Continuous Precipitation of Hydroxyapatite from Ca/Citrate/Phosphate Solutions using Microwave Heating

The precipitation of hydroxyapatite (HAp) in a continuous process using microwave heating and Ca/citrate/phosphate solutions is presented. Calcium deficient HAp particles in the nanometric size range (<100 nm), with needle-like morphology, were obtained. These chemical and morphological characteristics do not change with the residence time, and are similar to those of HAp obtained in a batch process using also microwave heating and Ca/citrate/phosphate solutions. On the other hand, the steady state is reached faster than in the precipitation of HAp in a MSMPR reactor using non-complexing solutions and conventional heating. In the latter process submicronic (<1 mikrom) needle-like particles are obtained.