Simulated Radioactive Solutions Research Articles

Effective adsorption of metal ions by modified clinoptilolite zeolite from simulated radioactive solution

A natural clinoptilolite zeolite was modified through high temperature and chemical process to use for adsorption Mn2+, Ni2+, Co2+ and Cs+ from simulated radioactive solution. A series of analyses techniques including SEM, XRD and FTIR were applied to characterize the modification samples. The adsorption and kinetics were finely described by Langmuir isotherms and the pseudo second-order model. The adsorption rate constants denoted the adsorption rate had the following priority: Cs+ > Mn2+ > Ni2+ > Co2+. The thermodynamic parameters denoted that the adsorption of Mn2+, Ni2+, and Co2+ onto the modification sample were endothermic processes, and that of Cs+ was an exothermic process.

Removal of U(VI) from Nuclear Waste Solutions by Bio-sorbents

Six bio-sorbents were used to remove uranium from simulated radioactive solutions UO2(NO3)2. Three types of peats, Polytrichium moss, Eichhórnia crássipes water plant and Cladonia stellaris lichen were used. About 2.7mg of uranium per 1g of sorbent was found in the peat samples after their interaction with UO2(NO3)2 solution (uranium initial concentration was 26mg/L, pH 4.4) during 24hours. Polytrichium moss, Cladonia stellaris lichen and Eichhórnia crássipes water plant were less effective: 2.3, 2.1 and 0.6mg of uranium per g of the sorbent respectively. The sorption on the peats is described by Freundlich isotherm. Numerous spherical compounds containing uranium 10 nanometers in diameter were found in the newly formed biotic sediments on the Polytrichium moss after the experiment.

Adsorption of thorium(IV) from simulated radioactive solutions using a novel electrospun PVA/TiO2/ZnO nanofiber adsorbent functionalized with mercapto groups: Study in single and multi-component systems

The novel polyvinyl alcohol/titanium oxide/zinc oxide (PVA/TiO2/ZnO) nanofiber adsorbent functionalized with 3-mercaptopropyltrimethoxysilane (TMPTMS) was prepared by electrospinning method and its potential was investigated for the adsorption of thorium from single and multi-metal aqueous solutions. The prepared adsorbent was characterized by FTIR, SEM and BET analysis. The influences of different operational parameters such as pH, ionic strength, equilibrium time, initial concentration and temperature were studied in batch mode. Investigation of ionic strength effect showed that the addition of NaNO3 to metal solution has a slight effect on the thorium adsorption, whereas pH value has a serious effect on the thorium adsorption at pH values lower than 4. The double-exponential model described the adsorption of Th(IV) ions much better than other kinetic models within both the single and multi-component systems. Among various isotherm models used, the equilibrium data of Th(IV) conformed the Langmuir isotherm in the single system, while those were best fitted by Dubinin–Radushkevich (D-R) isotherm in multi-component system. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° indicated that the nature of adsorption process was spontaneous, endothermic and thermodynamically favored. The inhibitory effect of other metal ions on the adsorption capacity of Th(IV) was in order of Al(III)>Cu(II)>Cd(II)>Ni(II)>U(VI)>Fe(II).

Adsorption characteristics of UO 22+ and Th 4+ ions from simulated radioactive solutions onto chitosan/clinoptilolite sorbents

Adsorption features of UO 2 2+ and Th 4+ ions from simulated radioactive solutions onto a novel chitosan/clinoptilolite (CS/CPL) composite as beads have been investigated compared with chitosan cross-linked with epichlorohydrin. The effects of contact time, the initial metal ion concentration, sorbent mass and temperature on the adsorption capacity of the CS-based sorbents were investigated. The adsorption kinetics was well described by the pseudo-second order equation, and the adsorption isotherms were better fitted by the Sips model. The maximum experimental adsorption capacities were 328.32 mg Th 4+/g composite, and 408.62 mg UO 2 2+/g composite. The overall adsorption tendency of CS/CPL composite toward UO 2 2+ and Th 4+ radiocations in the presence of Cu 2+, Fe 2+ and Al 3+, under competitive conditions, followed the order: Cu 2+ > UO 2 2+ > Fe 2+ > Al 3+, and Cu 2+ > Th 4+ > Fe 2+ > Al 3+, respectively. The negative values of Gibbs free energy of adsorption indicated the spontaneity of the adsorption of radioactive ions on both the CS/CPL composite and the cross-linked CS. The desorption level of UO 2 2+ from the composite CS/CPL, by using 0.1 M Na 2CO 3, was around 92%, and that of Th 4+ ions, performed by 0.1 M HCl, was around 85%, both values being higher than the desorption level of radiocations from the cross-linked CS, which were 89% and 83%, respectively.