Precipitation of nesquehonite from homogeneous supersaturated solutions

✍ Scribed by Wenting Cheng; Zhibao Li

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 553 KB
• Volume: 44
• Category: Article
• ISSN: 0232-1300
• DOI: 10.1002/crat.200900286

✦ Synopsis

The homogeneous (unseeded) precipitation of nesquehonite (MgCO 3 •3H 2 O) was studied over the temperature range of 10-40 °C. Precipitation was triggered by the supersaturation created by mixing MgCl 2 solution (0.5-1.5 M) with Na 2 CO 3 solution in the same concentration range. The Meissner's method was adopted in the calculation of supersaturations during the MgCl 2 -Na 2 CO 3 reaction to monitor the precipitation. Solids were identified using X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) images. In the temperature range of 10-40 °C, MgCO 3 •3H 2 O with needle-like or gel-like morphology was precipitated. It was seen that the length, width and surface smoothness of the particles changed with reaction temperature and supersaturation. The supersaturation (S) was in the range of 1.09-58.68 during titration of Na 2 CO 3 solution. The dimension of the crystals increased with longer addition time (or lower initial concentration of reactant) at the same temperature. Slower addition via titration of 2 h followed by 2 h of equilibration at 40 °C proved successful in producing well developed needle-like MgCO 3 •3H 2 O crystals of 30-50 µm long and 3-6 µm wide. MgCO 3 •3H 2 O obtained were calcined to produce highly pure magnesium oxide (MgO) at 800 °C. The morphology of MgO was similar to that of their corresponding precursors.