Crystal Size Distribution of Hydroxyapatite Precipitated in a MSMPR Reactor

This paper is aimed to analyse the crystal size distribution (CSD) of hydroxyapatite (HA) Ca5 (OH)(PO4)3 obtained in a continuous flow MSMPR reactor at 85 °C and pHconstant = 9.0, at steady state. The kinetic of precipitation is calculated and the mechanism of particle formation is discussed. The method of moments in crystal volume coordinates, supposing a nucleation-growth-agglomeration mechanism for particle formation, has been used to solve the population balance equation and to calculate the nucleation rate (Bo), volume growth rate (Gv) and the aggregation kernel (β). The crystal size distribution graphs of precipitates and the low values of the nucleation rate show the inconsistency of this classical model to explain HA precipitation. However, they are in agreement with a mechanism of nucleation-aggregation-agglomeration-growth followed by a large-scale aggregation.