A novel U(vi)-imprinted graphitic carbon nitride composite for the selective and efficient removal of U(vi) from simulated seawater

Abstract

Extracting uranium(VI) from seawater for future long-term development of nuclear energy in the world is an urgent issue. However, there are still enormous challenges to selectively extract U(VI) from seawater. In this paper, a high selectivity surface U(VI)-imprinted graphitic carbon nitride/β-cyclodextrin composite sorbent was synthesized through a cross-linking method with U(VI) ions, β-cyclodextrin and epichlorohydrin as the template ion, the functional ligand and the cross-linking agent, respectively. The prepared ion-imprinted β-cyclodextrin modified graphitic carbon nitride polymer (IIP-g-C₃N₄/β-CD) was used for selective extraction of U(VI) from aqueous solution. Effects of different conditions were examined such as solution pH, oscillation time, temperature, etc. The results suggested that the IIP-g-C₃N₄/β-CD exhibits wonderful adsorption capacity and outstanding selectivity for U(VI) extraction at the ppm level compared to the nonimprinted material. The adsorption process closely correlates with the Langmuir adsorption isotherm model. In addition, the calculated maximum adsorption capacity was 859.66 mg g⁻¹ at 25 °C, which confirmed that the adsorption process is a monolayer chemisorption process. Accordingly, the IIP-g-C₃N₄/β-CD showed excellent selective adsorption of U(VI) and cycling stability after five adsorption–desorption cycles with little adsorption capacity loss. Moreover, IIP-g-C₃N₄/β-CD exhibited outstanding U(VI) adsorption efficiency for simulated seawater indicating that IIP-g-C₃N₄/β-CD can be used as a potential sorbent for the efficient selective adsorption of U(VI) from simulated seawater.