From ash to oxides: Recovery of rare-earth elements as a step towards valorization of coal fly ash waste

Dardona, Mohammed; Mohanty, Sanjay K.; Allen, Matthew J.; Dittrich, Timothy M.

doi:10.1016/j.seppur.2023.123532

Cited by 16 publications

(4 citation statements)

References 63 publications

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“…The REE can then be recovered as high purity end-products via solvent extraction, ion-exchange, or selective precipitation with oxalic acid to produce oxalates which are subsequently converted to rare earth oxides via roasting . Similarly, there has been significant research into different processes to recover REE from coal ash which are significantly more efficient and environmentally friendly than mining REE from ore deposits. − …”

Section: Resultsmentioning

confidence: 99%

Rare Earth Element Adsorption to Clay Minerals: Mechanistic Insights and Implications for Recovery from Secondary Sources

Bishop,

Alam,

Flynn

et al. 2024

Environ. Sci. Technol.

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The energy transition will have significant mineral demands and there is growing interest in recovering critical metals, including rare earth elements (REE), from secondary sources in aqueous and sedimentary environments. However, the role of clays in REE transport and deposition in these settings remains understudied. This work investigated REE adsorption to the clay minerals illite and kaolinite through pH adsorption experiments and extended X-ray absorption fine structure (EXAFS). Clay type, pH, and ionic strength (IS) affected adsorption, with decreased adsorption under acidic pH and elevated IS. Illite had a higher adsorption capacity than kaolinite; however, >95% adsorption was achieved at pH ∼7.5 regardless of IS or clay. These results were used to develop a surface complexation model with the derived binding constants used to predict REE speciation in the presence of competing sorbents. This demonstrated that clays become increasingly important as pH increases, and EXAFS modeling showed that REE can exist as both inner-and outer-sphere complexes. Together, this indicated that clays can be an important control on the transport and enrichment of REE in sedimentary systems. These findings can be applied to identify settings to target for resource extraction or to predict REE transport and fate as a contaminant.

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Section: Resultsmentioning

confidence: 99%

Rare Earth Element Adsorption to Clay Minerals: Mechanistic Insights and Implications for Recovery from Secondary Sources

Bishop,

Alam,

Flynn

et al. 2024

Environ. Sci. Technol.

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“…23−41 Modifications to the solid supports studied for the isolation of rare-earth elements include changing the size of the pores, degree of crosslinking, and degree of functionalization as well as selection of different ligands or functional groups to include on solid supports. 27,28,42,43 Modification of solid supports with ligands is an important technique to separate rare-earth elements based on coordinating angle (bite angle), donor atoms, functional groups, cavity size, range of pK a , or denticity. 24,26,44,45 With increasing specificity of the supported ligand, increased separation efficiencies become possible.…”

Section: Introductionmentioning

confidence: 99%

“…Different solid-phase extractants have been studied with respect to their selectivity for rare-earth elements. − Modifications to the solid supports studied for the isolation of rare-earth elements include changing the size of the pores, degree of crosslinking, and degree of functionalization as well as selection of different ligands or functional groups to include on solid supports. ,,, Modification of solid supports with ligands is an important technique to separate rare-earth elements based on coordinating angle (bite angle), donor atoms, functional groups, cavity size, range of p K a , or denticity. ,,, With increasing specificity of the supported ligand, increased separation efficiencies become possible. Therefore, we hypothesized that 2.2.2-cryptand covalently linked to a solid support would enable the separation of lanthanides from each other as a function of size and charge because 2.2.2-cryptand preferentially binds divalent lanthanides relative to trivalent lanthanides .…”

Section: Introductionmentioning

confidence: 99%

Cryptands on a Solid Support for the Separation of Europium from Gadolinium

Kulasekara,

Kajjam,

Praneeth

et al. 2023

ACS Appl. Mater. Interfaces

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With the great demand for europium in green-energy technologies comes the need for innovative methods to isolate the elements. We introduce a solid−liquid extraction method using a 2.2.2-cryptand-modified solid support to separate europium from gadolinium using their differences in electrochemical potential. The method overcomes challenges associated with the separation of those two ions that have similar coordination chemistry in the +3 oxidation state. A competitive adsorption study in the cryptand system between Eu II /Eu III and Gd III shows greater affinity for Eu II relative to Gd III . After separation from Gd III , Eu was released by oxidizing Eu II to Eu III with 99.3% purity. The purity of separated Eu is unaffected by pH between pH 3.0 and 5.5. Overall, we demonstrate that by modifying a solid support with 2.2.2-cryptand, divalent europium can be separated from trivalent gadolinium based on the differences of affinities of 2.2.2cryptand for the two ions.

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“…Praseodymium is a rare earth element with various applications, including magnet production [1], lighting [2], lasers [3], and more. The increasing demand for its manufacturing has driven research into alternative sources of praseodymium [4,5]. Industrial aqueous waste could serve as an additional source for its production [6].…”

Section: Introductionmentioning

confidence: 99%

Improved Sorption of Praseodymium Ions From Nitrate Solutions by Activated Ion Exchangers

Jumadilov,

Myrzabay,

Ibragimova

2023

Chem. J. of Kaz.

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In this research, we investigated the praseodymium ions sorption by the ion exchangers KU-2-8 (H+form) and AV-17-8 (OH-form) as an interpolymer system called "KU-2-8:AV-17-8" (X:Y) with the molar ratio of ionic groups X:Y (6:0, 5:1, 4:2, 3:3, 2:4, 1:5, and 0:6) in praseodymium nitrate solution. To be clear, two cross-linked polymers having active functional groups that are in the same solution but not in direct contact form an interpolymer system. The purposeof our research to demonstrate how activating ion exchangers as functional polymers by remote contact in an aqueous medium enhances the sorption of a variety of valuable metals and their compounds from industrial waste solutions, including praseodymium. Objects.Ion exchangers that are mutually activated in an aqueous medium undergo conformational and electrochemical changes that lead to a shift in their state from neutral to highly ionized and an increase in their sorption activity toward target metal ions. Results.The experimental findings showed that the sorption activity of the interpolymer system KU-2-8:AV-17-8 (5:1) increased significantly when compared to praseodymium ions (43 %), but the sorption activity of the raw KU-2-8 (6:0) and raw AV-17-8 (0:6) had the same values of 25 % and 5 %, respectively. Conclusion. This research sheds light on a novel and promising approach to improve the efficiency of ion exchangers, opening possibilities for the effective recovery and removal of valuable metals from complex solutions. Additionally, it holds practical implications for sustainable waste management and resource recycling, contributing to the advancement of environmental protection and resource conservation in various industrial sectors. Further investigations and optimization of the interpolymer system could yield substantial benefits for greener and more resource-efficient future sorption technologies.

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From ash to oxides: Recovery of rare-earth elements as a step towards valorization of coal fly ash waste

Cited by 16 publications

References 63 publications

Rare Earth Element Adsorption to Clay Minerals: Mechanistic Insights and Implications for Recovery from Secondary Sources

Rare Earth Element Adsorption to Clay Minerals: Mechanistic Insights and Implications for Recovery from Secondary Sources

Cryptands on a Solid Support for the Separation of Europium from Gadolinium

Improved Sorption of Praseodymium Ions From Nitrate Solutions by Activated Ion Exchangers

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