Precipitation of stoichiometric hydroxyapatite by a continuous method

In this paper we present the precipitation of hydroxyapatite (HA), Ca,(OH)( PO,),, from highly concentrated CaCl2 and K2HPO4 solutions, carried out by a continuous method in a MSMPR reactor. The procedure consists of adding th e reagents in a ratio Ca to P equal to 1.67, maintaining a temperature of 8 5 degreesC, inert N-2 atmosphere inside the reactor, and monitoring and adj usting automatically the pH by means of a pH-stat system (pH = 9.0 +/- 0.1) . Under these conditions KA with a Ca to P ratio equal or close to the stoi chiometric composition (Ca/P=1.667), with a high yield (up to 99%) and a hi gh production rate (up to 1.17 g/l.min) is obtained at steady state. The CS D, morphology, crystallinity of the precipitates and impurities present fit the requirement for its biomedical applications.