Nano-hematite prepared by activation of natural siderite and its performance on immobilization of Eu(III)

Nano-hematite was synthesized by calcining siderite (FeCO3) and characterized using TEM, XRD, FT-IR, XPS, specific surface area and potentiometric titration. The characterization results showed that nano-hematite was synthesized by calcining FeCO3 under atmospheric conditions. The batch experiments indicated the adsorption of Eu(III) on nano-hematite significantly increased with increasing pH 2.0-6.0 while the Eu(III) adsorption was independent of ionic strength. The presence of CO32− promoted the adsorption of Eu(III) on nano-hematite over a wide range of pH conditions. The adsorption kinetics and isotherms of Eu(III) on nano-hematite were fitted well by pseudo-second kinetic model and Langmuir model, respectively. The maximum adsorption capacity of Eu(III) on nano-hematite calculated by Langmuir equations was 13.02 mg/g at pH 5.5 and T = 293 K. The desorption experiments revealed that the adsorption of Eu(III) on nano-hematite was an irreversible process. According to the XPS analysis, the oxygen-containing functional groups of nano-hematite (i.e., Fe-OH) played a crucial role in the Eu(III) adsorption. These findings demonstrated that the nano-hematite could be used as a valuable adsorbent for preconcentration and immobilization of Eu(III) from aqueous solutions in the environmental cleanup.