CMPO-Functionalized Silica Sorbents for pH-Tunable Separation and Enrichment of Rare-Earth Elements from Environmental Matrices

Sakr, Ahmed K.; Praneeth, Sai; Roy, Preetom K.; Dittrich, Timothy M.

doi:10.1021/acssuschemeng.5c11109

Title: CMPO-Functionalized Silica Sorbents for pH-Tunable Separation and Enrichment of Rare-Earth Elements from Environmental Matrices

Journal Article · Sun Feb 15 00:00:00 UTC 2026 · ACS Sustainable Chemistry & Engineering

DOI: https://doi.org/10.1021/acssuschemeng.5c11109 · OSTI ID:3021377

^[1]; Praneeth, Sai ^[2]; Roy, Preetom K. ^[1];

^[1]

Wayne State University, Detroit, MI (United States)
Wayne State University, Detroit, MI (United States); Indian Institute of Technology Hyderabad, Telangana (India)

Rare-earth elements (REEs) are crucial in many applications, yet mutual separation is challenging due to their similar chemical behavior. Octylphenyl- N,N-diisobutyl carbamoyl methyl phosphine oxide (CMPO) is an organophosphorus ligand originally developed for extracting actinides and lanthanides from spent nuclear fuel. Here, we report a pH-tunable CMPOfunctionalized silica sorbent for selective REE separation from complex aqueous matrices. A CMPO-associated silica gel sorbent was synthesized and characterized by Brunauer−Emmett−Teller (BET) surface area, scanning electron microscopy, and X-ray photoelectron spectroscopy to confirm the surface functionalization and binding behavior. Sorbent performance was evaluated by using a synthetic 46- element solution and a real phosphate rock fertilizer leachate. Notably, REEs were successfully eluted with ultrapure water, demonstrating reversible desorption controlled by pH adjustment. Packed-bed column studies increased the REE mass fraction from 3.6% to 64% (20-fold enrichment), with up to 30-fold enrichment of neodymium. The adsorption process follows the Langmuir isotherm behavior and follows pseudo-second-order kinetics. The uptake capacity of 1 μmol of REEs per 4.2 μmol of CMPO supports the formation of a predominantly 4:1 ligand:rare earth element(III) pseudocomplex. These results demonstrate CMPO-functionalized silica as a selective, water-elutable, and low-chemical-input platform for sustainable REE recovery from environmental and industrial sources.

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Research Organization:: GlycoSurf, LLC, Salt Lake City, UT (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Office of SBIR/STTR Programs (SBIR/STTR)

Grant/Contract Number:: FE0031565; SC0021702

OSTI ID:: 3021377

Journal Information:: ACS Sustainable Chemistry & Engineering, Journal Name: ACS Sustainable Chemistry & Engineering Journal Issue: 8 Vol. 14; ISSN 2168-0485

Publisher:: American Chemical Society (ACS)Copyright Statement

Country of Publication:: United States

Language:: English

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Title: CMPO-Functionalized Silica Sorbents for pH-Tunable Separation and Enrichment of Rare-Earth Elements from Environmental Matrices

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