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

Abstract

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, D_a, was found to be a function of the molar ratio of COO^–/CO₃^2–. In the case of adding tartrate and phthalate, D_a was varied as having a local minimum value at the molar ratio of 1-5. In the case of adding oxalate and citrate, D_a 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.