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

• Published in: Journal of environmental radioactivity Vol. 136; pp. 56 - 63
• Main Authors: Li, Dien, Kaplan, Daniel I, Knox, Anna S, Crapse, Kimberly P, Diprete, David P
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• Subjects: Contamination; Groundwater; Liquids; Sediments; Sorbents; Surfactants; Uptakes; Zeolites
• ISSN: 0265-931X
• DOI: 10.1016/j.jenvrad.2014.05.010

Technetium-99 ( super(99)Tc), iodine-129 ( super(129)I), and cesium-137 ( super(137)Cs) are among the key risk-drivers for environmental cleanup. Immobilizing these radionuclides, especially TcO sub(4) super(-) and I super(-), has been challenging. TcO sub(4) super(-) and I super(-) bind very weakly to most sediments, such that distribution coefficients (K sub(d) values; radionuclide concentration ratio of solids to liquids) are typically <2 mL/g; while Cs sorbs somewhat more strongly (K sub(d) similar to 50 mL/g). The objective of this laboratory study was to evaluate 13 cost-effective sorbents for TcO sub(4) super(-), I super(-), and Cs super(+) uptake from contaminated groundwater and sediments. Two organoclays sorbed large amounts of TcO sub(4) super(-) (K sub(d) > 1 x 10 super(5) mL/g), I super(-) (K sub(d) greater than or equal to 1 x 10 super(4) mL/g), and Cs super(+) (K sub(d) > 1 x 10 super(3) mL/g) and also demonstrated a largely irreversible binding of the radionuclides. Activated carbon GAC 830 was effective at sorbing TcO sub(4) super(-) (K sub(d) > 1 x 10 super(5) mL/g) and I super(-) (K sub(d) = 6.9 x 10 super(3) mL/g), while a surfactant modified chabazite was effective at sorbing TcO sub(4) super(-) (K sub(d) > 2.5 x 10 super(4) mL/g) and Cs super(+) (K sub(d) > 6.5 x 10 super(3) mL/g). Several sorbents were effective for only one radionuclide, e.g., modified zeolite Y had TcO sub(4) super(-)K sub(d) > 2.3 x 10 super(5) mL/g, AgS had I super(-) K sub(d) = 2.5 x 10 super(4) mL/g, and illite, chabazite, surfactant modified clinoptilolite, and thiol-SAMMS had Cs super(+)K sub(d) > 10 super(3) mL/g. These low-cost and high capacity sorbents may provide a sustainable solution for environmental remediation.