In situ NiO dissolution behavior in (Li + Na)CO3 melts under pressurized oxidant gas atmospheres

The dissolution behavior of in situ oxidized NiO is investigated under pressurized oxidant gas conditions as a function of pressure, temperature and lithium content in (Li + Na)CO3 melts. For the measurement of NiO solubility, a high performance liquid chromatography (HPLC) method was employed. It is found that NiO solubility is proportional to CO2 partial pressure (0.1 ≤ pCO2 ≤ 3.6 atm at pO2 = 0.9 atm) but not to the O2 partial pressure (0.1 ≤ pO2 ≤ 3.6 atm at pCO2 = 0.9 atm). This indicates that NiO dissolution under pressurized condition follows the acidic dissolution mechanism. On increasing temperature from 823 to 973 K under a total pressure of 5 atm with an air/CO2 mixture results in decreasing NiO dissolution because the melts shifted to more basic media. Similarly, increasing the lithium content from 40 to 70 mol% increases the basicity of the carbonate melt. This also resulted in decreasing NiO solubility.