Effect of Various Acid Solutions on the CO₂ Dissolution Rate, Morphology, and Particle Size of Precipitated Calcium...

In this study, the influence of acid solutions on the production of precipitated calcium carbonate (PCC) using seashells was investigated. In terms of the Ca dissolution efficiency and atmosphere for dissolving CO₃^2-, the results indicate that HCl, HNO₃, CH₃COOH, and HCOOH at 1.0 M were the most ideal among the acid solutions. The use of weak acids resulted in the low degree of dissolution of Al and Fe. These impurities could be mostly removed through the pH adjustment process, leading to PCC with a purity of 99% or more. Further, CH₃COOH and HCOOH exhibited low CaCO₃ carbonation efficiency owing to the hydrogen bonding of the carboxyl group and its hindering effect on the growth of CaCO₃ particles. In addition, in the presence of the carboxyl group, the morphology tended to be oval, and the particle size was small. Particularly, when CH₃COOH was used, the combined effect of the low initial Ca ion concentration and slow CO₂ dissolution rate resulted in minimal changes during the carbonation time and the smallest particle size. However, variations in the degree of Ca concentration with a change in the acid solution concentration influenced the dominance of nucleation and particle growth, leading to variations in the particle size. The results of this study revealed that when manufacturing PCC using seashells, the appropriate acid solution must be selected to obtain the required PCC properties.