New measurements of the solubility of zinc oxide from 150 to 350°C

The solubility of zincite (ZnO) has been re-evaluated in noncomplexing solutions over a wide range of pH and from 150 to 350degreesC at pressures ranging from slightly above saturation vapor pressure to significantly higher pressures in NaOH, NH3, F3CSO3H/F3CSO3 Na(HTr/ NaTr), CH3COOH/NaOH, and HTr/NH3 solutions using a hydrogen-electrode concentration cell (HECC) and a flow-through cell with downstream acid injection. The new results, coupled with our earlier results at 75-100degreesC, indicate that the solubility of zinc oxide is higher than we recently reported,((1)) but substantially lower than previous estimates available in the scientific literature. It is believed that deposition of ZnO or a zinc hydroxide phase must have occurred near the solubility minimum in the HECC sample lines in our earlier study; a problem that is overcome in the flow cell by injecting acid into the sample line before the solution is depressurized and cooled to room temperature.