Dissertation
THERMODYNAMICS OF LANTHANIDE GLUCONIC ACID COMPLEXES UNDER NEUTRAL TO ALKALINE CONDITIONS: TOWARD A MORE ENVIRONMENTALLY FRIENDLY LANTHANIDE BENEFICIATION PROCESS
Doctor of Philosophy (PhD), Washington State University
01/2020
Handle:
https://hdl.handle.net/2376/111134
Abstract
While comparatively little was known about the chemistry of the rare earth elements about 50 years ago, they have more recently become irreplaceable components of many of our modern life technologies. Little active mining is currently going on around the globe, and China is responsible for about 90% of rare earths supply, while only accounting for 25% of the world’s reserves. Rare earths are not easily accessible and are generally too low in concentration to be extracted economically. Their production, usually as by-product of a more lucrative mining activity, often requires large amount of reagents both organic and inorganic. This situation is mainly due to the semi-selectivity of the main step involved in rare earths production process. The development of better strategies to ensure a global and sustainable supply of rare earth could include better extraction and processing of their ore. The goal of this study is to evaluate the chelating properties of gluconic acid under conditions relevant to rare earths processing. This was done by measuring the stability constants of its complexes with rare earth metals by pH potentiometry. The analysis of spectrophotometric data obtained by UV-Vis and fluorescence confirms that the deprotonation of hydroxy groups on the backbone of gluconic acid at high pH allows for an increase in stability and enables lanthanide solubility under neutral to alkaline pH conditions. Fluorescence lifetime measurements done on europium complexes clearly indicated the formation of polynuclear species involving hydroxide bridges as well as partially deprotonated gluconate ligands. The data reported in this work has been interpreted to indicate a change in speciation across the lanthanide series related to the steady decrease in ionic radius (and resulting increase in charge density of the trivalent cations). Such data can help probe the selectivity of gluconic acid and model the speciation and distribution of the metals of interest in rare earth processing relevant systems.
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Details
- Title
- THERMODYNAMICS OF LANTHANIDE GLUCONIC ACID COMPLEXES UNDER NEUTRAL TO ALKALINE CONDITIONS: TOWARD A MORE ENVIRONMENTALLY FRIENDLY LANTHANIDE BENEFICIATION PROCESS
- Creators
- Guy Richard Henri Dutech
- Contributors
- Kenneth L Nash (Advisor)James M Boncella (Committee Member)Nathalie A Wall (Committee Member)Peter Reilly (Committee Member)Peter R Zalupski (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Chemistry, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 176
- Identifiers
- 99900581614001842
- Language
- English
- Resource Type
- Dissertation