Synthesis and characterization of magnetic mesoporous FeO@mSiO-DODGA nanoparticles for adsorption of 16 rare earth elements.

In this study, novel magnetic mesoporous FeO@mSiO-DODGA nanoparticles were prepared for efficiently adsorbing and recycling REEs. FeO@mSiO-DODGA was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The adsorption behavior of FeO@mSiO-DODGA was investigated by ICP-OES. The results showed that the content of DODGA in the adsorbent was 367 μmol g. FeO@mSiO-DODGA exhibited the highest adsorption rates for 15 REEs, except Tm, in a 2 mol L nitric acid solution. Among these elements, the adsorption rates for Nd, Sm, Eu, Dy, Ho, Yb, Lu, Y and Sc ranged from 85.1% to 100.1%. The desorption rates for all 16 REE ions reached their maximum values when 0.01 mol L EDTA was used as the eluent. The desorption rates for Nd, Ce, Sm, Eu, Ho, Yb, Lu, Y, and Sc were 87.7-99.8%. FeO@mSiO-DODGA had high stability in 2 mol L HNO and could be used five times without significant loss of adsorption capacity. Moreover, these nanoparticles had high selectivity, and their adsorption rate was not affected even in a high-concentration solution of a coexisting ion. Therefore, 8 REE ions (Nd, Sm, Eu, Ho, Yb, Lu, Y, and Sc) were selected for the study of adsorption kinetics and adsorption isotherm experiments. It was demonstrated that the values of (equilibrium adsorption capacity) for Nd, Sm, Eu, Ho, Yb, Lu, Y, and Sc were 14.28-60.80 mg g. The adsorption of REEs on FeO@mSiO-DODGA followed the pseudo-second-order kinetic model, Elovich model and Langmuir isotherm model, which indicated that the adsorption process of FeO@mSiO-DODGA for REEs comprised single-layer adsorption on a non-uniform surface controlled by chemical adsorption. It was concluded that FeO@mSiO-DODGA represents a new material for the adsorption of REEs in strongly acidic solutions.