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Use of engineered nanoparticles is increasing. Especially zinc oxide
nanoparticles (ZnO NP) have been used in a wide range of consumer
products. With this use release of ZnO NP is inevitable. However, little is
known of the behavior of ZnO NP in the environment. Consequently, the
aim of this study was to:
• Investigate the adsorption and desorption behavior of ZnO
nanoparticles at a soil-water interface using two different standardized
soils (LUFA 2.2 and LUFA 2.3)
• Use the Freundlich isotherm to estimate adsorption and desorption
behavior
Introduction & aim
• Rapid adsorption was observed for both LUFA 2.2 and 2.3
• Higher adsorption capacity was observed for LUFA 2.3 compared
to 2.2
• Rapid desorption but high residual adsorbed to the soil after 24
hours
• Good fitting of adsorption and desorption behavior with Freundlich
isotherm
ZnO NP with a nominal size of 35 nm was tested. The NP were
characterized with ICP-MS, DLS, BET and TEM (Table 1 and Figure 3). A
stock solution of ZnO NP was prepared in 0.01 M CaCl2. The suspension
was ultra sonicated with a micro tip for 15 minutes (400 W) directly prior
to use.
The experiments were based on preliminary adsorption - desorption tests
following OECD 106 Adsorption - Desorption Using a Batch Equilibrium
Method. Adsorption was evaluated at 3.35 mg Zn/L during 24 hours
followed by 24 hours of desorption. Soils used were LUFA 2.2 and 2.3.
Isotherm studies were carried out using 1, 2.5, 5 and 10 mg Zn/L.
ADSORPTION AND DESORPTION BEHAVIOR OF ZNO NANOPARTICLES AT THE SOIL-WATER
INTERFACE USING STANDARDIZED SOIL L. M. Skjolding1*, M. Winther-Nielsen2 and A. Baun1
1Department of Environmental Engineering, Technical University of Denmark, Building 113, Kgs. Lyngby, Denmark
2DHI, Agern Allé 5, DK-2970 Hørsholm, Denmark
*Corresponding author: lams@env.dtu.dk
Materials & Methods
Results – Adsorption and desorption
Conclusions Characterization
Results – Isotherm
Figure 1: A) Adsorption of LUFA 2.2 (triangles) and LUFA 2.3 (squares)
after equilibration with 3.35 mg Zn/L of ZnO NP and B) desorption of
adsorbed ZnO NP in 0.01 M CaCl2.
Figure 2: Fitted linearized Freundlich isotherm for A) adsorption and B)
desorption with the fitted equation and R2 using LUFA 2.2.
Technique ZnO NP
ICP-MS 80.2 % Zn
BET 0.4841 cm3 /g, 12.9 nm
TEM 30 ± 17 nm
DLS
132.9 nm (90 sec)
134.3 nm (24h)
Zeta-potential 29.1 mV
Table 1: Characterization of ZnO NP
used in the experiment by application
of ICP-MS, BET, TEM, DLS and Zeta-
potential (made by LEITAT and ICN).
Figure 3: TEM image of ZnO-
NP dry powder. The bar
indicates 500 nm. A high
homogenity of NP was found
along the grid (made by ICN).
0
20
40
60
80
100
0 10 20 30
Deso
rb
ed
[%
]
Equilibration time [h]
0
20
40
60
80
100
0 10 20 30
Ad
so
rb
ed
[%
]
Equilibration time [h]
A B
y = 0.7855x + 1.2732 R² = 0.9312
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5
Lo
g Z
nS
oil [
µg
/g
]
Log Znwater [µg/cm3]
y = 1.6426x + 0.9174 R² = 0.9635
-0.5
0
0.5
1
1.5
2
2.5
-1 -0.5 0 0.5 1
Lo
g Z
nS
oil [
µg
/g
]
Log Znwater [µg/cm3]
A B
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