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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]

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]

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]

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]

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]