Canada - Memorial University of Newfoundland

4.0 SOLUBILITY AND REACTION KINETICS OF SODIUM NICKEL
HYDROXY-PHOSPHATE
4.1 Solubility of the Nickel Oxide-Sodium-Phosphate Reaction
Nickel oxide undergoes reversible reactions with aqueous sodium phosphate
solutions at elevated temperatures and pressures to fonn sodium nickel hydroxy
phosphate, SNHP, according 10 the reaction (Ziemniak and Opalka, 1988):
In our solubility runs, samples were taken from different parts ofthe reaction vessel to
confirm that the reaction product that had formed was indeed SNHP. Firstly, powder
XRD analysis confirmed that both NiO and SNHP wefe present in the reaction matrix,
and secondly, SEM elemental analysis showed that sodium, nickel, and phosphorus were
indeed present in the crystals of reaelion product. Figures 4.la and b show the SEM
images of a solid sample taken from the basket and the bottom ofthe vessel, respectively.
Again, as previously observed, bundles or clumps ofcrystalline solid can be observed in
both images indicating that SNHP is indeed present.
A complete description ofthe procedurcs used to dctennine temperaturc4
dependant solubilitics can be found in Section 2.5.2. Two separate runs were perfonned
to dctcnnine the solubility ofSNHP. The sodium-phosphate solution mole ratio was 2.5
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