Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The solubility of nesquehonite and calcite in carbonated water with CO2 pressure between 1 and 5 MPa was measured at 293.15 to 343.15 K by the inductively coupled plasma optical emission spectrometry analysis method. The results showed that the solubility increased with CO2 pressure but decreased with temperature in all the studied situations and for the ones the two solutes coexisted, nesquehonite's solubility changed little from the solo existing cases while calcite's declined one order of magnitude. The solubility was correlated with both temperature and CO2 pressure by empirical equations in a concise form. 1. INTRODUCTION Carbonation method is often used to produce basic magnesium carbonate or magnesium oxide from minerals rich in magnesium such as magnesite, dolomite and boron mud.1-10 During our research of leaching magnesium hydroxide from boron mud11, we found that pressurized leaching under CO2 pressure of 1 to 5 MPa had good effect as the MgO concentration in the solution increased considerably while the impurities' concentrations, especially the CaO concentration, kept acceptably low. The solubility of nesquehonite and calcite, the precipitated solid phases during the carbonation, was considered to be the critical reason. However, few reported experimental studies focused on this system under the pressurized carbonation conditions. Nesquehonite's solubility in water was measured mainly under CO2 pressures up to 1 atmosphere12-19 and infrequently under certain CO2 pressures between 2 to 21 atmospheres at certain temperatures19-21. Similarly, besides those measured at either temperatures higher than 348.15 K or too much high CO2 pressures22-26, most solubility data of calcite in water was for CO2 pressures up to 1 atmosphere18, 27-38 and sparse for certain CO2 pressures between 2 to 56 atmospheres at certain temperatures20, 38-40. The solubility of nesquehonite and calcite in carbonated water where the two solutes coexisted was measured under the condition of CO2