: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Synthesis of amidoxime-functionalized Fe3O4@SiO2 core–shell magnetic microspheres for highly efficient sorption of U(VI)

Polymer-based nanocomposites for heavy metal ions removal from aqueous solution: a review

The recovery of uranium (U) from seawater has been investigated for over six decades in efforts to secure uranium sources for future energy production. The majority of the research activities have focused on inorganic materials, chelating polymers, and nanomaterials. Previous studies of uranium adsorption from aqueous solutions, mainly seawater, are reviewed here with a focus on various adsorbent materials, adsorption parameters, adsorption characterization, and marine studies. Continuous progress has been made over several decades, with adsorbent loadings approaching 3.2 mg U/g adsorbent in equilibrium with seawater. Further research is needed to improve first, the viability including improved capacity, selectivity, and kinetics, and second, the sorbent regeneration for multicycle use. An overview of the status of the uranium adsorption technology is provided and future research needs to make this technology commercially competitive are discussed.

Recovery of Uranium from Seawater: A Review of Current Status and Future Research Needs

There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO22+) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of Sx-LDH composites (LDH is Mg/Al layered double hydroxide, [Sx]2– is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (qm = 330 mg/g), large KdU values (104–106 mL/g at 1–300 ppm U concentration), and high % removals (>95% at 1–100 ppm, or ∼80% for ppb level seawater) for UO22+ species. The Sx-LDHs are exceptionally efficient for selectively and rapidly capturing UO22+ both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value KdU of 3.4 × 106 mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca2+/Na+, Sx-LDH exhibits superior selectivi...

Efficient uranium capture by polysulfide/layered double hydroxide composites.

Lead removal by polyacrylamide-bentonite and zeolite composites: effect of phytic acid immobilization.

Composite of polyacrylamide-bentonite (PAA-B) was prepared by direct polymerisation of PAA in a suspension of bentonite (B). Adsorption and thermodynamic features of phytic acid (Phy) adsorption onto B, PAA and PAA-B, and those of Fe3+, Zn2+, UO2
2+ adsorption onto PAA-B and its modification by Phy (PAA-B-Phy) have been investigated. The reusability, storagability, ion selectivity and recoverability of sorbed ions with 1 M HCl have also been considered. The chemical and physical structure of adsorbents has been characterised by means of FT-IR and XRD. All adsorption isotherms for Phy and the ions were L-type of the Giles classification except, the one which is S type for adsorption of Phy onto PAA. The maximum adsorption capacities for the ions adsorbed were in order of UO2
2+ > Fe3+ > Zn2+ for PAA-B and Zn2+ > Fe3+ > UO2
2+ for PAA-B-Phy. Langmuir equilibrium constants for the adsorption of ions onto PAA-B-Phy were significantly higher than those found for PAA-B; the magnitude of increase for UO2
2+ was about 100. The thermodynamic parameters indicated that adsorption reactions are spontaneous in terms of adsorption free enthalpy. The chemical structure of PAA-B-Phy was not changed at the end of the studies of reusability and storagability. The composite was selective for UO2
2+ of the ions of interest. The composite of PAA-B and its modification by Phy have been used for the first time in this investigation. It is proposed that the composites can be practically used in the investigations and applications of adsorption.

Investigations for Modification of Polyacrylamide-Bentonite by Phytic Acid and its Usability in Fe3+, Zn2+ and UO22+ Adsorption

Synthesis and characterization of a composite polymeric material including chelating agent for adsorption of uranyl ions.

Removal of uranyl ions in aquatic mediums by using a new material: gallocyanine grafted hydrogel.

A combined molecular dynamic simulation, DFT calculations, and experimental study of the eriochrome black T dye adsorption onto chitosan in aqueous solutions.

Selçuk Şimşek

Papers

Lead removal by polyacrylamide-bentonite and zeolite composites: effect of phytic acid immobilization.

Investigations for Modification of Polyacrylamide-Bentonite by Phytic Acid and its Usability in Fe3+, Zn2+ and UO22+ Adsorption

Synthesis and characterization of a composite polymeric material including chelating agent for adsorption of uranyl ions.

Removal of uranyl ions in aquatic mediums by using a new material: gallocyanine grafted hydrogel.

A combined molecular dynamic simulation, DFT calculations, and experimental study of the eriochrome black T dye adsorption onto chitosan in aqueous solutions.