Efficient removal of U(VI) from aqueous solution by hydroxyapatite/graphene oxide composite microspheres

Effective treatment of uranium-containing wastewater is of great significance to the sustainable development of nuclear power and the protection of ecological environment. In this study, a highly efficient uranium adsorbent, graphene oxide (GO)/nano-hydroxyapatite (nHA) composite microspheres (nHA@rGO) was synthesized, which could effectively remove uranium from aqueous solution. Under the condition of pH = 3.5, T = 298 K, the maximum adsorption capacity reached 1672.96 mg/g. The results of batch experiments showed that the adsorption capacity of nHA@rGO microspheres was higher than that of nHA microspheres, indicating the enhancement of GO. The adsorption kinetics conformed to the pseudo second-order model. The changes of nHA@rGO microspheres before and after uranium adsorption were analyzed by FT-IR, XPS and XRD. The mechanisms of U(VI) ions adsorption onto nHA@rGO microspheres involved precipitation, surface complexation and ion exchange, in which the hydroxyl and phosphoric acid groups played important roles. The results showed that the prepared nHA@rGO microspheres can be used as an efficient and promising adsorbent for the treatment of uranium-containing wastewater.