Rational design and synthesis of monodispersed hierarchical SiO₂@layered double hydroxide nanocomposites for efficient removal of pollutants from aqueous solution

Hierarchical silicon dioxide-@-layered double hydroxide (SiO₂@LDH) nanocomposites were synthesized by a facile in situ co-precipitation method, and characterized by XRD, FESEM, FT-IR and XPS in detail. The sorption of uranium (U(VI)) and methyl orange (MO) on SiO₂@LDH were investigated as a function of pH, ionic strength, contact time and temperature. The results indicated that the sorption of U(VI) and MO were strongly dependent on pH, and weakly dependent on ionic strength, demonstrating that the interaction of U(VI) was mainly dominated by inner-sphere surface complexation and the sorption of MO was mainly attributed to electrostatic attraction due to the high removal efficiency (∼98% within 4 h for U(VI) ions, and ∼92% within 10 min for MO). The kinetics sorption of U(VI) and MO both followed the pseudo-second-order model well, suggesting that the sorption processes were chemical sorption. The sorption isotherms of U(VI) and MO on SiO₂@LDH were well fitted by the Langmuir model, and the maximum sorption capacities of SiO₂@LDH were calculated to be 303.1 mg·g⁻¹ for U(VI) and 166.1 mg·g⁻¹ for MO. The thermodynamic parameters revealed that the sorption of U(VI) and MO was spontaneous process. Integrating the experimental result analysis, the hierarchical SiO₂@LDH may be a promising material for the efficient elimination of radionuclides and dyes from aqueous solutions in natural environmental pollution cleanup.