

Resin Synthesis

HO OH

resorcinol

OH OH NaOH, H 2 O HCOH NaOH, H 2 O HCOH

catechol

HO OH OH OH n n 7-8

• •

Resins

Structure Randomness in crosslinking produces disordered structure



Range of distances between sites



Environments

*

Near organic backbone or mainly interacting with solution Sorption based resins Organic with long carbon chains (XAD resins) Sorbs organics from aqueous solutions Can be used to make functionalized exchangers

7-9

Organic Resin groups

Linkage group Chloride

CH 2 Cl SO 3 H

Cation exchange

CH 2 N(CH 3 ) 3 Cl

Anion exchange

7-10

Resin Structure

7-11

•

Inorganic Resins

More formalized structures Silicates (SiO 4 ) Alumina (AlO 4 )



Both tetrahedral



Can be combined

*

(Ca,Na)(Si 4 Al 2 O 12 ).6H

2 O



Aluminosilicates

*

zeolite, montmorillonites

* *

Cation exchangers Can be synthesized Zirconium, Tin- phosphate

7-12

Zeolite

7-13

Inorganic Ion Exchanger

OH Zr O OPO(OH) 2 OH Zr O Zr O OPO(OH) Zr 2 OPO(OH) 2 OPO(OH) 2 OPO(OH) 2 OPO(OH) 2 • •

Easy to synthesis Metal salt with phosphate Precipitate forms



Grind and sieve Zr can be replaced by other tetravalent metals Sn, Th, U

7-14

• • • • • •

Kinetics

Diffusion controlled Film diffusion



On surface of resin Particle diffusion



Movement into resin Rate is generally fast Increase in crosslinking decrease rate Theoretical plates used to estimate reactions Swelling Solvation increases exchange Greater swelling decreases selectivity

7-15

• • •

Selectivity

Distribution Coefficient D=Ion per mass dry resin/Ion per volume The stability constants for metal ions can be found Based on molality (equivalents/kg solute) Ratio (neutralized equivalents)



Equilibrium constants related to selectivity constants Thermodynamic concentration based upon amount of sites available Constants can be evaluated for resins



Need to determine site concentration

7-16

7-17

7-18

7-19

7-20

7-21

7-22

7-23

7-24

7-25

7-26

7-27

7-28

• • • • •

Radioactive considerations

High selectivity Cs from Na Radiation effects Not sensitive to radiation



Inorganics tend to be better than organics High loading Need to limit resin change Limited breakthrough Ease of change Flushing with solution Good waste form Radioactive waste

7-29

7-30

• • • •

Hanford Tanks

177 Tanks Each Tank 3,800,000 Liters Three sections Salt cake Sludge Supernatant Interested in extracting Cs, Sr, Tc, and Actinides with Silicatitanates Resorcinol formaldehyde CS-100 (synthetic zeolite)

7-31

• • • •

Ion Selective Resins

Selected extraction of radionuclides Cs for waste reduction Am and Cm from lanthanides



Reprocessing



Transmutation Separation based on differences in radii and ligand interaction size and ligand Prefer solid-liquid extraction Metal ion used as template

7-32

Characteristics of Resins

• • • • •

Ability to construct specific metal ion selectivity Use metal ion as template Ease of Synthesis High degree of metal ion complexation Flexibility of applications Different functional groups Phenol Catechol Resorcinol 8-Hydroxyquinoline

7-33

Resin Synthesis

•

Catechol-formaldehyde resin (CF)

•

Resorcinol-formaldehyde resin (RF)

•

Phenol-8-hydroxyquinoline formaldehyde resin (PQF)

•

Catechol-8-hydroxyquinoline formaldehyde resin (CQF)

•

Resorcinol-8-hydroxyquinoline formaldehyde resin (RQF) Resins analyzed by IR spectroscopy, moisture regain, and ion exchange capacity

7-34

HO OH OH OH n Resorcinol Formaldehyde Resin n Catechol Formaldehyde Resin OH OH x OH N n m x = 0, Phenol-8-Hydroxyquinoline Formaldehyde Resin x = 1, Catechol-8-Hydroxyquinoline Formaldehyde Resin 7-35 x = 1, Resorcinol-8-Hydroxyquinoline Formaldehyde Resin

Experimental

• • •

IR spectroscopy Resin characterization



OH, C=C Aromatic , CH 2 , CO Moisture regain 24 hour heating of 0.1 g at 100°C Ion exchange capacity Titration of 0.25g with 0.1 M NaOH

7-36

Resin CF RF PQF CQF RQF

Moisture Regain and IEC

Moisture % 20 40 10 20 19 IEC meq/g 8.6

11.5

5.9

9.6

9.9

Theory IEC % 55 74 80 70 70

•

Phenolic resins have lower IEC

•

8-hydroxyquinoline increase IEC

7-37

•

Experimental

Distribution studies With H + and Na + 0.05 g resin forms 10 mL of 0.005-.1 M metal ion Metal concentration determined by ICP AES or radiochemically Distribution coefficient D



C i



C i = initial concentration C f = final solution concentration V= solution volume (mL) C f C f m = resin mass (g) V m

7-38

0.8

0.6

0.4

0.2

0 1.8

1.6

1.4

1.2

1 Li

Cesium Extraction

catechol resorcinol Na K Alkali Metals Rb Cs

7-39

Distribution Coefficients for Group 1 elements.

All metal ions as hydroxides at 0.02 M, 5 mL solution, 25 mg resin, mixing time 5 hours Resin Li PF RF CF 10.5

D (mL/g (dry) Na 0.01

93.9

59.4

128.2 66.7

K 8.0

71.9

68.5

Rb Cs 13.0 79.8

85.2 229.5

77.5 112.8

Selectivity Cs/Na Cs/K 7980 3.9

1.7

10 3.2

1.6

7-40

Cesium Column Studies with RF

pH 14, Na, Cs, K, Al, V, As 40 35 30 25 20 15 10 5 0 0 2 0.1 M HCl Cs Na K Al 4 6 8 10

Volume Eluant (mL)

12 1.0 M HCl 14 16 7-41

Eu/La Competitive Extraction

Distribution Coefficients, 2.5 mM Eu,La, pH 4 Resin CF RF PQF CQF RQF La 2.38x10

6 2.59x10

64.4

98.1

78.4

6 Eu 2.03x10

6 2.18x10

6 400 672 817 Eu/La 0.85

0.84

6.21

6.85

9.91

7-42

[Eu] = [La] = 0.0025 mol L-1, T(shaking) = 20h, m = 0.05g

7-43

Eu-La Separation

12 10 8 6 4 2 0 0 CQF PQF RQF 20 40 60 80

Mixing Time (Hours)

100 120 140 7-44

Studies with

243

Am

• • • • •

Conditions similar to Eu studies 10 mL solution 0.05 g resin



RF, CF, PQF, RQF, CQF millimolar Am concentration Analysis by alpha scintillation >99% of Am removed by CF, RF, PQF ≈ 95% of Am removed by CQF, RQF 243 Am removed from resin by HNO 3

7-45

Ion Specific Resins

• • • • •

Effective column separation possible Phenol exhibits selectivity Incorporation of 8-hydroxyquinoline leads to selectivity, but lower extraction Eu/La separation possible Possible to prepare ion specific resins for the actinides

7-46