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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]

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 uncalcined glycerol-modified nanocrystallined Mg/Al layered double hydroxides (named as G-LDH) and calcined G-LDH (named as G-LDO) with molar ratio of Mg:Al = 3:1 were successfully synthesized using an easy and green hydrothermal method, and were characterized by scanning electron microscopy, transmission electron microscopy, N 2 Brunauer–Emmett–Teller surface area measurement, Fourier transformed infrared (FT-IR) spectroscopy and X-ray diffraction (XRD). The as-synthesized G-LDH and G-LDO were applied as adsorbents to remove methyl orange (MO) from aqueous solutions at different experimental conditions, and the results showed that the interaction of MO with G-LDH and G-LDO were strongly pH-dependent and ionic strength-independent. Kinetic study indicated the MO adsorption on G-LDH and G-LDO were well simulated by pseudo-second-order model. The MO adsorption on G-LDH and G-LDO were well simulated by Langmuir model, and the maximum adsorption capacity of G-LDO (q max = 1062.3 mg/g) was much higher than that of G-LDH (q max = 443.5 mg/g) at pH = 4.5. The thermodynamic parameters calculated from temperature-dependent isotherms indicated that the adsorption was spontaneous and exothermal process. The FT-IR and XRD analysis further evidenced that the interaction of MO with G-LDH was mainly dominated by electrostatic interaction, ion exchange, hydrogen bonding and surface complexation, whereas the uptake of MO to G-LDO was mainly attributed to electrostatic interaction and surface complexation. These results suggested that the G-LDO was a promising material for the efficient removal of organic pollutants in real environmental pollution cleanup. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 nanoparticles were synthesized by hydrothermal technique and then modified with tetraethyl orthosilicate to form Fe 3 O 4 @SiO 2 nanospheres through Stöber method. The characterization results of X-ray diffraction, Fourier transformed infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and magnetic measurements evidenced the successful synthesis of Fe 3 O 4 @SiO 2 nanospheres. The as-prepared Fe 3 O 4 @SiO 2 was applied as adsorbent to remove congo red (CR) from aqueous solutions at different experimental conditions, and the results indicated that CR adsorption on Fe 3 O 4 @SiO 2 was strongly pH-dependent and weakly ionic strength-dependent at relative low pH values, indicating that the adsorption was mainly dominated by electrostatic interactions. The maximum adsorption capacities of CR on Fe 3 O 4 @SiO 2 were calculated to be 54.64 mg/g from Sips model and 50.54 mg/g from Langmuir model at T = 308 K and pH = 5.3. The thermodynamic parameters calculated from temperature-dependent isotherms indicated that the adsorption of CR on Fe 3 O 4 @SiO 2 was an spontaneous and endothermic process. The CR-adsorbed Fe 3 O 4 @SiO 2 nanospheres could be easily separated from aqueous solutions using magnetic separation technique within 40 s. These results suggested that the Fe 3 O 4 @SiO 2 nanospheres might be suitable materials for the efficient separation of dye pollutants from aqueous solutions in possible real applications. [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]

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]

Herein, a practical and simple calcination method was used to synthesize layered double oxides (denoted as LDO) and layered double oxides/carbon dots nanocomposites (denoted as LDO-C) for U(VI) efficient removal. The U(VI) adsorption on LDO and LDO-C were investigated under various experimental conditions, and the results indicated that U(VI) uptake on LDO and LDO-C were consumingly dependent on pH and ionic strength at pH > 6, and independent of ionic strength at pH < 6. The adsorption processes of U(VI) on LDO and LDO-C were spontaneous and endothermic, and well simulated by pseudo-second-order model. The maximum adsorption capacity of U(VI) on LDO-C was calculated to be 354.2 mg/g at pH = 5.0 and T = 298 K, which was significantly higher than that of U(VI) on LDO (237.6 mg/g). Particularly, BET, F T-IR, XPS and EXAFS analysis suggested that the higher adsorption capacity of LDO-C was mainly attributed to higher specific surface area and more abundant surface oxygen-containing functional groups (e.g. C-OH), and the main interaction mechanisms were surface complexation and electrostatic interactions. In addition, LDO-C also showed higher adsorption capacity of 241 Am(III) than LDO. All in all, the efficient removal performance and superior versatility of LDO-C indicated that it could be applied as promising candidate for efficient immobilization of radioactive pollutant in environmental pollution management. [ABSTRACT FROM AUTHOR]

Graphical abstract A novel arginine modified hydroxyapatite carbon microsphere (C@HAp/Arg) composite were synthesized by a facile and green method and exhibited superior adsorption efficiency for removal of U(VI). Abstract Uranium was not only the main source of nuclear energy but also one of the long-lived radionuclide. Herein, a novel arginine modified hydroxyapatite carbon microsphere composites (defined as C@HAp/Arg) obtained promptly via a one-step mild hydrothermal method, was applied to remove U(VI) from aqueous solutions. Based on the characterization of transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), the synthesized C@HAp/Arg presented globular morphology and abundant functional groups (e.g., COO−), which were beneficial to its combination with U(VI). The interaction mechanism and removal capability of U(VI) on C@HAp/Arg were studied by batch adsorption technique and spectroscopy analysis. The results implied that U(VI) can form strong surface complexes on C@HAp/Arg. The kinetics adsorption of U(VI) followed pseudo-second-order kinetic model with high removal efficiency (∼95% within 5 h at pH 5.0). The adsorption isotherms were well fitted by Langmuir model, implying that U(VI) uptake on C@HAp/Arg was monolayer coverage. It was found that the maximum adsorption capacities of CSs, C@HAp and C@HAp/Arg toward U(VI) were calculated to be 23.16, 72.09 and 569.66 mg/g, respectively, at 298.15 K and pH 5.0, and thermodynamic parameters revealed that the adsorption processes of U(VI) were spontaneous and endothermic. In addition, effect of co-existed ions and CO 3 2− concentrations demonstrated that U(VI) adsorption on C@HAp/Arg was weakly interfered by foreign ions and carbonate concentrations. More importantly, the adsorption performance of U(VI) on C@HAp/Arg was still over ∼87% after five cycles. Therefore, it was noted that the versatile C@HAp/Arg could be potentially used as a powerful building block for the enrichment and disposal of U(VI) from aqueous solutions, which could efficiently reduce the potential toxicity of U(VI) in the U(VI)-contaminated water. [ABSTRACT FROM AUTHOR]

• The synthesis strategies of ZIFs are briefly introduced and summarized. • Batch experiment, spectral analysis and DFT are used to explore mechanisms. • The mechanisms mainly ascribe to coordination and electrostatic interaction. • Large SSA and sufficient functional groups endow ZIFs excellent performance. • Multi-factor influences demonstrate the practical application potential of ZIFs. With the rapid economic globalization and energy development, heavy metal ions/radionuclides are inevitably discharged into aqueous system and cause pollution, which seriously endanger human health and environmental sustainability. In recent years, zeolitic imidazolate frameworks (ZIFs) with huge specific surface area, excellent pore structure and abundant surface functional groups show great potential in the elimination of heavy metal ions/radionuclides. This review systematically summarizes the research progress of ZIFs and ZIF-based materials for capturing heavy metal ions/radionuclides. Firstly, the preparation and modification of ZIF-based materials are briefly introduced. Then, the removal behaviors and possible interaction mechanisms between ZIF-based materials and pollutants are explored through macro-batch experiments, micro-spectroscopy analyses and theoretical calculations. In addition, the partition coefficient as evaluation indicator was employed to objectively compare the removal performance of ZIFs and other commonly used traditional adsorbents for heavy metal ions/radionuclides. Finally, the challenges and prospects of ZIF materials in environmental governance are briefly discussed so as to provide references for future research and practical applications. [ABSTRACT FROM AUTHOR]

Highly porous zeolitic imidazolate frameworks (ZIFs), with disparate metal ions (ZIF-8 and ZIF-67), disparate organic ligands (ZIF-9 and ZIF-67), single or double central metal atoms (ZIF-8, Zn/Co-ZIF and ZIF-67) were prepared and used in the elimination of typical radionuclide U(VI). The detailed interaction mechanisms were studied by batch experiments, spectral analyses and DFT calculation. Langmuir isotherms model revealed a decreasing tendency to remove U(VI): ZIF-8 (540.4 mg/g) > Zn/Co-ZIF (527.5 mg/g) > ZIF-9 (448.6 mg/g) > ZIF-67 (368.2 mg/g). Based on the effects of pH and foreign ions, FTIR and XPS spectra analyses, the possible interaction mechanisms of U(VI) onto ZIFs were surface complexation and electrostatic interaction. Among them, ZIF-8 with Zn metal center and 2-methylimidazolate organic ligand had the best elimination capacity for U(VI) because of its large surface area, active metal ion and abundant nitrogen-containing groups (e.g., C–N, Zn–N and C N). Specially, the adsorption energy of ZIF-8-Zn2-UO 2 2+ structure was −2.299 eV obtained by DFT calculation, illustrating that U(VI) and N atoms were formed the most stable bidentate coordination compounds. This paper highlights the effects of the hydroxylated metals, the functional groups of the imidazole ring on the elimination of U(VI), which can provide constructive suggestions for further adsorbent materials amelioration. Image 1 • ZIF-8, ZIF-9, ZIF-67 and Zn/Co-ZIF were fabricated by stirring at room temperature. • Excellent structural performances endowed four ZIFs outstanding sorption capacity. • The differences in adsorption mechanism of four ZIFs were investigated in detail. • The N atoms of ZIF-8 formed bidentate coordination compounds with U(VI). [ABSTRACT FROM AUTHOR]