Selective and efficient removal of radioactive ions from water with well-dispersed metal oxide nanoparticles@N-doped carbon

Abstract

Nuclear pollution in the environment is increasingly serious recently, which directly endangers human health and environmental quality. Herein, this paper proposes a COF-absorption-pyrolysis strategy to confine MgO NPs in COF-derived N-doped porous carbon matrix. The MgO NPs in the obtained materials were evenly anchored on a carbon matrix with a diameter of less than 10 nm confirming by HRTEM analysis. With the characters of porous structure, large specific surface area, and the evenly loading of MgO NPs, MgO@NCt derived from COF shows a significant removal capacity for U(VI), the removal amounts of U(VI) on MgO@NC400 (389.91 mg/g), MgO@NC500 (947.91 mg/g) and MgO@NC600 (880.60 mg/g) at 298 K were remarkably greater than that of NC500 (180.18 mg/g) and other reported carbon-based materials. Moreover, MgO@NC500 still maintains a high selective removal capacity for U(VI) in the existence of Mg2+, Ca2+, Na+, PO43-, SO42- ions. Characteristic analysis shows that the removal process of U(VI) mainly includes ions exchange, the conversion of MgO to Mg(OH)2, and the complexation between the high-affinity O-H of Mg(OH)2 and U(VI). The ultra-high removal capacity of the MgO@NCt can be restored by pyrolyzing, and it is further proved to be an efficient adsorbent. In addition, MgO@NC500 has excellent removal capacity for methylene blue and tetracycline. Therefore, the synthesis strategy of confining MgO NPs in the COF-derived N-doped carbon provides a new insight for the treatment of heavy metals and organic pollutants in wastewater.