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Environmental fate & pathways

Adsorption / desorption

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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:

Key value for chemical safety assessment

Koc at 20 °C:
5 480 283

Additional information

No data is available on yttrium oxide but this substance is closed to lanthanum oxide regarding the physico-chemical, toxicological and ecotoxicological properties. Indeed, both substances are high melting point solids (form: powder) of low water solubility and they does not present any classification regarding health and environmental hazards. Read across is trust possible from lanthanum oxide for which an adsorption / desorption study has been conducted in 3 soils following the OECD 106 guideline and under GLP. Kd values were 5451 to 216905 ml/g and Kocs were 230978 to 11476472 ml/g (mean 5480283 ml/g).

Depending on the prevailing environmental conditions, formation of different yttrium species may occur. Considering the adsorption of the rare earth element (i.e. yttrium) is thus a key point. For this reason, it seems also relevant to consider the data available on other yttrium compounds. In this context, three other publications tested the adsorption capacity of Y radionuclids (under carbonate and chloride form) in differents kind of soil confirmed the same behavior of adsorption than GLP study on lanthanum oxide. Kd values for yttrium were assessed to be between: -46000 ml/g and 61300 ml/g for soils and around 9390 ml/g for soils from which organic matter and calcium carbonate were intentionally removed. The publication of Tao (2000) showed the adsorption capacity of lanthanids in different soils and proved that this capacity is very similar for the whole category of lanthanids and is function of chemical interaction (especially including chemical bound energy).