Search

Abstract In recent years, the heavy metal ions have been immoderately released into the ecological system and result in potential hazardous to public health. Herein, the sodium dodecyl sulfate intercalated molybdenum disulfide (SDS-MoS 2) was synthesized for the adsorption of Cr(VI). The SDS molecule was flat and vertically intercalated into the interlayer of MoS 2 , which was further evidenced by density functional theory calculations. The capture of Cr(VI) on the sphere-like SDS-MoS 2 relied on solution pH. The retention of Cr(VI) on SDS-MoS 2 attained 63.92 mg/g, and the removal process was endothermic, spontaneous and increased with temperature increasing. The main removal mechanism of Cr(VI) onto SDS-MoS 2 was Cr(VI) fixing on the surface of the composites by chemisorption involving possible Cr-S coordination bonding. More importantly, Cr(VI) passed into the increased interlamination and reacted at the interlamination of SDS-MoS 2 , which was further proved at molecular level. The results can provide critical information for the application of SDS-MoS 2 in Cr(VI) elimination or other kinds of pollutants removal in natural aquatic environment. Graphical abstract Image 1 Highlights • SDS-MoS 2 was fabricated by simple hydrothermal method and applied for Cr(VI) elimination. • The adsorption of Cr(VI) on SDS-MoS 2 was pH- and ionic strength-dependent. • The adsorption of Cr(VI) on SDS-MoS 2 was chemisorption involving possible Cr-S coordination bonding. • Cr(VI) ions entered into the increased interlayer and reacted at the interlamination of SDS-MoS 2. Capsule abstract. The well-designed sphere-like SDS-MoS 2 showed high sorption of Cr(VI) through chemisorption involving Cr-S coordination bonding, and further passed into the interlamination of SDS-MoS 2 , indicating the efficient elimination of Cr(VI) from wastewater. [ABSTRACT FROM AUTHOR]

In this study, polyaniline rafted to the surface of AlOOH (PANI/AlOOH) composites were successfully synthesized and applied for chromium (Cr(VI)) adsorption from aqueous solutions. Cr(VI) adsorption isotherms were described by Langmuir model well and the maximum adsorption capacity was 66.77 mg/g at pH=5 and T=298 K. Cr(VI) adsorption was attributed to chemisorption and outer‐sphere surface complexation. The interaction mechanism was further investigated by Fourier transform infrared spectroscopy, transmission electron microscopy‐energy dispersive spectroscopy and X‐ray photoelectron spectroscopy techniques, and the results suggested the partially reduction of Cr(VI) to Cr(III). Cr(VI) removal was mainly related with the electrostatic attraction and chelation of different Cr(VI)/Cr(III) species with protonated nitrogen‐containing functional groups (‐NH+, ‐NH‐) on PANI/AlOOH. PANI/AlOOH composites were synthesized and applied as adsorbent for Cr(VI) adsorption from aqueous solutions. Surface adsorbed Cr(VI) could be reduced to Cr(III). Cr(VI) removal was mainly related with the electrostatic attraction and chelation of different Cr(VI)/Cr(III) with protonated nitrogen‐containing functional groups (‐NH+, ‐NH‐) on PANI/AlOOH. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CMN and CCMN were prepared via a single-step hydrothermal technique and calcination process. • The maximal removal capacities of U(VI) on CMN and CCMN were 585.6 and 973.7 mg/g, respectively. • Metal-oxygen functional groups played an important role in the elimination of U(VI). • Interaction mechanism was attributed to strong inner-surface complexation. Abstract Uranium is considered to be a strategic means for the nuclear power as well as a worldwide highly toxic pollutant. For the enhanced U(VI) elimination from wastewater, novel Co-Mo-Ni ternary hydroxide (CMN) and calcined CMN (CCMN) nanocomposites were prepared via a simplistic single-step hydrothermal technique and calcination process. The elimination process and adsorption property of U(VI) on CMN and CCMN were analysed by batch experiment as well as spectroscopy analysis, and the researches showed that U(VI) was formed stable and strong complexes with the surface groups of CMN and CCMN. The maximal removal capacities of U(VI) on CMN and CCMN amounted to be 585.6 and 973.7 mg/g at pH = 5.0 and T = 298 K, correspondingly, that exhibited competitiveness with the majority of the reported adsorbents. The U(VI) uptake was substantially impacted by the tested solution pH and not affected by the ionic strength, which revealed that the interaction mechanism was primarily inner-sphere surface complexation, which received further confirmation by the XPS analysis. Based on the above analyses, the facile synthesis process and excellent U(VI) elimination performance denoted that the ternary (hydr)oxide materials were applicable as an attractive adsorbent for the radionuclides preconcentration and removal from aqueous solutions in natural environmental management. [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]

Water pollution, a worldwide issue for the human society, has raised global concerns on environmental sustainability, calling for high-performance materials in effective pollution treatments. Boron nitride (BN) with a structure similar to graphene possesses many extraordinary properties such as high surface areas, high oxidization resistance at high temperature, and high chemical stability. This review presents the outstanding removal percentage and environmental restoration of BN-based nanomaterials for the elimination of various pollutants from the last ten years. Notably, recent advances in the removal of organic/inorganic pollutants and interaction mechanism are outlined. BN-based materials can not only preferably remove contaminants, but also can be directly regenerated by burning in air. The BN-based materials have satisfactory sorption capacities for inorganic pollutants (e.g. heavy metal ions) and organic pollutants (e.g. dyes and pharmaceutical molecules). The interaction mechanisms between pollutants and BN-based materials are mainly surface complexation, π-π stacking, and electrostatic interactions. This paper is beneficial to further comprehend the interactions of pollutants with BN-based materials, which is also helpful for the improvement of BN-based materials and potential areas for future applications in environment remediation. [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]

The biological toxicity and negative environmental effect of graphene oxide (GO) have attracted wide public concern due to its potential risks. To assess the transport behavior and to reduce the environmental hazardous of GO in natural environment, ZnO and MgO were used as coagulant for GO removal from aqueous solutions. The results indicated that GO coagulation on ZnO and MgO were scarcely affected by ionic strength. At neutral pH, the GO removal capacities could reach 232.8 mg/g on MgO and 210.8 mg/g on ZnO. The high removal capacity and short coagulation time showed the enormous advantages for the high-efficiency removal of GO from aqueous solutions, which were important for the real application of MgO and ZnO in reality. The coagulation mechanisms of GO on ZnO and MgO could be attributed to electrostatic attraction and hydrogen bond, which were further demonstrated by DFT calculations. Considering the cost, efficiency, removal capacity and reusability, one can conclude that metal oxides can be promising materials for GO efficient removal by a simple and rapid coagulation process. The findings can provide critical information about the physicochemical behavior of GO in aquatic natural environment, which is significant to decrease the environmental toxicity of GO. [ABSTRACT FROM AUTHOR]

In this study, chitosan-metal oxide composites (CS-MO) were prepared for graphene oxide (GO) removal from aqueous solutions. The results showed that the GO coagulation on CS-MO was dependent on pH and ionic strength. The maximum GO removal capacities reached 442.5 mg/g on CS-AlO, 425.0 mg/g on CS-ZnO and 421.2 mg/g on CS-MgO, respectively, showing a huge advantage in the efficient elimination of GO from natural water system. The coagulation of GO on CS-MO was dominated by electrostatic attraction in acidic conditions and by hydrogen bonds in neutral and alkaline conditions. The findings are helpful to improve the current understanding of the environmental behavior of GO in natural aqueous systems. [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]

The graphene oxides (GOs) have been studied extensively in multidisciplinary areas owing to their excellent physicochemical properties. The high theoretical surface areas and large amounts of oxygen-containing functional groups at the basal planes and the edge sites ensure their high sorption capacity for heavy metal ions and radionuclides from large volumes of aqueous solutions. Herein, the GOs were applied as adsorbents to remove U(VI) from aqueous solutions at different experimental conditions, and the results showed that the sorption of U(VI) on GOs was strongly dependent on pH and was not affected by ionic strength obviously. The sorption capacity of U(VI) on GOs is calculated to be 1330 mg/g at pH 4.5 and T = 20 °C, which is much higher than any other today’s materials. The interaction mechanism of U(VI) on GOs was simulated by the computational DFT calculations, and the results evidenced that the variation in pH values led to significant changes in the circumstance of functional groups on GOs. As the pH value increased, the weak physical sorption/outer-sphere surface complexation between the GOs and U(VI) at low pH turned into strong chemical sorption/inner-sphere surface complexation with the negative charged –O − or –COO − groups induced by the deprotonation of the functional groups at high pH. [ABSTRACT FROM AUTHOR]

Both environment and human beings were menaced by the widespread application of radioactive uranium, high-performance and effective elimination of uranium from wastewater is of important meaning for development of environmental sustainability in the future. In this study, the water-stable MOF material and the highly crystalline COF were compounded by a mild hydrothermal strategy, which achieved efficient removal of U(VI) through the synergistic effect. The composites showed the characteristics of both COFs and MOFs, which will possess higher stability, larger surface area and faster adsorption efficiency that cannot be carried out by a single component. Batch experiments and characterizations (SEM, TEM, XRD, FT-IR, BET, XPS, etc.) indicated that UiO-66-NH 2 @LZU1 had more stable and multi-layer pore structure and rich active functional groups. The Langmuir model and the pseudo-second-order kinetics fitting was more suitable for the U(VI) elimination process. The greatest uranium adsorbing capacity of UiO-66-NH 2 @LZU1 (180.4 mg g−1) was observed to exceed the UiO-66-NH 2 (108.8 mg g−1) and COF-LZU1 (65.8 mg g−1), which reached the excellent hybrid effects. Furthermore, FT-IR and XPS analyses confirmed that the most nitrogen-containing group from COF-LZU1 and oxygen-containing group of UiO-66-NH 2 could be combined with U(VI). In addition, electrostatic interaction was also a mechanism during the removal process. This work displayed that UiO-66-NH 2 @LZU1 was a prospective hybrid material for radioactive waste remediation. The compound method and application mentioned in this work had provided a theoretical basis for designing and developing multi-functional composite adsorbents, which contributed to the development of new materials for radioactive wastewater treatment technologies. [Display omitted] • UiO-66-NH 2 @LZU1 composite material was obtained by solvothermal method. • Highly efficient uranium adsorbent, adsorption capacity reached 163.1 mg g−1. • Abundant nitrogen/oxygen functional groups promote uranium removal. • Main removal mechanism included electrostatic interaction and surface complexation. [ABSTRACT FROM AUTHOR]

With the advantages of high atomic utilization, clear and uniform active sites, high catalytic activity, outstanding stability, excellent selectivity and recyclability, iron single-atom materials have shown promising application in the fields of electrocatalysis, hydrogen production, batteries, and sensors. However, the research work on the efficient removal of various toxic and hazardous pollutants from aqueous solutions using iron single-atom materials was still limited. Their properties such as environmental compatibility, high specific surface area and functionality have unrivaled natural advantages in degrading pollutants in aqueous solutions, which deserve in-depth exploration by researchers. However, pure single-atom materials were thermodynamically unstable and tended to aggregate into nanoclusters and particles. Therefore, single-atom materials were often loaded onto different support materials, while the activity of materials depended mainly on the physicochemical properties of the support materials and the coordination mode between the single-atoms and the support materials. In this review, the preparation and physicochemical properties of iron single-atom materials supported by commonly used carrier materials (such as g-C 3 N 4 , MOFs, COFs, biochar, etc.) were summarized firstly. The applications of different materials for organic pollutants degradation and heavy metal ions removal in aqueous environment were further analyzed, and influence factors and reaction mechanisms for pollutants treatment were investigated. The main mechanism of organic pollutants degradation was catalytic degradation, while the mechanism of heavy metal ions removal was adsorption and redox. Finally, prospects and personal insights were provided for the utilization of iron single-atom materials in environmental pollution decontamination. [Display omitted] • The preparation and properties of iron single-atom materials are summarized. • The influencing factors of removing environmental pollutants are introduced. • The mechanisms mainly include catalytic degradation, adsorption and redox. • The possible degradation pathways of typical pollutants are predicted. • The opportunities and challenges of iron single-atom materials are presented. [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]

l -cysteine intercalated Mg/Al layered double hydroxide (Cys-LDH) composites were fabricated and applied for treating the U(VI) contaminated wastewater under various conditions. Interaction mechanisms and adsorption properties were investigated by using batch experiments with spectroscopy analysis. The adsorption isotherms and kinetics were fitted perfectly with the Langmuir isotherm and the pseudo-second-order model, respectively. The significant maximum adsorption capacity of Cys-LDH (211.58 mg/g) compared to LDH was attributed to the larger number of functional groups on Cys-LDH. The presence of humic acid (HA) decreased U(VI) elimination on Cys-LDH at high pH but increased U(VI) removal at low pH. Typically, the presence of various anions (such as NO 3 − , Cl − , ClO 4 − and SO 4 2− ) did not obviously affect U(VI) adsorption on Cys-LDH, while the coexisted CO 3 2− significantly affected U(VI) elimination. The predominate adsorption were determined to be the formation of Cys-U(VI)-Cys complexes with cysteine in the Cys-LDH interlayers. The results demonstrated that the Cys-LDH are promising adsorbents for efficient elimination and extraction of radionuclides in actual environmental contamination management. [ABSTRACT FROM AUTHOR]

A novel low-cost, effective and environmental-friendly laminated carbon nitride decorated with polydopamine (PDA) and grafted with polyethyleneimine (PEI) brush ( l -C 3 N 4 /PDA/PEI 3 ) was successfully synthesized and applied as environmental cleaner for removing U(VI) ions from aqueous solutions under various environmental conditions. The adsorption isotherms fitted well by the Langmuir model, suggesting that the removal of U(VI) on l -C 3 N 4 /PDA/PEI 3 was monolayer coverage. The effects of different PEI contents were also investigated and the results demonstrated that the adsorption capacity of U(VI) on l -C 3 N 4 /PDA/PEI x decreased at higher content of PEI. Typically, various cations (Ca 2+ and Mg 2+ ) and SO 4 2− could inhibit the adsorption through competitive coordination with U(VI), while CO 3 2− promoted U(VI) sorption owing to the formation of indissolvable complexes. The main driving force between U(VI) and l -C 3 N 4 /PDA/PEI 3 was surface complexation with various functional groups (C C, C O, N C C, and C C or C H) and electrostatic attraction. According to the analysis of EXAFS spectra, the occurrence of U-C and U-U shell revealed that inner-sphere complexation and surface co-precipitation dominated the adsorption of U(VI) on l -C 3 N 4 /PDA/PEI 3 at pH 5.0. The composites were also applied to remove 243 Am(III), Cu(II) and Pb(II) ions at different pH values, and similar results were also found for these metal ions. Such a facile synthesis method and efficient removal performance suggested that the l -C 3 N 4 /PDA/PEI 3 materials might be a promising adsorbent for efficient elimination of radionuclides and heavy metal ions in environmental pollution management. [ABSTRACT FROM AUTHOR]

The surface tensions of 2‑diethylaminoethanol (DEAE)‑ N ‑(2‑aminoethyl)ethanolamine (AEEA), DEAE‑ N ‑methyl‑1,3‑propane‑diamine (MAPA) and DEAE‑1,4‑butanediamine (BDA) aqueous solutions have been measured by using the BZY-1 surface tension meter. The mass fractions of DEAE and AEEA/MAPA/BDA respectively ranged from 0.300 to 0.500 and 0.050 to 0.150. The temperature ranged from 303.2 K to 323.2 K. A thermodynamic equation was proposed to model the surface tension and the calculated results agreed well with the experiments. The effects of temperature and mass fraction of amines on the surface tension were demonstrated on the basis of experiments and calculations. The surface thermodynamics including surface enthalpy and surface entropy of blended amine aqueous solutions were also determined, and their temperature and mass fraction dependences were analyzed. • Surface tensions of DEAE and AEEA/MAPA/BDA aqueous solutions were measured. • Experiments were modeled satisfactorily by using a thermodynamic equation. • Surface thermodynamics including surface enthalpies and entropies were determined. • Effects of temperature and mass fraction on surface properties were illustrated. [ABSTRACT FROM AUTHOR]