Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Kevin O'Shea

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Yong Cai

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Jeffrey Joens

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Watson Lees

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Barry Rosen

Fifth Advisor's Committee Title

Committee member

Keywords

Humic acid-coated magnetite nanoparticles, photocatalysis, arsenic, strontium, wetland, organoclays, attenuation of iodine

Date of Defense

3-21-2023

Abstract

The development of effective remediation technologies is essential to effectively mitigate trace metals and radionuclides from the aquatic environments. Our studies confirm the strong adsorption properties of humic acid coated magnetite nanoparticle (HA-MNP) for arsenic species, As(III) and As(V), and illustrate modest enhancement of As(III) removal from solution with simultaneous UVA irradiation in the presence or absence of dissolved oxygen. The photochemical characteristics of HA-MNP were assessed via the detection and quantification of the generated reactive oxygen species. HA-MNP may offer a possible option for the photo-transformation and removal of arsenic from contaminated waters.

The adsorption of strontium (Sr) from aqueous solution by the use of HA-MNP is effective with > 90 % removal of strontium from the solution within thirty minutes. Detailed kinetic studies revealed the adsorption of Sr onto HA-MNP occurs in different phases, first by film diffusion, subsequent intraparticle diffusion, via electrostatic interactions and/or inner-sphere complexation. The removal of Sr by HA-MNP is found to be modestly inhibited by the presence of calcium, a common species in the groundwater.

A portion of the dissertation research focuses on the elucidation of the attenuation and release mechanisms of 129I occurring at the Savannah River Site wetland. The temperature and redox conditions influence the initial uptake of I and IO3 species. By comparing the uptake of iodide and iodate by soils at different depths under an oxic environment at different temperatures, we found the organic matter, minerals, and microbes present in the soil have a significant influence on the uptake of iodide and iodate. Under anoxic conditions, iodo-pollutants undergo reductive dehalogenations causing the release of iodine into aqueous solution. Under reducing conditions via natural organic matter, Fe/Mn minerals, and microbes, iodate undergoes reduction to reactive iodine species, i.e., HIO and I2, prior to adsorbing onto natural organic matter.

The environmentally friendly sorbents, organoclays PM-199 and MRM, were tested as potential remediation of 129I. Iodide and iodate were effectively separated from aqueous solution and the fast removal is primarily driven by the strong adsorption onto the organoclays exhibiting high removal capacity for 129I at the wetland under ambient conditions.

Identifier

FIDC011077

Previously Published In

Phuong Pham, Mamun Rashid, Yong Cai, Masafumi Yoshinaga, Dionysios D. Dionysiou, Kevin O'Shea. Removal of As(III) from Water Using the Adsorptive and Photocatalytic Properties of Humic Acid-Coated Magnetite Nanoparticles. Nanomaterials, 2020, 10, 1604; doi:10.3390/nano10081604

Available for download on Wednesday, April 23, 2025

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