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Comprehension the extent and rate of U(VI) adsorption on some mineral surfaces are significant to predict their migration and transformation properties in the environmental systems. Herein, iron oxides particles supported reduced graphene oxide composites (MRGO) were successfully synthesized by in-situ chemical precipitation approach. The MRGO composites which illustrated high saturation magnetization could be likely separated using an external magnet. The experimental data illustrated that U(VI) ions could be interacted with MRGO composites through different interaction mechanisms depending on different environmental conditions. The adsorption kinetic results can be well simulated using the pseudo-second-order pattern. The pH-dependent adsorption behavior illustrated an favorable pH value of 7.5 for removal of U(VI) ions using MRGO composites. Furthermore, the adsorption regeneration of MRGO composites in simulated wastewater disposal systems was tested. Based on above mentioned, it was clear that MRGO composites could be potentially used as adsorbent for removal of actual U(VI)-bearing wastewaters. [ABSTRACT FROM AUTHOR]

Herein, β -cyclodextrin ( β -CD) was conjugated on the surfaces of Fe 3 O 4 particles to synthesize magnetic Fe 3 O 4 /CD nanocomposite using a novel low temperature plasma technique. The Fe 3 O 4 /CD samples were applied in the removal of radionuclides and heavy metal ions contaminations from aqueous solutions. The synthesized Fe 3 O 4 /CD nanocomposite which showed high saturation magnetization could be likely separated by using an external magnet. The adsorption performance and underlying mechanism of Fe 3 O 4 /CD nanocomposite toward nickel ions were studied using batch technique. The adsorption kinetic of nickel ions on Fe 3 O 4 /CD surfaces could be obtained within the time period of 8 h. The surface conjugated CD can obviously improve adsorption performance towards Ni(II) ions. The Fe 3 O 4 /CD samples show propitious adsorption property toward Ni(II) ions from wastewater. The experimental findings showed that Fe 3 O 4 /CD nanocomposite could be used as a highly effective adsorbent for the removal of Ni(II) ions from large volumes of aqueous solution. [ABSTRACT FROM AUTHOR]

Herein, the surface properties of oxidized multiwalled carbon nanotubes (MWCNs) were characterized by adopting XRD, SEM and FTIR. The sorption behaviors of U(VI) from wastewater by oxidized MWCNs were investigated by adopting batch technique. The experimental results demonstrated that sorption behaviors of U(VI) on oxidized MWCNs were dependent on ionic strength at low pH, and independent of ionic strength at high pH. The ion exchange and outer-sphere surface complexation were main mechanism for sorption of U(VI) on oxidized MWCNs at low pH, whereas inner-sphere surface complexation and coinstantaneous co-precipitation were primary mechanism at high pH. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic multiwalled carbon nanotube/iron oxide composite (Fe3O4/MWCNT) was synthesized as an adsorbent for the preconcentration of U(VI) from aqueous solutions. The surface properties of Fe3O4/MWCNT were characterized via adopting FTIR, SEM and potentiometric acid–base titration. The sorption behaviors of U(VI) on the surface of Fe3O4/MWCNT were investigated under environmental conditions by using batch technique, such as pH, ionic strength and contact time. The pH-dependent U(VI) sorption behavior on Fe3O4/MWCNT illustrated that sorption mechanism of U(VI) was achieved by outer-sphere surface complexation at low pH values, while the sorption of U(VI) was achieved by inner-sphere surface complexation and simultaneous precipitation at high pH values. Besides, the pH-dependent sorption also demonstrated an optimal and feasible pH value of 7.0 by adopting Fe3O4/MWCNT in the preconcentration of U(VI) from aqueous solutions. The sorption kinetic experimental data could be well simulated by using the pseudo-second-order pattern. The Langmuir and Freundlich patterns were employed to simulate sorption isotherms of U(VI) at three different temperatures, the experimental results demonstrated that sorption process was favorable at higher environmental temperature. The maximum sorption capacity of U(VI) on Fe3O4/MWCNT was higher than that of major materials reported. Related experimental data further indicated that Fe3O4/MWCNT had satisfactory treatment performance for the simulated wastewater. The Fe3O4/MWCNT particles having strong magnetism could be favorably and easily separated from aqueous solution under an external magnetic field. The correlative experimental results further demonstrated that the Fe3O4/MWCNT composite could be a promising adsorbent for the preconcentration of radionuclides from large volumes of aqueous solution. [Copyright &y& Elsevier]

Abstract: Graphene has been extensively concerned in multidisciplinary research fields due to its remarkably physicochemical characteristics. Herein, magnetic graphene/iron oxides composite (Fe3O4/GO) which was synthesized from graphene using a chemical reaction approach had been employed as a novel adsorbent for the preconcentration and solidification of U(VI) ions from aqueous solutions. The sorption behavior of U(VI) on the surface of Fe3O4/GO was carried out under ambient conditions such as contact time, pH and ionic strength according to concentration of C U(VI)initial =1.12×10−4 mol/L. The Langmuir and Freundlich models were adopted to simulate sorption isotherms of U(VI) at three different temperatures relying on the concentration of C U(VI)initial =2.25×10−5 to 2.24×10−4 mol/L, the experimental results suggested that the sorption reaction was favored at higher temperature. The pH-dependent and ionic strength-independent U(VI) sorption on Fe3O4/GO demonstrated that the sorption mechanism of U(VI) was inner-sphere surface complexation at low pH values, whereas the removal of U(VI) was achieved by simultaneous precipitation and inner-sphere surface complexation at high pH values. The maximum sorption capacity of U(VI) on Fe3O4/GO at T=293K and pH=5.5±0.1 was about 69.49mg/g higher than majority of materials and nanomaterials reported. Magnetic separation has been considered as an effective and quick technique for separating magnetic particles, without filtration and centrifugation. The Fe3O4/GO can be favorably separated from aqueous solution under an applied magnetic field from large volumes of aqueous solutions. The experimental results show that the Fe3O4/GO is a promising adsorbent for the removal of radionuclides and heavy metal ions from large volumes of aqueous solution. [Copyright &y& Elsevier]

To better understand the application of NKF-6 zeolite as an adsorbent for the removal of U(VI) from radionuclides and heavy metal ions polluted water, herein, NKF-6 zeolite was employed to remove U(VI) at different experimental conditions. The influence of solid/liquid ratio, contact time, pH, ionic strength, humic substances and temperature on sorption of U(VI) to NKF-6 zeolite was investigated using batch technique under ambient conditions. The experimental results demonstrated that the sorption of U(VI) on NKF-6 zeolite was strongly dependent on pH. The sorption property of U(VI) was influenced by ionic strength at pH < 7.0, whereas was independent of ionic strength at pH > 7.0. The presence of fulvic acid or humic acid promoted the sorption of U(VI) on NKF-6 zeolite at low pH values while restrained the sorption at high pH values. The thermodynamic parameters (i.e., Δ S, Δ H, and Δ G) calculated from the temperature-dependent sorption isotherms demonstrated that the sorption process of U(VI) on NKF-6 zeolite was endothermic and spontaneous. At low pH values, the sorption of U(VI) was dominated by outer-sphere surface complexation and ion exchange with Na/H on NKF-6 zeolite surfaces, while inner-sphere surface complexation was the main sorption mechanism at high pH values. From the experimental results, one can conclude that NKF-6 zeolite can be used as a potential adsorbent for the preconcentration and solidification of U(VI) from large volumes of aqueous solutions. [ABSTRACT FROM AUTHOR]

To better understand the application of kaolinite as an adsorbent for the decontamination of Ni(II) from radionuclide contaminated aqueous systems, herein, the sorption behavior of radionuclide Ni(II) on kaolinite as a function of contacting time, pH, coexistent electrolyte ions, adsorbent concentration, fulvic acid and humic acid was investigated using batch technique. At low pH values, ion exchange and/or outer-sphere surface complexation was the main mechanism of Ni(II) sorption on kaolinite, whereas, the sorption of Ni(II) was dominated by inner-sphere surface complexation at high pH values. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni(II) on kaolinite to some extent. The Langmuir and Freundlich models were used to simulate the sorption isotherms of Ni(II) at three different temperatures of 288, 313 and 338 K. The thermodynamic parameters (i.e., Δ S°, Δ H°, and Δ G°) calculated from the temperature-dependent sorption isotherms indicated that the sorption reaction of Ni(II) on kaolinite was endothermic and spontaneous. The findings in this present study demonstrates that the kaolinite can be used as a cost-effective adsorbent for the solidification and pre-concentration of Ni(II) from large volumes of aqueous systems. [ABSTRACT FROM AUTHOR]