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A novel adsorbent of magnetic graphene oxide/chitosan (MGOC) composite has been prepared via chemical cross-linking method, and exhibits an extraordinary sorption capacity (about 59.82 mg/g) towards cobalt ions. The batch experiments revealed that MGOC is weakly affected by ionic strength and pH-dependent for cobalt ions sorption. The sorption process is spontaneous and endothermic according to thermodynamic parameters, following the pseudo-second-order model. In view of low price, high adsorption capacity, great saturation magnetization and perfect reusability, the MGOC composite maybe has a potential value in treatment of radiocobalt-containing wastewater. [ABSTRACT FROM AUTHOR]

Chitosan-clinoptilolite composite was prepared and tested for removing radiocobalt from aqueous solution. The composite was characterized with Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy coupled with energy dispersive X-ray analysis. The sorption of Co(II) on chitosan-clinoptilolite composite was pH-dependent and ionic strength-independent. The kinetic sorption was fitted well by a pseudo-second-order rate equation. The thermodynamic parameters (Δ H, Δ S, Δ G) revealed that the sorption of Co(II) on chitosan-clinoptilolite composite was spontaneous and endothermic. The study showed that chitosan-clinoptilolite composite had excellent potential for the treatment of wastewater containing radiocobalt. [ABSTRACT FROM AUTHOR]

A systematic investigation of the transport of I in compacted GMZ bentonite containing Fe-Oxides, Fe-minerals or CuO additive was carried out by through-diffusion method. The obtained results indicate that all of the additives have positive effects on retarding the I diffusion in compacted GMZ bentonite. Especially for the CuO additive, the corresponding effective diffusion coefficient is greatly reduced. It is mainly attributed to the particular interactions between the metal ions introduced by additives and iodide ions. [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]

Humic acid is ubiquitous in soils and water. It affects the migration of radionuclides by complexation or redox reactions. The effect of humic acid on the diffusion of ReO in GMZ bentonite was investigated at dry density from 1,300 to 1,800 kg/m. The effective diffusion coefficient D and rock capacity factor α were measured by through-diffusion method. The D decreased from 5.5 to 0.59 × 10 m/s and α decreased from 0.2 to 0.12 with the dry density increasing from 1,300 to 1,800 kg/m. The retardation factor R in GMZ bentonite at three dry densities was obtained, which were less than one. Archie's law was used to describe the relationship between accessible porosity ε and D. An empirical parameter n ( n = 2.2 ± 0.2) was obtained for Re diffusion in GMZ bentonite in the presence of humic acid. [ABSTRACT FROM AUTHOR]

The sorption behavior of Se(IV) on Fe- and Al-modified bentonite is studied through batch experiments. In order to introduce active centers for Se(IV) sorption, bentonite was modified with iron, iron oxocations and aluminum oxocations at 400, 600 and 800 °C. It was found that calcined temperature had great effect on the sorption with above 80 % sorption at 400 °C, whereas with only 5 % sorption at 800 °C. The sorption capacities for Se(IV) were 112.5 mg/g by FeOH-B, 60.1 mg/g by AlOH-B and 71.9 mg/g by Fe-B, respectively. The pH-dependent and ionic strength-independent Se(IV) sorption on these modified bentonites demonstrated that the sorption mechanism of Se(IV) was inner-sphere surface complexation at low pH values. [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]

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]