Calcium Carbonate Morphology and Structure in the Presence of Seawater Ions and Humic Acids

Abstract

The effectiveness of some seawater components, such as magnesium, potassium, sodium, sulfate and chloride ions, and humic acid, in the control of calcium carbonate composition, morphology, and phase distribution was studied. These components were tested singularly, in pairs, and all together. It was observed that magnesium ions phase distribution control is influenced by the presence of other ions and that in the presence of a high content of magnesium ions monohydrocalcite precipitates. Moreover, in the presence of magnesium or potassium ions the calcite crystals show modified rhomohedral morphologies, while the presence of sulfate ions favors their aggregation. Humic acids have an inhibition effect on calcium carbonate precipitation, induce the formation of empty spheres of vaterite, and modify the calcium carbonate phase distribution. The isomorphic substitution of magnesium to calcium in the calcite structure is favored by some seawater ions and enhanced by the presence of humic acids.