Transcript Radionuclide Sorption to Volcanic Tuff in the Presence of

Sorption of Radionuclides to
Tuff in the Presence of
Shewanella oneidensis (MR-1)
Sherry Faye1, Jen Fisher2, Duane
Moser2, Ken Czerwinski1
1 University of Nevada, Las Vegas Radiochemistry PhD Program
2 Desert Research Institute, Las Vegas, NV
Outline

Objective, Background and Goals


Experimental






Influence of bacteria on radioelement sorption
Tuff characterization
Bacteria preparation
Sorption
Results
Conclusions
Future directions
Research Objectives


Obtain data on sorption kinetics, equilibrium and
fundamental surface interactions of
radionuclides with tuff.
Obtain a better understanding of interactions of
the Shewanella oneidensis (MR-1) culture with
tuff and radionuclides.
Background

Studies from literature include:




Radionuclide sorption to various rock and minerals.
Interactions of radionuclides with bacteria.
Combined systems including rocks and minerals,
radionuclides and bacteria.
A combined system will be studied based on
conditions at the Nevada Test Site.


Determine if bacteria can influence sorption.
Use results to evaluate against environmental
conditions
Research Goals

Characterize tuff.




Use scanning electron microscopy (SEM) to examine
surface morphology.
Use energy dispersive spectroscopy (EDS) to
determine elemental composition.
Use X-ray diffraction (XRD) for phase identification.
Perform sorption studies with radionuclides in
the absence and presence of bacteria.
Scanning Electron Microscopy
Si, O, Al, K, Na
Tuff, 50X
X-ray Diffraction



Sanidine
KAlSi3O8
Cristobalite
SiO2
α-Quartz
SiO2
Bacteria Background
MR-1 can be found in
diverse environments.
 MR-1 can grow with or
without oxygen and can
use a variety of alternate
electron acceptors.
 Well known for its metal
reduction capabilities.

Courtesy of Jen Fisher
Preparation of MR-1 Cultures
Stock cultures stored
at -80° C in glycerol
are thawed on ice
Cells pelleted
(centrifuged @
3500 rpm for 15 min)
Plated on Luria
Bertani agar
Cells resuspended
with PO4- and
CO3- free buffer
Single colony picked and
grown 24 h in liquid LB
to density of ~109
cells/mL
1 mL (~109 cells) added
to FEP tubes
Courtesy of Jen Fisher
Sample Composition

Prepare solution phase

Radionuclide



Buffer



pH range 6 to 8
Dilutant – up to 20 mL DI
Add tuff



50 – 100 Bq mL-1 241Am
50 – 200 Bq mL-1 233U
Select particle size 500 – 600 μm
Select fraction of solid phase (Bq g-1)
Solution to solid ratio
Batch Experiments


Vortex for 2 minutes.
Centrifuge samples for 2 minutes.



Time based on previous kinetic studies
Liquid scintillation counting (100 μL into 10 mL
liquid scintillation cocktail).
Collect samples every 10-15 minutes for the first
two hours.
* All samples were created in 50 mL FEP centrifuge tubes
RESULTS
Results –

241Am
Samples contain:
 Solution phase:




100 or 200 Bq mL-1 241Am
NaHCO3 to obtain a pH of ~8
20 mL total volume, adjusted with DI
Solid phase:

1 gram tuff, ground to 500-600 μm
Equilibrium Results –
241Am
100 Bq/mL
200 Bq/mL
120
100
% Sorbed
80
60
40
20
0
0
50
100
Time (h)
150
200
Kinetics Results –
241Am
100 Bq/mL
200 Bq/mL
120
100
% Sorbed
80
60
40
20
0
0
0.5
1
Time (h)
1.5
2
Results –

241Am
with MR-1
Nine samples, each had 20 mL of solution phase
adjusted to pH 7 with NaOH. Bacteria were
present in 5 samples ~ 1E+08 cells mL-1:
Concentration (Bq/mL)
Mass Tuff (g)
Am:tuff (Bq/g)
50
0
---
50
10
100
50
4
250
50
2
500
100
2
1000
Results –
241Am
with MR-1
100 Bq/g
No Bacteria
10^8 cells/mL
100
% Sorbed
80
60
40
20
0
0
0.5
1
Time (h)
1.5
2
Results –
241Am
with MR-1
500 Bq/g
No Bacteria
10^8 cells/mL
80
70
% Sorbed
60
50
40
30
20
10
0
0
0.5
1
Time (h)
1.5
2
Results –

233U
To determine ideal conditions for sorption
kinetic studies:
Concentration (Bq/mL) Mass Tuff (g)
Buffer
U:tuff (Bq/g)
NaHCO
100
1
3
2000
100
1
NaOH
2000
NaHCO
50
10
3
75
50
10
NaOH
75
Kinetics Results –
233U
75 Bq/g NaOH
2000 Bq/g NaOH
75 Bq/g NaHCO3
2000 Bq/g NaHCO3
100
% Sorbed
80
60
40
20
0
0
0.5
1
Time (hours)
1.5
2
Kinetics Results –

233U
Six samples were created to obtain kinetics and
equilibrium data, all contained 20 mL solution
phase and had a pH of ~7 using NaOH:
Concentration (Bq/mL)
Mass Tuff (g)
U:tuff (Bq/g)
50
10
75
62.5
5
250
125
5
500
125
2.5
1000
187.5
2.5
1500
100
1
2000
Results –
233U
75 Bq/g
500 Bq/g
1500 Bq/g
250 Bq/g
1000 Bq/g
2000 Bq/g
100
% Sorbed
80
60
40
20
0
0
0.5
1
Time (h)
1.5
2
Results –

233U
with MR-1
Six samples, each had 20 mL of solution phase
adjusted to pH 7 with NaOH:
Concentration (Bq/mL)
Mass Tuff (g) Bacteria (cells/mL)
100
1
0
100
0
1010
100
1
104
100
1
106
100
1
108
100
1
1010
Results –
233U
with MR-1
No Bacteria
10^4
10^8
No Tuff
10^6
10^10
100
% Sorbed
80
60
40
20
0
0
0.5
1
Time (hour)
1.5
2
CONCLUSIONS
AND FUTURE WORK
Conclusions



Quick sorption kinetics were obtained for 241Am
and 233U.
Sorption of 233U affected by carbonate formation
when using NaHCO3 as a buffer.
Sorption of 241Am and 233U to MR-1/growth
medium.
Future Work



Repeat 241Am and 233U sorption in the presence
of bacteria with replicates.
Perform sorption experiments in the presence of
bacterial growth medium and absence of MR-1
Repeat sorption experiments with other
radionuclides of interest.

Tc, Np, Pu
Acknowledgements






Richard Gostic
Megan Bennett
Dr. Ralf Sudowe
Dr. Thomas Hartmann
Tom O’Dou and Trevor Low
Funding provided by DOE/EPSCoR Partnership
Grant DE-FG02-06ER46295
UNLV Radiochemistry
Extra Slides
Results –
241Am
with MR-1
1000 Bq/g
No Bacteria
10^8 cells/mL
100
% Sorbed
80
60
40
20
0
0
0.5
1
1.5
2
Time (h)
2.5
3
3.5
Results –
241Am
with MR-1
250 Bq/g
No Bacteria
10^8 cells/mL
100
% Sorbed
80
60
40
20
0
0
0.5
1
1.5
2
Time (h)
2.5
3
3.5
Equilibrium Results –
233U
75 Bq/g NaOH
75 Bq/g NaHCO
3
2000 Bq/g NaOH
2000 Bq/g NaHCO
100
3
% Sorbed
80
60
40
20
0
0
50
100
Time (hours)
150
200