Synthesis of shape and structure-dependent hydroxyapatite nanostructures as a superior adsorbent for removal of U(VI)

[Display omitted] •Shape and structure-dependent HAP nanostructures were hydrothermally synthesized.•The temperature was a vital factor affecting the morphology and structure of HAP.•Growth mechanism involved anisotropic growth, further growth and Ostwald ripening.•HAP-180 exhibits excellent performance on removal of radioactive uranium.•Removal mechanism involved adsorption, complex reaction and precipitation. Highly efficient removal of U(VI) from uranium-containing wastewaters is urgently needed with the global nuclear energy exploitation. Herein, we design a large-scale fabrication of shape and structure-dependent hydroxyapatite (HAP) nanostructures produced using a facile hydrothermal method in absence of any organic solvents and templates. It was found that the hydrothermal reaction temperature was a vital factor affecting the morphology (turned from nanosheets to nanoribbons and finally to nanoblocks) and structure (turned from monetite to hydroxyapatite and from calcium hydrogen phosphate hydrate to hydroxyapatite) of HAP. Moreover, the obtained HAP-180 exhibits highly efficient removal of U(VI) (99.3% removal of U(VI) within 30 s), and with the maximum adsorption capacity of 2024 mg/g, which is higher than those of HAP-120, HAP-150 and other materials previously reported. The superior removal performance is ascribed to the specific structure of HAP-180 and effective complexation with U(VI) ions. The findings of this work indicate that the morphology and structure of HAP can be feasible adjustment, and it is promising as environmental remediation material for U(VI) clean-up.