Effect of carboxylate additives on CaCO3 particle size by precipitation method using scallop shell

The effect of carboxylate on the particle size of CaCO3 derived from scallop shells was investigated. Shell was dissolved in HCl solution and used as a raw material for CaCO3 particles. As the carboxylate additives, tartrate, oxalate, phthalate, and citrate were employed. The average diameter of particles, Da, was found to be a function of the molar ratio of COO–/CO32–. In the case of adding tartrate and phthalate, Da was varied as having a local minimum value at the molar ratio of 1-5. In the case of adding oxalate and citrate, Da was varied as reaching the minimum value at the molar ratio of 1-2. These sizes were about 0.1-0.25 times smaller than those without adding (21 m). The characterization of the particles was conducted by SEM images and X-ray diffraction patterns. Particles were found to have a crystal structure of calcite, however, in the case of tartrate and phthalate, calcium tartrate tetrahydrate and vaterite were found.