Sorption of 137Cs from aqueous solutions onto layered double hydroxides containing the Fe(CN) 6 4− ion in the interlayer space

Abstract

Sorption of 137Cs from aqueous solution onto layered double hydroxides (LDHs) of the composition LDH-M2+-M3+-Fe(CN)6 (M2+ = Mg, Cu, Ni, Zn; M3+ = Al, Fe) was studied. The LDH-Mg-M3+-Fe(CN)6 solid phases (M3+ = Al, Fe) take up 137Cs from 10−5 M aqueous CsNO3 solutions extremely weakly, whereas the LDH-M2+-M3+-Fe(CN)6 solid phases (M2+ = Cu, Ni, Zn; M3+ = Al, Fe) efficiently take up 137Cs. After 15-min contact of the solid and liquid phases, the apparent distribution coefficient K d* of 137Cs ranges from ≈3 × 102 to ≈104 mL g−1 for M2+ = Cu, from ≈4 × 103 to ≈2 × 104 mL g−1 for M2+ = Ni, and from ≈5 × 103 to ≈3 × 104 mL g−1 for M2+ = Zn at V/m = 50 mL g−1. As the NaOH concentration in the solution is increased, the sorption performance of the examined LDHs, except LDH-Ni-Al-Fe(CN)6, drastically decreases, which is due to the formation of LDH-M2+-M3+-OH (M2+ = Ni, Zn; M3+ = Al, Fe) having low ability to take up 137Cs.