Study on the preparation and properties of CaCO₃ ultrafine powder derived from waste eggshell

In this study, eggshell-derived CaCO₃ ultrafine powder was prepared from waste eggshell with the method of omnidirectional planetary ball mill. The particle size distribution was measured by laser particle size analyzer. Then, the parameters of grinding kinetic equation of eggshell powder were obtained by software fitting, and the grinding model and characteristic equation of particle-size distribution of the eggshell-derived CaCO₃ powder were discussed. The results showed that the best grinding conditions were as follows: using 3 mm zirconia grinding ball, 400 rpm, 50% filling rate, 50% slurry concentration, and ball-milling time of 30 min. The grinding kinetic equation can well simulate the eggshell crushing process. The equation showed that with the prolongation of milling time, the large particle size of the eggshell powder gradually decreased, and the milling efficiency was 0 after 60 min. The Rosin–Rammler–Bennet distribution model could be used to describe the distribution characteristics of the cumulative particle size of the eggshell powder, and the fitting degree of particle size distribution at each milling time could reach R²> 0.99. No chemical change occurred in the eggshell powder before and after grinding. However, the calcite crystal structure of eggshell-derived CaCO₃ ultrafine powder becomes incomplete.