Tetrapotassium pyrophosphate

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Meets generally accepted scientific standards, well documented and acceptable for assessment, however data is not sufficient to determine a Kd value for risk assessment.

Data source

Reference

Reference Type:

publication

Title:

Hydrolysis and sorption reactions of orthophosphate, pyrophosphate, tripolyphosphate and trimetaphosphate anions added to an elliot soil

Author:

Blanchar RW and Hossner LR

Year:

1969

Bibliographic source:

Soil sci. soc. Amer. Proc. 33: 141-144

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

An estimation of sorption onto soil was determined by shaking 30 mL of phosphate solutions with 3 g of oven dried soil for given periods of time. At the end of the specified time period, the soil to water ratio was adjusted to 1:10, the flasks were shaken for 15 secs and centrifuged. The total phosphate and pyrophosphate content of the solution phase were determined.

GLP compliance:

not specified

Type of method:

other: Sorption study

Media:

soil

Test material

Test material information

Constituent 1

Reference substance name:

Tetrasodium pyrophosphate

EC Number:

231-767-1

EC Name:

Tetrasodium pyrophosphate

Cas Number:

7722-88-5

Molecular formula:

H4O7P2.4Na

IUPAC Name:

tetrasodium diphosphate

Details on test material:

- Name of test material (as cited in study report): sodium pyrophosphate
- Molecular formula (if other than submission substance): Na4P2O7.10H2O
- Analytical purity: 97.4%
- Impurities (identity and concentrations): 2.6% orthophosphate

Radiolabelling:

no

Study design

Test temperature:

No data

Batch equilibrium or other method

Analytical monitoring:

not specified

Details on matrix:

COLLECTION AND STORAGE
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Air dried and screened to pass 8 mesh.

PROPERTIES:
- pH: 1 part soil to 1 part water mix = 5.6
- Extractable Cations (Ca, Mg, Na, K, H) (MEQ/100 g):
Exchangeable Ca: 19.1
Mg: 5.8
K: 0.4
H: 6.1
-Water content: 24% at 1/3 atm

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Type:

Koc

Value:

149

Adsorption coefficient 2

Type:

log Koc

Value:

2.17

Any other information on results incl. tables

The relationship between P added and solution content of P for sodium pyrophosphate follows the Freundlich equation prediction very closely. The data shows that sodium pyrophosphate was strongly absorbed to soil. An estimate of the hydrolysis during the sorption study was made by determining phosphate content of the solution phase of the most concentrated sample. The pyrophosphate sample was 28% orthophosphate and 72% pyrophosphate.

Although some hydrolysis of pyrophosphate was seen to occur, an approximation of sorption capacity for pyrophosphate was determinined from the Langmuir adsorption isotherm.

The sorption capacity was found to be 965 µg/ P/g soil.

 

 

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified