Sorption of Radionuclides to Tuff in the Presence of Shewanella oneidensis (MR-1)

1. 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

2. Outline • Objective, Background and Goals • Influence of bacteria on radioelement sorption • Experimental • Tuff characterization • Bacteria preparation • Sorption • Results • Conclusions • Future directions

3. 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.

4. 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

5. 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.

6. Scanning Electron Microscopy Si, O, Al, K, Na Tuff, 50X

7. X-ray Diffraction • Sanidine KAlSi3O8 • Cristobalite SiO2 • α-Quartz SiO2

8. 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

9. Preparation of MR-1 Cultures Stock cultures stored at -80° C in glycerol are thawed on ice Plated on Luria Bertani agar Single colony picked and grown 24 h in liquid LB to density of ~109 cells/mL Cells pelleted (centrifuged @ 3500 rpm for 15 min) Cells resuspended with PO4- and CO3- free buffer 1 mL (~109 cells) added to FEP tubes Courtesy of Jen Fisher

10. Sample Composition • Prepare solution phase • Radionuclide • 50 – 100 Bq mL-1241Am • 50 – 200 Bq mL-1233U • Buffer • pH range 6 to 8 • Dilutant – up to 20 mL DI • Add tuff • Select particle size 500 – 600 μm • Select fraction of solid phase (Bq g-1) • Solution to solid ratio

11. 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

12. RESULTS

13. 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

14. Equilibrium Results – 241Am

15. Kinetics Results – 241Am

16. 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:

17. Results – 241Am with MR-1

18. Results – 241Am with MR-1

19. Results – 233U • To determine ideal conditions for sorption kinetic studies:

20. Kinetics Results – 233U

21. 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:

22. Results – 233U

23. Results – 233U with MR-1 • Six samples, each had 20 mL of solution phase adjusted to pH 7 with NaOH:

24. Results – 233U with MR-1

25. CONCLUSIONS AND FUTURE WORK

26. 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.

27. 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

28. 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

29. UNLV Radiochemistry

30. Extra Slides

31. Results – 241Am with MR-1

32. Results – 241Am with MR-1

33. Equilibrium Results – 233U