Highlights

• Novel extractant DOAM-PPA demonstrates breakthrough in heavy rare earth element separation with wider operating window and higher extraction efficiency.
• Research shows 2.45-times greater saturation capacity for lutetium and improved separation factor compared to conventional extractants.
• Promising solution for sustainable and environmentally friendly rare earth element extraction with potential industrial scalability.

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A research team led by Meiying Xie from the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences (opens in a new tab), developed a novel extractant, ((diethylamino)methyl) phenyl phosphonic acid (DOAM-PPA), for the efficient separation and recovery of heavy rare earth elements (HREEs). The study, published as a preprint in Separation and Purification Technology (opens in a new tab), hypothesized that introducing benzene and tertiary amine functional groups into the phosphonic acid structure would enhance HREE extraction performance across a wide acidity range.

The researchers synthesized DOAM-PPA through a one-step process and demonstrated its effectiveness compared to conventional extractants such as P204, P507, and Cyanex 272. DOAM-PPA achieved a wider operating window (pH 4.00–1.25 and 0.1–2 mol/L HCl) and superior separation performance, with a Lu/Y separation factor (βLu/Y) of 53.55—substantially higher than that of existing extractants. The extractant also exhibited a 2.45 times greater saturation capacity for Lu compared to P204 and maintained its efficiency over six extraction-stripping cycles. Additionally, it showed good recycling performance and high compatibility with industrial-scale applications, including the direct processing of lutetium-yttrium silicate (LYSO) leachate.

The authors declare, “We believe that DOAM-PPA has great potential for HREE separation and recovery applications.”

Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences

Limitations

Key limitations include the study’s reliance on laboratory-scale experiments, which may not fully reflect industrial conditions. While DOAM-PPA showed minimal extraction of impurities like silicon, further tests on long-term operational stability and ecological impact are needed. Moreover, as the study is a preprint, its findings have not undergone peer review.

A Future?

This research presents DOAM-PPA as a promising solution for environmentally friendly and efficient HREE separation. Future work should focus on scaling up the process, evaluating economic feasibility, and addressing potential environmental concerns. If validated, DOAM-PPA could significantly enhance the sustainability of HREE extraction.