Scavenging Cobalt & Other Transition Metals From Radwaste: The Next Generation of Filter Media for Nuclear Applications

International Low Level Waste ConferenceLoews Resort Hotel, Orlando, FL

Prepared & Presented by John Thomas & Leo Kaledin June 22, 2016

This presentation is proprietary to Argonide Corporation and Nano Technologies Inc. (NTI) and is furnished for the exclusive use of the attendees of the 2016 EPRI International Low Level Waste Conference.

INTRODUCTION

• PROBLEM: • Source Term & Dose Reduction For “Ex-Core” Radiation

• Cobalt daughters 58Co & 60Co: Responsible for as much as 80 % of ex-core radiation. • These isotopes and complexes identified as colloids (size range > 1 nm & < 100 nm)

• Ion exchange resins and conventional filter media problematic for removal

• SOLUTION: DEAL• In water, nano-coated, ceramic alumina - boehmite - AlO(OH) filter media (DEAL18) has

measured zeta potential greater than +80 mV in a packed column under micro-capillary (average pore size ~2.5 mm) flow conditions • 3rd party testing has demonstrated that through a single-pass column, AlO(OH) nano-coated filter

media has the ability to remove & retain colloidal 60Co with 99 % efficiency

3

Water Borne Contaminants

• 3 contaminants

Dissolved Solids (DS)

Suspended Solids (SS)

Colloids

• 3 mechanisms of filtration

Direct Interception

(Conventional/Sieving)

Inertial Impaction

(Conventional)

Electroadsorption

AlO(OH) nanocoating technologies: quantum dots (QD) & quantum wires (QW)

• Mechanism of filtration – electrostatic and electro kinetic adsorption

• The nano-coating material’s: Aluminum oxide/hydroxide (boehmite)

• The boehmite is deposited on the porous substrate as “quantum dots”. “dot” is only 1.2 nm (high) x 2-3 nm (diameter)

Boehmite nanofibers bonded to microfiber “quantum wire” [1]

Coating on DE

NanoWire on Microfiber

α-Al2O3·H2O quantum dots deposited onto DE surface

• Boehmite crystals grow with preference along plates about 10 times the unit cell dimension along a- & c-axes[4]

• BET surface area of aluminized DE18 increased by 157% as compared to the uncoated DE

• mean pore volume increased by 185% as compared to the uncoated DE [3]

b=12.1 Å

10×c=37.0 Å10×a=28.7 Å

wc=wa=8.4 Å

wa=wc=8.4 Å

b=12.1 Å

Zeta potential for AlO(OH) nano-coated media

• Diatomaceous Earth (DE) substrate is strongly electronegative (- 70 mV)

• For AlO(OH) loading greater than 17% (one layer of 10⨯10 ⨯1 monocrystals in quantum dot) , the base substrate is transformed from electronegative to strongly electropositive (> +50 mV) [2]

• In water, when AlO(OH) loading is increased to 50% by weight (a stack of three layers of 10⨯10 ⨯3 monocrystals, the zeta potential is ~ + 80 mV [2]

-100

-50

0

50

100

0 10 20 30 40 50Z

eta

po

ten

tia

l, m

V

Al solids content, wt%

/ 2.6cluster

AlOOH DES S

/ 5.5( )cluster

AlOOH DES S estimated

++++++++ +++

s1 s2 s1 s2

Z

Y

++++++++ +++

Patch #1 Patch #1Patch #2 Patch #2

Wall

Flow directionDp>0

SLOW

vz

FAST

vz

vySLOW

vz

vy vy

FAST

vz

Aluminized DE particles

Flow in a capillary

• The non-uniform surface charge will affect the value of the zeta potential • A larger surface-charge density leads to a larger backflow of ions, producing an enhanced retardation of the velocity

in the z-direction labeled "SLOW" and "FAST".

• To preserve conservation of mass, fluid is sucked in from above, generating a y-velocity, vy, toward the surface while the opposite occurs in going from patch # 2 to patch #1

• These y-velocities are generated despite the fact that no pressure drop is applied in the y-direction.

Surface forces: Surface roughness (on DE) in theory and experiment

• Colloid stability is often predicted by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, which was developed for smooth, homogeneous particles with ideal geometries and with no double layer overlap

• Recently, the DLVO model has been found unable to fully describe biotic and abioticcolloidal behavior in aqueous media [5].

• Roughness is found to preserve the decay rate of exponentially decaying forces, amplifying them by a factor of exp(σ2/λ2) where σ is roughness [6].

• For 17-wt%AlOOH loading, the estimated roughness value of σ~1.2 nm and the amplifying factor is estimated to be greater than ~100 at high pH (>9) and high salinity (>1M)

3 GOOD THINGS TO KNOW:

• Electroadsorption has two components:

• (i) static (double layer thickness (Debye length, l)), roughness &

• (ii) dynamic interactions (y-velocities are generated perpendicular to surface)

• Higher the BET surface area and smaller the pore size and roughness the higher the resulting zeta potential z in the capillary flow

• Experimental data suggest that more important is the difference in absolute magnitudes of||s1| -|s2||.

• Don’t mix electropositive and electronegative sorbents with similar z-potentials

Cobalt-59 removal efficiencies by nano-coated AlO(OH) DE60 filter media in short column configurations

BV, dm3 pH Input 59Co concentration, ppb

Column depth, inches

Flow rate at DP of 35 psi, GPM/ft2

Ten BV, dm3

Output 59Co concentration, ppb

Removal efficiency, %

0.16 10 635±0.096 2” 15 1.6 <5 >99.2

0.32 4” 9 3.2 <5 >99.2

0.64 8” 5 6.4 <5 >99.2

0.16 8 656±0.096 2” 15 1.6 <5 >99.2

0.32 4” 9 3.2 <5 >99.2

0.64 8” 5 6.4 <5 >99.2

Initial removal efficiency (~10 Bed Volume/BV) of cobalt (59Co) by DEAL60 powders packed into a column differential pressure DP of 35 psi

DEAL REMOVES COBALT AT GREATER THAN 99 %

Sub-0.1 μm Colloidal Cobalt Removal & Retention

Scavenging Cobalt from Radwaste... Performance You Can See !

Nano-coated AlO(OH) Removal Efficiency of Radionuclides from Radwaste Water

Next Steps for AlO(OH) Nano-coated Filter Media

• CONTINUE NANO-COATED SCREENING IN “HOT LABS” • Initial screening of the nano-coated, aluminized filter media was undertaken in a “hot lab” of a Duke

Energy PWR, in late 2014.

• PWR TESTING • Samples of nano-coated, aluminized filter media have been delivered to a PWR for bench-scale testing

on radwaste water. Testing is scheduled for summer 2016.

• More PWR & BWR beta test sites are being solicited.

• D etermine a pathway forward for user-centric testing • E valuate nano-coated, aluminized filter media• A ccumulate information re. process requirements • L ink information to test results for successful applications

Cool picture of Activated Colloid & Sub-0.1 Micron Retention in Nuclear Filtration Applications

See John Thomas

Nano Technologies Inc. Booth

REFERENCES

• 1. L.A. Kaledin, F. Tepper, and T. G. Kaledin, Pristine point of zero charge (p.p.z.c.) and zeta potentials of boehmite’s nanolayer and nanofiber surfaces, Int. J. Smart and NanoMaterials, 7:1, 1-21, 2016

• 2. L.A. Kaledin, F. Tepper, and T. G. Kaledin, US 9,309,131

• 3. L.A. Kaledin, F. Tepper, and T.G. Kaledin, Long-range attractive forces extending from the alumina’s nanolayer surface in aqueous solutions, Int. J. Smart Nano Mater. DOI:10.1080

• 4. X. Bokhimi, J.A. Toledo-Antonio, M.L. Guzman-Castillo, and F. Hernandez-Beltran. Relationship between crystallite size and bond lengths in boehmite. J. Solid State Chem. 159 (2001), pp. 32– 40.

• 5. D. Grasso, K. Subramaniam, M. Butkus, K. Strevett, J. Bergendahl A review of non-DLVO interactions in environmental colloidal systems, Reviews in Environmental Science and Biotechnology, 2002, vol. 1, pp 17-38

• 6. D F. Parsons, R. B. Walsh, and V. S. J. Craig. Surface forces: Surface roughness in theory and experiment. J. Chem. Phys 140, 164701 (2014)

• 7. R. R. Cohen and C. J. Radke, Streaming potentials of nonuniformly charged surfaces. J. Colloid and Interface Science, Vol. 141, No. 2, pp.338-347, 1991

• The End