Uranium adsorption by polyvinylpyrrolidone/chitosan blended nanofibers

PVP/chitosan blended nanofibers have been prepared and investigated as adsorbent material for the removal of hexavalent uranium (U(VI)) from aqueous solutions. The nanofibers have been characterized prior and after U(VI) adsorption by SEM and FTIR measurements, and the effect of various parameters such as metal-ion concentration temperature and contact time on the adsorption efficiency has been investigated by batch-type experiments. The material presents increased sorption capacity (q_max= (167 ± 25) g kg^-1 at pH 6.0) and increased chemical affinity for U(VI), which is attributed to the fibrous structure of the material and the presence of polar groups (e.g. carbonyl groups) on the blended nanofibers. FTIR spectroscopic measurements indicate the formation of inner sphere complexes between U(VI) and the surface moieties, and thermodynamic and kinetic data reveal a relatively fast (k₁ = 0.01 min^-1), entropy-driven process (ΔH^o = 56.3 kJ mol^-1 and ΔS^o = 293.7 J K^-1 mol^-1). Recycling experiments have shown that the material can be used up to four times with less than 10% efficiency loss.