Cation‐Exchange Characteristics of Sintered Hydroxyapatite in the Strongly Acidic Region

Abstract

The ion‐exchange behavior of hydroxyapatite (Ca 10 (PO 4 ) 6 ‐OH) 2 ) (HAp), fired at high temperatures, has been investigated in the strongly acidic region (pH 2 and 3). According to the present study, HAp fired above 1000°C can exchange ions from Ca 2+ to Pb 2+ , even at pH 2, without dissolution. The molar ratios of Pb 2+ /Ca 2+ after ion exchange are approximately unity in all cases. Ion exchange occurs in a thin layer near the surface of HAp particles fired at 1300°C. After ion exchange, Pb‐Cl‐apatite crystals are created in the strongly acidic region (pH 2).