Interaction of radionuclides with natural and manmade materials using XAFS technique

Selective biosorption of Li+ in aqueous solution by lithium ion-imprinted material on the surface of chitosan/attapulgite

The extraction of Li+ from liquid lithium resources is a pivotal focus of current research endeavors. Attapulgite (ATP), characterized by its distinctive layered structure and inherent ion exchange properties, emerges as an exceptional material for fabricating lithium-ion sieve. Ion-imprinted chitosan/ATP composite materials are successfully synthesized, demonstrating efficacy in selectively absorbing Li+. The results emphasize the rich functional groups present in H-CTP-2, enhancing its absorbability and selectivity, with an adsorption capacity of 37.56 mg•g-1. The adsorption conforms to the Langmuir and pseudo-second-order kinetic model. Li+ coordination involves amino and hydroxyl group, indicating a chemisorption process. Furthermore, the substantial pore structure and significant specific surface area of ATP significantly promote Li+ adsorption, suggesting its participation not only in chemisorption but also in physical adsorption. The fabricated ion-imprinted materials boast substantial adsorption capacity, exceptional selectivity, and rapid kinetics, highlighting their potential for effectively separating Li+ from aqueous solution.

Nanometal Oxides with Special Surface Physicochemical Properties to Promote Electrochemical Detection of Heavy Metal Ions

Heavy metal ions (HMIs) are one of the major environmental pollution problems currently faced. To monitor and control HMIs, rapid and reliable detection is required. Electrochemical analysis is one of the promising methods for on-site detection and monitoring due to high sensitivity, short response time, etc. Recently, nanometal oxides with special surface physicochemical properties have been widely used as electrode modifiers to enhance sensitivity and selectivity for HMIs detection. In this work, recent advances in the electrochemical detection of HMIs using nanometal oxides, which are attributed to specific crystal facets and phases, surficial defects and vacancies, and oxidation state cycle, are comprehensively summarized and discussed in aspects of synthesis, characterization, electroanalysis application, and mechanism. Moreover, the challenges and opportunities for the development and application of nanometal oxides with functional surface physicochemical properties in electrochemical determination of HMIs are presented.

X-ray absorption spectroscopy principles and practical use in materials analysis

The X-ray Absorption Fine Structure (XAFS) with its subregions X-ray Absorption Near-edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) is a powerful tool for the structural analysis of materials, which is nowadays a standard component of research strategies in many fields. This review covers a wide range of topics related to its measurement and use: the origin of the fine structure, its analytical potential, derived from the physical basis, the environment for measuring XAFS at synchrotrons, including different measurement geometries, detection modes, and sample environments, e. g. for in-situ and operando work, the principles of data reduction, analysis, and interpretation, and a perspective on new methods for structure analysis combining X-ray absorption with X-ray emission. Examples for the application of XAFS have been selected from work with heterogeneous catalysts with the intention to demonstrate the strength of the method providing structural information about highly disperse and disordered systems, to illustrate pitfalls in the interpretation of results (e. g. by neglecting the averaged character of the information obtained) and to show how its merits can be further enhanced by combination with other methods of structural analysis and/or spectroscopy.

Environmental remediation of heavy metal ions by novel-nanomaterials: A review

Recently, novel-nanomaterials with excellent sorption capacities, mild stability, and environmental-friendly performance, have enabled massive developments in capturing heavy metal ions. This review firstly introduces the preparation and modification of novel-nanomaterials (e.g., MOFs, nZVI, MXenes, and g-C₃N₄). Then, the heavy metal ions' sorption properties and the impact of environmental conditions have been discussed. Subsequently, the sorption mechanisms are verified through batch experiments, spectral analysis, surface complexation models, and theoretical calculations. Finally, the applications prospects of novel-nanomaterials in removing heavy metal ion polluted water have also been discussed, which provide perspective for future in-depth research and practical applications.

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.

Recent advances in layered double hydroxide-based nanomaterials for the removal of radionuclides from aqueous solution

Layered double hydroxides (LDHs), one of the most important two-dimensional layered compounds, have enabled massive developments in effective pollution treatments. Their derivative materials have also attracted multidisciplinary attention owing to the intrinsic advantages of their moderate chemiostability, low cost and nontoxicity. Over the past few decades, significant advances have been made in the synthesis of novel LDH-based composites and the optimization of characterization techniques. In this review, we give an overview of the recent advances in LDH-based nanomaterials, from a brief introduction to their preparation and modification methods to an overview of their application in the removal of radionuclides and an exploration of their underlying adsorption mechanisms. In the end, a summary and outlook are also briefly addressed. This review intends to provide deep insight into the design of high-performance LDH-based materials for the potential elimination of radionuclides from aqueous solutions during environmental pollution cleanup.

Synthesis of rod-like metal-organic framework (MOF-5) nanomaterial for efficient removal of U(VI): batch experiments and spectroscopy study

With the widespread application of radionuclide ²³⁵U(VI), it is inevitable that part of U(VI) is released into the natural environment. The potential toxicity and irreversibility impact on the natural environment has become one of the most forefront pollution problems in nuclear energy utilization. In this work, rod-like metal-organic framework (MOF-5) nanomaterial was synthesized by a solvothermal method and applied to efficiently adsorb U(VI) from aqueous solutions. The batch experimental results showed that the sorption of U(VI) on MOF-5 was strongly dependent on pH and independent of ionic strength, indicating that the dominant interaction mechanism was inner-sphere surface complexation and electrostatic interaction. The maximum sorption capacity of U(VI) on MOF-5 was 237.0 mg/g at pH 5.0 and T = 298 K, and the sorption equilibrium reached within 5 min. The thermodynamic parameters indicated that the removal of U(VI) on MOF-5 was a spontaneous and endothermic process. Additionally, the FT-IR and XPS analyses implied that the high sorption capacity of U(VI) on MOF-5 was mainly attributed to the abundant oxygen-containing functional groups (i.e., CO and CO). Such a facile preparation method and efficient removal performance highlighted the application of MOF-5 as a candidate for rapid and efficient radionuclide contamination's elimination in practical applications.

Enhanced removal of iodide ions by nano Cu2O/Cu modified activated carbon from simulated wastewater with improved countercurrent two-stage adsorption

A newly developed adsorbent nano Cu₂O/Cu-modified activated carbon composite (nano Cu₂O/Cu-C) was used to remove radioactive iodide ions (I^-) from simulated wastewater. The emphasis of this research is to improve adsorption performance and obtain higher I^- removal efficiency compared with the single-stage adsorption. To fully develop the amount of adsorption by nano Cu₂O/Cu-C, and to increase the decontamination factor (DF) of I^-, an improved countercurrent two-stage adsorption (ICTA) process was introduced. In the ICTA process, measures dealing with desorption of loaded adsorbent in the stage-two adsorption were taken and more extensive application of countercurrent two-stage adsorption (CTA) process could be made after the improvement to ICTA process in this study. Furthermore, in order to analyze the process and determine the I^- concentration in the effluent, a calculation method was devised based on the Langmuir isotherm equations and adsorption accumulation principle. The mean DFs were 177, 166, and 89.7, respectively, when the initial I^- concentrations were 5.00, 10.0, and 20.0 mg/L; and the adsorbent dosage was 1.25 g/L. These results were approximately 8.76, 8.97, and 6.79 times higher, respectively, than with conventional single-stage adsorption. The experimental values of the I^- concentration were higher than the calculated ones, which could be ascribed to desorption of the residual loaded adsorbent and formation of CuI in the adsorption at stage 1. Formation of CuI in the adsorption at stage 1 was considered to be the predominant reason.

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.

Incorporation of Cadmium and Nickel into Ferrite Spinel Solid Solution: X-ray Diffraction and X-ray Absorption Fine Structure Analyses

The feasibility of incorporating Cd and Ni in hematite was studied by investigating the interaction mechanism for the formation of Cd_xNi_1-xFe₂O₄ solid solutions (CNFs) from CdO, NiO, and α-Fe₂O₃. X-ray diffraction results showed that the CNFs crystallized into spinel structures with increasing lattice parameters as the Cd content in the precursors was increased. Cd²⁺ ions were found to occupy the tetrahedral sites, as evidenced by Rietveld refinement and extended X-ray absorption fine structure analyses. The incorporation of Cd and Ni into ferrite spinel solid solution strongly relied on the processing parameters. The incorporation of Cd and Ni into the CNFs was greater at high x values (0.7 < x ≤ 1.0) than at low x values (0.0 ≤ x ≤ 0.7). A feasible treatment technique based on the investigated mechanism of CNF formation was developed, involving thermal treatment of waste sludge containing Cd and Ni. Both of these metals in the waste sludge were successfully incorporated into a ferrite spinel solid solution, and the concentrations of leached Cd and Ni from this solid solution were substantially reduced, stabilizing at low levels. This research offers a highly promising approach for treating the Cd and Ni content frequently encountered in electronic waste and its treatment residues.

Efficient elimination of U(vi) by polyethyleneimine-decorated fly ash

The easily-synthesized FA@PEI showed an excellent performance in the elimination of U(vi) from wastewater, with the adsorption mechanism being explored.

Highly efficient Pb(ii) and Cu(ii) removal using hollow Fe3O4@PDA nanoparticles with excellent application capability and reusability

The easily synthesized Fe₃O₄@PDA material showed excellent performance for Pb(ii) and Cu(ii) elimination from wastewater, and its adsorption mechanism was revealed.

New Synthesis of nZVI/C Composites as an Efficient Adsorbent for the Uptake of U(VI) from Aqueous Solutions

New nanoscale zerovalent iron/carbon (nZVI/C) composites were successfully prepared via heating natural hematite and pine sawdust at 800 °C under nitrogen conditions. Characterization by SEM, XRD, FTIR, and XPS analyses indicated that the as-prepared nZVI/C composites contained a large number of reactive sites. The lack of influence of the ionic strength revealed inner-sphere complexation dominated U(VI) uptake by the nZVI/C composites. Simultaneous adsorption and reduction were involved in the uptake process of U(VI) according to the results of XPS and XANES analyses. The presence of U-C/U-U shells demonstrated that innersphere complexation and surface coprecipitation dominated the U(VI) uptake at low and high pH conditions, respectively. The uptake behaviors of U(VI) by the nZVI/C composites were fitted well by surface complexation modeling with two weak and two strong sites. The maximum uptake capacity of U(VI) by the nZVI/C composites was 186.92 mg/g at pH 4.0 and 328 K. Additionally, the nZVI/C composites presented good recyclability and recoverability for U(VI) uptake in regeneration experiments. These observations indicated that the nZVI/C composites can be considered as potential adsorbents to remove radionuclides for environmental remediation.

Synthesis of molybdenum disulfide/reduced graphene oxide composites for effective removal of Pb(II) from aqueous solutions

In this work, a facile method was adopted to synthesize molybdenum disulfide/reduced graphene oxide (MoS₂/rGO) composites through an l-cysteine-assisted hydrothermal technique. The as-prepared MoS₂/rGO composites were firstly applied as adsorbents for efficient elimination of Pb(II) ions. Batch adsorption experiments showed that the adsorption of Pb(II) on MoS₂/rGO followed pseudo-second-order kinetic model well. The adsorption of Pb(II) was intensely pH-dependent, ionic strength-dependent at pH < 9.0 and ionic strength-independent at pH > 9.0. The presence of humic acid (HA) enhanced Pb(II) adsorption obviously. The MoS₂/rGO composites exhibited excellent adsorption capacity of 384.16mgg^-1 at pH 5.0 and T=298.15K, which was superior to MoS₂ (279.93mgg^-1) and many other adsorbents. The thermodynamic parameters suggested that the adsorption process of Pb(II) on MoS₂/rGO composites was spontaneous (ΔG^θ<0) and endothermic (ΔH^θ>0). The interaction of Pb(II) and MoS₂/rGO was mainly dominated by electrostatic attraction and surface complexation between Pb(II) and oxygen-containing functional groups of MoS₂/rGO. This work highlighted the application of MoS₂/rGO as novel and promising materials in the efficient elimination of Pb(II) from contaminated water and industrial effluents in environmental pollution management.