Preparation and characterization of self-suspended CaCO₃ nanoparticles derived from scallop shells

In this study, self-suspended CaCO₃ nanoparticles (M-SCC) derived from thermal activated scallop shells were prepared through the hydration–carbonation reaction and surface modification with sodium hexametaphosphate (SHMP). The characterization results proved the successful synthesis and modification of cubic-like CaCO₃ particles. Suspension stability of CaCO₃ particles was improved greatly after modification. The effects of additive amount of SHMP, modification temperature and time on degradation of SHMP and interaction between SHMP and CaCO₃ were discussed using settling height, particle size distribution, zeta potential and viscosity measurements, and the optimum modification sample (M-SCC-OP) with excellent suspension stability was obtained under the condition of 3.0% of SHMP, 55 °C and 40 min. Zeta potential results indicated that surface charge property of CaCO₃ was changed from positive to negative, and low viscosity (6.62 mPa·s) for the suspension of M-SCC-OP (23.8 wt.%) further proved strong composite forces among particles. Compared with original CaCO₃ particles, suspension rate in a dietary calcium simulation system was improved from 14.2% to 67.6%. This study may help to solve the problem of limited application of CaCO₃ in granule products for low solubility and poor suspension stability.