Preparation of porous β-tricalcium phosphate using starfish-derived calcium carbonate as a precursor

Porous β-tricalcium phosphate (β-TCP) was successfully prepared from starfish-derived calcium carbonate (sf-bone) under several hydrothermal conditions. The sf-bone, obtained from Patiria Pectinifera by bleaching to remove organic substances, was Mg-containing calcite granules with an interconnected microporous structure of approximately 10−50 µm of pore, and was hydrothermally treated with ammonium phosphate aqueous solutions at various pHs and temperatures. The sf-bone was converted to Mg-containing β-TCP with maintaining its microporous structure by the hydrothermal treatment for 1 day or longer in (NH4)2HPO4 aqueous solution at 200 °C. This conversion was based on dissolution-reprecipitation process of Mg-containing calcite in the phosphate salt aqueous solution. Thus, conditions during the conversion, pH and temperature, affected the morphologies and crystal phases of sf-bone after the treatment depended upon both calcite dissolution and calcium phosphate-formation rates.