Selective capture of uranium and zirconium from strong HNO3 solution by ethenylphosphonic acid copolymerized polymer

Abstract

The nuclear fuel rod contains mainly uranium (U) as the fuel and zirconium (Zr) as the cladding material. Improper disposition of the dissolved solution of the exhausted fuel rod releases radioactive acidic aqueous solution, which is a waste of U and Zr resources and also poses a great threat to the environment and living beings. The present work aims to selectively capture U and Zr from a 4 mol/L HNO3 aqueous solution in the presence of competing ions including La, Zn, Cd, Gd, Ce, Sr, Mn, Cu and Ba. Trimethylolpropane trimethacrylate (TMPTMA) copolymerized with ethenylphosphonic acid (EPA). TMPTMA improved the mesoporous character and adsorption ability of the adsorbent towards U and Zr. The synthesized polymer adsorbent was characterized by SEM, EDS, FT-IR, TGA, XRD, BET, XPS, and NMR to study the adsorption. The results indicated that the EPA-POP-2 adsorbent showed considerable adsorption capacity towards U(VI) (374.1 mg g−1) and Zr(IV) (217.4 mg g−1) in a strong HNO3 medium. Langmuir isotherm model fitted well to the experimental data, indicating that the monolayer adsorption process was dominating. The fitted pseudo-second-order (PSO) model represents that the adsorption mechanism is chemisorption. XPS, FT-IR, and DFT calculation results revealed that this adsorption capacity towards U and Zr was because of the P = O ligands present in the adsorbent. Van’t Hoff graph for U and Zr were also drawn to calculate the enthalpy, entropy, and Gibb’s free energy of the reaction. The reusability test showed that the adsorption capacity of synthesized adsorbent was high enough towards the U and Zr even after five consecutive cycles of adsorption and desorption.