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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #419336
Research Project: Innovative Manure Treatment Technologies and Enhanced Soil Health for Agricultural Systems of the Southeastern Coastal Plain

Location: Coastal Plain Soil, Water and Plant Conservation Research

Title: Uptake of technetium and iodine (I-, IO3- and organo-I) by pecan biochar

Author
item LIN, PENG - University Of Georgia
item FERGUSON, BRENNAN - University Of Georgia
item GREENE, KAREN - University Of Georgia
item XING, WEI - University Of Georgia
item XU, CHEN - Texas A&M University
item BAGWELL, CHRISTOPHER - Pacific Northwest National Laboratory
item Watts, Donald
item KAPLAN, DANIEL - University Of Georgia

Submitted to: Journal of Environmental Radioactivity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: When found as an environmental contaminant, radionuclides (unstable chemical elements that release radiation as they decay), can pose a risk to human health. To reduce the risks posed by these elements, technologies need to be evaluated for their potential to bind and immobilize radionuclides in the environment, thereby reducing their bioavailability. This study examined the potential of biochar, a carbon-rich material often used as a remediation tool, to bind to two radionuclides, iodine-129 and technetium-99. Biochars were created by treating pecan shells, an agricultural waste product, at high temperatures followed by an acid activation. Analysis of the biochars indicate that they were capable of binding both radionuclides. These results demonstrate that biochars, created from easily accessible agricultural residues, can be created and deployed to clean up contaminants of concern, thereby reducing risks to the environment and human health.

Technical Abstract: Remediation of land and groundwater that is contaminated with anionic-radionuclides, such as iodine-129 (I-129) and technetium-99 (Tc-99), which are high risk drivers, remains an intractable problem. The objective of this study was to evaluate biochar materials as a low-cost and highly effective sorbent that could be used at contaminated sites for the sequestration of Tc-99 and three iodine species, iodide, iodate, and organic iodine. Batch studies were conducted with biochar derived from pecan shells, a local agricultural by-product, that underwent two pyrolysis temperatures (500ºC and 700ºC) and two types of acid-activation (H3PO4 and HCl). Acid-activated biochar had much higher sorption capacities (in terms of distribution coefficient, Kd, Csolid/Caq) for Tc-99 and different iodine species, than non-acid-activated biochar. The H3PO4-activated biochar (500ºC) was the most effective sorbent for Tc-99 Kd of 49,390±14,268 mL/g, iodide Kd of 2,433±312 mL/g, iodate Kd of 410±168 mL/g, and organic iodine Kd of 857±181 mL/g. For context, most soils have I and Tc Kd values <5 mL/g. The HCl-activated biochar (700ºC) was also effective at sequestering Tc-99 (Kd of 7,864±5,585 mL/g) and iodide (Kd of 2,481±237 mL/g) but not for iodate/organic iodine. Solid-state 13C-nuclear magnetic resonance (NMR) analysis suggested that the strong sorption capacity for these two biochars may be due to the formation of abundant alkene, aromatic and heteroaromatic functional groups. BET surface area measurements and SEM images indicated that the H3PO4-activated biochar (500ºC) had especially high surfaces areas. Functionalized biochar may provide a cost effective and highly effective sorbent for sequestering I-129 and Tc-99 from the biosphere, thereby reducing human risk.