Controlled crystallization of lamellar calcium carbonate crystals induced by solution of sticky rice polysaccharide (from Oryza sativa)

Abstract

Rhombohedral calcium carbonate (CaCO₃) crystals with lamellar texture have been obtained by employing sticky rice polysaccharide as an additive in the growth medium. The results in this work indicate that the morphology of the CaCO₃ crystals changes with mineralization conditions, such as the concentration of calcium ions (Ca²⁺), reaction time, and temperature. The rhombohedral CaCO₃ crystals with specific lamellar texture are prepared using a sticky rice solution mass fraction of 0.5%, a Ca²⁺ concentration of 0.4 mol L⁻¹, a reaction time of 2 h and a reaction temperature of 25 °C. In addition, most of the CaCO₃ particles are calcite when mineralized in the solution of sticky rice. The possible formation process of the CaCO₃ crystals with lamellar texture is proposed. It may be ascribed to the preference for sticky rice solution and self-assembly of CaCO₃ particles. The interesting sticky rice polysaccharide can be extended to prepare other composites.