Recovery of uranyl from aqueous solutions using amidoximated polyacrylonitrile/exfoliated Na-montmorillonite composite

• Na-Mont–APAN was synthesized and characterized using FT-IR, XRD, TEM, and CHN.
• Na-Mont–APAN exhibited high salt-tolerance, and selectivity for uranyl.
• The adsorption equilibrium can be attained within 30 min at pH 4.0–5.5.
• The adsorption process was endothermic and spontaneous.
• A dominant binding mechanism of η2 coordination was proposed.

A novel material, amidoximated polyacrylonitrile/exfoliated Na-montmorillonite composite (Na-Mont–APAN) was synthesized and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), CHN analysis, and potentiometric titration. The material was nonporous, amidoximated, montmorillonite-exfoliated and expected to be used for the recovery of uranyl from aqueous solutions. Effects of pH, contact time, temperature and background electrolyte on the adsorption were investigated. The results showed that the adsorption process strongly depended on pH and ionic strength, fitted well with Langmuir model and presented endothermic, spontaneous properties. The prepared material exhibited high adsorption capacity (736 mg/g at pH 4.0 and 318 K) and excellent selectivity for uranyl, indicating a potential application in the recovery/removal of uranyl from aqueous solutions. The binding mechanism of uranyl with Na-Mont–APAN was demonstrated with the help of FT-IR, XPS and Ruranyl/AO. As a result, a dominant binding mode i.e. η2 coordination was proposed.