Effects of contact time, pH, and temperature on Eu(III) sorption onto MX-80 bentonite

Abstract

MX-80 bentonite is considered a popular buffer/backfill material for the construction of artificial barriers. In particular, it plays an important role in the disposal of high-level nuclear waste in deep geological repositories. In the present study, the sorption of Eu(III) on MX-80 bentonite was investigated using a batch technique; furthermore, a comprehensive analysis was performed on the influence of contact time, pH, temperature, and concentration on sorption. The results showed that the sorption regime leveled off within 30 min and the Eu(III) sorption capacity of MX-80 bentonite was approximately 46.06 mg/g under certain conditions. A second-order kinetic equation was used to fit the equilibrium sorption data. Additionally, the variation in the sorption capacity of MX-80 bentonite increased as the pH increased from 1 to 9. The optimum pH value was determined to be 7.0 at a temperature of 293.15 K. The negative value of enthalpy change (ΔH°) indicates that the temperature had a negative effect on the sorption. The sorption process was most accurately described by the Langmuir isotherm model. These results will definitely be benefit to the artificial barriers in the disposal of high-level nuclear waste.