Abstract
Polyamidoximes (pAMD) are known to have strong affinities for uranyl cations. Grafting pAMD onto the surface of functionalized maghemite nanoparticles (MNP) leads to a nanomaterial with high capacities in the extraction of uranium from wastewaters by magnetic sedimentation. A diamidoxime (dAMD) specifically synthesized for this purpose showed a strong affinity for uranyl: Ka = 105 M-1 as determined by Isothermal Titration Calorimetry (nano-ITC). The dAMD was grafted onto the surface of MNP and the obtained sorbent (MNP-dAMD) was characterized. The nanohybrids were afterward incubated with different concentrations of uranyl and the solid phase recovered by magnetic separation. This latter was characterized by zeta-potential measurements, X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Fluorescence spectroscopy (XRF), whereas the supernatant was analyzed by Inductively Coupled Plasma coupled to Mass Spectrometry (ICP-MS). All the data fitted the models of Langmuir, Freundlich and Temkin isotherms very well. These isotherms allowed us to evaluate the efficiency of the adsorption of uranium by MNP-dAMD. The saturation sorption capacity (qmax) was determined. It indicates that MNP-dAMD is able to extract up to 120 mg of uranium per gram of sorbent. Spherical aberration (Cs)-corrected High-Resolution Scanning Transmission Electron Microscopy (HRSTEM) confirmed these results and clearly showed that uranium is confined at the surface of the sorbent. Thus, MNP-dAMD presents a strong potential for the extraction of uranium from wastewaters.
Highlights
Uranium is one of the most widely used radioactive elements in civilian power plants.[1]
Batch experiments were carried out by contact of 5 mg of maghemite nanoparticles (MNP)-dAMD sorbent with 15 mL of uranyl solution at pH 5.8 with uranium concentrations of 0, 20, 40, 60, 80 and 125 mg.L-1
Nano-ITC was used to determine the affinity of dAMD for uranyl cation
Summary
Iron oxide nanoparticles are the most investigated magnetic materials, as they are easy to synthesize at low cost. They can be collected and removed from a complex multiphase system by an external magnetic field.[9] There are different kinds of iron oxide materials with wide domains of application.[10,11] The most studied polymorphic crystallites are magnetite (Fe3O4), maghemite (γ-Fe2O3) and hematite (α-Fe2O3). It should be emphasized that our main goal here is to elaborate a sorbent based on MNP-dAMD able to reduce, efficiently confine and remove, radioactive waste, uranyl, from contaminated water
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