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  • www.helsinki.fi/yliopisto 1

    Pirkko Hltt Suvi Niemiaho

    Outi Elo

    University of Helsinki (UH) Department of Chemistry

    Laboratory of Radiochemistry

    Bentonite colloid studies

    BELBaR Helsinki 5.-7.3.2013

  • www.helsinki.fi/yliopisto

    Finnish Research Programme on Nuclear Waste Management (KYT2014/BOA/KOLORA) Formation and stability of colloids Radionuclide sorption EU FP7 BELBaR WP3 Colloid/radionuclide and host rock interaction Grimsel Test Site Phase VI, Colloid formation and migration (CFM)

    2 BELBaR Helsinki 5.-7.3.2013

    Colloid projects

  • www.helsinki.fi/yliopisto

    To determine the release and stability of inorganic colloids in different groundwater conditions To study bentonite erosion To determine radionuclide sorption (Kd) on MX-80

    bentonite powder and bentonite colloids as a function of ionic strength, pH and particle size To Study colloid/radionuclide and host rock

    interaction in dynamic conditions To test and apply colloid characterization

    methods

    BELBaR Helsinki 5.-7.3.2013 3

    Objectives

  • www.helsinki.fi/yliopisto BOA kick off 4.3.2011

    Characterization methods Dynamic light scattering (DLS: Malvern Zetasizer

    Nano ZS) Asymmetrical flow field-flow fractionation (AsFlFFF) ICP- MS, ICP-OES Field emission scanning electron microscopy

    (FESEM/EDX) DualBeam focused ion beam/scanning electron

    microscope with EDS Atomic force microscopy (MultiMode V scanning

    probe microscope) X-ray diffraction (XRD), small-angle X-ray scattering

    (SAXS)

    4

  • www.helsinki.fi/yliopisto

    The release and stability of bentonite colloids have been followed in diluted OLSO reference groundwater, sodium chloride and calcium chloride solutions (I = 0.001 0.1 M) Colloidal particle size distribution and zeta

    potential has been determined applying the dynamic light scattering (DLS) method. Colloid concentration determination: A standard series made from MX-80 bentonite applying

    the DLS measurement count rate. Al determination (ICP-MS)

    5 BELBaR Helsinki 5.-7.3.2013

    Formation and stability of bentonite colloids

  • www.helsinki.fi/yliopisto BELBaR Helsinki 5.-7.3.2013 6

    OLSO 0.001- 0.03 M

    NaCl 0.001- 0.1 M

    CaCl2 0.001- 0.1 M

  • www.helsinki.fi/yliopisto 7 BELBaR Helsinki 5.-7.3.2013

    Zeta potential as a function of ionic strength in sodium chloride, calcium chloride and OLSO solutions after 2.5 years.

    Stability of bentonite colloids

  • www.helsinki.fi/yliopisto 8 BELBaR Helsinki 5.-7.3.2013

    Mean zeta potential of bentonite colloids in diluted OLSO reference groundwater.

    Stability of bentonite colloids

    -60

    -40

    -20

    0

    20

    0 200 400 600 800 1000

    Zeta

    pot

    entia

    l [m

    V]

    Time [d]

    0.1 M

    0.04 M

    0.02 M

    0.01 M

    0.005 M

    0.001 M

  • www.helsinki.fi/yliopisto 9 BELBaR Helsinki 5.-7.3.2013

    Bentonite colloid concentration

    Estimated particle concentration of bentonite colloids in diluted OLSO reference groundwater.

    0

    5

    10

    15

    20

    25

    0 200 400 600 800 1000

    Part

    icle

    conc

    entr

    atio

    n (g

    L-1

    )

    Time (d)

    0.001

    0.005

    0.01

    0.02

    0.03

  • www.helsinki.fi/yliopisto 10 BELBaR Helsinki 5.-7.3.2013

    Radionuclide sorption

    Determinations as a function of ionic strength, a batch method, 4 parallel samples. 85Sr and 152Eu sorption onto bentonite powder (MX-80) NaCl and CaCl2 solutions (I = 0.001 0.1 M) 152Eu sorption on bentonite colloids, separated from MX-80. NaCl and CaCl2 solutions and diluted OLSO (I = 0.5 M) Solutions of 10 ionic strengths (I = 0.001 0.1 M) 85Sr sorption determination on bentonite colloids is under

    way. Radionuclide sorption reversibility in static and dynamic

    conditions. method development under way

    .

  • www.helsinki.fi/yliopisto

    20 mL NaCl/CaCl2-solution Sr-85 or 120 l Eu-152 tracer 1 g Bentonite powder pH ~ 8 (Adjusted)

    Shaking (1h/1-2 d/7 d) Sentrifugation (7500 rpm/30 min)

    10 mL aliquot Radioactivity measurement (5 min) (Wizard 3'' gamma counter) Particle size and zeta potential determination

    Filtration 1.2 m (Isopore polycarbonate filter ) Radioactivity measurement (5 min) Particle size and zeta potential determination (Zetasizer)

    Filtration 0.05 m (Isopore polycarbonate filter ) Radioactivity measurement (5 min) Particle size and zeta potential determination (Zetasizer)

    Drying and weighing of the filters

    Desorption experiments

    KYT1014 BOA seminar 31.1.2012 11

    Sorption onto powdered bentonite

  • www.helsinki.fi/yliopisto

    90 mL OLSO/NaCl/CaCl2-solution Sr-85 or Eu-152 tracer Bentonite colloids solution

    4.5 mL aliquot after 1h/1-2 d/7 d Ultracentrifugation (90000 rpm/60 min)

    Solution: Radioactivity measurement (10 min) (Wizard 3'' gamma counter) Particle size determination (Zetasizer)

    Solid phase: Drying and weighing

    Desorption experiments

    KYT1014 BOA seminar 31.1.2012 12

    Sorption onto colloids

  • www.helsinki.fi/yliopisto 13 BELBaR Helsinki 5.-7.3.2013

    Colloid concentration Bentonite powder in NaCl

    Eu-152 sorption

  • www.helsinki.fi/yliopisto 14 BELBaR Helsinki 5.-7.3.2013

    Eu-152 sorption on colloids

    0

    10

    20

    30

    40

    50

    60

    0 0.02 0.04 0.06 0.08

    K d (m

    3 /kg

    )

    Ionic strength (M)

    1d

    3d

    7d

  • www.helsinki.fi/yliopisto

    Old fracture columns from Olkiluoto tonalite New crushed rock columns from Kuru Grey

    granite and strongly altered tonalite and. The hydraulic properties have been

    determined using non-sorbing tracers (36Cl, 125I) without colloids

    Experiments 85Sr and 152Eu with and without colloids are under way

    Natural fracture (0.9 m x 0.9 m) in Kuru Grey granite block Experiments will start in the near future

    15 BELBaR Helsinki 5.-7.3.2013

    Colloid/radionuclide and host rock interaction

  • www.helsinki.fi/yliopisto 16 BELBaR Helsinki 5.-7.3.2013

    0

    0.0001

    0.0002

    0.0003

    0.0004

    0.0005

    0 200 400 600 800 1000 1200 1400

    dA/A

    0 dt

    (1/h

    )

    Time (h)

    Sievi crushed rock column Sr-85 with and without colloids

  • www.helsinki.fi/yliopisto 17 BELBaR Helsinki 5.-7.3.2013

    The formation and stability of bentonite colloids depends strongly on the ionic strength of the medium and the valence of the cations. In NaCl (0.001-0.1 M), CaCl2 and OLSO (0.001-

    0.01 M) zeta potential was lower than -30 mV indicating stable colloids. Colloids were smaller and more stable in

    monovalent (Na+) than in divalent (Ca2+) dominated solutions. The colloid concentration increased only in

    0.001-0.01 M solutions.

    Conclusions

  • www.helsinki.fi/yliopisto 18 BELBaR Helsinki 5.-7.3.2013

    Thank you and welcome to laboratory of radiochemistry!

    Slide Number 1Slide Number 3Characterization methodsSlide Number 6Stability of bentonite colloidsStability of bentonite colloidsBentonite colloid concentrationSlide Number 11Slide Number 12Slide Number 13Eu-152 sorption on colloidsSlide Number 16ConclusionsThank you and welcome to laboratory of radiochemistry!