1-Propanaminium, 2-hydroxy-N-(2-hydroxypropyl)-N,N-dimethyl-, esters with fatty acids, C16-18 (even numbered) and C18 unsatd., Me sulfates (salts)

Adsorption / desorption

Link to relevant study record(s)

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:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.1110 (Activated Sludge Sorption Isotherm)

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil/sewage sludge

Specific details on test material used for the study:

- Name of test material: MDIPA-Esterquat C16-18 and C18 unsatd.
- Physical state: waxy solid
- Analytical purity: 100%

hot material: 61.5 µCi/mg (2.28 MBq/mg)

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 volume^1) (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 Va^A(in DPM)				mm^ads(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.	maq^ads(in µg)				ms^ads(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 volume^1) (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 Va^A(in DPM)				mm^ads(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.	maq^ads(in µg)				ms^ads(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	KF^ads (mL/g)	KF,oc^ads (mL/g)	KF,oc^des (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 K_D 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	KF^ads (mL/g)	KF,oc^ads (mL/g)	KF,oc^des (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 K_Dof 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.

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

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

K_D for raw sewage sludge, settled sewage sluge and effluent sewage sludge were set to the same value as calculate for activated sewage sludge with K_D= 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]