Innovative Technology to Sequester Depleted Uranium from Test and Training Range Soil Fines

Chris Griggs | U.S. Army Engineer Reserch and Development Center

ER-201321

Objective

Testing and training with depleted uranium (DU) munitions has resulted in the production and accumulation of contaminated impact sands. These sands are toxic as well as radioactive, requiring disposal in a hazardous waste/radioactive landfill. Dust emissions from these soils also are a respiratory hazard, and contaminated runoff water can further contaminate surface water resources. To satisfy the need for rapid, cost-effective remediation of these sands at Department of Defense (DoD) training and industrial sites, this project will demonstrate a technology that uses an innovative amendment proven to sequester DU as well as other metals. The objectives are to: (1) evaluate reactive materials for adsorption and immobilization of DU and other metals from solution; (2) design and assemble the DU-sequestration reactive material into a metal removal system and determine scale-up parameters; (3) assemble a pilot-scale version of the metal removal system for demonstration using DU-contaminated site soil; and (4) perform a field demonstration with commercially available equipment that incorporates the metal removal system. The project will also develop standard protocols for use of the metal removal system, as well as long-term performance monitoring and maintenance procedures and a detailed life cycle cost analysis.

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Technology Description

Physical separation technologies will remove more than 90% of DU munition fragments from impact sands that have been weathered less than 2 years. However, aged DU adsorbs strongly to soil fines with a high organic component, making aged DU oxides inaccessible to physical separation technologies for soil cleaning. Commercial chemical separation technologies, such as heap leaching used in the mining industry, can be used to remove the strongly sorbed DU from the soil fines; however, heap leaching is a long-term process. The technology to be demonstrated uses a mildly acidic extraction solution to remove the DU from the soil particles and combines that with an innovative immobilization amendment for DU (and other metals) to sequester the DU from the process water, reducing the remediation time. A number of extraction fluids have been investigated to optimize DU removal. Two amendments will be evaluated: biogenic phosphate and electrospun chitin prepared with a DU-reactive ligand. Both amendments are re-purposed waste materials - fishbones and shrimp shells. The fishbones are treated to remove organic matter, a process that reduces biological activity and increases the metal sorptive ability for both lead and uranium, and can then be functionalized with the reactive chemicals nano-iron and nano-magnesium, Chitin from waste shellfish material will be separated in an ionic liquid and electrospun into nanofibers. After extended spinning, the fibers are collected into a non-woven mat. The chitin mat can then be functionalized with a DU selective ligand such as an amidoxime-based system. The heap leach process water can then be recycled through the leaching system.

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Benefits

The expected benefits to DOD include more rapid and complete remediation of DU-contaminated soil from a variety of sources, as well as removal of other metals. The principal life-cycle cost advantage is the ability to use existing treatment systems, shorten the time to site closure, sequester the DU and other heavy metals in a way that will reduce the volume of hazardous waste, and allow on-site re-use of the impact soils. This technology could also be adapted to provide in situ protection of surface waters. (Anticipated Project Completion - 2018)

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Points of Contact

Principal Investigator

Dr. Chris Griggs

U.S. Army Engineer Reserch and Development Center (ERDC)

Phone: 601-634-4821

Fax: 601-634-3518

Program Manager

Environmental Restoration

SERDP and ESTCP

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