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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-08-14 to 2013-10-18
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study, GLP
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Qualifier:
according to
Guideline:
EPA OPPTS 835.1110 (Activated Sludge Sorption Isotherm)
GLP compliance:
yes (incl. certificate)
Type of method:
batch equilibrium method
Media:
soil/sewage sludge
Radiolabelling:
yes
Test temperature:
20 ± 2°C
Analytical monitoring:
yes
Details on sampling:
Determination of approproate soil:solution ratio
- Concentrations:
initial substance concentration 0.5 mg/l
sludge:solution ratios: 1:10, 1:50, 1:250
- Sampling interval:
24 hours
- Sample storage before analysis: no

Determination of approproate sludge:solution ratio
- Concentrations:
initial substance concentration 0.5 mg/l
sludge:solution ratios: 1:50, 1:100, 1:200
- Sampling interval:
2, 4 hours
- Sample storage before analysis: no

Determination of equilibrium time (soil adsorption/desorption kinetics)
- Concentrations:
initial substance concentration 0.5 mg/l
soil:solution ratio 1:50 for Speyer 2.2 and Speyer 2.3 soil;
soil:solution ratio of 1:500 for Speyer 6S soil
- Sampling interval:
2, 4, 6 and 24 hours
- Sample storage before analysis: no


Determination of equilibrium time (sludge adsorption/desorption kinetics)
- Concentrations:
initial substance concentration 0.5 mg/l
- Sampling interval:
0.5, 1, 2, 3 hours
- Sample storage before analysis: no
Details on matrix:
SOIL

Speyer 2.2 soil
COLLECTION AND STORAGE
- Geographic location:
Hanhofen, Rheinland-Pfalz, Germany
- Soil preparation (e.g.: 2 mm sieved; air dried etc.):
Sieved (2 mm) air-dried soil samples were taken from storage. Storage of soils was at ambient temperature and did not exceed three years. Moisture content was determined by oven-drying.

PROPERTIES
- Soil texture: loamy sand
Characteristics
pH-CaCl2 5.5
Nitrogen % 0.18
Organic carbon% 1.74
Organic matter % 3.00
Cationic exchange capacity
(meq/100 g soil) 10.2

Particle size distribution (USDA)
% clay (< 2 µm; w/w) 8.2
% silt (2-50 µm; w/w) 15.3
% sand (50-2000 µm; w/w) 76.5
Texture (USDA) Loamy sand


Speyer 2.3 soil
COLLECTION AND STORAGE
- Geographic location:
Offenbach, Rheinland-Pfalz, Germany
- Soil preparation (e.g.: 2 mm sieved; air dried etc.):
Sieved (2 mm) air-dried soil samples were taken from storage. Storage of soils was at ambient temperature and did not exceed three years. Moisture content was determined by oven-drying.

PROPERTIES
Characteristics
pH-CaCl2 6.8
Nitrogen % 0.09
Organic carbon% 1.00
Organic matter % 1.72
Cationic exchange capacity
(meq/100 g soil) 10.7
Particle size distribution (USDA)
% clay (< 2 µm; w/w) 8.7
% silt (2-50 µm; w/w) 28.2
% sand (50-2000 µm; w/w) 63.1
Texture (USDA) Sandy loam


Speyer 6S soil
COLLECTION AND STORAGE
- Geographic location:
Siebeldingen, Rheinland-Pfalz, Germany
- Soil preparation (e.g.: 2 mm sieved; air dried etc.):
Sieved (2 mm) air-dried soil samples were taken from storage. Storage of soils was at ambient temperature and did not exceed three years. Moisture content was determined by oven-drying.

Characteristics
pH-CaCl2 7.1
Nitrogen % 0.18
Organic carbon% 1.66
Organic matter % 2.86
Cationic exchange capacity
(meq/100 g soil) 26.9
Particle size distribution (USDA)
% clay (< 2 µm; w/w) 40.7
% slit(2-50 µm; w/w) 34.5
% sand (50-2000 µm; w/w) 24.8
Texture (USDA) Clay




SLUDGES
Aa en Maas sludge
- Type of sludge: sludge
- Source of sludge:
RWZI AA en Maas, ’s Hertogenbosch, The Netherlands
- Oxygen status: aerob
- Laboratory culture: no
- Pretreatment:
Sludges were sampled freshly and sieved through a 1 mm sieve. Sludge particles were allowed to settle and overlying water was removed as most as possible. To prevent biodegradation of the test substance, activated sludge samples were autoclaved and treated with 0.05% (w/v) sodium azide. The dry weight of the sludges was determined by oven-drying
pH-CaCl2 6.5
Nitrogen % n.d.
Organic carbon% 33.6
Organic matter % 58.0
Cationic exchange capacity
(meq/100 g soil) n.d.

Tilburg sludge
- Type of sludge: sludge
- Source of sludge:
RWZI Tilburg-Noord, Tilburg, The Netherlands
- Oxygen status: aerob
- Laboratory culture: no
- Pretreatment:
Sludges were sampled freshly and sieved through a 1 mm sieve. Sludge particles were allowed to settle and overlying water was removed as most as possible. To prevent biodegradation of the test substance, activated sludge samples were autoclaved and treated with 0.05% (w/v) sodium azide. The dry weight of the sludges was determined by oven-drying
pH-CaCl2 7.0
Nitrogen % n.d.
Organic carbon% 40.2
Organic matter % 69.3
Cationic exchange capacity
(meq/100 g soil) n.d.


Details on test conditions:
TEST CONDITIONS
- Buffer: no
- pH:
pH of supernatants after soil adsorption and desorption kinetics experiment
Test system after adsorption after desorption
Speyer 2.2 soil 5.71 5.48
Speyer 2.3 soil 5.98 5.91
Speyer 6S soil 6.21 6.79
Control 6.18 -
pH of supernatants after sludge adsorption and desorption kinetics experiment
Test system after adsorption after desorption
Aa en Maas sludge 6.57 6.72
Tilburg sludge 6.99 6.27
Control 6.07 6.32

- Suspended solids concentration:
soil:solution ratio of 1:50 for Speyer 2.2 and Speyer 2.3 soil and 1:500 for Speyer 6S soil
sludge : solution ratio of 1:1 for both sludges

TEST SYSTEM
- Type, size and further details on reaction vessel:
polypropylene tubes

- Water filtered (i.e. yes/no; type of size of filter used, if any):
Milli-Q water Tap water purified by a Milli-Q water purification system (Millipore, Bedford, MA, USA)

- Amount of soil/sediment/sludge and water per treatment (if simulation test): see below
- Soil/sediment/sludge-water ratio (if simulation test):
- Number of reaction vessels/concentration: 2 (3 kinetic experiment)

- Measuring equipment: see analytics

- Test performed in closed vessels due to significant volatility of test substance:
yes but test substance not volatile
- Test performed in open system:
no


- Method of preparation of test solution:
The sludge/soil slurries and 0.01 M CaCl2 solution (as much as appropriate) were equilibrated in polypropylene tubes at 20 ± 2°C on a roller mixer overnight in the dark prior to spiking.

- Are the residues from the adsorption phase used for desorption:
yes
Type:
Koc
Value:
114.3 L/kg
Temp.:
20 °C
% Org. carbon:
33
Remarks on result:
other: Sludge Aa en Maas
Type:
Koc
Value:
54.6 L/kg
Temp.:
20 °C
% Org. carbon:
40.2
Remarks on result:
other: sludge Tilburg
Type:
Koc
Value:
25 374 L/kg
Temp.:
20 °C
% Org. carbon:
1.74
Remarks on result:
other: soil Speyer 2.2
Type:
Koc
Value:
50 220 L/kg
Temp.:
20 °C
% Org. carbon:
1
Remarks on result:
other: soil Speyer 2.3
Type:
Koc
Value:
360 594 L/kg
Temp.:
20 °C
% Org. carbon:
1.66
Remarks on result:
other: soil Speyer6S
Type:
other: Kf oc ads [mL/g], Freundlich adsorption coefficient
Value:
125 L/kg
Temp.:
20 °C
% Org. carbon:
33.6
Remarks on result:
other: sludge Aa en Maas
Type:
other: Kf oc ads [mL/g], Freundlich adsorption coefficient
Value:
51 L/kg
Temp.:
20 °C
% Org. carbon:
40.2
Remarks on result:
other: sludge Tilburg
Type:
other: Kf oc ads [mL/g], Freundlich adsorption coefficient
Value:
41 331 L/kg
Temp.:
20 °C
% Org. carbon:
1.74
Remarks on result:
other: soil Speyer2.2
Type:
other: Kf oc ads [mL/g], Freundlich adsorption coefficient
Value:
184 790 L/kg
Temp.:
20 °C
% Org. carbon:
1
Remarks on result:
other: soil Speyer2.3
Type:
other: Kf oc ads [mL/g], Freundlich adsorption coefficient
Value:
609 217 L/kg
Temp.:
20 °C
Remarks on result:
other: soil Speyer6S
Phase system:
other: Kd [mL/g], Freundlich desorption coefficient
Type:
other: Kd [mL/g], Freundlich desorption coefficient
Value:
38.4 L/kg
Remarks on result:
other: sludge Aa en Maas; 33.6% OC
Phase system:
other: Kd [mL/g], Freundlich desorption coefficient
Type:
other: Kd [mL/g], Freundlich desorption coefficient
Value:
22 L/kg
Remarks on result:
other: sludge Tilburg; OC 40.2%
Phase system:
other: Kd [mL/g], Freundlich desorption coefficient
Type:
other: Kd [mL/g], Freundlich desorption coefficient
Value:
442 L/kg
Remarks on result:
other: soil Speyer2.2, OC 1.74%
Phase system:
other: Kd [mL/g], Freundlich desorption coefficient
Type:
other: Kd [mL/g], Freundlich desorption coefficient
Value:
502 L/kg
Remarks on result:
other: soil Speyer2.3; OC 1.00%
Phase system:
other: Kd [mL/g], Freundlich desorption coefficient
Type:
other: Kd [mL/g], Freundlich desorption coefficient
Value:
5 986 L/kg
Remarks on result:
other: soil Speyer6S; OC 1.66%
Phase system:
other: Koc geometric mean, Sludges
Type:
other: Koc geometric mean, Sludges
Value:
79 L/kg
Phase system:
other: Koc geometric mean, Soils
Type:
other: Koc geometric mean, Soils
Value:
77 166 L/kg
Phase system:
other: Koc geometric mean, total
Type:
other: Koc geometric mean, total
Value:
4 915 L/kg
Adsorption and desorption constants:
Table 9 Freundlich adsorption isotherm parameters for HH-2012-459 in soil
Test system KFads
(mL/g) KF,ocads
(mL/g) 1/n r2 data points
Speyer 2.2 soil 719 41331 1.00 0.997 10
Speyer 2.3 soil 1848 184790 1.05 0.998 10
Speyer 6S soil 10113 609217 0.99 0.997 10


Table 10 Freundlich desorption isotherm parameters for HH-2012-459 in soil
Test system KFdes
(mL/g) KF,ocdes
(mL/g) 1/n r2 data points
Speyer 2.2 soil 1234 70937 0.97 0.995 10
Speyer 2.3 soil 1986 198620 0.92 0.995 10
Speyer 6S soil 1149 69199 0.93 0.974 8


Table 11 Freundlich adsorption isotherm parameters for HH-2012-459 in sludge
Test system KFads
(mL/g) KF,ocads
(mL/g) 1/n r2 data points
Aa en Maas sludge 41.9 222 0.96 0.983 10
Tilburg sludge 20.6 127 0.96 0.997 10


Table 12 Freundlich desorption isotherm parameters for HH-2012-459 in sludge
Test system KFdes
(mL/g) KF,ocdes
(mL/g) 1/n r2 data points
Aa en Maas sludge 627 3319 1.01 0.992 10
Tilburg sludge 183 1128 0.94 0.994 10
Recovery of test material:
Mass balances for test systems after soil adsorption-desorption kinetics experiment (% of applied)
Test system Recovery after adsorption phase Recovery after desorption phase
Speyer 2.2 soil 101 94
Speyer 2.3 soil 101 101
Speyer 6S soil 92 92

Mass balances for test systems after sludge adsorption-desorption kinetics experiment (% of applied)
Test system Recovery after adsorption phase Recovery after desorption phase
Aa en Maas sludge * 102
Tilburg sludge * 95
* sample was lost

Table16         Adsorption kineticsexperiment (sludge)

Test system

Code

Weighed sludge (g)

Dry mass of sludge

msludge(g)

Water volume in

weighed test system (mL)

Spike volume1)

(mL)

m0

(µg)

0.01 M CaCl2

added (mL)

V0

(mL)

C0

(µg/mL)

Aa en Maas

A

45.0159

0.5198

44.4961

0.0252

21.2713

44.5213

0.4778

45.0159

B

45.0352

0.5200

44.5152

0.0252

21.2713

44.5404

0.4776

45.0352

Bl

45.0401

0.5200

44.5201

0.0252

 

44.5453

 

45.0401

Tilburg

A

45.0592

0.9702

44.0890

0.0252

21.2713

44.1142

0.4822

45.0592

B

45.1147

0.9714

44.1433

0.0252

21.2713

44.1685

0.4816

45.1147

Bl

45.1955

0.9731

44.2224

0.0252

 

44.2476

 

45.1955

1 To the blanks, 0.01 M CaCl2solution was spiked instead of spike solution

 

Table 16 (continued)

Sludge/soil

Code

Activity in VaA(in DPM)

mmads(tn) (in µg)

t1

t2

t3

t4

t1

t2

t3

t4

Aa en Maas

A

9814.46

11025.19

9262.14

8516.34

0.07162

0.08048

0.06755

0.06212

B

11215.99

9744.78

9907.22

9918.59

0.08187

0.07112

0.07227

0.07237

Bl

16.20

15.54

21.18

17.89

 

 

 

 

Tilburg

A

11522.34

9024.08

10382.93

8435.04

0.08411

0.06583

0.07570

0.06156

B

11313.11

7005.26

9114.47

9710.86

0.08258

0.05108

0.06643

0.07089

Bl

16.26

18.05

26.93

13.47

 

 

 

 

t1: 0.5 h, t2: 1 h, t3:26 h, t4: 3 h


Table 16 (continued)

Sludge/soil

repl.

maqads(in µg)

msads(in µg)

Ati (in %)

t1

t2

t3

t4

Dt1

Dt2

Dt3

Dt4

t1

t2

t3

t4

Aa en Maas

A

15.9441

17.8349

14.9022

13.6427

5.3271

-1.8907

2.9327

1.2595

25.04

16.16

29.94

35.86

B

18.2326

15.7675

15.9493

15.9006

3.0387

2.4651

-0.1818

0.0487

14.29

25.87

25.02

25.25

Tilburg

A

18.5519

14.4551

16.5462

13.3939

2.7193

4.0968

-2.0911

3.1523

12.78

32.04

22.21

37.03

B

18.2370

11.2287

14.5376

15.4423

3.0343

7.0083

-3.3089

-0.9047

14.26

47.21

31.66

27.40

t1: 0.5 h, t2: 1 h, t3:26 h, t4: 3 h

Table14         Kineticsexperiment (soil)

Test system

Code

% Moisture

Weighed test

system (g)

Dry mass of soil

msoil(g)

Water volume in

weighed test system (mL)

Spike volume1)

(mL)

m0

(µg)

0.01 M CaCl2

added (mL)

V0

(mL)

C0

(µg/mL)

Speyer 2.2

A

1.09

0.9018

0.8920

0.0098

0.0163

22.3503

45.0142

45.0403

0.4962

B

1.09

0.9022

0.8924

0.0098

0.0163

22.3503

44.9783

45.0044

0.4966

Bl

1.09

0.9004

0.8906

0.0098

0.0163

 

45.0286

45.0547

 

Speyer 2.3

A

1.06

0.9006

0.8911

0.0095

0.0163

22.3503

44.9851

45.0109

0.4966

B

1.06

0.9015

0.8919

0.0096

0.0163

22.3503

44.9950

45.0208

0.4964

Bl

1.06

0.9029

0.8933

0.0096

0.0163

 

45.0186

45.0444

 

Speyer 6S

A

3.67

0.0900

0.0867

0.0033

0.0163

22.3503

45.0253

45.0449

0.4962

B

3.67

0.0907

0.0874

0.0033

0.0163

22.3503

45.0000

45.0196

0.4965

Bl

3.67

0.0900

0.0867

0.0033

0.0163

 

45.0379

45.0575

 

1 To the blanks, 0.01 M CaCl2solution was spiked instead of spike solution

 

Table 14 (continued)

Sludge/soil

Code

Activity in VaA(in DPM)

mmads(tn) (in µg)

t1

t2

t3

t4

t1

t2

t3

t4

Speyer 2.2

A

985.10

971.28

975.15

1445.03

0.00708

0.00697

0.00700

0.01044

B

975.78

838.97

1325.81

1414.11

0.00701

0.00600

0.00956

0.01021

 

Bl

16.76

17.60

18.04

17.38

 

 

 

 

Speyer 2.3

A

664.41

522.69

594.90

1163.61

0.00473

0.00367

0.00421

0.00839

B

683.39

565.73

559.02

1406.36

0.00487

0.00399

0.00395

0.01017

 

Bl

17.82

20.12

18.45

15.48

 

 

 

 

Speyer 6S

A

748.13

844.04

654.10

1064.69

0.00535

0.00605

0.00466

0.00766

B

690.39

705.68

731.80

1162.31

0.00492

0.00504

0.00523

0.00838

 

Bl

16.76

16.12

16.55

16.13

 

 

 

 

t1: 2 h, t2: 4 h, t3: 6 h, t4: 24 h


Table 14 (continued)

Sludge/soil

repl.

maqads(in µg)

msads(in µg)

Ati (in %)

t1

t2

t3

t4

Dt1

Dt2

Dt3

Dt4

t1

t2

t3

t4

Speyer 2.2

A

1.5941

1.5630

1.5616

2.3189

20.7562

0.0311

0.0014

-0.7573

92.87

93.01

93.01

89.62

B

1.5775

1.3451

2.1320

2.2668

20.7728

0.2324

-0.7870

-0.1348

92.94

93.98

90.46

89.86

Speyer 2.3

A

1.0637

0.8231

0.9399

1.8637

21.2866

0.2406

-0.1168

-0.9237

95.24

96.32

95.79

91.66

B

1.0952

0.8938

0.8816

2.2582

21.2551

0.2014

0.0122

-1.3766

95.10

96.00

96.06

89.90

Speyer 6S

A

1.2041

1.3570

1.0403

1.7033

21.1462

-0.1529

0.3167

-0.6630

94.61

93.93

95.35

92.38

B

1.1084

1.1296

1.1665

1.8608

21.2419

-0.0212

-0.0369

-0.6944

95.04

94.95

94.78

91.67

t1: 2 h, t2: 4 h, t3: 6 h, t4: 24 h

Validity criteria fulfilled:
yes
Conclusions:
For MDIPA-Esterquat C16-18 and C18 unsatd. Koc (Kd) were determined to be (geometric mean)
for sludges: Koc = 79.0 mL/g (Kd=29.1 mL/g), logKoc = 1.90,
for soils: Koc=77166 mL/g (Kd=1099 mL/g), logkoc = 4.89,
total: logKoc = 3.69.
Executive summary:

The adsorption-desorption behavior of MDIPA-Esterquat C16 -18 and C18 unsatd. was tested according to OECD Guideline 106. For testing, the hot material "N-14CH3 - MDIPA-Esterquat C16 -18 and C18 unsatd." had the same composition (according to CoAs) as the cold material. Tests were done with two sludges (Aa en Maas sludge 33.6% OC, Tilburg sludge 40.2% OC) and three soils (Speyer 2.2: loamy sand, 2.74%OC, cationic exchange capacity (CEC) 10.2 meq/100g soil; Speyer 2.3: sandy loam, 1.0% OC, CEC 10.7 meq/100g soil; Speyer 6S: clay, 1.66% OC, CEC 26.9 meq/100g soil).

Adsorption and desorption kinetics were determined at an initial MDIPA-Esterquat C16-18 and C18 unsatd. concentration of approximately 0.5 mg/L. Adsorption and desorption isotherms were determined over a substance concentration range from approximately 0.01 to 1 mg/L. The adsorption-desorption experiments were carried out at 20±2°C in the dark on a roller mixer at a sludge concentration of 11.5 g/L (Aa en Maas) and 21.5 g/L (Tilburg) and soil: 0.01M CaCl2solution ratio of 1:50 (Speyer 2.2 and Speyer 2.3 soil) and 1:500 (Speyer 6S soil).

 

Adsorption and desorption equilibrium was reached after 2-3 hours contact time in the presence of both sludge and soil.

 

MDIPA-Esterquat C16-18 and C18 unsatd. adsorption and desorption isotherms could be described by the Freundlich equation. Freundlich adsorption and desorption coefficients, Koc and logKoc are summarised in the table below.

 

Test system

Texture

%oc

KFads

(mL/g)

KF,ocads

(mL/g)

KF,ocdes

(mL/g)

KD

(mL/g)

KOC

(mL/g)

logKoc

Aa en Maas

Sludge

33.6

42

125

1867

38.4

114.3

2,06

Tilburg

Sludge

40.2

21

51

455

22.0

54.6

1,74

Geom. mean

sludge

 

 

 

 

 

29.1

79

1.90

Speyer 2.2

Loamy sand

1.74

719

41331

70937

442

25374

4,40

Speyer 2.3

Sandy loam

1.00

1848

184790

198620

502

50220

4,70

Speyer 6S

Clay

1.66

10113

609217

69199

5986

360594

5,56

Geom. mean

soil

 

 

 

 

 

1099.2

77166

4.89

Geom. mean

total

 

 

 

 

 

257.0

4915

3.69

The very high KD of 5986 for Speyer 6S soil compared to 38 -502 for the other soils and sludges doesn't correlate with organic carbon content but with the high cationic exchange capacity of 26.9 meq/100g soil of Speyer 6S.

Description of key information

For MDIPA-Esterquat C16-18 and C18 unsatd., the geometric mean of Koc (Kd) were determined to be: for sludges: Koc = 79.0 mL/g (Kd=29.1 mL/g), log Koc = 1.90,  and for soils: Koc=77166 mL/g (Kd=1099 mL/g),  log koc = 4.89,  total: logKoc = 3.69.

Key value for chemical safety assessment

Koc at 20 °C:
4 914.79

Other adsorption coefficients

Type:
log Kp (solids-water in soil)
Value in L/kg:
3.041
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
2.997
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in suspended matter)
Value in L/kg:
2.925
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in raw sewage sludge)
Value in L/kg:
1.372
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in settled sewage sludge)
Value in L/kg:
1.372
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in activated sewage sludge)
Value in L/kg:
1.463
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in effluent sewage sludge)
Value in L/kg:
1.463
at the temperature of:
20 °C

Additional information

The adsorption-desorption behaviour of MDIPA-Esterquat C16 -18 and C18 unsatd. was tested according to OECD Guideline 106. For testing, the hot material "N-14CH3 - MDIPA-Esterquat C16 -18 and C18 unsatd." had the same composition (according to CoAs) as the cold material. Tests were done with two sludges (Aa en Maas sludge 33.6% OC, Tilburg sludge 40.2% OC) and three soils (Speyer 2.2: loamy sand, 2.74%OC, cationic exchange capacity (CEC) 10.2 meq/100g soil; Speyer 2.3: sandy loam, 1.0% OC, CEC 10.7 meq/100g soil; Speyer 6S: clay, 1.66% OC, CEC 26.9 meq/100g soil).

Adsorption and desorption kinetics were determined at an initial MDIPA-Esterquat C16-18 and C18 unsatd. concentration of approximately 0.5 mg/L. Adsorption and desorption isotherms were determined over a substance concentration range from approximately 0.01 to 1 mg/L. The adsorption-desorption experiments were carried out at 20±2°C in the dark on a roller mixer at a sludge concentration of 11.5 g/L (Aa en Maas) and 21.5 g/L (Tilburg) and soil: 0.01M CaCl2solution ratio of 1:50 (Speyer 2.2 and Speyer 2.3 soil) and 1:500 (Speyer 6S soil).

 

Adsorption and desorption equilibrium was reached after 2-3 hours contact time in the presence of both sludge and soil.

 

MDIPA-Esterquat C16-18 and C18 unsatd. adsorption and desorption isotherms could be described by the Freundlich equation. Freundlich adsorption and desorption coefficients, Koc and log Koc are summarised in the table below.

Test system

Texture

%oc

KFads

(mL/g)

KF,ocads

(mL/g)

KF,ocdes

(mL/g)

KD

(mL/g)

KOC

(mL/g)

logKoc

Aa en Maas

Sludge

33.6

42

125

1867

38.4

114.3

2,06

Tilburg

Sludge

40.2

21

51

455

22.0

54.6

1,74

Geom. mean

sludge

 

 

 

 

 

29.1

79

1.90

Speyer 2.2

Loamy sand

1.74

719

41331

70937

442

25374

4,40

Speyer 2.3

Sandy loam

1.00

1848

184790

198620

502

50220

4,70

Speyer 6S

Clay

1.66

10113

609217

69199

5986

360594

5,56

Geom. mean

soil

 

 

 

 

 

1099.2

77166

4.89

Geom. mean

total

 

 

 

 

 

257.0

4915

3.69

   

The very high KDof 5986 for Speyer 6S soil compared to 38 -502 for the other soils and sludges doesn't correlate with organic carbon content but with the high cationic exchange capacity of 26.9 meq/100g soil of Speyer 6S.

KDsediment of KD= 992.52 L/kg is calculated from KDs for soils and sludges with the assumption of an OC content of 5% for sediment (rationale: attached document)

KDsuspended matter of KD= 841.51 L/kg is calculated from KDs for soils and sludges with the assumption of an OC content of 10% for suspended matter (rationale: attached document)

KD for raw sewage sludge, settled sewage sluge and effluent sewage sludge were set to the same value as calculate for activated sewage sludge with KD= 29.07 as derived from test results for two sludges stated in the table above.

Similar results were obtained with two structurally related source substances, MDEA-Esterquat C16-18 and C18 unsatd. and DODMAC (dioctadecyl dimethyl ammonium chloride).

 

The adsorption/desorption of MDEA-Esterquat C16-18 and C18 unsatd. was investigated in a study conducted according to guideline. During the stability test and the adsorption/desorption kinetic experiment it was found that[Me-14C] MDEA-Esterquat was not fully stable under the experimental conditions based on TLC results. Therefore, the results described should be applied to [Me-14C] MDEA-Esterquat and its degradation products. A Koc=20225 was calculated as the geometric mean of the two sludges and the two soils whereas a Koc=828 was calculated as geometric mean for the two sludges and a Koc=494 x 10³ as geometric mean for the two soils.

 

According to HERA, 2008, the “predictive power of the log Kow for the partitioning to soil, sediment and sludge or its bioaccumulation potential is considered to be limited, because the common Koc derivations are not valid for surface active substances like the esterquats. Therefore the log Kow values can not be used to derive the environmental distribution constants. Instead as a more reliable basis, the experimentally determined sorption and bioaccumulation figures of DODMAC are used. […] When esterquats enter the aquatic environment, it is likely that a large amount of the esterquats is not truly dissolved but is adsorbed onto suspended matter or included in vesicles together with other organics (e.g. humic acids, surfactants). The sorption behaviour of the esterquats in soils, sediment and sludge will be governed by two processes; partitioning to organic matter and ionic interaction with negatively charged particles. Under environmental conditions, sorption due to ionic interaction is expected to be the predominant process for cationic surfactants. The higher the cationic exchange capacity (CEC) of the sorbent, the higher the sorption will be. Under these conditions, the chain length of the esterquats is expected to be of minor importance for sorption/desorption behaviour onto soil, sediment or sludge. The sorption behaviour of esterquats is expected to be comparable to that of DHTDMAC or DODMAC, due to structural similarities. Therefore, the value reported for DODMAC [DODMAC, EU 2002] of 10,000 l/kg dw is assumed to be a realistic estimate for the estimation of both Kp-sed and Kp-soil and has been taken in the absence of measured data”.

 

The reviewed investigations demonstrated that DODMAC can be bound very strongly by some minerals, while in others relatively small distribution constants were estimated. Under environmental conditions, the sorption properties of DODMAC probably vary in a wide range depending on the nature of the adsorbant. The authors chose a value of 10,000 L/kg dw for both Kp(sed) and Kp(soil).

[LogKoc: 3.69]