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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/TiO 2) 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/TiO 2 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/TiO 2 (441.3 mg/g) was observed to outperform the GO (280.0 mg/g), rGO (140.9 mg/g) and TiO 2 (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/TiO 2 revealed good removal performance for uranyl ions, which showed a great potential application to control the nuclear industrial pollution. Image 1 • 3D GA/TiO 2 composite was prepared via a facile and green method. • Synergistic effects improved the capture ability for U(VI) on 3D GA/TiO 2 than GO, rGO and TiO 2. • The adsorption energy of U(VI) onto 3D GA/TiO 2 was calculated to be 1.60 eV. • Interaction mechanism was electrostatic interaction and inner-sphere surface complexation. Three-dimensional graphene/titanium dioxide nanoparticle hybrids (3D GA/TiO 2) were fabricated and revealed excellent removal properties for uranyl ions. [ABSTRACT FROM AUTHOR]

ZIF-8, a sort of zeolitic imidazolate frameworks (ZIFs), had showed superior adsorptive property of typical radionuclide U(VI), but it reminded uncertain how the performance of ZIF-8 would be affected by adding humic acid (HA). HA could significantly change the surface charge of ZIFs and the transport of U(VI) in natural settings, which affected the eradication of U(VI) in aquatic ecology. Thus the impact of HA for the U(VI) removal by ZIF-8 as well as its mechanism had been analyzed by batch experiments and spectral analyses. It was demonstrated that the addition of HA increased the maximum removal capacity towards U(VI) from 781.2 mg g−1 to 1398.5 mg g−1. Moreover, removal property in acidic solution was improved, and the influence of background ions on ZIF-8 was reduced. The detailed mechanism was further explored by microscopic spectral analysis. The zeta potential showed that HA enhanced the electronegativity of ZIF-8 thus enhancing the electrostatic interaction with positive ions. Moreover, FT-IR and XPS further indicated that HA enhanced the removal capacity by affecting the surface complexation phenomena and strong chemical interactions between U(VI) and ZIF-8. Also, investigations indicated that the incorporation of HA improved the removal efficiency for U(VI), which had far-reaching significance for the application of ZIF-8 in practical environment. [Display omitted] • The effect of humic acid on the physicochemical properties of ZIF-8 was studied. • A fresh thinking for future research in practical application are prompted. • The influence of HA on the adsorption of uranium by ZIF-8 was studied. • The mechanisms are surface complexation and electrostatic interactions. • HA as a natural substance is more environmentally friendly in wastewater treatment. [ABSTRACT FROM AUTHOR]

Abstract 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-C 3 N 4). 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. Graphical abstract Image 1 Highlights • Novel-nanomaterials have shown excellent sorption capacity for toxic heavy metal ions and can reach the equilibrium quickly. • The effect of environmental conditions on sorption behavior of novel-nanomaterials has been discussed, providing reference for practical application. • The reaction mechanisms mainly include adsorption, reduction, and oxidation. • The cost, toxicity, large-scale applications of novel-nanomaterials in commercial production are analyzed and the solutions are given. The preparation and surface modification of novel nanomaterials and their application in environmental pollution were overviewed. The sorption mechanism was discussed from spectroscopy analysis, surface complexation and theoretical calculations. [ABSTRACT FROM AUTHOR]

Heavy metal pollution of water sources has raised global environmental sustainability concerns, calling for the development of high-performance materials for effective pollution treatment. Herein, we report a facile approach to synthesize carbonaceous nanofiber/Ni Al layered double hydroxide (CNF/LDH) nanocomposites for high-efficiency elimination of heavy metals from aqueous solutions. The CNF/LDH nanocomposites were characterized by three-dimensional architectures formed by the gradual self-assembly of flower-like LDH on CNF. The nanocomposites exhibited excellent hydrophilicity and high structural stability in aqueous solutions, guaranteeing the high availability of active sites in these environments. High-efficiency elimination of heavy metal ions by the CNF/LDH nanocomposites was demonstrated by the high uptake capacities of Cu(II) (219.6 mg/g) and Cr(VI) (341.2 mg/g). The sorption isotherms coincided with the Freundlich model, most likely because of the presence of heterogeneous binding sites. The dominant interaction mechanisms consisted of surface complexation and electrostatic interaction, as verified by a combination of X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy analyses and density functional theory calculations. The results presented herein confirm the importance of CNF/LDH nanocomposites as emerging and promising materials for the efficient removal of heavy metal ions and other environmental pollutants. [ABSTRACT FROM AUTHOR]

The hierarchical core-shell and yolk-shell magnetic titanate nanosheets (Fe 3 O 4 @TNS) were successfully synthesized by employing magnetic nanoparticles (NPs) as interior core and intercrossed titanate nanostructures (NSs) as exterior shell. The as-prepared magnetic Fe 3 O 4 @TNS nanosheets had high specific areas (114.9 m 2  g −1 for core-shell Fe 3 O 4 @TNS and 130.1 m 2  g −1 for yolk-shell Fe 3 O 4 @TNS). Taking advantage of the unique multilayer structure, the nanosheets were suitable for eliminating U(VI) from polluted water environment. The sorption was strongly affected by pH values and weakly influenced by ionic strength, suggesting that the sorption of U(VI) on Fe 3 O 4 @TNS was mainly dominated by ion exchange and outer-sphere surface complexion. The maximum sorption capacities ( Q max ) calculated from the Langmuir model were 68.59, 121.36 and 264.55 mg g −1 for core-shell Fe 3 O 4 @TNS and 82.85, 173.01 and 283.29 mg g −1 for yolk-shell Fe 3 O 4 @TNS, at 298 K, 313 K and 328 K, respectively. Thermodynamic parameters (Δ H 0 , Δ S 0 and Δ G 0 ) demonstrated that the sorption process was endothermic and spontaneous. Based on X-ray photoelectron spectroscopy (XPS) analyses, the sorption mechanism was confirmed to be cation-exchange between interlayered Na + and UO 2 2+ . The yolk-shell Fe 3 O 4 @TNS had more extraordinary sorption efficiency than core-shell Fe 3 O 4 @TNS since the yolk-shell structure provided internal void space inside the titanate shell to accommodate more exchangeable active sites. The flexible recollection and high efficient sorption capacity made core-shell and yolk-shell Fe 3 O 4 @TNS nanosheets promising materials to eliminate U(VI) or other actinides in wastewater cleanup applications. [ABSTRACT FROM AUTHOR]

With the extensive application of graphene oxide (GO), it is noticeable that part of GO is directly/indirectly released into the environment and widespread research indicated that it had adverse influences on human health and ecological balance. In this work, a novel nanobelt-like Ca/Al layered double hydroxides (CA-LDH) was synthesized and applied as efficient coagulant for the removal of GO from aqueous solutions. The results indicated that neutral pH, co-existing cations and higher temperature were beneficial to the coagulation of GO. The sequence of cation effect for promoting of GO coagulation was Ca 2+ > Mg 2+ > K + > Na + , whereas the effect of anions on GO coagulation was PO 4 3− > CO 3 2− > SO 4 2− > Cl − . Comparing with anions, the cations showed more dominate effect for GO coagulation than anions. Hydrogen bonds and electrostatic interaction were the main coagulation mechanisms for GO coagulation, which were evidenced by FT-IR and XPS analysis. Specifically, for the first time, the reclaimed product of CA-LDH after GO coagulation (CA-LDH + GO) was applied as adsorbents for the secondary application in the removal of heavy metal ions from aqueous solutions. Interestingly, the CA-LDH + GO still had high adsorption capacities, i.e., the maximum adsorption capacities ( q max ) for Cu(II), Pb(II), and Cr(VI) were 122.7 mg/g, 221.2 mg/g and 64.4 mg/g, respectively, higher than other similar materials. This paper highlighted the LDH-based nanomaterials are promising materials for the elimination of environmental pollutants and the migration and transformation of carbon nanomaterials in the natural environment. [ABSTRACT FROM AUTHOR]

Uranium(VI) has become one of the most potential contaminants due to its productive and irreversibility impact on the surrounding environment. Titanate nanowires (TNWs) have attracted significant attention because of its high ion exchange ability and facile synthesis. Herein the TNWs were synthesized, and the morphology and structure of TNWs were investigated by Fourier transformed infrared spectroscopy, scanning electron microscope, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy in detail. The application of TNWs in U(VI) removal was studied under various environmental conditions using batch technique, and the results indicated that the sorption of U(VI) on TNWs was strongly affected by pH and weakly affected by ionic strength. The presence of PO 4 3- and CO 3 2- could overwhelmingly influence U(VI) interaction with TNWs, which was mainly attributed to the formation of anionic and electro-neutral complexes. From the Langmuir model simulation, the maximum sorption capacities were calculated to be 358, 384, and 410 mg g −1 at the temperatures of 298 K, 313 K and 328 K, respectively. The thermodynamic results revealed that the interaction process was spontaneous and endothermic. The extraordinary ion exchange capacity and facile synthesis under mild conditions made TNWs promising materials for the potential application in the efficient elimination of U(VI) or other lanthanides and actinides from aqueous solutions in the environmental radioactive pollution cleanup. [ABSTRACT FROM AUTHOR]

Uranium mainly exists in the form of uranyl carbonate in seawater. [UO 2 (CO 3) 3 ]4- has strong stability, which increases the difficulty of uranium extraction from seawater. Meanwhile, the complex marine environment, a large number of coexisting competing ions and biological pollution are all non-negligible disturbing factors. Herein, we introduced amidoxime (AO) groups into the surface of Ti 3 C 2 and grafted polyamides (PA) by a simple one-step hydrothermal method to produce an efficient seawater uranium extraction adsorbent Ti 3 C 2 -AO-PA. Owing to the amidoxime groups, the material was highly selective for uranium. And the large number of amino groups in the polyamides gave it ideal resistance to biofouling. The possibility of Ti 3 C 2 -AO-PA as an adsorbent for uranium extraction from seawater was confirmed by various characterization techniques, numerous adsorption batch experiments, simulated seawater experiments and antibacterial performance tests. It was demonstrated that the uptake of [UO 2 (CO 3) 3 ]4- by Ti 3 C 2 -AO-PA showed fast reaction kinetics (about 120 min), brilliant absorption capacity (81.1 mg·g−1 at pH 8.3), significant high selectivity (32.8 mg-U/g-Ads) and outstanding anti-biological contamination performance (92.9% antibacterial rate). XPS and DFT further indicated that the high extraction ability of Ti 3 C 2 -AO-PA for uranium was mainly attributed to the strong complexation of AO and –NH 2 with [UO 2 (CO 3) 3 ]4-. These conclusions showed that Ti 3 C 2 -AO-PA not only had an ideal application prospect for uranium extraction from seawater, but also provided an available strategy for rapid and selective uranium adsorption from real seawater. [Display omitted] • Polyamide enhanced amidoxime-functionalized Ti 3 C 2 nanosheet was constructed. • The uranium extraction capacity was highly enhanced. • Ti 3 C 2 -AO-PA showed excellent selectivity and antimicrobial properties. • Synergistic interactions of amidoxime and polyamide with uranium ions in seawater. [ABSTRACT FROM AUTHOR]

Because the pollutants produced by human activities have destroyed the ecological balance of natural water environment, and caused severe impact on human life safety and environmental security. Hence the task of water environment restoration is imminent. Metal-organic frameworks (MOFs), structured from organic ligands and inorganic metal ions, are notable for their outstanding crystallinity, diverse structures, large surface areas, adsorption performance, and excellent component tunability. The water stability of MOFs is a key requisite for their possible actual applications in separation, catalysis, adsorption, and other water environment remediation areas because it is necessary to safeguard the integrity of the material structure during utilization. In this article, we comprehensively review state-of-the-art research progress on the promising potential of MOFs as excellent nanomaterials to remove contaminants from the water environment. Firstly, the fundamental characteristics and preparation methods of several typical water-stable MOFs include UiO, MIL, and ZIF are introduced. Then, the removal property and mechanism of heavy metal ions, radionuclide contaminants, drugs, and organic dyes by different MOFs were compared. Finally, the application prospect of MOFs in pollutant remediation prospected. In this review, the synthesis methods and application in water pollutant removal are explored, which provide ways toward the effective use of water-stable MOFs in materials design and environmental remediation. [Display omitted] • The synthesis strategies of water-stable MOFs are briefly introduced. • The mechanisms mainly ascribe to coordination and electrostatic interaction. • Sufficient functional groups endow MOFs excellent performance. • Multi-factor influences demonstrate the practical application potential of MOFs. [ABSTRACT FROM AUTHOR]