Aqueous 99Tc, 129I and 137Cs removal from contaminated groundwater and sediments using highly effective low-cost sorbents

Abstract

Technetium-99 (99Tc), iodine-129 (129I), and cesium-137 (137Cs) are among the key risk-drivers for environmental cleanup. Immobilizing these radionuclides, especially TcO4- and I-, has been challenging. TcO4- and I-bind very weakly to most sediments, such that distribution coefficients (Kd values; radionuclide concentration ratio of solids to liquids) are typically <2mL/g; while Cs sorbs somewhat more strongly (Kd~50mL/g). The objective of this laboratory study was to evaluate 13 cost-effective sorbents for TcO4-, I-, and Cs+ uptake from contaminated groundwater and sediments. Two organoclays sorbed large amounts of TcO4- (Kd>1×105mL/g), I-(Kd≥1×104mL/g), and Cs+ (Kd>1×103mL/g) and also demonstrated a largely irreversible binding of the radionuclides. Activated carbon GAC 830 was effective at sorbing TcO4- (Kd>1×105mL/g) and I-(Kd=6.9×103mL/g), while a surfactant modified chabazite was effective at sorbing TcO4- (Kd>2.5×104mL/g) and Cs+ (Kd>6.5×103mL/g). Several sorbents were effective for only one radionuclide, e.g., modified zeolite Y had TcO4-Kd>2.3×105mL/g, AgS had I-Kd=2.5×104mL/g, and illite, chabazite, surfactant modified clinoptilolite, and thiol-SAMMS had Cs+Kd>103mL/g. These low-cost and high capacity sorbents may provide a sustainable solution for environmental remediation. © 2014.