Recovery of Rare Earth Elements

Certain ligating molecules can be used as selective extractants for lanthanides recovery (Rare Earth Elements,REEs). Marshallton Research Laboratories offers a tool box of extractants for the separation of actinides and lanthanides, and the purification of individual elements from within these groups. Chemically, the ligands fall in several main categories: diamides, phosphonates, diphosphonates. Listed below are the molecules from the synthetic portfolio which are attractive candidates for the sequestration of REEs through ore processing or recycling.

 

Diglycolamides (DGAs): e.g. TODGA, T2EHDGA, DMDODGA, TEDGA, DGA6

Diglycolamides (DGAs) were first developed for actinide/ lanthanide partitioning in the nuclear fuel cycle. ^a  They are emerging as an effective alternative to organophosphorus acids (e.g. PC88A) for the separation of heavy REEs from light REEs.^b  DGAs operate without consuming large quantities of acids and bases, eliminating a secondary salt waste stream.^c 

 

• • • TODGA (R=R’=n-octyl)
    • T2EHDGA R=R’=2-ethylhexyl)
    • TEDGA (R=R’= ethyl)
    • DMDODGA (R=methyl, R’=n-octyl)
    • SDGA (R=3,5,5-trimethylhexyl, R’=n-octyl)

 

Next generation DGAs

Patent application US 2022/0002840 A1 (ORNL, INL) discloses a new class of DGAs with increased extraction and separation throughput of light REEs. DGA6 ^d  US 17/366,172  is a superior product specifically designed to increase extraction and separation throughput of light REEs with markedly improved phase disengagement behavior. As a licensee, Marshallton Research Laboratories is making these advanced extractants available for REE applications.

_{a) Tachimoris, et al. Ion Exchange and Solvent Extraction; Vol. 19, pp 1 – 65 (2010)}

_{b) Ellis, R.J. Inorganic Chemistry  2017, 56(3) 1152}

_{c) Lee, M.-S. et al.  Separation Purification Technology, 2005, 46(1), 72}

_{d)  Jansone-Popova,S. et al.  US Patent Application, 17/366,172}

Dioxaoctanediamides (DOODAs) ^(e): e.g. DOODA(C1), DOODA(C2), DOODA (C8)

• • • DOODA(C1)   (R=methyl)
    • DOODA(C2)   (R= ethyl)
    • DOODA(C8)   (R=n-octyl)

Diamides of this class facilitate separation of Am, Cm and lanthanides.

_{e)  Sasaki, Y. et al. Solvent Extraction Research and Development, Japan Vol.18, 93-101 (2011)}

2-Ethylhexyl-Bis(N,N’-di(2-ethylhexyl)acetamidoamine, ADAAM(EH)^(f) 

 

 

 

 

 

 

 

 

This aminodiamide ligand has been used in extraction of Am(III) and Eu(III) from nitric acid media.

_{f) H. Suzuki, et al. (2016) “Highly Practical and Simple Ligand for Separation of Am(III) and Eu(III) from Highly Acidic Media”  Analytical Sciences  32: 477-479}

Organophosphous extractants^(g-i): e.g. HEH[EHP], DBBP, TBMDP

This class of ligands has been successfully used in separations of trivalent actinides from transuranic elements and separations of REEs.

• • • HEH[EHP]   (R1=R2=2-ethylhexyl, R3=H)
    • DBBP (R1=R2=R3=butyl)
    • DAAP (R1=R2=R3= amyl)

• • • TBMDP  (R=butyl)
    • TAMDP (R=amyl)

Tetraalkyl methylene diphosphonate are excellent agents for extracting lanthanides and actinides.

_{g) D. Li (2019) “Development Course of Separating Rare Earth with Acid Phosphorus Extractants: A Critical Review”.  Journal of Rare Earths, 37(5):468-486.}

_{h) G.J.Lumetta (2010) “Review: Solvent Systems Combining Neutral & Acidic Extractants for Separating Trivalent Lanthanides from the Transuranic Elements” Solvent Extraction and Ion Exchange 28(3): 287-312}

_{i) Eliar, A. et al.  (1996) Hydrometallurgy 40, 189-194}