Nucleation and Crystal Growth Kinetics of Strengite, FePO4,2H2O, in Aqueous Solution
Main Article Content
Crystallization kinetics of strengite, FePO4 2 ,2H O, has been investigated by direct mixing of
ammonium phosphate solution with a solution containing either iron(III) or iron(II) plus
hydroxylamine, the latter acting as oxidant on the surface of growing iron phosphate crystals.
Nucleation rate was determined by light scattering and crystal growth rate from pH recording.
From the former was found a relatively uncertain surface fre energy of 127 mJ/m² with Fe(III) and
a much more precise value of 55 mJ/m² with Fe(II) + HONH2. Crystal growth was shown to take
place mainly by surface nucleation, either the mononuclear or the polynuclear mechanism, and
yielded edge free energies of 86-92 pJ/m with Fe(III) and 13-22 pJ/m with Fe(II) + HONH2. The
large differences may be interpreted in terms of a Fe(II)-rich monolayer on crystals growing from
solution containing iron(II) and hydroxylamine.
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