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EC number: 231-099-0 | CAS number: 7439-91-0
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
The following adsorption/desorption distribution coefficients were obtained for the analogous test material Lanthanum oxide at the soil-to-solution ratio of 1/50:
- Mean Koc value: 5480283
- Mean Koc, des value: 358213
Key value for chemical safety assessment
- Koc at 20 °C:
- 5 480 283
Additional information
The adsorption/desorption behaviour of the test material on soil was determined using three soils and the batch equilibrium method in accordance with the standardised guideline OECD 106.
Initially, a preliminary test was performed in order to investigate the adsorption behaviour of the test material. For this purpose, three soils, a test concentration of 0.64 mg/L and three soil (dry weight) to aqueous phase ratios: 1/50 (1 g/50 mL), 1/25 (1 g/25 mL) and 1/5 (5 g/25 mL) were used. Very high adsorption was observed for all three ratios. After 48 hours of agitation, virtually all of the initial amount of test material was adsorbed (≥99 %).
Therefore, for the subsequent screening test, the maximum soil-to-solution ratio of 1/50 was selected together with a test material concentration of 1.29 mg/L and the same three soils. The adsorption/desorption kinetics of the test material were determined after 2, 4 or 5, 24 and 48 hours of agitation. After 2 hours of agitation, adsorption represented 96, 100 and 100 % for soils I to III, respectively. Only low desorption was observed during the 48-hour desorption period (maximum of 3 % of test material desorbed for all three soils).
The mass balance was performed during the screening test at the soil to solution ratio of 1/50. The amount of applied test material recovered from the samples represented 62, 79 and 76 % for soils I to III, respectively. Most of the applied amount was extracted from the soils, with only ≤0.5 % of applied detected in the supernatants. The mass balance results confirmed the strong adsorption of the test material to soil.
The following adsorption/desorption distribution coefficients were obtained for the soils at the selected ratio of 1/50:
- Mean Koc value: 5480283
- Mean Koc, des value: 358213
[LogKoc: 6.36]
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