Coupling g-C3N4 nanosheets with metal-organic frameworks as 2D/3D composite for the synergetic removal of uranyl ions from aqueous solution

Uranium is not merely a momentous resource for nuclear energy, but also a highly toxic pollutant which has aroused global attention. The efficient handling of uranium from contaminated water is urgent. Herein, to acquire the improved performance of MOFs for U(VI) capture, a 2D/3D hybrid NH2-UiO-66/g-C3N4 (NU6CN) adsorbent was designed and fabricated through one-step hydrothermal approach. With the newly synthesized efficient NU6CN composite, the U(VI) loading amount could reach 195.55 mg.g(-1), which significantly outperformed that of the individual NH2-UiO-66 (134.09 mg.g(-1)) and g-C3N4 (53.69 mg.g(-1)) at pH 5.0 and 298 K. The adsorption process conformed to the Langmuir and pseudo-second-order model. Subsequently, based on this system, the underlying interaction mechanism between U(VI) and NU6CN was carefully investigated. The formation of an inner-sphere complex on NU6CN surface was determined by the macroscopic and microscopic data. In the light of XPS analysis, the adsorption of U(V1) on NU6CN was attributable to the synergism of the ample nitrogen- and oxygen-bearing functional groups (e.g., N-C=N, O-C=O, C-O) derived from g-C3N4 and NH2-UiO-66. Additionally, NU6CN revealed good recoverability and recyclability by adsorption/desorption test. These findings presented herein demonstrated the remarkable potential of as-prepared adsorbents for the uranium-contaminated water remediation. (C) 2019 Elsevier Inc. All rights reserved.