Selective Extraction of Heavy and Light Lanthanides from Aqueous Solution by Advanced Magnetic Nanosorbents

Huijin Zhang, Rocklan G. Mcdowell, Leigh R. Martin, You Qiang

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76 Scopus citations

Abstract

Rare earth elements (REEs) make unique and vital contributions to our current world of technology. Separating and recycling REEs is of great importance to diversify the sources of REEs and advance the efficient use of REE resources when the supply is limited. In light of separation nanotechnology, diethylenetriamine-pentaacetic acid (DTPA) functionalized magnetic nanosorbents have been synthesized and investigated for the highly selective extraction of heavy (Sm-Ho) and light (La-Nd) lanthanides (Ln) from aqueous solutions. The results demonstrated that the separation factor (SF) between heavy-Ln and light-Ln groups reached the maximal value of 11.5 at low pH value of 2.0 in 30 min. For example, the SFs of Gd/La and Dy/La pairs were up to 10 times higher than that reported by other studies. Besides the excellent selectivity, our double-coated magnetic nanoparticles coupled with diethylenetriaminepentaacetic acid (dMNP-DTPA) nanosorbents are more advantageous in that the Ln(III) sorption was effectively and quickly (in 30 min) achieved in acid solutions with pH values as low as 2.0. Such attributes ensure a stronger adaptability to the harsh environments of REE recycling processes. Displacement phenomena were subsequently observed between the heavy-Ln and light-Ln ions that were coexisting in solution and competing for the same sorption sites, causing the increase in sorption capacity of heavy Ln on the surface of nanosorbents with time. The order of affinity of Ln(III) to DTPA-functionalized magnetic nanosorbents perfectly followed the corresponding stability constants between Ln(III) and nonimmobilized DTPA. Displacement phenomena and lanthanide contraction, as well as the surface nanostructures of DTPA-functionalized nanosorbents, significantly improved the separation factors of heavy-Ln/light-Ln pairs. The Ln(III) interaction with DTPA-functionalized magnetic nanosorbents followed the pseudo-second-order kinetics with a correlation coefficient extremely high and close to unity.

Original languageEnglish
Pages (from-to)9523-9531
Number of pages9
JournalACS Applied Materials and Interfaces
Volume8
Issue number14
DOIs
StatePublished - Apr 27 2016
Externally publishedYes

Funding

This work is financially supported by U.S. Department of Energy (DOE) under contract no. DE-FC07-08ID14926 and DOE INL-CAES LDRD under contract no. DE-AC07-05ID14517 at the University of Idaho as well as under Chinese 111 Research Project no. B13029. The authors thank Dr. YQ Wu from Center for Advanced Energy Studies, Idaho Falls, for the help in TEM characterization.

Keywords

  • magnetic nanoparticles
  • magnetic separation
  • nanosorbents
  • rare earth elements
  • selective sorption
  • trivalent lanthanides

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