Synthesis and characterization of magnetic mesoporous Fe3O4@mSiO2–DODGA nanoparticles for adsorption of 16 rare earth elements?

RSC Advances Pub Date: 2018-11-22 DOI: 10.1039/C8RA07762B

Abstract

In this study, novel magnetic mesoporous Fe3O4@mSiO2–DODGA nanoparticles were prepared for efficiently adsorbing and recycling REEs. Fe3O4@mSiO2–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 Fe3O4@mSiO2–DODGA was investigated by ICP-OES. The results showed that the content of DODGA in the adsorbent was 367 μmol g?1. Fe3O4@mSiO2–DODGA exhibited the highest adsorption rates for 15 REEs, except Tm, in a 2 mol L?1 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?1 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%. Fe3O4@mSiO2–DODGA had high stability in 2 mol L?1 HNO3 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 Qe (equilibrium adsorption capacity) for Nd, Sm, Eu, Ho, Yb, Lu, Y, and Sc were 14.28–60.80 mg g?1. The adsorption of REEs on Fe3O4@mSiO2–DODGA followed the pseudo-second-order kinetic model, Elovich model and Langmuir isotherm model, which indicated that the adsorption process of Fe3O4@mSiO2–DODGA for REEs comprised single-layer adsorption on a non-uniform surface controlled by chemical adsorption. It was concluded that Fe3O4@mSiO2–DODGA represents a new material for the adsorption of REEs in strongly acidic solutions.

Graphical abstract: Synthesis and characterization of magnetic mesoporous Fe3O4@mSiO2–DODGA nanoparticles for adsorption of 16 rare earth elements
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