Enhancement of Calcium Carbonate Precipitation in Seawater through Carbonation Process

This study discusses the effect of Magnesium ions on the polymorphic
crystallization of calcium carbonate by precipitating carbonate minerals from
seawater solutions containing different concentrations of Magnesium ions at various
temperatures. Precipitated calcium carbonate were synthesized via the carbonation
process, the morphology changes and the particles structure were identified by the
scanning electron microscopy, SEM and X-Ray Diffraction, XRD, respectively. The
experimental results indicated that the concentration of Magnesium ions and
temperature affect remarkably the calcite and aragonite formation. At lower
suspension concentration, 0.5 M MgCl2, cubic calcite particles were formed; calcite
coexisted with aragonite in medium suspension, 1.0 M MgCl2 and as the suspension
grew higher, 1.5 M MgCl2, needle-like aragonite particles were obtained. As for the
effect of temperature variations, the formation of calcite was favoured at lower
temperature, 30°C. Aragonite starts to appear together with calcite as temperature
increases at 50°C and 70°C. Relevant theories from literature were applied as
reference in the experimental work and it was found that results obtained from the
study corresponded to previous experiments done. Conclusively, the study has
proven that Magnesium ion addition and temperature variation has effect on the
morphology of precipitated calcium carbonate particles in seawater. These findings
would be beneficial in contributing to the production of precipitated calcium
carbonate due to the raw materials availability and their low costs, as well as natural
sequestrating carbon dioxide and storing it in the form of CaCO3.