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Nanobased magnetic particles are synthesized by a one-pot hydrothermal precipitation of chitosan in the presence of iron­(II) and iron­(III) salts. The material is then chemically modified by grafting alanine and serine amino acids. These materials are characterized by elemental analysis, FTIR spectrometry, XRD analysis, TEM observations, and VSM (vibrating-sample magnetometry). In a second step, these materials are tested for uranium­(VI) sorption. The effect of pH on sorption performance is first investigated before evaluating uptake kinetics (which are fitted by the pseudo-second-order rate equation) and sorption isotherms (which are modeled by the Langmuir equation). Metal desorption and sorbent recycling are finally carried out for five successive cycles of sorption/desorption. Thermodynamic parameters are determined by investigating sorption properties at different temperatures. Maximum sorption capacities reach 85 and 116 mg U g–1 for alanine- and serine-based sorbents, respectively. The magnetic properties of the particles allow their efficient separation from the solution by external magnetic field.

The recovery of three rare earth (RE) metals ions [Yb(III), Dy(III) and Nd(III), belonging to heavy, mild and light REs, respectively] was investigated using hybrid chitosan-magnetic nano-based particles functionalized by diethylenetriamine (DETA). The effect of pH on sorption performance was analyzed: the optimum initial pH value was found close to 5 (equilibrium pH value close to 6.5). The nanometric size of sorbent particles (30-50 nm) minimized the contribution of resistance to intraparticle diffusion on the control of uptake kinetics, which is efficiently modeled using the pseudo-second order rate equation: under selected experimental conditions the contact time required for reaching equilibrium was less than 1 h. Sorption isotherms were efficiently modeled using the Langmuir equation: maximum sorption capacities reached about 50 mg metal g -1 , regardless of the RE. The temperature had a very limited effect on sorption capacity (in the range 300-320 K). The thermodynamic parameters were determined: the sorption was endothermic (positive values of DH°), spontaneous (negative values of DG°) and contributed to increasing the disorder of the system (positive values of DS°). The three REs have similar sorption properties on DETA-functionalized chitosan magnetic nano-based particles: the selective separation of these elements seems to be difficult. The sorbed metal ions can be removed from loaded sorbents using thiourea, and the sorbent can be recycled for at least five sorption/desorption cycles with a limited loss in sorption performance (by less than 6 %). The saturation magnetization was close to 20 emu g -1 ; this means that nano-based superparamagnetic particles can be readily recovered by an external magnetic field, making the processing of these materials easy.