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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]

Aniline is toxic and hard to be degraded, and thereby causes the environmental pollution seriously. Herein, a practical and green hydrothermal method was applied to fabricate terephthalic acid and pyromellitic acid intercalated layered double hydroxides (LDH) (named as TAL and PAL) for aniline efficient removal. The sorption of aniline on LDH-based materials were investigated at different experimental conditions, and the results indicated that aniline sorption on LDH, TAL and PAL were strongly dependent on pH and independent of ionic strength. The maximum sorption capacities of aniline on TAL and PAL at pH 5.0 and 293 K were 90.4 and 130.0 mg/g, respectively, which were significantly higher than that of aniline on LDH (52.6 mg/g). Based on the BET, FTIR and XPS analysis, the higher sorption capacities of TAL and PAL were mainly due to high surface area and basal spacing as well as the abundant functional groups (e.g. –COO − ). The interactions of aniline with TAL and PAL were mainly dominated by hydrogen bonds and electrostatic interactions. Such a facile synthesis method, efficient removal performance and superior reusability indicated that the aromatic acid modified LDH materials had potential application for efficient treatment of organic pollutants in environmental pollution cleanup. [ABSTRACT FROM AUTHOR]

To contribute to the understanding of Eu(III) interaction preperties on hydrous alumina particles in the absence and presence of fulvic acid (FA), the complexation properties of Eu(III) with hydrous alumina, FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy (TRLFS) techniques. The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(III). Eu(III) is adsorbed onto alumina particles as outer-sphere surface complexes of ≡(Al−O)−Eu· (OH)· 7HO and ≡(Al−O)−Eu· 6HO at low pH values, and as inner-sphere surface complexes as ≡(Al−O)−Eu· 4HO at high pH. In FA solution, Eu(III) forms complexes with FA as (COO)Eu(HO) and the hydration water number in the first coordination sphere decreases with pH increasing. The formation of ≡COO−Eu−(O−Al≡)· 4HO is observed on FA-alumina hybrids, suggesting the formation of strong inner-sphere surface complexes in the presence of FA. The surface complexes are also characterized by their emission spectra [the ratio of emission intensities of D → F ( λ=594 nm) and D → F ( λ=619 nm) transitions] and their fluorescence lifetime. The findings is important to understand the contribution of FA in the complexation properties of Eu(III) on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(III), or its analogue trivalent lanthanide and actinide ions in natural environment. [ABSTRACT FROM AUTHOR]

Understanding the rate and extent of 63 Ni(II) sorption and desorption on/from mineral surfaces are important to predict its mobility performance in the natural environment. We herein systematically investigated the effects of pH, electrolyte cations, humic acid (HA) and temperature on 63 Ni(II) sorption/desorption on/from Na-montmorillonite. The results indicated that the sorption/desorption of 63 Ni(II) on/from Na-montmorillonite were strongly dependent on pH and electrolyte cations. Desorption abilities of 63 Ni(II) were Na + ≈ K + > Ca 2+ ≈ Mg 2+ at the cationic concentration of 0.2 mol/L, which was associated with the clay tactoid size. The kinetic results suggested that 63 Ni(II) sorption/desorption initially increased rapidly and remained constant as time increasing. The presence of HA influenced 63 Ni(II) sorption clearly and promoted 63 Ni(II) desorption as a result of the dissolution of ternary surface complexes. Increasing temperature was favorable for the sorption reaction owing to the formation of strong inner-sphere complexes, however, hampered the desorption reaction because of the increased stability of inner-sphere complexes or the aggregation of montmorillonite. The results are crucial to understand the physicochemical behavior of radionickel in the natural environment. [ABSTRACT FROM AUTHOR]

Radioactive waste is usually sealed in steel canisters surrounded by a layer of compacted clay back-fill, and permanent buried in a deep geological repository. Unavoidably, the radionuclide contaminants can be released from repository and then sorbed onto the waste container corrosion products or the Fe-rich minerals. Herein, we characterized the Fe(III)-saturated montmorillonite (Fe(III)-MMT) by using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET), and found the changes of the surface incorporating Fe(III) and surface micropores. The sorption of U(VI) on Fe(III)-MMT and Na-montmorillonite (Na-MMT) was investigated by batch experiments. The larger surface area and cation exchange capacity, and the existence of Fe(III) (hydr)oxide phases in Fe(III)-MMT contributed greatly to its sorption capacity. In the whole pH range, the sorption of U(VI) on Fe(III)-MMT was higher than on Na-MMT, and the sorption was strongly depended on pH and ionic strength. The sorption isotherms were simulated well by the Langmuir and Freundlich models. The thermodynamic parameters ( ΔH, ΔS and ΔG) calculated from the temperature dependent sorption isotherms indicated that the sorption of U(VI) on Fe(III)-MMT was an endothermic and spontaneous process. The observations suggest that the interactions between U(VI) and Fe(III)-MMT are important in controlling U(VI) retention. The phenomena need to be considered in risk assessment and reactive transport modeling. [ABSTRACT FROM AUTHOR]

The removal of Pb(II) from wastewater by Ca-rectorite was investigated as various environmental factors containing contact time, pH, ionic strength, solid content, coexisting ions, humic acid (HA), and temperature. The kinetic sorption of Pb(II) on Ca-rectorite was well described by the pseudo second-order model. The sorption process was strongly dependent on pH and ionic strength. The results indicated that the presence of HA and coexisting ions influenced the sorption of Pb(II) on Ca-rectorite obviously. Besides, the Langmuir and Freundlich models were employed to simulate the sorption isotherms. The thermodynamic parameters indicated that the sorption process was spontaneous and endothermic. It is possible to conclude that Ca-rectorite has a good potential for disposal of lead-contaminated wastewater. [ABSTRACT FROM PUBLISHER]

Clay minerals have been studied extensively due to their strong sorption and complexation ability toward various environmental pollutants. In this study, the sorption of 90 Sr(II) on Na-montmorillonite was studied as a function of various environmental conditions such as pH, ionic strength, humic acid (HA) and temperature. The results indicated that the sorption of 90 Sr(II) on Na-montmorillonite was strongly dependent on pH and ionic strength. The experimental data of 90 Sr(II) sorption was simulated by the diffuse-layer model (DLM) well with the aid of Visual Minteq 3.0. At low pH, the sorption of 90 Sr(II) was dominated by outer-sphere surface complexation and ion exchange with Na + /H + on Na-montmorillonite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of HA enhanced 90 Sr(II) sorption at pH < 7.0 but decreased 90 Sr(II) sorption at pH > 7.0. Langmuir and Freundlich models were used to simulate the sorption isotherms of 90 Sr(II) at three different temperatures of 303, 318 and 333 K. The thermodynamic parameters (Δ H , Δ S and Δ G ) calculated from the temperature-dependent sorption isotherms indicated that the sorption of 90 Sr(II) on Na-montmorillonite was an endothermic and spontaneous process. The thermodynamic parameters calculated from temperature-dependent sorption data were crucial to understand the interaction behavior of 90 Sr(II) with Na-montmorillonite. [ABSTRACT FROM AUTHOR]

Review: 212 refs. [ABSTRACT FROM AUTHOR]

The effect of soluble silicate on the sorption of U(VI) to γ -Al 2 O 3 was investigated by batch experiments and extended X-ray absorption fine structure (EXAFS) method. The presence of silicate enhanced the sorption of U(VI) on γ -Al 2 O 3 surface and the sorption was attributed to inner-sphere surface complexation. The structure of the adsorbed U(VI) and silicate on γ -Al 2 O 3 was investigated in the analysis of EXAFS spectra. The fitting of the experimental EXAFS data was obtained by including two uranium coordination shells with 2 axial (O ax ) and 5 equatorial (O eq ) oxygen atoms at 1 . 79 ± 0 . 02 and 2 . 43 ± 0 . 02 Å, respectively, and the third coordination shells with Al atom at ∼3.35 Å. Silicate contributed to the formation of ternary inner-sphere surface complexes, acting as “bridge” between U(VI) and γ -Al 2 O 3 and enhanced the sorption of U(VI). The observations suggested that the interactions between U(VI) and silicate were important in controlling U(VI) retention. [ABSTRACT FROM AUTHOR]

Graphical abstract Rod-like metal-organic framework (MOF-5) nanomaterial for efficient removal of U(VI) from aqueous solutions. Abstract 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., C O and C O). 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. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) was applied as adsorbent to efficiently eliminate the heavy metal ions from wastewater because of its large amount of functional surface groups and high surface areas. However, the contribution of different functional surface groups on the high preconcentration of heavy metal ions to GO is still unclear. Herein the GO was applied as adsorbent for the efficient preconcentration of Co(II) and the effect of functional surface groups on Co(II) removal was studied by batch sorption experiments. The results showed that the maximum sorption capacities of Co(II) on GO, NGO, MGO and NMGO were 43.6, 27.3, 23.2 and 14.6 mg/g, respectively. The elimination of Co(II) was significantly influenced by ionic strength and pH, indicated that the interaction mechanism was primarily controlled by strong surface complexation. The DFT calculation further evidenced that the oxygen-containing surface groups could form shorter bond distance with Co(II) ions than the nitrogen-containing functional groups, and the calculated adsorption energies ( E ad ) for GO–COOH–Co (44.05 kcal/mol) and GO–OH–Co (16.44 kcal/mol) were much higher than that for NGO–Co (6.33 kcal/mol). The density of states (DOS) and charge density differences of combined complexes further illustrated the strong surface complexes were formed between Co(II) and the oxygen-containing surface groups of GO surfaces. This work highlighted that the oxygen-containing surface groups played a vital role in the formation of surface complexes with Co(II) on GO, which is crucial for the preparation and application of GO in the radioactive pollution cleanup. [ABSTRACT FROM AUTHOR]

Hydrangea-like carbon sphere@layered double hydroxide (CS@LDH) nanocomposite was fabricated by one-step hydrothermal synthesis strategy using carbon sphere and Ni-Al LDH as monomer molecules. The CS@LDH nanocomposites were then applied as adsorbents to eliminate U(VI) from aqueous solutions and showed excellent elimination performance to U(VI) from aqueous solutions because of its strong synergistic effects between metal-oxygen functional groups (Ni-O and Al-O) and free-metal functional groups (C O, C O C, and O C O). The removal of U(VI) on CS@LDH was mainly dominated by inner-sphere surface complexation, which was confirmed with batch sorption experiments, FTIR and XPS analysis. Furthermore, the maximum sorption capacity of U(VI) on CS@LDH (0.6 mmol/g) was 2.0 times higher than that of U(VI) on Ni-Al LDH (0.3 mmol/g) and approximately 1.5 times higher than that of U(VI) on CS (0.4 mmol/g) at pH = 5.0 and T  = 298 K. The thermodynamic parameters suggested that the sorption of U(VI) was a typical spontaneous and endothermic process. The sorption isotherms were well simulated by Langmuir model, suggesting that the sorption was monolayer coverage. The CS@LDH can be used as superior adsorbent for efficient elimination of radionuclides in environmental pollution remediation. This study also demonstrated a new strategy to improve the physicochemical properties of other low efficiency adsorbents through polymerization reaction. [ABSTRACT FROM AUTHOR]

The nanoscaled zero-valent iron (nZVI) supported zeolite MCM-41 composites (nZVI/MCM) were synthesized, and applied for the immobilization of Cr(VI) from aqueous solutions. The precise role of MCM-41 and nZVI in the immobilization and reduction of Cr(VI) was characterized using SEM, TEM, HRTEM, HRTEM-EDS, XPS and EXAFS techniques. Comparing to the bare nZVI nanoparticles, the as-synthesized nZVI/MCM composites showed higher efficiency on Cr(VI) immobilization due to the high synergistic effect of Cr(VI) reduction by nZVI and sorption by MCM-41. The morphology and visualizing analysis indicated that nZVI was uniformly distributed on the surfaces of MCM-41, which reduced the aggregation of nZVI apparently and thereby increased the reduction activity. XPS and EXAFS analysis showed that nZVI could promote Cr(VI) reduction into Cr(III), and the sorption and reduction reactions were occurred on bare nZVI. MCM-41 acted as a scavenger for the insoluble products, which could improve the reduction activity of nZVI. The high performance of nZVI/MCM composites showed the promising strategy for the efficient decontamination of Cr(VI) pollution in environmental pollution cleanup. [ABSTRACT FROM AUTHOR]

Uranium has attracted sustained attention due to its high mobility and biotoxicity. Among various techniques, sorption is considered as the most effective technique to treat the U(VI)-containing wastewater. In serving for low-cost adsorbents, layered double hydroxides (LDHs) have been proved to be promising candidates. However, the interaction mechanism of U(VI) with LDHs is still unclear, although plenty of LDHs have been used in this field. Herein, we developed two novel methods to fabricate ternary LDHs (MgFeAl LDHs and NiFeAl LDHs) and applied the ternary LDHs as adsorbents to investigate their sorption performance towards U(VI). The results showed that the sorption was endothermic and followed the pseudo-second-order kinetics through the formation of inner-sphere surface complexes, and the sorption isotherms were simulated by the Langmuir model well. Furthermore, systematic spectroscopy characterization indicated that the sorption occurred on the surface sites of Mg-OH and Ni 2+ –OH, while the CO 3 2− in the gallery space also played an important role. This work highlighted the synthesis of high-efficient materials and their application in wastewater treatment. [ABSTRACT FROM AUTHOR]

Hierarchical silicon dioxide-@-layered double hydroxide (SiO 2 @LDH) nanocomposites were synthesized by a facile in situ co-precipitation method, and characterized by XRD, FESEM, FT-IR and XPS in detail. The sorption of uranium (U(VI)) and methyl orange (MO) on SiO 2 @LDH were investigated as a function of pH, ionic strength, contact time and temperature. The results indicated that the sorption of U(VI) and MO were strongly dependent on pH, and weakly dependent on ionic strength, demonstrating that the interaction of U(VI) was mainly dominated by inner-sphere surface complexation and the sorption of MO was mainly attributed to electrostatic attraction due to the high removal efficiency (∼98% within 4 h for U(VI) ions, and ∼92% within 10 min for MO). The kinetics sorption of U(VI) and MO both followed the pseudo-second-order model well, suggesting that the sorption processes were chemical sorption. The sorption isotherms of U(VI) and MO on SiO 2 @LDH were well fitted by the Langmuir model, and the maximum sorption capacities of SiO 2 @LDH were calculated to be 303.1 mg·g −1 for U(VI) and 166.1 mg·g −1 for MO. The thermodynamic parameters revealed that the sorption of U(VI) and MO was spontaneous process. Integrating the experimental result analysis, the hierarchical SiO 2 @LDH may be a promising material for the efficient elimination of radionuclides and dyes from aqueous solutions in natural environmental pollution cleanup. [ABSTRACT FROM AUTHOR]

• Core-shell Fe 3 O 4 @MoS 2 and MoS 2 @Fe 3 O 4 composites were synthesized. • Both Fe 3 O 4 @MoS 2 and MoS 2 @Fe 3 O 4 showed high removal capability for Cr(VI). • Both Fe 3 O 4 @MoS 2 and MoS 2 @Fe 3 O 4 are superparamagnetic. • Fe 3 O 4 @MoS 2 and MoS 2 @Fe 3 O 4 are eco-friendly during the synthesis process and wastewater treatment. • Synergetic reduction makes F@M an outstanding material for Cr(VI) removal. In this investigation, two novel magnetic core-shell Fe 3 O 4 @MoS 2 (F@M) and MoS 2 @Fe 3 O 4 (M@F) composites were synthesized and exploited for Cr(VI) elimination. Eco-friendly preparation methods were applied for the synthesis of Fe 3 O 4 and MoS 2 composites. The experimental results showed that both F@M and M@F have high saturation magnetization values (43.2 emu/g for F@M and 49.9 emu/g for M@F), excellent maximum sorption capacities of Cr(VI) at pH 5.0 and 298 K (324.3 mg/g for F@M, 290.2 mg/g for M@F), remarkable Cr(VI) removal efficiencies (Cr(VI) sorption equilibrium by both F@M and M@F can be reached in 90 min) and nice regeneration properties (the sorption capabilities of F@M and M@F decreased slightly after five consecutive sorption/desorption cycles). Chemical reduction of Cr(VI) to Cr(III) occurred on the surface of F@M and M@F, and the synergetic reduction of sulfur and ferrous ions made F@M an outstanding material for Cr(VI) removal. This paper highlights F@M and M@F as potential, eco-friendly and ultrahigh-efficiency materials for Cr(VI) pollution cleanup. [ABSTRACT FROM AUTHOR]