Nickel Oxide Stability in Aqueous Sodium Phosphate Solutions at Elevated Temperatures

摘要

Nickel oxide (NiO) is shown to transform to a sodium nickel hydroxyphosphate compound in concentrated sodium phosphate solutions at elevated temperatures via NiO(s) + 2Na sup + + HPO sub 4 /sup =/ in equilibrium Na sub 2 Ni(OH)PO sub 4 (s). The thermodynamic equilibrium for this reaction was investigated in the system Na sub 2 O-P sub 2 O sub 5 -NiO-H sub 2 O for 2 < Na/P < 3. Based on observed reaction threshold values for sodium phosphate concentration and temperature, the respective standard free energy and enthalpy of formation for Na sub 2 Ni(OH)PO sub 4 were calculated to be -1739.4 and -1800.6 kJ/mole. 8 refs., 1 fig., 4 tabs. (ERA citation 11:036420)