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In recent years, hazardous radionuclides and heavy metal ions contaminations in wastewaters have caused serious harm to the public and environment. Thus the application of remediation technology is more challenging. Herein, carboxymethyl cellulose supported magnetic graphene oxide composites (CMC/MGOs) are successfully synthesized using novel low temperature plasma technique. The SEM, TEM, XRD, FTIR, TGA and Raman spectra analysis can provide favorable evidence for the successful addition of CMC onto MGOs composite surfaces. The kinetics and isotherms of sorption of U(VI) onto CMC/MGOs composites can be excellently simulated by the pseudo-second-order kinetics model and the Langmuir model, respectively. The maximum capacity of CMC/MGOs composites for U(VI) calculated from the Langmuir model at pH 5.5 and 301 K is 7.94 × 10−4 mol/g. The experimental data indicate that uranium ions can interact with CMC/MGOs through inner-sphere surface complexation over the entire range of pH values. The experimental results suggest that CMC/MGOs composites can be regarded as potential adsorbent to remove uranium ions from wastewater systems. [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]

A synthetic zeolite, commercially available as permutite was tested for removing radiocobalt from aqueous solutions by sorption. The sorption process was studied as a function of contact time, pH, ionic strength and solid content by batch technique. The results revealed that the process is dependent on the pH and ionic strength under ambient conditions. The kinetic sorption was fitted well by a pseudo-second-order rate equation. The thermodynamic parameters (Δ H, Δ S, Δ G) suggested that sorption behavior of Co(II) is a spontaneous and endothermic process. The study shows that permutite has excellent potential for disposal of wastewaters containing radiocobalt. [ABSTRACT FROM AUTHOR]

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]

In this study, the removal of radionuclide Co(II) from wastewater by Ca-rectorite was studied as a function of various environmental parameters such as contact time, pH, ionic strength, coexisting electrolyte ions, humic substances (HS) and temperature under ambient conditions. The results indicated that the sorption of Co(II) on Ca-rectorite was strongly dependent on pH and ionic strength. The Langmuir and Freundlich models were used to simulate the sorption isotherms of Co(II) at three different temperatures of 298.15, 318.15 and 338.15 K. The thermodynamic parameters ( $$ \Updelta H^{0} ,\,\Updelta S^{0} $$ and $$ \Updelta G^{0} $$) calculated from the temperature-dependent sorption isotherms indicated that the sorption process of Co(II) on Ca-rectorite was spontaneous and endothermic. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange with Ca/H on Ca-rectorite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that Ca-rectorite has good potentialities for cost-effective disposal of radiocobalt bearing wastewaters. [ABSTRACT FROM AUTHOR]