Calcium phosphate powders synthesized from CaCO₃ and CaO of natural origin using mechanical activation in different media combined with solid-state interaction

The highly pure and crystalline calcium carbonate (CaCO₃) and calcium oxide (CaO) with small amounts of As, Cd, Hg, and Pb were prepared by calcinating shells of a golden apple snail. Solid-state reaction and mechanical activation between the CaCO₃ and CaO from calcined golden apple snail shells and dibasic calcium phosphate dihydrate (CaHPO₄•2H₂O, DCPD) were performed to develop calcium phosphate powders. The effects of the milling media used on the mechanical activation were examined. A solid-state reaction of manually mixed CaCO₃ or CaO with DCPD powders at a temperature of 1100 °C produced mostly β-tricalcium phosphate (β-TCP). Hydroxyapatite (HAp) with a small quantity of β-TCP could be produced from a mixed CaCO₃ + DCPD powder using dry and wet mechanical activations with distilled water, alcohol and acetone and from a mixed CaO + DCPD powder using dry mechanical activation combined with a solid-state reaction at a temperature of 1100 °C. A phase change of milled powders to β-TCP was clearly observed from a wet mechanical activation of CaO + DCPD powder with distilled water or alcohol in a solid-state reaction. The thermal instability of HAp powders from a combined mechanical activation with solid-state reaction of CaCO₃ or CaO and DCPD powders could result from two factors. The first is that the pollution was released from the balls and pot mill materials during the mechanical process. Another factor is a reduced level of calcium in the CaO + DCPD mixed powder due to a reaction between CaO and water or alcohol during mechanical milling.