Introduction & aim Materials & Methods Results – Adsorption and

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: [email protected]

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