Separation of cerium from other lanthanides by leaching with nitric acid rare earth(III) hydroxide-cerium(IV) oxide mixtures

Mioduski, T.; Hao, Dong Anh; Luan, Hoang Hong

doi:10.1007/bf02060982

Cited by 16 publications

(8 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…We recently initiated a program to develop earth-abundant lanthanide photocatalysts, especially for cerium. − Cerium has a relative abundance of ∼10 1.5 atoms per 10 6 atoms of Si in the earth’s upper continental crust and is more abundant than ruthenium (10 –3 ) and iridium (<10 –5 ) . Cerium is a waste product in light rare earth element separations and can be simply separated from mixtures through oxidation . It is therefore readily available.…”

Section: Introductionmentioning

confidence: 99%

Lanthanide Photocatalysis

2018

View full text Add to dashboard Cite

Conspectus The use of earth-abundant, cheap, potent, and readily available lanthanide photocatalysts provides an opportunity to complement or even replace rare and precious metal photosensitizers. Moreover, lanthanide photosensitizers have been demonstrated for the generation of a variety of reactive species, including aryl radicals, alkyl radicals, and others, by single-electron-transfer (SET) and hydrogen atom transfer (HAT) pathways under mild reaction conditions. Some lanthanide photocatalysts have unprecedented reducing power from their photoexcited states, achieving the activation of challenging organic substrates that have not otherwise been activated by reported organic or transition-metal photosensitizers. In this Account, we describe our recent advances in the rational design and strategic application of lanthanide photo(redox)catalysis. Our research goals include understanding the photophysics of lanthanide luminophores and incorporating them into new photocatalysis. Among the lanthanides, we have focused on cerium because of the doublet to doublet 4f → 5d excitation and emission, which affords good conservation of energy without losses through spin-state changes, as well as a large natural abundance of that element. We have performed structural, spectroscopic, computational, and reactivity studies to demonstrate that luminescent Ce(III) guanidinate–amide complexes can mediate photocatalytic C(sp3)–C(sp3) bond forming reactions. Taking advantage of the strong reducing power of the cerium excited states and the cerium–halogen bond forming enthalpies, we determined that the reactive, excited-state cerium metalloradical abstracts chloride anion from benzyl chloride to generate the benzyl radical. To control and predict the photocatalytic reactivities, we have also performed photophysical and photochemical studies on a series of mixed-ligand Ce(III) guanidinate–amide and guanidinate–aryloxide complexes to establish structure–property relationship for Ce(III) photocatalysts. We discovered that the emission color is directly related to ligand type and rigidity of the coordination sphere and that the photoluminescent quantum yield is correlated to variation in steric encumbrance around the cerium centers. The low excited-state reduction potentials (E 1/2 * ≈ −2.1 to −2.9 V versus Cp2Fe0/+) and relatively fast quenching rates (k q ≈ 107 M–1 s–1) toward aryl halides enabled the Ce(III) guanidinate–amide complexes to participate in photocatalytic C(sp2)–C(sp2) bond forming reactions through either inner-sphere or outer-sphere SET processes. We have also reported a simple, potent, and air-stable ultraviolet A photoreductant, the hexachlorocerate(III) anion ([CeIIICl6]3–). This complex is a potent photoreductant (E 1/2 * ≈ −3.45 V versus Cp2Fe0/+) and exhibits a fast quenching kinetics (k q ≈ 109–1010 M–1 s–1) toward organohalogens. The [CeIVCl6]2− redox partner can also act as a potent photo-oxidant though a (presumably) long-lived chloride-to-cerium(IV) charge transfer excited state (ε = ∼6000 M–1 cm...

show abstract

Section: Introductionmentioning

confidence: 99%

Lanthanide Photocatalysis

2018

View full text Add to dashboard Cite

show abstract

“…Cerium has a similar abundance to copper in Earth’s upper continental crust with relative abundance of ∼10 1.5 (atoms per 10 6 atoms of Si) and is more abundant than tungsten (10 0 ), gold (10 –3 ), ruthenium (10 –3 ), and iridium (<10 –5 ), respectively . Cerium is also readily separated from other lanthanide elements using oxidation chemistry and is a waste byproduct in the separations chemistry of light rare earth elements.…”

Section: Introductionmentioning

confidence: 99%

Cerium Photosensitizers: Structure–Function Relationships and Applications in Photocatalytic Aryl Coupling Reactions

et al. 2016

View full text Add to dashboard Cite

Two complete mixed-ligand series of luminescent Ce(III) complexes with the general formulas [(Me3Si)2NC(N(i)Pr)2]xCe(III)[N(SiMe3)2]3-x (x = 0, 1-N; x = 1, 2-N, x = 2, 3-N; x = 3, 4) and [(Me3Si)2NC(N(i)Pr)2]xCe(III)(OAr)3-x (x = 0, 1-OAr; x = 1, 2-OAr, x = 2, 3-OAr; x = 3, 4) were developed, featuring photoluminescence quantum yields up to 0.81(2) and lifetimes to 117(1) ns. Although the 4f → 5d absorptive transitions for these complexes were all found at ca. 420 nm, their emission bands exhibited large Stokes shifts with maxima occurring at 553 nm for 1-N, 518 nm for 2-N, 508 nm for 3-N, and 459 nm for 4, featuring yellow, lime-green, green, and blue light, respectively. Combined time-dependent density functional theory (TD-DFT) calculations and spectroscopic studies suggested that the long-lived (2)D excited states of these complexes corresponded to singly occupied 5dz(2) orbitals. The observed difference in the Stokes shifts was attributed to the relaxation of excited states through vibrational processes facilitated by the ligands. The photochemistry of the sterically congested complex 4 was demonstrated by C-C bond forming reaction between 4-fluoroiodobenzene and benzene through an outer sphere electron transfer pathway, which expands the capabilities of cerium photosensitizers beyond our previous results that demonstrated inner sphere halogen atom abstraction reactivity by 1-N.

show abstract

“…The dried REEs concentrate was ground and then dissolved in 5% HCl with stirring for 4 h where the insoluble Ce(IV) was collected over the filter paper. The REEs filtrate free from Ce was treated with oxalic acid at pH 1.1 followed by calcination to prepare the working REEs concentrate [17]. On the other hand, Pr(III) standard solution (2 g L −1 ) was prepared by complete dissolution a weighted 0.2415 g of Pr 6 O 11 in hot 1.5 mol L −1 HCl and complete up to 100 mL in a volumetric measuring flask using double distilled water.…”

Section: Methodsmentioning

confidence: 99%

Development of a procedure for spectrophotometric determination of Pr(III) from rare earth elements (REEs) concentrate

2019

View full text Add to dashboard Cite

Rare earth elements concentrate (REEs) which has been prepared from Rosetta monazite assays 44, 23, 16.94 and 5.91% for Ce, La, Nd and Pr, respectively. Highly pure individual separation of Pr(III) from this concentrate was achieved using a cationic Dowex 50W-X8 ion exchange resin. An EDTA solution assaying 0.015 mol L −1 was used for the complete REEs elution. In this study, the proposed method was applied for the determination of individual Pr(III) after the separation of Ce(IV) by oxidation at 200 °C and separation of Pr(III) from REEs concentrate via ion exchange. Simple perchlorate method was applied at the achieved optimum conditions for the separate spectrophotometric determination of Pr(III) at λ max 444 nm using the fourth derivative spectrum. A fourth derivative molecular absorption spectrophotometric was used to overcome the overlapped interfering spectra to determine the individual components.

show abstract

Separation of cerium from other lanthanides by leaching with nitric acid rare earth(III) hydroxide-cerium(IV) oxide mixtures

Cited by 16 publications

References 2 publications

Lanthanide Photocatalysis

Lanthanide Photocatalysis

Cerium Photosensitizers: Structure–Function Relationships and Applications in Photocatalytic Aryl Coupling Reactions

Development of a procedure for spectrophotometric determination of Pr(III) from rare earth elements (REEs) concentrate

Contact Info

Product

Resources

About