Immobilization of selenium on Fe3O4 and Fe/FeC3 ultrasmall particles


Immobilization of selenium on Fe3O4 and Fe/FeC3 ultrasmall particles

López De Arroyabe Loyo, R.; Nikitenko, S.; Scheinost, A.; Simonoff, M.

Magnetic nanoparticles, NPs, have a number of features that make them ideally suited for the removal of toxic elements from liquid waste: high surface-area-to-volume ratio, high reactivity, easy dispersability, and simple recovery of the particles from solution using an external magnetic field. In this paper we studied the sorption of selenite ions onto Fe3O4 and Fe/Fe3C NPs in the aqueous solutions under anoxic conditions. The results show that Se(IV) sorption is extremely rapid : the equilibrium is reached in approximately 10 and 30 min for Fe3O4 and Fe/Fe3C NPs respectively at pH= 4.9÷5.1 in the solutions of 0.1M NaCl. The distribution coefficients are also very high for both kinds of NPs (Kd> 3000). Increasing pH to 10.3 or adsorption of organic ligands, like L-Lysine or dodecanoate, cause the decrease in Kd values. However, even in these cases Kd values exceed 150. Magnetic NPs loaded with selenium can be easily and completely removed from solution with 0.4T permanent magnet. XAS study revealed the absence of Se(IV) reduction during the sorption onto Fe3O4 NPs in the pH range of 4.8-8.0. By contrast, the removal of selenite ions with Fe/Fe3C NPs in anaerobic conditions occurs via Se(IV) reduction to Se(-II) followed by formation of iron selenide at the particles surface. Thus, the Fe/Fe3C NPs are superior to Fe3O4 NPs due to their ability to immobilize rapidly selenium via reductive mechanism. Presumably these particles could be also effective for the removal of other contaminants such as hexavalent chromium, actinides, technetium, and toxic organic compounds.

  • Environmental Science & Technology 42(2008)7, 2451-2456

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Publ.-Id: 10645