Transformation of Silver Nanoparticles:
From the Sewer to the Fly Ash
Ralf Kaegi ([email protected]), Andreas Voegelin, Basilius Thalmann
Eawag: Swiss Federal Institute of Aquatic Science and Technology
Urban wastewater
systems
Release of ENP from
Municipal and
Geranio, EST, 2009
Benn, JEQ, 2010
Kaegi, Water Res, 2013
Choi, Water Res, 2008
Kaegi, EST, 2011
Wang, J. Hazard. Mat.,
2012
industrial waste
consumer products
Sewer system
Transformation / deposition in
the sewer system
WWTP
Discharge into
surface waters
Lombi et al, Env. Poll,
2013
Coleman, PLOS,
2013
Anaerobic
digestion
Agriculture
Transformation / incorp.
into sewage sludge
Interaction with colloids,
environmental media
Transformation
Incineration
Impellitteri,
Water Res,
2013
Ag-NP in the sewer: setup
Dose P1
15’
P2
1h
P3
1h
0.8 g Ag-NP in 15 l dest. H2O, tdosing = 30 s, Vww = 30
l/s,
O2(Dose) = 6 mg/l, O2(P2) < 1 mg/l
500 m
2.4 km
5 km
Kaegi, Water Res, 47/12, 3866 – 3877, 2013
Ag-NP in the sewer:
Mass balance
Total amount of Ag-NP dosed to the sewer: 0.8g
A g c o n c e n tr a tio n ( µ g /l)
400
500m
2400m
5000m
101 %
300
109 %
200
107 %
100
0
0
2000
4000
6000
t im e [ s ]
8000
10000
Ag-NP in the sewer
Partial sulfidation
Efficient
transport
Ag
500m
2500m
5000m
101 %
350
109%
A g c o n c e n t r a t io n ( p p b )
300
107%
250
109 %
200
107 %
150
100
50
+
S
100
50
0
0
-5 0
0
1000
2000
3000
4000
5000
6000
7000
8000
EDX
150
c o u n ts
400
101%
200
9000
t im e [ s ]
2
2 .5
3
3 .5
e n e rg y [k e V ]
STEM (phase contrast)
Ag-NP reach the WWTP, sulfidized to various degrees.
(partically sulfidized Ag-NP are considerably less toxic than pristine AgNP (Reinsch et al., EST, 2012)
4
Urban wastewater
systems
Release of ENP from
Municipal and
Geranio, EST, 2009
Benn, JEQ, 2010
Kaegi, Water Res, 2013
Choi, Water Res, 2008
Kaegi, EST, 2011
Wang, J. Hazard. Mat.,
2012
industrial waste
consumer products
Sewer system
Transformation / deposition in
the sewer system
WWTP
Discharge into
surface waters
Lombi et al, Env. Poll,
2013
Coleman, PLOS,
2013
Anaerobic
digestion
Agriculture
Transformation / incorp.
into sewage sludge
Interaction with colloids,
environmental media
Transformation
Incineration
Impellitteri,
Water Res,
2013
n o r m a liz e d a b s o r p tio n
Fly ash
Particle size distribution (Laser diffraction)
Ag speciation
2 .5
A g (0 )
2
Ag S
2
A g -C u S
1 .5
A sh 3
A sh 2
1
A sh 1
0 .5
0
25450 25500 25550 25600 25650
in c id e n t p h o t o n e n e r g y [e V ]
Ag concentration in flyash:
10 – 12 mg/kg
Separation of the
colloidal fraction
Flyash (raw material)
Particle size distribution (SEM)
60
top
40
20
SPLITT flow channel
100’000
nm
0
0
2
4
6
d (µm)
8
10
20
12
bottom
15
10
5
0
0
2
4
6
8
10
12
Elemental compositions of individual
particles (SEM-EDX)
Click to edit Master subtitle style
Ag
N (tot) = 1205
Ag-NP in the colloidal fraction
EDX analysis suggests
Ag2S, but particles
seem NOT incorporated
in the ash matrix!
Conclusions
101%
400
109%
300
A g c o n c e n t r a t io n ( p p b )
Ag-NP sulfidize during their transport in
urban wastewater systems (sewer and
treatment plant)
500m
2500m
5000m
101 %
350
107%
250
109 %
200
107 %
150
100
50
0
-5 0
0
1000
2000
3000
4000
5000
t im e [ s ]
The degree of the sulfidation (kinetics) strongly
depends on the Ag-NP size. ‘Larger’ Ag-NP may
therefore remain partially metallic.
SEM results suggest that Ag-NP are not
incorporated into the ash matrix and thus
they may be re-released upon contact with
water (fly ash as fertilizer).
6000
7000
8000
9000

API 570 Effectivity Sheet

S and O

API 510 Effectivity Sheet