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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption

Description of key information

Key value for chemical safety assessment

Additional information

According to Annex VIII, Column 2 of REACh regulation EC (No) 1907/2006 adsorption/desorption screening does not need to be conducted if the substance can be expected to have a low potential for adsorption based on its physicochemical properties.

Based on the physicochemical properties of Silicic acid, sodium salt a relatively low adsorption potential to sediment and soil can be expected. Crystalline silicates such as Silicic acid, sodium salt are readily soluble in water and insoluble in alcohol. Due to the insolubility in alcohols, such as n-octanol, the determination of a log Kow is not feasible (CEES, 2003; Hera, 2005). The expected relatively low adsorption potential is confirmed by measurements on the removal of soluble silicates in several sewage treatment plants, where a marginal removal by sedimentation and adsorption of 10 % of the total amount was determined (van Dokkum et al., 2004). A precise prediction of the distribution of soluble silicates in various environmental compartments is not feasible, since a dynamic equilibrium between a variety of mono-, oligo- and poly-associated anions occurs, depending on the pH conditions and the substance concentration. Sediments and soil particles are thought to act as a buffering mechanism for the concentration of dissolved silica in natural waters through sorption and desorption of dissolved silica (Schleyer & Blumberg, 1982). In this process, the anthropogenic contribution to various environmental compartments will be negligible compared to the concentrations from natural silica flux. Furthermore, dissolved silica from commercial soluble silicates is indistinguishable from natural dissolved silica (Schleyer & Blumberg, 1982).

References:

CEES (2003). Soluble Silicates. Chemical, toxicological, ecological and legal aspects of production, transport, handling and application. Centre Européen d’ Étude des Silicates, Brussels, Belgium

 

Hera - Human & Environmental Risk Assessment on ingredients of European household cleaning products (2005). Soluble Silicates -draft-.

 

Schleyer WL and Blumberg JG (1982). Health, safety, and environmental aspects of soluble silicates. In: Soluble Silicates, ACS Symposium Series 194. American Chemical Society, Washington. Chapter 4, 49-69.

 

Van Dokkum HP, Hulskotte JHJ, Kramer KJM and Wilmot J (2004). Emission, Fate and Effects of Soluble Silicates (Waterglass) in the Aquatic Environment. Environ. Sci. Technol. 38, 515-521.