Award Date
5-15-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry and Biochemistry
First Committee Member
Artem Gelis
Second Committee Member
Kenneth Czerwinski
Third Committee Member
Daniel Koury
Fourth Committee Member
Jennifer Shusterman
Fifth Committee Member
Alexander Barzilov
Number of Pages
198
Abstract
Neptunium (Np) is a radioactive element that is generated during nuclear energy production and in nuclear explosions. Its chemistry is an important consideration in the nuclear fuel cycle and in the forensic analysis of nuclear debris. In aqueous systems, neptunium is known for its broad range of available oxidation states- (III) to (VII)- many of which can easily interconvert. Each oxidation state has its own unique properties and behavior, which presents challenges for the separation and characterization of Np. This dissertation first explores the highest oxidation state of Np, (VII), in acidic media, where its properties are still poorly understood. Numerous techniques are developed to generate highly oxidizing conditions in solution with the goal of generating observable quantities of the heptavalent form of Np. An updated UV-Vis-NIR spectrum of Np(VII) in perchloric acid is presented. With general chemical and electrolytic approaches for Np oxidation established, they could be adapted to operate on microliter scales for the separation of Np in microfluidic processes. A microfluidic supported liquid membrane extraction for neptunium is developed by using bromate and various chemical reductants to control the distribution of Np between the 5+ and 6+ states and promote its extraction. The microfluidic system is expanded to include electrolytic oxidation of Np in a 3D-printed bulk electrolysis flow cell. The electrochemical module is then coupled to the supported liquid membrane extraction to demonstrate an integrated microfluidic separation of Np based on electrochemical redox.
Keywords
Electrolysis; Heptavalent; Microfluidics; Neptunium; Oxidation; Redox
Disciplines
Chemical Engineering | Chemistry | Radiochemistry
File Format
File Size
3600 KB
Degree Grantor
University of Nevada, Las Vegas
Language
English
Repository Citation
Cicchetti, Nic, "Chemical and Electrolytic Techniques for Neptunium Oxidation State Control: An Investigation of Heptavalent Neptunium in Acidic Media and the Development of Microfluidic Approaches for Neptunium Oxidation and Extraction" (2025). UNLV Theses, Dissertations, Professional Papers, and Capstones. 5520.
https://oasis.library.unlv.edu/thesesdissertations/5520
Rights
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