Effect of ferricenium salts on the crystal growth of hydroxyapatite in aqueous solution

The crystal growth of hydroxyapatite (HAP), the thermodynamically most stable calcium phosphate phase at 37°C, pH 7.40 and ionic strength 0.15 M in the presence of ferrocene complexes has been investigated by the constant composition technique. The kinetic results showed a surface diffusion controlled mechanism. The presence of ferricenium salts inhibited the crystal growth of HAP possibly through adsorption onto the active growth sites for crystal growth. The kinetic results favored a Langmuir-type isotherm, suggesting a high affinity of ferricenium salts for HAP.