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Part of an Excellence Ph.D. Course
Politecnico di Torino – June 27th, 2012
A talk on:
Transport of colloids and nanoparticles in saturatedporous media for environmental remediation
Rajandrea SETHI, Tiziana TOSCO and GROUNDWATER ENGINEERING GROUP
DIATI – Politecnico di Torino
DITAG
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ZVI Permeable reactive barrier
2
3
Degrades
� Transformation and immobilization of inorganiccontaminants� Degradation of organiccontaminants
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TCE degradation pathways
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5
MillimetricMillimetricMillimetricMillimetric ironironironiron NanoscaleNanoscaleNanoscaleNanoscale ironironironiron
0.25 0.25 0.25 0.25 – 2 mm2 mm2 mm2 mm 15 15 15 15 – 100 100 100 100 nmnmnmnm
Use of ZVI to remediate contaminated
aquifers
Fre
yri
a e
t al. 2
007
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ZVIPlume treatment
0.25 – 2 mm
� Installation:
� High costs
� Difficult, depth <30m
� Standard practice
MZVI & NZVI
Source & plume treatment
15 nm → 100 µm
� Installation:
� Low costs
� Injected, depth < 70m
� Under development
ZVI vs MZVI & NZVI
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7
High specific surface area1 kg of nanoscale iron = 2 x Stadio Olimpico (Roma)
∼30000 m2
FESEM (Tecnogranda)
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Degradation kinetics
� Degradation kinetics:� dove k pseudocinetica del I ordine [T-1], kSA cinetica all’unità di SA e cFe [LT-1], kMcinetica all’unità di cFe [L3M-1T-1], SSA superficie specifica [L2M-1], cFeconcentrazione di ferro per volume di acqua [ML-3], cTCE concentrazione del contaminante.
( ) ( ) TCEFeSATCEFeMTCETCE ccSSAkcckkc
dt
dc⋅⋅⋅−=⋅⋅−=−=
Fe0 + RCl + H+→ RH + Fe2+ + Cl-
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9
MZVI & NZVI: suspension
stability
MZVI(1-100 µm)
relevant mass,
high density
NZVI(15–100 nm)
particle – particle
attraction
gravitational sedimentation aggregation (single domain)
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NZVI: aggregation
� The application is hindered by aggregation
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11
MZVI(1-100 µm)
relevant mass,
high density
NZVI(15–100 nm)
particle – particle
attraction
MZVI & NZVI: suspension
stability
sedimentation & aggregation
� Reactivity:
□ Lower, due to reduced surface area
� Injection:
□ Sedimentation during pumping and inside the wells
□ Reduced radius of influence
� Transport:
□ Filtered/strained in the porous medium, reduced contact with contaminants
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NZVI: Thermodynamic stabilization
� Modification of surface properties: low concentrations of
polymers adsorbed on particles surface providing:
� Electrostatic stabilization:
repulsive forces due to the surface
charge of the polymer layer
□ short-ranged
□ affected by ionic strength
� Steric stabilization:
repulsion due to osmotic
and elastic forces
□ long-ranged if MW is high
□ indifferent to ionic strength
IS
With polimer
No polimer
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MZVI & NZVI: stabilization
� Stabilization: via addition of green polymers (guar gum and xanthan gum)
1. GREEN: natural origins from the seed of the guar
plant
2. INEXPENSIVE: Sigma-Aldrich: 44.60 €/kg
Commercial: ~2 €/kg
3. COMMERCIALLY AVAILABLE: food industry
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NZVI: Thermodynamic stabilization
� DLS measurements (guar gum 0.5 g/l):
Decrease of the hydrodynamic radius Reduced aggregation
0 1000 2000 3000 4000
200
300
400
500
Initial Particle Size
Initial Particle Size
Bare Particles
Particles in solution of Guar Gum 0.5 g/L
10mM NaCl
Radiu
s (
nm
)
Time (s)154 mg/l 231 mg/l
0
100
200
300
400
500
600
Hydro
dyna
mic
Ra
diu
s (
nm
)
Particle Concentration (mg/L)
Bare particles
MRNIP
Guar gum-coated particles
Tiraferri, A.; Chen, K.L.; Sethi, R.; Elimelech, M. Reduced aggregation and sedimentation of zero-valent iron nanoparticles in the presence of guar gum. Journal of Colloid and Interface Science 2008, 324(1-2), 71-79.
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15
MZVI: Kinetic stabilization
� Modification of fluid properties: reduced frequency of
particle collisions.
� Shear-thinning solution of xanthan, guar gum (3-10 g/l)
Comba, S.; Dalmazzo, D.; Santagata, E.; Sethi, R. Rheological characterization of NZVI suspensions for injection in porous media.Journal of Hazardous Materials (submitted) 2010.
Guar gum
solution
water
High viscosity at
low shear rate
↓
Reduced
sedimentation
& aggregation
Low viscosity at
low shear rate
↓
Easily injected
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� Sedimentation curves for MZVI in guar gum (5.5 g/l) proved increased stability:
Sedimentation curves
MZVI: Kinetic stabilization
MZVI in water
MZVI in guar gum
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Column tests: experimental
setup
� Column transport tests:� Packed column:
□ L = 0.46 m, din = 2.5 cm, n = 0.49
□ Q = 6.74 ·10-4 l/s
� Sand (Sibelco & Dorsilit):
□ d50 = 0.69 mm
□ Silica, K-feldspar (minor)
� Particles (20 g/l):
□ MZVI (Basf)
□ NZVI (Toda Kogyo corp.)
� Steps:
□ Injection (particles+dispersant)
□ Flushing (water)
� Dispersant during injection:
□ Water (DI)
□ Xanthan (3 g/l) in DI or 12.5 mM
manometer
susceptimeter
column
IN
OUT
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Column tests: experimental setup
� Column transport tests:� Packed column:
□ L = 0.46 m, din = 2.5 cm, n = 0.49
□ Q = 6.74 ·10-4 l/s
� Sand (Sibelco):
□ d50 = 0.69 mm
□ Silica, K-feldspar (minor)
� Particles (20 g/l):
□ MZVI (Basf)
□ NZVI (Toda Kogyo corp.)
� Steps:
□ Injection (particles+dispersant)
□ Flushing (water)
� Dispersant during injection:
□ Water (DI)
□ Xanthan (3 g/l) in DI or 12.5 mM
MZVI
dc = 1.1 µmComp.: 98.4% Fe0
0.69% C0.66% N
NZVIdc = 70 nmComp.: 35% Fe0
65% Fe3O4
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Time (s)
0 2000 4000 6000 8000
0
0.2
0.4
0.6
0.8
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Column tests: experimental
setup
� Column transport tests:� Packed column:
□ L = 0.46 m, din = 2.5 cm, n = 0.49
□ Q = 6.74 ·10-4 l/s
� Sand (Sibelco):
□ d50 = 0.69 mm
□ Silica, K-feldspar (minor)
� Particles (20 g/l):
□ MZVI (Basf)
□ NZVI (Toda Kogyo corp.)
� Steps:
□ Injection (particles+dispersant)
□ Flushing (water)
� Dispersant during injection:
□ Water (DI)
□ Xanthan (3 g/l) in DI or 12.5 mM
INJECTION FLUSHING
MZVI or NZVI
+ water
water or xanthan 3 g/l
(7 or 26 PVs) (26 or 15 PVs)
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� Iron concentrations measured with susceptibility sensors� Linear correlation between measured susceptibility and particle
concentration
□ Breakthrough curves
□ Total concentration profiles
Column tests: concentration measurements
Dalla Vecchia, E.; Luna, M.; Sethi, R. Transport in Porous Media of Highly Concentrated Iron Micro- and Nanoparticles in the Presence of Xanthan Gum. Environmental Science & Technology 2009, 43(23), 8942-8947.
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Column tests: experimental
results
� Continuous in-line measurement of iron concentration at column outlet:
non destructive measurement
MZVI NZVI
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Column tests: experimental results
� Concentration profiles after injection (before flushing): non
destructive measurement
NZVI
MZVI
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Modeling approach: key aspects
� Key aspects:
1. Particle interactions with the porous matrix
□ Physical filtration/straining
□ Physical-chemical interactions: blocking, ripening
2. Clogging:
□ Influence of particle deposits on porous medium properties
□ Coupled problem
3. Viscosity of the dispersant fluid
□ Shear-thinning behavior
□ Darcy’s law for non-Newtonian fluids
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Modeling approach: (1) Particle-porous medium interactions
� Modified ADE accounts for interaction mechanisms:Then...
First...
filtration/
straining
physical-chemical
interactions
( )( )
( )
( )( )
0
,
b
m m m
b
s cc q c D
t t x x x
sf c s
t
ρε ε
ρ
∂∂ ∂ ∂ ∂ + + − =
∂ ∂ ∂ ∂ ∂
∂= ∂
Cle
an
bed
Rip
en
ing
Blo
ckin
g
mec
hanism
smec
hanism
smec
hanism
smec
hanism
s
Str
ain
ing
Str
ain
ing
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Modeling approach: (2) Clogging
� Clogging: Deposited particles reduce porosity and
permeability:
V , g g
ε V , g g
εV ,
g gε
Tosco, T.; Sethi, R. Transport of non-Newtonian suspensions of highly concentrated micro- and nanoscale iron particles in porous media: a modeling approach. Environmental Science & Technology (submitted) 2010.
( ) sAAsAc
b
cρ
ρθ+=
0
( ) snss
bm
ρ
ρε −=↓ porosity
( )2
3
A
nCsK =
↑ surface area
↓ permeability
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� Xanthan or guar gum gel (shear-thinning)
→ non-Newtonian fluid
Cross model:
Extended Darcy’s law:
Modeling approach: (3) Non-Newtonian viscosity
( )xmm ccf ,,γµ &=
( )( ) x
p
cc
sKq
xmm
m∂
∂−=
,,γµ &
Comba, S.; Dalmazzo, D.; Santagata, E.; Sethi, R. Rheological characterization of NZVI suspensions for injection in porous media.Journal of Hazardous Materials (submitted) 2010.
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Modeling approach: coupled model
E-MNM1Dhttp://areeweb.polito.it/ricerca/groundwater/software/EMNM1D.ht
ml
� Model structure:
� Implementation:� Finite differences, 1D
� Evolution of MNM1D model for colloid transport
Transport
equations
Darcy’s law
Permeability
coefficient
Fluid viscosityMedium porosity
Tosco, T.; Sethi, R. Transport of non-Newtonian suspensions of highly concentrated micro- and nanoscale iron particles in porous media: a modeling approach. Environmental Science & Technology (submitted) 2010.
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� Download:www.polito.it/groundwater/software
E-MNM1D:www.polito.it/groundwater
( )( ) x
p
cc
sKq
xmm
m∂
∂−=
,,γµ &
Darcy’s law:
( )( )
( )[ ] ( )c
mm
mxm
mxmmmc
cccc
χγλ
µµµγµ
&
&
⋅+
−+=
∞
∞1
,,,
,0,
,
( ) ( )ssK
q
m
mm
εαγ γ=&
Fluid viscosity:
( ) snss
b
mρ
ρε −=
Porosity:
( ) ( )0
2
0
0
3
K
sAA
A
n
ssK
c
bc
m
+
=
ρ
ρϑ
ε
Permeability:
Transport equations:
( ) ( )
( ) ( ) ( ) ( )
( ) ( )
( )
−
+=
∂
∂
−+=∂
∂
=
∂
∂
∂
∂−
∂
∂+
∂
∂+
∂
∂+
∂
∂
=
∂
∂
∂
∂−
∂
∂+
∂
∂
22,
50
2,
2
11,111,
1
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1
1
1
1
0
0
skcd
xk
t
s
skcsAkt
s
x
cD
xcq
xt
s
t
sc
t
x
cD
xcq
xc
t
dbamb
dbamb
mmbb
m
xmxmxm
ρερ
ρερ
ερρ
ε
εε
β
β
E-MNM1D
Tosco, T.; Sethi, R. Transport of non-Newtonian suspensions of highly concentrated micro- and nanoscale iron particles in porous media: a modeling approach. Environmental Science & Technology 2010.
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Modeling approach: information
from experimental data
� Pressure drop
at column ends clogging&
viscosity
� Outlet
particle
concentration
Depositiondynamics
� Concentration
profiles after
injection
Time (s)0 2000 4000 6000 8000
0
0.2
0.4
0.6
0.8
1
Time (s)
0
0.2
0.4
0.6
0.8
1
0 2000 4000 6000 8000
x (m)0.1 0.2 0.3 0.4 0.5
1
1.5
2
2.5
3
3.5
4
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Modeling approach: fitting of experimental data
MZVI NZVI
Tosco, T.; Sethi, R. Transport of non-Newtonian suspensions of highly concentrated micro- and nanoscale iron particles in porous media: a modeling approach. Environmental Science & Technology (submitted) 2010.
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Permeability changes
� Changes in permeability are manly due to changes in surface area:
( ) ( )0
2
0
0
3
K
sAA
A
n
ssK
c
bc
m
+
=
ρ
ρϑ
ε
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E-MNM radial and spherical geometry
� Accounts for variable:� flow velocity� viscosity� attachment and detachment coefficients
� EEEE----MNMMNMMNMMNM (Enhanced Micro- and Nanoscale transport Model):� Homogeneous permeation;� Radial and spherical geometry.
Unpublished data
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Reagent delivery
(reactive zones)
� Injection methods:� Gravity� Fracturing
□ Hydraulic□ Pneumatic
� Jetting� Pressure Pulse Technology� Direct push
� Soil mixing
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Direct push system
� Hydraulically-powered machines� Environmental sampling (soil, gas, groundwater)� Grouting and reagents injection
www.carsico.it
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Direct push system
Pumps and injection tips
� High pressure (69-127 bar) suitable for viscous fluids� Average pumping rates� Injection (Top-down or bottom-up)
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Recirculation
Sethi
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Field injection of MZVI
� FP7 AQUAREHAB� Injection 16/11/2011� Site description (Belgium):
� Contamination of chlorinated hydrocarbons� Sandy-loam aquifer� Injection depth: 8.5 – 10.5 m� 5 injection points
TCE
TCA
clayey sand
coarse
sand
7m
20m
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Field injection of MZVI
� Fracturing injection:� Direct push system (Geoprobe GS200)� High pressure bottom-up injection (10-40 bar)
� Sospension:� MZVI: D50 = 50 µm, 50 g/l� Guar gum: 6 g/l� Volume: 1.6 m3
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Field injection of MZVI
� Installazione della rete di monitoraggio:
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Conclusions
� Stability:� Guar gum and xanthan (green biopolymers) provide thermodynamic and
kinetic stabilization:
□ MZVI: sedimentation prevention
□ NZVI: aggregation and sedimentation prevention
� Transport in porous media:� Transportability: guar gum & xanthan increase breakthrough concentration
� Modeling: successful modeling of particle transport with
□ Extension of Darcy’s law for non-Newtonian fluids
□ Changing of hydrodynamic parameters due to clogging
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Projects and Acknowledgements
� The work was partially funded by the EU Research
project (VII Framework Program) “AQUAREHAB –
Development of rehabilitation technologies and
approaches for multipressured degraded waters and the
integration of their impact on river basin management” –
project coordinator Dr. L. Bastiaens (VITO, Belgium)
� Acknowledgement to:
� DITAG, Politecnico di Torino: Alberto Tiraferri, Elena Dalla Vecchia, Michela Luna, Francesca Gastone, Xue Dingqui, Silvia Comba, Francesca Messina, Matteo Icardi
� DISAT, Politecnico di Torino: Daniele Marchisio, Barbara Bonelli,
Federica Lince, Francesca Freyria
� INRIM, Torino: Marco Coisson
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References
� Tosco T, Bosch J, Meckenstock RU, Sethi R. Transport of ferrihydrite nanoparticles in saturated porous media: role of ionic strength and flow rate.Environ Sci Technol. 2012 Apr 3;46(7):4008-15� Freyria F.S.; Bonelli B.; Sethi R.; Armandi M.; Belluso E.; Garrone E. (2011). Reactions of Acid Orange 7 with Iron Nanoparticles in Aqueous Solutions. In: JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES, vol. 115 n. 49, pp. 24143-24152. - ISSN 1932-7447� Tosco, T.; Tiraferri, A.; Sethi, R. Ionic Strength Dependent Transport of Microparticles in Saturated Porous Media: Modeling Mobilization and Immobilization Phenomena under Transient Chemical Conditions. Environmental Science & Technology 2009200920092009, 43(12), 4425-4431.� Tosco, T.; Sethi, R. MNM1D: a numerical code for colloid transport in porous media: implementation and validation.American Journal of Environmental Sciences 2009200920092009, 5(4), 517-525.� Tosco, T.; Sethi, R. Transport of non-Newtonian suspensions of highly concentrated micro- and nanoscale iron particles in porous media: a modeling approach. Environmental Science & Technology (submitted) 2010201020102010.� Tiraferri, A., T. Tosco, e R. Sethi (2010), Transport and Retention of Microparticles in Packed Sand Columns at Low and Intermediate Salinities: Experiments and Mathematical Modeling. Environmental Earth Sciences (submitted) 2010201020102010.� Tiraferri, A.; Chen, K.L.; Sethi, R.; Elimelech, M. Reduced aggregation and sedimentation of zero-valent iron nanoparticles in the presence of guar gum. Journal of Colloid and Interface Science 2008200820082008, 324(1-2), 71-79.� Tiraferri, A.; Sethi, R. Enhanced transport of zerovalent iron nanoparticles in saturated porous media by guar gum. J Nanopart Res 2009200920092009, 11(3), 635-645.� Dalla Vecchia, E.; Coisson, M.; Appino, C.; Vinai, F.; Sethi, R. Magnetic Characterization and Interaction Modeling of Zerovalent Iron Nanoparticles for the Remediation of Contaminated Aquifers. Journal of Nanoscience and Nanotechnology 2009200920092009, 9(5), 3210-3218.� Comba, S.; Dalmazzo, D.; Santagata, E.; Sethi, R. Rheological characterization of NZVI suspensions for injection in porous media. Journal of Hazardous Materials (submitted) 2010201020102010.� Dalla Vecchia, E.; Luna, M.; Sethi, R. Transport in Porous Media of Highly Concentrated Iron Micro- and Nanoparticles in the Presence of Xanthan Gum. Environmental Science & Technology 2009200920092009, 43(23), 8942-8947.