Document Type

Thesis

Degree

Master of Science (MS)

Major/Program

Chemistry

First Advisor's Name

Yong Cai

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Yi Xiao

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Yelena Katsenovich

Third Advisor's Committee Title

Committee Member

Keywords

Uranium, Remediation, Ammonia, Hanford, Vadose Zone

Date of Defense

7-19-2018

Abstract

Of the many toxic chemicals released into the Hanford vadose zone over the decades of nuclear weapons production, uranium has emerged as a contaminant of significant interest. The ammonia gas injection remediation method has been identified as a promising approach towards mitigating the risks to the ecosystem by limiting the mobility of the radionuclide in the vadose zone. The remediation method was replicated using synthetic porewater solutions with a range of constituent concentrations equal to that of the Hanford 200 Area vadose zone. The uranium-bearing products of the remediation method were characterized using kinetic phosphorescence analysis for aqueous uranium, scanning electron microscopy with energy dispersive spectroscopy and electron microprobe for imaging and elemental analysis, and a sequential extraction procedure modified for the sample precipitates. Evaluation revealed that the resultant uranium-bearing solids likely took the form of uranium-silicates and uranium carbonates, with the latter being precipitated primarily in mid-to-high bicarbonate samples.

Identifier

FIDC007055

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