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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption/desorption:

Parent substance: Low potential for adsorption due to very rapid hydrolysis in water

Tris(1-methylethyl)silanol: log Koc = 2.1 (QSAR

Key value for chemical safety assessment

Additional information

The substance hydrolyses to tris(1-methylethyl)silanol and acrylic acid.

A log Koc value of 2.1 at 20 - 25°C was obtained for the silanol hydrolysis product, tris(1-methylethyl)silanol using a validated QSAR method. The result is considered to be reliable.

Adsorption and desorption of acrylic acid was reported in EU Risk Assessment Report (ECB 2002). The adsorption and desorption of acrylic acid were observed using five different soil types. The adsorption phase has a Kp soil ranging from 0.28 - 0.63 l/kg, more wide scattering of the Kp values for three desorption phases were observed with reported Kp of 0.38 - 3.85 l/kg. The adsorption and desorption of acrylic acid proved to be independent from organic matter contents of the soil. It was therefore assumed that the adsorption behaviour of the anionic acrylic acid primarily depends on the inorganic fraction of the different soils and a uniform value of 1.1 l/kg for all partition coefficients (Kp soil, Kp sediment, Kp susp and Kp sludge) was used. Kocvalues of 6 – 137 are reported in the ECHA dossier for acrylic acid (citing Chemosphere 40: 29-38, 2000). Koc (for the non-ionised form of acrylic acid) is predicted to be <10 l/kg by both MCI and log Kow-based QSAR methods (KOCWIN).

Reference:

ECB (2002). European Union Risk Assessment Report acrylic acid CAS No: 79-10-7 EINECS No: 201-177-9 Risk Assessment, PL-1 Vol 28, 2002.