Spherical and Porous Particles of Calcium Carbonate Synthesized with Food Friendly Polymer Additives

Abstract

Porous calcium carbonate particles were synthesized by adding solutions of Ca2+ to solutions of CO32– containing polymeric additives. Under optimized conditions well-defined aggregates of the anhydrous polymorph vaterite formed. A typical sample of these micrometer-sized aggregates had a pore volume of 0.1 cm3/g, a pore width of ∼10 nm, and a specific surface area of ∼25–30 m2/ g. Only one mixing order (calcium to carbonate) allowed the formation of vaterite, which was ascribed to the buffering capacity and relatively high pH of the CO32– solution. Rapid addition of the calcium chloride solution and rapid stirring promoted the formation of vaterite, due to the high supersaturation levels achieved. With xanthan gum, porous and micrometer-sized vaterite aggregates could be synthesized over a wide range of synthetic conditions. For the other food grade polymers, hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and sodium carboxyl methylcellulose, several intensive and extensive synthetic parameter...