Synthesis of bi-functional chelating sorbent for recovery of uranium from aqueous solution: sorption, kinetics and reusability studies

A bi-functional chelating sorbent is synthesised by introducing two different functionalities (amine and amidoxime groups) subsequently on the surface of an earlier synthesized cross-linked poly-acrylonitrile beads. The cross-linked base polymer beads are normally synthesised through suspension polymerisation using acrylonitrile and styrene as monomers and divinyl benzene as cross-linking agent. The bi-functionality is introduced by amination of base polymer in the first step by reacting with diethylenetriamine followed by amidoximation reaction with hydroxylamine hydrochloride in the second step. The incorporation of functional groups on beads are identified and confirmed with FTIR spectroscopy while the surface morphology, porosity and pores dimensions are evaluated by SEM and BET techniques. The saturation sorption capacity of synthesized beads for uranyl ion is tested and found ~ 45 mg g⁻¹, which is significantly higher than the beads functionalized with sole amidoxime group. These bi-functional beads are quite efficient over a wide pH (1–10) range. The kinetics measurements indicate that the synthesized sorbents reach its saturation sorption capacity within 2 h at ~25 °C under neutral pH. In this study, the sorbed uranyl ions are eluted out with 1 M HCl efficiently. These beads exhibit excellent reusability up to three cycles without losing much of its capacity, suggesting better usability in real samples.