Low-temperature synthesis of nanometric apatite from biogenic sources

Nanosized calcium deficient carbonated apatite was synthesized from three different natural resources, namely chicken eggshells (calcite), cuttlefish bones (aragonite) and mussel shells (aragonite/calcite). The calcium precursors were ball-milled in (NH4)2HPO4 or H3PO4 – containing aqueous medium for different times and then dried at temperatures ranging from 20 °C to 150 °C. The formation of hydroxyapatite (HA) is shown to be strongly affected by such treatment, the amount of synthesized HA increasing with temperature. Aragonite from cuttlebones and the aragonitic fraction of mussels is found to be transformed more easily with respect to the calcite from eggshells. The reaction is also favored by an acidic milling media with respect to basic one. The feasibility of the synthesis process at nearly room temperature described in the present work has interesting potentialities in the retention of the organic portions of the original biological resource in the produced nanometric inorganic compound.