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Environmental fate & pathways

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Disodium hexafluorosilicate undergoes dissociation as follows:

 Na2SiF6→ 2NaF + SiF4

After, it undergoes further hydrolysis, providing the following overall reaction:

Na2SiF6+ 4H2O → 6NaF + Si(OH)4

The extent that it occurs depends highly on the pH, since although dissociation of salts readily occurs in aqueous solution, hydrolysis is very much influenced by pH. However, at environmental pH, hydrolysis is complete affording 100% fluoride.

Since disodium hexafluorosilicate is an inorganic substance, it does not undergo biodegradation (microbial degradation to CO2and H2O) as it does not contain any C or H atoms. It is degradated by means other than biodegradation.

The total dissociation and hydrolysis of disodium hexafluorosilicate at environmental pH prevents that it adsorbs onto particulates or accumulate as such in living tissues.

Nonetheless, fluorides, as degradation products, may be absorbed in living tissues.Metabolism of fluoride has been studies in IPCS_INCHEM_1984.