The synergistic elimination of uranium (VI) species from aqueous solution using bi-functional nanocomposite of carbon sphere and layered double hydroxide

Hydrangea-like carbon sphere@layered double hydroxide (CS@LDH) nanocomposite was fabricated by one-step hydrothermal synthesis strategy using carbon sphere and Ni-Al LDH as monomer molecules. The CS@LDH nanocomposites were then applied as adsorbents to eliminate U(VI) from aqueous solutions and showed excellent elimination performance to U(VI) from aqueous solutions because of its strong synergistic effects between metal-oxygen functional groups (Ni-O and Al-O) and free-metal functional groups (C–O, C–O–C, and O–C[dbnd]O). The removal of U(VI) on CS@LDH was mainly dominated by inner-sphere surface complexation, which was confirmed with batch sorption experiments, FTIR and XPS analysis. Furthermore, the maximum sorption capacity of U(VI) on CS@LDH (0.6 mmol/g) was 2.0 times higher than that of U(VI) on Ni-Al LDH (0.3 mmol/g) and approximately 1.5 times higher than that of U(VI) on CS (0.4 mmol/g) at pH = 5.0 and T = 298 K. The thermodynamic parameters suggested that the sorption of U(VI) was a typical spontaneous and endothermic process. The sorption isotherms were well simulated by Langmuir model, suggesting that the sorption was monolayer coverage. The CS@LDH can be used as superior adsorbent for efficient elimination of radionuclides in environmental pollution remediation. This study also demonstrated a new strategy to improve the physicochemical properties of other low efficiency adsorbents through polymerization reaction.