Sonochemical effect on size reduction of CaCO3 nanoparticles derived from waste eggshells

A novel combination of mechanochemical and sonochemical techniques was developed to produce high-surface-area, bio-based calcium carbonate (CaCO3) nanoparticles from eggshells. Size reduction of eggshell achieved via mechanochemical and followed by sonochemical method. First, eggshells were cleaned and ground, then ball milled in wet condition using polypropylene glycol for ten hours to produce fine particles. The ball milled eggshell particles were then irradiated with a high intensity ultrasonic horn (Ti-horn, 20 kHz, and 100 W/cm2) in the presence of N,N-dimethylformamide (DMF); decahydronaphthalene (Decalin); or tetrahydrofuran (THF). The ultrasonic irradiation times varied from 1 to 5 h. Transmission electron microscopic (TEM) studies showed that the resultant particle shapes and sizes were different from each solvent. The sonochemical effect of DMF is more pronounced and the particles were irregular platelets of ∼10 nm. The BET surface area (43.687 m2/g) of these nanoparticles is much higher than that of other nanoparticles derived from eggshells.

► Bio-CaCO3 nanoparticles derived from eggshells using the top–down synthesis approach.
► TEM studies clearly showed that the particles are irregular platelet shaped ∼10 nm.
► The as-synthesized particles are highly crystalline and porous in nature.
► Surface area measurements (BET) showed that these particles are ∼180% higher than the starting eggshell powders.