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

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 <2 mL/g; while Cs sorbs somewhat more strongly (Kd ∼ 50 mL/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 × 105 mL/g), I− (Kd ≥ 1 × 104 mL/g), and Cs+ (Kd > 1 × 103 mL/g) and also demonstrated a largely irreversible binding of the radionuclides. Activated carbon GAC 830 was effective at sorbing TcO4− (Kd > 1 × 105 mL/g) and I− (Kd = 6.9 × 103 mL/g), while a surfactant modified chabazite was effective at sorbing TcO4− (Kd > 2.5 × 104 mL/g) and Cs+ (Kd > 6.5 × 103 mL/g). Several sorbents were effective for only one radionuclide, e.g., modified zeolite Y had TcO4−Kd > 2.3 × 105 mL/g, AgS had I− Kd = 2.5 × 104 mL/g, and illite, chabazite, surfactant modified clinoptilolite, and thiol-SAMMS had Cs+Kd > 103 mL/g. These low-cost and high capacity sorbents may provide a sustainable solution for environmental remediation.