Cesium formate

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:

1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

not specified

Test temperature:

Room temperature

Details on study design: HPLC method:

Not applicable

Analytical monitoring:

yes

Details on sampling:

Preliminary study
- Concentrations: 100 mg/L Formate
- Sampling interval: 24 h
- Sample storage before analysis: Stored under refrigeration (4 °C) prior to analysis to minimise biodegradation

Adsorption Equilibrium
- Concentrations: 250, 500, 750 and 1000 mg/L Formate
- Sampling interval: 48 h
- Sample storage before analysis: Stored under refrigeration (4 °C) prior to analysis to minimise biodegradation

Adsorption Isotherm
- Concentrations: For soil 98104 and soil 98108, target conc. was 100 mg/L Formate
For soil 98107, target conc. was 300 mg/L Formate
- Sampling interval: 4, 8, 12, 24 and 48 h
- Sample storage before analysis: Stored under refrigeration (4 °C) prior to analysis to minimise biodegradation

Details on matrix:

#1. Soil 98104 (Normandin)

COLLECTION AND STORAGE
- Geographic location: Perryville, Maricopa County, Arizona


PROPERTIES
- Soil texture
- % clay: 2.0-32.0 (13.0)
- Soil taxonomic classification: USDA soil taxonomy
- Soil series: Laveen loam (Coarse-loamy, mixed,superactive, hyperthermic Typic Haplocalcids)
- Soil order: Aridisol
- pH: 7.56-7.95 (7.70)
- Organic carbon (%): 0.08-2.1 (0.79)
- CEC (meq/100 g): 4.6-27.6 (8.7)
- Moisture at 1/3 atm (%): 1.43 % (dry weight basis)

#2. Soil 98107 (Tangent)

COLLECTION AND STORAGE
- Geographic location: Adair Village, in Marion County, Oregon
- Sampling depth (cm): 0-6 inch


PROPERTIES
- Soil texture
- % clay: 5.0-54.0 (33.0)
- Soil taxonomic classification: USDA soil taxonomy
- Soil series: Jory silty clay loam (Fine, mixed, active, mesic Xeric Palehumults)
- Soil order: Ultisol
- pH: 4.42-7.38 (4.70)
- Organic carbon (%): 0.90-3.2 (1.95)
- CEC (meq/100 g): 8.1-94.3 (26.2)
- Moisture at 1/3 atm (%): 7.54 %

#3. Soil 98108 (Bonanza)

COLLECTION AND STORAGE
- Geographic location: Clarkedale, Arkansas


PROPERTIES
- Soil texture
- % clay: 1.0-28.0 (8.8)
- Soil taxonomic classification: USDA soil taxonomy
- Soil series: Dundee silt loam (Fine-silty, mixed, thermic Aeric Ochraqualf)
- Soil order: Alfisol
- pH: 4.84-6.56 (6.26)
- Organic carbon (%): 0.52-1.8 (0.70)
- CEC (meq/100 g): 3.4-77.3 (7.7)
- Moisture at 1/3 atm (%): 0.94 %

Note: Values in brackets are median values

Details on test conditions:

TEST SYSTEM

- Type, size and further details on reaction vessel: 80 mL PET vials with snap caps
- Water filtered (i.e. yes/no; type of size of filter used, if any): No data
- Amount of soil/sediment/sludge and water per treatment (if simulation test): 8 g
- Soil/sediment/sludge-water ratio (if simulation test): 1:5
- Number of reaction vessels/concentration: 10
- Measuring equipment: HPLC
- Method of preparation of test solution:
Air-dried soil samples (8 g dry equivalent) were equilibrated by shaking with about 36 mL of 0.01 M CaCl2 solution (less moisture content) for 12 h. Then 4 mL of stock solution (1000 mg/L Formate) was added to the test vials and the mixture was further agitated for 24 h.
- Are the residues from the adsorption phase used for desorption: Yes

Sample No.:

#1

Duration:

48 h

Initial conc. measured:

ca. 100 other: mg/L

Sample No.:

#2

Duration:

48 h

Initial conc. measured:

ca. 300 other: mg/L

Sample No.:

#3

Duration:

48 h

Initial conc. measured:

ca. 100 other: mg/L

Computational methods:

Included in the next section

Key result

Type:

Koc

Value:

>= 71.28 - <= 870.43 dimensionless

Key result

Type:

log Koc

Value:

>= 1.858 - <= 2.939 dimensionless

Details on results (HPLC method):

Not applicable

Adsorption and desorption constants:

Preliminary coefficients
Adsorption coefficients were 4.83, 1.45 and 5.97 mLg-3, respectively, for samples 1, 2 and 3

Adsorption Isotherm
Adsorption coefficients for sample no. 1 is 2224.8 and for sample no. 2 is 374.9.

No determination of desorption constants was made.

Recovery of test material:

Recovery was not done

Concentration of test substance at end of adsorption equilibration period:

Presented as table in remarks section

Concentration of test substance at end of desorption equilibration period:

Not applicable as Formate could not be recovered from the adsorbed soil samples either by CaCl2 or by HCl.

Sample no.:

#1

Duration:

24 h

% Adsorption:

ca. 49.12

Sample no.:

#2

Duration:

24 h

% Adsorption:

ca. 22.64

Sample no.:

#3

Duration:

24 h

% Adsorption:

ca. 54.41

Sample no.:

#1

Duration:

48 h

% Adsorption:

ca. 83.58

Sample no.:

#2

Duration:

48 h

% Adsorption:

ca. 29.14

Sample no.:

#3

Duration:

48 h

% Adsorption:

ca. 100

Transformation products:

no

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- Sample purity:
- Weighed soil: 8 g
- Volume of CaCl2 solution: 36 mL
- Initial test substance concentration: 1000 mg/L
- Test substance concentration in final solution: 100 mg/L
- Analytical test substance concentration in final solution: No data

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Test material was stable throughout study
- Experimental conditions maintained throughout the study: Yes
- Buffer/test substance interactions affecting sorption: No
- Further chemical interactions: None
- Buffer-catalyzed degradation of test substance: No
- Anomalies or problems encountered (if yes): None

Statistics:

Not applicable

A. Screening Test: Adsorption

Percent adsorption of formate during the 24 h agitation period was 49 %, 23 %, and 54 %, respectively, for soil sample numbers 1, 2 and 3. The corresponding adsorption coefficients were 4.83, 1.45 and 5.97 mLg^-3, respectively, for soil sample numbers 1, 2 and 3.

Soil ID	Test	Total Formate Remaining in Solution (mg/L formic acid)	Adsorption %	Adsorption Coefficient
				K' mLg^-3	K'oc mLg^-3
1	Blank	10*	-	-	-
	1	69.2	49.12	4.83	610.96
	2	69.2	49.12	4.83	610.96
	Control	136	-	-	-
	Mean	-	49.12	4.83	610.96
2	Blank	1	-	-	-
	1	316	23.49	1.53	78.71
	2	324	21.55	1.37	71.28
	Control	413	-	-	-
	Mean	-	22.52	1.45	74.57
3	Blank	10*	-	-	-
	1	62.7	53.90	5.85	835.04
	2	61.3	54.93	6.09	870.43
	Control	136	-	-	-
	Mean	-	54.41	5.97	852.73

B. Advanced Test: Adsorption Equilibrium

Percent adsorption increased with increasing agitation time for soil no. 1 and soil no. 3 whereas it remains constant for soil no.2.

Soil ID	Test		Agitation Time, h
			4	8	12	24	48
1	Formate Conc. in Solution mg/L	Control	132	130	132	136	137
		Blank	10*	10*	10*	10*	10*
		1	121	99	96	69.2	24
		2	112	105	101	69.2	21
	% Adsorption		11.74	21.54	25.38	49.12	83.58
2	Formate Conc. In Solution mg/L	Control	408	413	413	413	429
		Blank	1	1	2	1	1
		1	304	311	302	316	295
		2	313	302	315	323	313
	% Adsorption		24.39	25.79	24.82	22.64	29.14
3	Formate Conc. In Solution mg/L	Control	132	130	132	136	137
		Blank	10*	10*	10*	10*	10*
		1	127	110	98	62.7	10*
		2	129	104	101	61.3	10*
	% Adsorption		3.03	17.69	24.62	54.41	100.00

* denotes higher than reported detection limit due to interference

C. Advanced Test: Adsorption Isotherm

Adsorption by soil no.1 decreased with increasing Formate concentrations, whereas the adsorption by soil no. 2 increased with increasing Formate concentrations.  Adsorption by soil no. 3 reached a maximum at target 500 mg/L Formate, and then decreased with increasing Formate concentrations.

The adsorption coefficients were calculated to be 2224.8 for soil no. 1 and 374.9 for soil no. 2.

Validity criteria fulfilled:

not specified

Conclusions:

Under the study conditions the adsorption coefficients for the three samples in screening test ranged between 71.28 and 870.43 and the corresponding log Koc value ranged between 1.85 and 2.93. The adsorption coefficients in advanced test for sample no. 1 and 2 were calculated to be 2224.8 and 374.9 respectively.

Executive summary:

A study was conducted to determine the adsorption/desorption of the test substance solution in soil samples according to OECD Guideline 106. A preliminary screening adsorption test was performed with three different soil samples. The soil samples were agitated with CaCl2 solution and then with test solution (at 100 mg/L) in 80 mL PET vials for 24 h. In the next phase, determination of adsorption equilibrium was performed by agitation of the soil samples with CaCl2 and test solution (at 100 and 300 mg/L) for 4, 8, 12, 24 and 48 h. The final phase of determining adsorption isotherm was performed by agitation of the soil samples with CaCl2 and test solution (at 250, 500, 750 and 1000 mg/L) for 48 h. All samples were centrifuged immediately after agitation period and the supernatant were analysed for formate in HPLC. Both the screening test and the advance adsorption test clearly indicated that formate was adsorbed by the soils used. It is possible that the adsorbed formate then undergoes biodegradation, resulting in no recovery by either CaCl2or HCl.  Further tests could be conducted to investigate this possibility by using sterilized soils. Under the study conditions the adsorption coefficients for the three samples in screening test ranged between 71.28 and 870.43 and the corresponding log Koc value ranged between 1.85 and 2.93. The adsorption coefficients in advanced test for sample no. 1 and 2 were calculated to be 2224.8 and 374.9, respectively (Gibb, 1998).

Key value for chemical safety assessment

Koc at 20 °C:

374.9

Additional information

A study was conducted to determine the adsorption/desorption of the test substance solution in soil samples according to OECD Guideline 106. A preliminary screening adsorption test was performed with three different soil samples. The soil samples were agitated with CaCl2 solution and then with test solution (at 100 mg/L) in 80 mL PET vials for 24 h. In the next phase, determination of adsorption equilibrium was performed by agitation of the soil samples with CaCl2 and test solution (at 100 and 300 mg/L) for 4, 8, 12, 24 and 48 h. The final phase of determining adsorption isotherm was performed by agitation of the soil samples with CaCl2 and test solution (at 250, 500, 750 and 1000 mg/L) for 48 h. All samples were centrifuged immediately after agitation period and the supernatant were analysed for formate in HPLC. Both the screening test and the advance adsorption test clearly indicated that formate was adsorbed by the soils used. It is possible that the adsorbed formate then undergoes biodegradation, resulting in no recovery by either CaCl2or HCl.  Further tests could be conducted to investigate this possibility by using sterilized soils. Under the study conditions the adsorption coefficients for the three samples in screening test ranged between 71.28 and 870.43 and the corresponding log Koc value ranged between 1.85 and 2.93. The adsorption coefficients in advanced test for sample no. 1 and 2 were calculated to be 2224.8 and 374.9, respectively (Gibb, 1998).

[LogKoc: 2.93]