Date of Award

12-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Dr. Brian A. Powell, Committee Co-Chair

Committee Member

Dr. Stephen Moysey, Committee Co-Chair

Committee Member

Dr. Daniel Kaplan

Abstract

Understanding the transformations of iodine during sorption to soils present in redox transition zones is critical for understanding risks from iodine-129 release into the environment. In this work, sorption of iodine to a wetland soil from the Savannah River Site was monitored as a function of time and total iodine concentrations from initially iodide or iodate sources. Batch experiments were performed in order to investigate the effects of organic matter on total iodine sorption and to investigate the rates of iodate and iodide sorption and desorption in a wetland soil. Sorption of iodide was slower than sorption of iodate. Indirect iodine speciation analysis showed that the formation of organoiodine on the surface is important in the sorption process, as aqueous organoiodine is desorbing as iodate continues to sorb to soil. Desorption behavior of initially iodide and iodate showed similar trends, indicating that iodine transforms into the same species regardless of starting speciation (i.e. iodide or iodate). Most likely, the iodine is transforming via a surface-mediated process to organoiodine; due to the indirect methods of determining iodine speciation, the desorbing iodine species is uncertain, but it is most likely organoiodine. A numerical solution was created to approximate the desorption behavior observed in experiments starting with both iodide and iodate and a single set of forward and reverse rate constants was required to describe all of the data. Multiple rate laws were examined to fit both the sorption and desorption data but none followed standard laws with integer reaction stoichiometries.

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