A direct
approach was presented to graft phosphonate groups on
magnetic mesoporous carbon by an impregnation method with environmentally
friendly precursors unlike the conventional methods involving a series
of complicated steps and harsh conditions. Through the in situ reduction
of Fe3+, magnetite particles of ∼10 nm were successfully
embedded into the mesopores, which was confirmed by HR-TEM. Surface
characterization by X-ray photoelectron spectroscopy and Fourier transform
infrared revealed phosphonate functional groups anchored through multidentate
bonding with the surface of P–Fe–CMK-3. Due to the combined
advantages of mesoporous pore size (5.5 nm), phosphonate ligands (1.42
mmol g–1), and magnetic sensitivity (5.20 emu g–1), this multifunctional adsorbent captured >85%
of
UO2
2+ within 5 min and the maximum adsorption
capacity was 150 mg g–1 at pH 4. The exceptionally
high selectivity and efficiency of P–Fe–CMK-3 toward
uranyl capture even in groundwater (K
d = 1 × 105 mL g–1), radioactive
wastewater (K
d = 3 × 104 mL g–1), and seawater (K
d = 1 × 104 mL g–1) at V/m = 1000 mL g–1 was better than that
of the previously reported adsorbents. Importantly, the adsorbent
maintained UO2
2+ adsorption efficiency >99%
over five cycles due to the excellent chemical and structural stabilities.
Above all, the adsorbent could be manipulated for UO2
2+ capture with help of a magnetic field in the real world,
especially in case of nuclear accidents, decommissioning of nuclear
power plants and/or uranium recovery from seawater.