Dy(III) recovery from dilute solutions using magnetic-chitosan nano-based particles grafted with amino acids

Magnetic-chitosan nano-based particles were successfully prepared by a simple one-pot co-precipitation method before being functionalized with three different amino acid groups (i.e., alanine, serine, and cysteine) using epichlorohydrin as the linking agent. The structural and functional characteristics of the nanosorbents were investigated by elemental analysis, Fourier transform infrared spectrometer, X-ray diffraction, TEM, and vibrating sample magnetometry. The sorption properties of these materials were tested for Dy(III) recovery from aqueous solution: pH effect, uptake kinetics, and sorption isotherms were investigated. Sorbent particles are super-paramagnetic and their size is in the range of 15–40 nm. Kinetic profiles are successfully modeled with the pseudo second-order rate equation. The Langmuir and the Dubinin–Radushkevich equations fit well-sorption isotherms. The maximum sorption capacities at pH 5 (optimum pH, and at T: 27 ± 1 °C) are close to 14.8, 8.9, and 17.6 mg Dy g⁻¹ for alanine, serine, and cysteine type, respectively. Cationic species RE(III) in aqueous solution appear to be sorbed by combined chelation and anion-exchange mechanisms. The sorption process begins at low-metal concentration by a physical monolayer sorption at low ion concentration before metal ions can be sorbed at higher metal concentration by coordination. The values of the thermodynamic parameters ΔG° and ΔH° indicate the spontaneous and endothermic nature of the mechanism, while the positive values of ΔS° show that during the sorption process the randomness increases. Finally, the sorbent can be efficiently regenerated using acidified thiourea: the amount of Dy(III) sorbed is hardly reduced, at least during the first four sorption/desorption cycles.