Mesoporous hydroxyapatite: Synthesis in molecular self-assembly and adsorption properties

A kind of mesoporous hydroxyapatite (HA) with high ordered structure was first synthesized in molecular self-assembly method. In this study, HA nanoparticles with an average diameter of about 12 nm were dissociated into HA molecules in a weak acidic buffer solution (NaH2PO4–Na2HPO4, PBS), and the molecules were assembled to form a HA polymerized framework on the surface of the micelles constructed by cetyltrimethylammonium bromide (CTAB, a template) under hydrothermal treatment. The mesoporous structure was finally formed by calcination to remove the template. High-resolution transmission electron microscopy (HRTEM) observed that there were regular and ordered channels in the mesoporous HA. The nitrogen sorption results of mesoporous HA indicated the specific surface area, total pore volume and maximum pore size distribution of mesoporous HA were 48.81 m2/g, 0.38 cm3/g and 1.93 nm, respectively. The porous material was found to have high adsorption capacities to some metal ions, such as Co2+ (299.46 mg/g), Ni2+ (309.35 mg/g), Cu2+ (248.03 mg/g), Zn2+ (276.11 mg/g) and Cd2+ (192.93 mg/g), and ion exchange and recrystallization of the metal salts were found to occur on the mesoporous material to give high adsorption capacities. The efficient and environment-friendly characteristics of materials open the doors for potential usage in real industrial processes.