Superparamagnetic Adsorbent Based on Phosphonate Grafted Mesoporous Carbon for Uranium Removal

Abstract

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.

Dual Effect of Acetic Acid Efficiently Enhances Sludge-Based Biochar to Recover Uranium From Aqueous Solution

“…Besides, the C1s spectrum could show C = O near 285.75 and 288.86 eV ( Zhao et al, 2019 ). Moreover, the blending energy of U4f 2/5 (382.4 eV, 385.2 eV) corresponded to U(VI) on the surface of ASBB-U ( Figure 6F ) ( Husnain et al, 2017 ; Tan et al, 2018 ), indicating that no redox reaction happened in uranium sorption process by ASSB.…”

Theoretical and experimental studies on uranium(vi) adsorption using phosphine oxide-coated magnetic nanoadsorbent

“…This behavior is similar to that reported for silica coated with alkylphosphine oxides, 32 as higher uranium( vi ) adsorption was attained at pH 5. At low pH values, the predominant uranium species is UO 2 2+ which competes with the abundant H + and H 3 O + ions for the binding sites on the Fe 3 O 4 @Cyanex-923 surface, 46 and consequently the adsorption is unfavorable at low pH. Additionally, the pH affects the entire surface charge of Fe 3 O 4 @Cyanex-923 and the protonation of oxygen atoms in the P O group at acidic media negatively affects the uranium( vi ) adsorption due to the strong electrostatic repulsion.…”

Phosphate group functionalized magnetic metal–organic framework nanocomposite for highly efficient removal of U(VI) from aqueous solution

“…Uranium mainly exists in the form of UO 2 2+ in aqueous solution at or below pH 4.0 68 . When pH < 3.1, the phosphate groups of Fe 3 O 4 @SiO 2 @UiO-66-TPP NPs were positive, and intense competition between H + and UO 2 2+ for bindng sites resulted in lower adsorption capacity of the adsorbent.…”