The synthesis of super-small nano hydroxyapatite and its high adsorptions to mixed heavy metallic ions

A "molecular cage" was possibly built in glucose alkaline solution to limit the chemical reaction in a tiny space to control the size and morphology of HA nanoparticles. A possible reaction mechanism of HA nanoparticles confined space synthesis was proposed in this work. The super-small HA nanoparticles were successfully obtained in the first time in mild and green condition which had a 7 nm diameter. The adsorptions to Pb2+, Zn2+, Ni2+, Cd2+ ions in their mixture solution by the synthesized HA nanoparticles were studied. The adsorbent showed huge adsorption capacities for the targets (Pb2+ = 3289 mg/g, Zn2+ = 3150 mg/g, Ni2+ = 3061 mg/g and Cd2+ = 2784 mg/g), which indicated an excellent performance of the synthesized nano material in water treatment. Freundlich equation analysis and SEM images of the adsorption products suggested multilayer adsorptions to the targets, and a new recrystalline type adsorption on the surface of the host was found. Some Ca atoms in HA nanoparticles were also found to be substituted by the heavy metallic elements in the initial stage of the adsorptions. The synthesized nano material exhibits better application prospect in wastewater treatment field for its easy synthesis, low-cost and environmental friendly properties.