Open AccessElectrochemical Oxidation and Speciation of Lanthanides in Potassium Carbonate Solution
Author(s) -
Poki Tse,
Nathan P. Bessen,
Shane S. Galley,
Samuel A. Bryan,
Amanda M. Lines,
Jenifer C. Shafer
Publication year - 2022
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ac6704
Subject(s) - lanthanide , cerium , chemistry , carbonate , inorganic chemistry , terbium , electrochemistry , redox , ionic radius , praseodymium , ion , electrode , organic chemistry
Increasing lanthanide demand to support energy goals drives the need to develop more efficient approaches to separate lanthanide metals. Most current approaches for intra-lanthanide separations are not very selective and are based on small differences in ionic radii. Concentrated potassium carbonate media has shown some potential to enable oxidation of Pr and Tb to their tetravalent states, which could enable a separation based on differences in oxidation states, but little is known regarding the general system chemistry. This work completes a detailed examination of cerium (Ce) redox chemistry in concentrated carbonate media to support the development of Pr and Tb oxidation studies. The half-wave potential (E 1/2 ) of the Ce(III)/(IV) redox couple is evaluated under various solution conditions and computational modeling of carbonate coordination environments is discussed. Cyclic voltammetry shows higher carbonate concentrations and temperatures can lower the potential required to oxidize Ce(III). Chronoabsorptometry shows Ce(III) and Ce(IV) carbonate complexes are chemically stable and reversible. Computational modeling suggests the most likely coordination environment for the Ce(IV) complex is Ce(CO 3 ) 4 (OH) 5- which is a less entropically favored complex than the lowest energy Ce(III) complex, Ce(CO 3 ) 4 5- .