ABRIDGED ACID-BASE WET-MILLING SYNTHESIS OF HIGH PURITY HYDROXYAPATITE

The use of calcium phosphates to produce hydroxyapatite (HA) usually leads to a mixture of several phases. Besides ionic contamination, most of the methods used are cumbersome, restricted to small volumes of product and require a lot of thermal energy. The acid-base route eliminates foreign ions or additives and its only by-product is water. Heterogeneous reaction drawback is that solid reactants do not easily come into contact with each other and therefore addition and stirring times become very lengthy and the product is still a mixture. The synthesis described started from calcium hydroxide and phosphoric acid (PA). Ball milling was used to favour kinetics and stoichiometry. Six sets of PA addition, paddle stirring and ball milling times were used. Products were evaluated by XRD, FTIR, SEM, XRF and Ca/P ratio. Chemical analysis for calcium proceeded through oxalate precipitate and phosphorus by the phosphomolybdate technique. A set of conditions yielding high purity HA was established. 22 refs.