Chemical modifications of chitosan nano-based magnetic particles for enhanced uranyl sorption

The grafting of diethylenetriamine (preferentially to the grafting of serine > cysteine > alanine) onto chitosan (immobilized on magnetic nano-based particles by combined polymer precipitation and hydrothermal treatment) allows synthesizing an efficient sorbent for uranyl at pH 4 (maximum sorption capacity close to 185 mg U g(-1)). Sorption isotherm (regardless of the sorbent) is fitted by the Langmuir equation, while uptake kinetics is well described by the pseudo-second order rate equation. The design of nano-based particles (10-50 nm) allows reducing the impact of resistance to intraparticle diffusion on uptake kinetics and the equilibrium contact time is close to 45-60 min. The super paramagnetic properties of the hybrid materials make their solid/liquid separation quite easy using an external magnetic field. Finally uranyl ions can be desorbed using acidic urea solution (0.5 M, pH >2) and the sorbents can be recycled for at least 5/6 cycles with a limited loss of sorption capacity (<9%). (C) 2016 Elsevier B.V. All rights reserved.