Removal of Eu(III) from aqueous solution using ZSM-5 zeolite

ZSM-5 zeolite is characterized by XRD, FT-IR and acid–base titration in detail. The results show that the sorption site distribution of ZSM-5 zeolite is affected by ionic strength obviously; the main sorption site are =XNa, =SOH and =SO− in all pH ranges. The sorption experiments of Eu(III) on ZSM-5 zeolite indicate that the sorption is strongly dependent on pH value and on ionic strength (ranged from I = 0.001 to 0.05 mol/L NaClO4) under ambient conditions. The sorption edges of Eu(III) on ZSM-5 zeolite in 0.1 and 0.01 mol/L NaClO4 and the sorption isotherm in 0.01 mol/L NaClO4, respectively, were modeled using a quasi-mechanistic sorption model (1-site protolysis non electrostatic surface complexation and cation exchange (1-SPNE SC/CE) model). The Eu(III) sorption edges in different ionic strengths could be modeled in the pH range 3–10 using cation exchange reactions for Eu3+/Na+ and three surface complexation reactions on the sorption sites by forming =SOEu, =SOEu(OH)+ and =SOEu(OH)2 inner-sphere surface complexes successively. The Eu(III)/ZSM-5 zeolite EXAFS analysis indicates that Eu(III) on ZSM-5 zeolite can be simulated (R = 0.045) by assuming a number of coordination oxygen N = 7.7(5) at d(Eu–O) = 2.31Å (σ = 0.01 Å).