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Environmental fate & pathways

Hydrolysis

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An experimental study on hydrolysis as a function of pH is not available for Boron orthophosphate (CAS 13308-51-5). Basically Boron orthophosphate is subject to hydrolysis in water forming boric species and hydrogen phosphate species under environmental pH, when release to water.

The chemical form of boron found in water is dictated by pH and other constituents (Sprague 1972). In natural waters, boron forms stable species and exists primarily as undissociated boric acid [B(OH)3] and complex polyanions (e.g., B(OH)4-) (Howe, 1998).These forms of boron are highly soluble and not easily removed from solution by natural mechanisms. Borate and boric acid are in equilibrium depending on the pH of the water. At an acidic pH, boron exists in solution mainly as undissociated boric acid, whereas at alkaline pH it is present as borate ions (Howe, 1998).

Boron can bind with clays, suspended matter, and sediments of aquatic systems (Maier and Knight 1991). Boron adsorption is also reported on clay minerals (Hingston 1964) and on hydrous oxides of Fe and Al (Sims and Bingham, 1968). The adsorption of Boron from solution by Ca forms will be described as a function of pH and boron concentration in solution. Thus, boron can be removed from water by adsorption. As well orthophosphate can be incorporated into either biological solids (e.g. microorganisms) or chemical precipitation and removed from water.

The inorganic phosphates are normally found in different forms. In dilute aqueous solution, phosphate exists in four forms (see attachment). In strongly-basic conditions, the phosphate ion (PO43−) predominates, whereas in weakly-basic conditions, the hydrogen phosphate ion (HPO42−) is prevalent. In weakly-acid conditions, the dihydrogen phosphate ion (H2PO4−) is most common. In strongly-acid conditions, aqueous phosphoric acid (H3PO4) is the main form.

 

References

Hem, J.D. (1970). Study and interpretation of the chemical characteristics of natural water, 2d ed. U.S. Geological Survey Water-Supply Paper 1473.

Hingston, F.J. (1964) Reactions between boron and clays. Aust. J. Soil Res. 2, 83-95

Howe, P.D. (1998). A review of boron effects in the environment. Biological Trace Element Research 66: 153-166.

Maier, K.J., and A.W. Knight (1991). The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity. Arch. Environ. Contam. Toxicol. 20: 282-287.

Sims , J.R. and Bingham, F.T. (1968) Retention of boron by layer silicates, sesquioxides and soil minerals. II. Sesquioxides. Proc. Soil Sci. Soc. Amer. 32, 364-369

Sprague, R.W. (1972) The ecological significance of boron. U.S. Borax Research Corporation, Anaheim, California. 58p.