Magnetically recoverable iron oxide–hydroxyapatite nanocomposites for lead removal

Magnetite–hydroxyapatite nanocomposites were prepared by in situ precipitation of the calcium phosphate phase in an iron oxide colloidal suspension. Homogeneous magnetic powders were obtained with iron oxide content up to 50 wt%, without perturbation of the magnetite structure nor formation of additional calcium phosphates. The surface area of the composite powder was significantly increased after incorporation of magnetite due to the better apatite particle dispersion. This results in an increased available reactive surface, favoring lead sorption and hydroxypyromorphite precipitation, both leading to an enhanced lead removal capacity of the composite materials. The magnetic properties of magnetite nanocrystals were preserved upon association with hydroxyapatite. Full recovery of the composite powder after lead removal could be achieved using a simple magnet at a relatively low iron oxide content (20 wt%). This indicates a strong interaction between hydroxyapatite and magnetite particles within the composite powder. The procedure is simple, easily scalable and involves only environmental friendly materials.