Silicic acid, aluminum magnesium sodium salt

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Jun. 4 - Nov. 18, 2019; experimental phase: Jun. 4 - 27, 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD 111

Version / remarks:

2004

Deviations:

no

Principles of method if other than guideline:

study on hydrolysis

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, aluminum magnesium sodium salt

EC Number:

234-919-5

EC Name:

Silicic acid, aluminum magnesium sodium salt

Cas Number:

12040-43-6

Molecular formula:

Na(0.017-1.739)Mg(0.008-0.823)Al(0.002-0.2473)SiO(2.018-3.837)

IUPAC Name:

aluminium(3+) magnesium(2+) sodium tris(oxosilanebis(olate))

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Name: Silicic acid, magnesium aluminium sodium salt
Batch no.: 201810LC007
Appearance: white fluffy powder
Composition: Sodium; Magnesium; Aluminium; Silica
Purity: >95%
Homogeneity: homogeneous
Specific surface area: 57.9 m²/g

Radiolabelling:

no

Study design

Details on study design:

The analytical determination of the test item was performed via measurement of Silicon (Si), Magnesium (Mg) and Aluminium (Al) via ICP-OES.

The same sample preparation was performed on day 0 and 5.
Before measurement of the solutions via ICP-OES for Si (blanks and test item solutions) tenfold dilution was performed: 0.5 mL of the solution were added to 4.5 mL water p.a. and measured via ICP-OES.

Buffer-Solution, pH 4
Parameter Amount
CH3COOH, 2 M 80 mL
CH3COONa, 1 M 40 mL
Water p.a. ad. 1000 mL
Three replicates were prepared and combined; pH was measured as 4.02 (batch A20190603).
For batch A20190613 (used in the Tier 1), two replicates were prepared and combined; pH was measured as 4.0.

Buffer-Solution, pH 7
Batch A20190604:
Parameter Amount
KH2PO4 8.7085 g
Water p.a. 500 mL
NaOH, 2 M 14.9 mL
Water p.a. ad. 1000 mL
Three replicates were prepared and combined; pH was adjusted with 2 M NaOH to 7.04.
Batch A20190613 (used in the Tier 1):
Parameter Amount
KH2PO4 8.7089 g / 8.7079 g (for replicate 1 and 2)
Water p.a. 500 mL
NaOH, 2 M 14.9 mL
Water p.a. ad. 1000 mL
Two replicates were prepared and combined; pH was adjusted with 2 M NaOH to 7.00.

Buffer-Solution, pH 9
Batch A20190604:
Parameter Amount
H3BO3 3.093 g
KCl 3.729 g
Water p.a. 500 mL
NaOH, 2 M 10.75 mL
Water p.a. ad. 1000 mL
Three replicates were prepared and combined; pH was adjusted with 2 M NaOH to 9.00.
Batch A20190613 (used in the Tier 1):
Parameter Amount
H3BO3 3.0927 g / 3.0926 g (for replicate 1 and 2)

Results and discussion

Transformation products:

no

Any other information on results incl. tables

The half saturated solutions with the nominal load 50 g/L in pH 4, 7 and 9 buffer solutions were measured for Si, Al and Mg on day 0 and after the storage of the test solutions at 49.7 – 50.2 °C for 5 days. The concentration of Al in pH 4, 7 and 9 buffer solutions was below the LOQ of the respective method at each sampling point (< 0.05 mg/L in pH 4 and 9 solutions and < 0.02 mg/L in pH 7 solutions). Therefore, the calculation of the stability of the test item in buffer solutions based on Al was not possible. All measurements lay below the LOD of the Tyndall device (< 3 mg/L particle concentration).

Recovery rate based on solid content reformation of inorganic salts (ICP-OES measured Si content): pH = 4: 102.9%; pH = 7: 92.2%, pH = 9: 93.4%. As the amount of Si and Mg after five days was more than 90% of the amount at the start of the test, the test item was considered to be stable (following OECD, t(0.5) at 25 °C is then greater than 1 year), and no further examination was made.

Applicant's summary and conclusion

Validity criteria

Validity criteria fulfilled:

yes

Conclusions:

The concentration of Al in pH 4, 7 and 9 buffer solutions lay below the LOQ of the respective method at each sampling point (< 0.05 mg/L in pH 4 and 9 solutions and < 0.02 mg/L in pH 7 solutions). Therefore, the calculation of the stability of Al in buffer solutions was not possible.
As the amount of Si and Mg after five days was more than 90 % of the amount at the start of the test, the test item was considered to be stable (following OECD, t(0.5) at 25 °C is then greater than 1 year), and no further examination was made.
Recovery rate based on solid content, reformation of inorganic salts (ICP-OES measured Si content):
pH=4: ca. 100 %; pH=7: 92.2 %; pH=9: 93.4 %

Executive summary:

This study was performed in order to determine the hydrolysis behaviour of Silicic acid, magnesium aluminium sodium salt and stability of dissolved test item in dependence of the pH.

Aqueous buffer solutions of different pH values (pH 4, 7 and 9) were treated with the test item and the filtrated test item solutions were incubated in the dark under controlled laboratory conditions (at constant temperature). After appropriate time intervals, buffer solutions were analysed for Silicon (Si), Magnesium (Mg) and Aluminium (Al) via ICP-OES. The concentration of Sodium (Na) was not determined as Sodium is present in all buffer solutions. Potentially available undissolved particles in the filtrated test item solution were measured using Tyndall device.