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).