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

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Ion Exchange Resins

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Ion exchange resins

Ion Exchange Resins

  • General resin information

    • Functional Groups

    • Synthesis

    • Types

    • Structure

  • Resin Data

    • Kinetics

    • Thermodynamics

    • Distribution

  • Radiation effects

  • Ion Specific Resins


Ion exchange resins1

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


Resins

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


Resins1

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


Organic resins

Organic Resins

  • Functional group

    • Functionalize benzene

      • Sulfonated to produce cation exchanger

      • Chlorinated to produce anion exchanger


Resin synthesis

Resin Synthesis

HO

OH

HO

OH

NaOH, H

O

2

HCOH

n

resorcinol

OH

OH

OH

OH

NaOH, H

O

2

HCOH

n

catechol

a

a

a


Resins2

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


Organic resin groups

Organic Resin groups

Linkage group

Cation exchange

Anion exchange

Chloride


Resin structure

Resin Structure


Inorganic resins

Inorganic Resins

  • More formalized structures

    • Silicates (SiO4)

    • Alumina (AlO4)

      • Both tetrahedral

      • Can be combined

        • (Ca,Na)(Si4Al2O12).6H2O

      • Aluminosilicates

        • zeolite, montmorillonites

        • Cation exchangers

        • Can be synthesized

    • Zirconium, Tin- phosphate


Zeolite

Zeolite


Inorganic ion exchanger

Inorganic Ion Exchanger

  • Easy to synthesis

    • Metal salt with phosphate

    • Precipitate forms

      • Grind and sieve

  • Zr can be replaced by other tetravalent metals

    • Sn, Th, U


Kinetics

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


Selectivity

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


Radioactive considerations

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


Hanford tanks

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)


Ion selective resins

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


Characteristics of resins

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


Resin synthesis1

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


Ion exchange resins

OH

HO

OH

OH

n

n

Catechol Formaldehyde Resin

Resorcinol Formaldehyde Resin

OH

OH

OH

N

x

m

n

x = 0, Phenol-8-Hydroxyquinoline Formaldehyde Resin

x = 1, Catechol-8-Hydroxyquinoline Formaldehyde Resin

x = 1, Resorcinol-8-Hydroxyquinoline Formaldehyde Resin


Experimental

Experimental

  • IR spectroscopy

    • Resin characterization

      • OH, C=CAromatic, CH2 , 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


Moisture regain and iec

Moisture Regain and IEC

ResinMoistureIECTheory IEC

%meq/g%

CF208.655

RF4011.574

PQF105.980

CQF209.670

RQF199.970

  • Phenolic resins have lower IEC

  • 8-hydroxyquinoline increase IEC


Experimental1

Experimental

  • Distribution studies

    • With H+ and Na+ forms

    • 0.05 g resin

    • 10 mL of 0.005-.1 M metal ion

    • Metal concentration determined by ICP-AES or radiochemically

    • Distribution coefficient

      Ci = initial concentration

      Cf = final solution concentration

      V= solution volume (mL)

      m = resin mass (g)


Cesium extraction

Cesium Extraction


Distribution coefficients for group 1 elements

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

D (mL/g (dry)Selectivity

ResinLiNaKRbCsCs/NaCs/K

PF10.50.018.013.079.8798010

RF93.959.471.985.2229.53.93.2

CF128.266.768.577.5112.81.71.6


Cesium column studies with rf

Cesium Column Studies with RF

pH 14, Na, Cs, K, Al, V, As


Eu la competitive extraction

Eu/La Competitive Extraction

Distribution Coefficients, 2.5 mM Eu,La, pH 4

ResinLaEuEu/La

CF2.38x1062.03x1060.85

RF2.59x1062.18x1060.84

PQF64.44006.21

CQF98.16726.85

RQF78.48179.91


Ion exchange resins

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


Eu la separation

Eu-La Separation


Studies with 243 am

Studies with 243Am

  • 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

  • 243Am removed from resin by HNO3


Ion specific resins

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


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