Uranium(VI) and zirconium(IV) sorption on magnetic chitosan derivatives – effect of different functional groups on separation properties

International audienceBACKGROUNDThe recovery of metal ions from aqueous solutions for environmental preservation or resource saving requires the development of new sorbents with enhanced separation properties. A new process has been designed for the functionalization of magnetic chitosan microparticles with grafting of either amidoxime (AO‐AHC) or hydrazinyl amine (HZ‐AHC). Their sorption properties have been tested for the recovery of uranium(VI) and zirconium(IV) from aqueous solutions.RESULTSA wide range of analytical tools is used for characterizing not only the chemical modifications but also the interaction mode between the sorbent and target metal ions; including elemental analysis and titration, Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) characterizations, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations, energy‐dispersive X‐ray spectroscopy (EDX) analysis and textural characterization. The optimum pH values were found in the range 4–5. The maximum sorption capacities depend on the metal and the kind of functionalization: up to 1.38 mmol U g−1 for AO‐AHC and up to 1.96 mmol Zr g−1 for HZ‐AHC. The small size of magnetic particles limits the contribution of diffusion mechanisms in the overall control of uptake kinetics and the equilibrium is reached within 40–60 min. Metal desorption is highly effective (almost quantitative over five successive cycles of sorption and desorption) using 0.3 M hydrochloric acid solutions.CONCLUSIONAO‐AHC sorbent is more selective than HZ‐AHC in terms of separation of uranium(VI) from zirconium(IV), especially at pH close to 4. The results obtained in the treatment of acidic ore leachates confirm these trends