Separate or Simultaneous Removal of Radioactive Cations and Anions from Water by Layered Sodium Vanadate-Based Sorbents

Nanofibers of sodium vanadate, consisting of very thin negatively charged layers and exchangeable sodium ions between the layers, are efficient sorbents for the removal of radioactive 137 Cs + and 85 Sr 2+ cations from water. The exchange of 137 Cs + or 85 Sr 2+ ions with the interlayer Na + ions eventually triggered structural deformation of the thin layers, trapping the 137 Cs + and 85 Sr 2+ ions in the nanofibers. Furthermore, when the nanofibers were dispersed in a AgNO 3 solution at pH >7, well-dispersed Ag 2 O nanocrystals formed by firmly anchoring themselves on the fiber surfaces along planes of crystallographic similarity with those of Ag 2 O. These nanocrystals can efficiently capture I – anions by forming a AgI precipitate, which was firmly attached to the substrates. We also designed sorbents that can remove 137 Cs + and 125 I – ions simultaneously for safe disposal by optimizing the Ag 2 O loading and sodium content of the vanadate. This study confirms that sorbent features such as fibril morphology, negatively charged thin layers and readily exchangeable Na + ions between the layers, and the crystal planes for the formation of a coherent interface with Ag 2 O nanocrystals on the fiber surface are very important for the simultaneous uptake of cations and anions.