Microstructures and speciation of radionuclides in natural environment studied by advanced spectroscopy and theoretical calculation

A cyclodextrin-based reagent for cis/trans-geometrical isomers separation by mobility measurements and chemical calculations

Identification of cis/trans-carbon-carbon double-bond (CC) isomers remain challenging. Herein, a simple and rapid method for the separation and analysis of cis/trans-maleic acid (MA) and aconitic acid (AA) using Trapped Ion Mobility Spectrometry (TIMS) was developed. α-, β-, γ-cyclodextrin (CD) were served as the separation reagent, slight difference in mobility separation was obtained by [CD-MA/AA-H]^-. Specially, with the addition of divalent metal ion (G²⁺) as coordination metal ion, the separation effect was much increased by [CD-MA/AA + G-H]⁺, and α-CD has better mobility separation effect than β-/γ-CD. Moreover, chemical calculations revealed the binary and ternary complexes are in the inclusion forms, and microscopic interactions between cis/trans-MA/AA, CDs, and G²⁺ are somewhat different that making their mobility separation. Finally, quantifications of cis/trans-isomers were analyzed in food samples, with good linearity (R² > 0.99) and recoveries obtained from 87.25 % to 100.73 %.

Three-dimensional graphene/titanium dioxide composite for enhanced U(VI) capture: Insights from batch experiments, XPS spectroscopy and DFT calculation

Efficient containment and capture of uranium (U(VI)) from aqueous solution is an essential component to ensure socially and environmentally sustainable development. Herein, the three-dimensional graphene/titanium dioxide composite (3D GA/TiO₂) was synthesized and applied as an effective adsorbent to remove U(VI) from wastewater as a function of contact time, temperature, pH and ion strength. The 3D GA/TiO₂ material was characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The batch experiments results indicated that the adsorption of U(VI) on materials were fitted with the pseudo-second order kinetics and Langmuir models. More specifically, 3D GA/TiO₂ (441.3 mg/g) was observed to outperform the GO (280.0 mg/g), rGO (140.9 mg/g) and TiO₂ (98.5 mg/g) at pH 5.0, which was attributable to the excellent cooperative effects. Furthermore, XPS analyses and DFT calculations confirmed the formation of surface complexes between oxygen-containing group and U(VI) with the U-O bonds length of 2.348 Å (U-O1) and 2.638 Å (U-O2). Meanwhile, the adsorption energy was calculated to be 1.60 eV, which showed a very strong chemisorption during the interaction process. It is believed that the 3D GA/TiO₂ revealed good removal performance for uranyl ions, which showed a great potential application to control the nuclear industrial pollution.

Highly efficient carbonaceous nanofiber/layered double hydroxide nanocomposites for removal of U(VI) from aqueous solutions

The three-dimensional (3D) carbonaceous nanofiber and Ni-Al layered double hydroxide (CNF/LDH) nanocomposite was successfully prepared by a facile one-step hydrothermal methodology. Characterization of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), XRD, and Fourier transformed infrared spectroscopy (FTIR) provided a demonstration that the modified CNF/LDH nanocomposite possessed abundant functional groups, for instance, metal-oxygen surface bonding sites (Ni–O as well as Al–O) and free-metal surface bonding sites (C–O, C–O–C, as well as O–C=O). The elimination of representative radionuclide (i.e. U(VI)) on the CNF/LDH nanocomposite from aqueous solutions was explored as a key function of pH, ionic strength, contact time, reaction temperature as well as radionuclide preliminary concentrations with the use of the batch methodology. As revealed by the findings, the sorption of radionuclides on CNF/LDH nanocomposite adhered to the pseudo-second-order kinetic model as well as Langmuir model. The maximum elimination capacity of U(VI) amounted to be 0.7 mmol/g. The independent of ionic strength shed light on the fact that inner-sphere surface complexation mainly overpowered radionuclide uptake by the CNF/LDH nanocomposite, which was further verified through the combination of FTIR and XPS spectral analyses. The abovementioned analyses shed light on the fact that the CNF/LDH nanocomposite can be regarded as a latent material to preconcentration radionuclides for environmental remediation.

Sorption of 17β-estradiol to the dissolved organic matter from animal wastes: effects of composting and the role of fulvic acid-like aggregates

Steroid estrogens, such as 17β-estradiol (E2), in animal manure pose a potential threat to the aquatic environment. The transport and estrogenicity of estrogens influence the sorption of estrogens to dissolved organic matter (DOM) in animal manure, and composting treatment alters the structure and composition of the manure. The objectives of the present study were to identify the contribution of the molecular composition of DOM of composted manure to the sorption of E2 and then elucidate the dominant mechanisms involved in the interaction of E2 with manure-derived DOM. The excitation-emission matrix (EEM) spectra and atomic force microscopy (AFM) showed that composting significantly altered the chemical composition and structure of DOM. A decrease in the atomic ratios of oxygen (O)/carbon (C) occurred in conjunction with the formation of DOM aggregates in the composted manure, indicating that the hydrophilicity and polarity of the DOM decreased after composting. Composting increased the sorption coefficients (K_DOC-E2) for E2 to DOM, and K_DOC-E2 was positively correlated with the proportion of the fulvic acid (FA)-like fraction and molecular weight (MW) fractions of the DOM (range of 1.0 × 10³-7.0 × 10³ Da and 7.0 × 10³-1.4 × 10⁴ Da). Specifically, E2 showed a tendency for sorption to medium-sized FA-like molecules of DOM aggregates in composted manure. Hydrophobic forces and π-π binding appeared to be the main mechanisms underlying the aforementioned interaction.

Retardation of hexavalent uranium in muscovite environment: a batch study

The sorption of hexavalent uranium on muscovite as a function of pH, background electrolyte, temperature and humic acid (HA) was investigated in detail using batch experiments. The results showed that the uranium sorpiton on muscovite was kinetic fast, the kinetic process was fitted well by pseudo-second-order kinetic model. The sorption of uranium depended strongly on pH while weakly on background electrolyte concentration, indicating that surface complexation dominated the sorption process. The escalation of temperature and humic acid concentration were favorable to uranium sorption on muscovite. The sorption isotherms at pH 6.0 could be described better by Langmuir model than Freundlich or Dubinin-Radushkevich (D-R) model, thermodynamic data indicated that the uranium sorption process on muscovite was spontaneous and endothermic process. The findings in present work can provide important experimental reference for understanding the environmental behavior of uranium in mica-rich terrains.

Enhanced performance for Eu(iii) ion remediation using magnetic multiwalled carbon nanotubes functionalized with carboxymethyl cellulose nanoparticles synthesized by plasma technology

Synthesis of sodium carboxymethyl cellulose/iron oxides/MWCNTs composites by a plasma technique and their application to the decontamination of europium ions from aqueous solutions under controlled laboratory conditions.