Adsorption of Rare Earth Elements to Kaolinite [dataset]

Dataset · Wed Jun 25 04:00:00 EDT 2025

DOI:https://doi.org/10.7936/6rxs-108281· OSTI ID:2570438

Ramazanova, Elimira ^[1]; Sharma, Neha; Flynn, Elaine D; Stagg, Olwen; Catalano, Jeffrey G; Giammar, Daniel E

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1. Washington University in St. Louis

Rare earth elements (REEs) are critical components of modern technology behind renewable energy, transportation, and electronics but have a limited current supply. A substantial portion of global REE production relies on ion adsorption deposits. A high abundance of kaolinite in REE enrichment zones within these deposits suggests that kaolinite controls the subsurface migration of REEs. This study aimed to improve the current understanding of REE binding to kaolinite under varying water chemistry conditions. We conducted batch experiments with kaolinite (KGa-2) and three REEs (Nd, Dy, and Yb) at varying pH, electrolyte concentration, dissolved inorganic carbon (DIC), low molecular weight organic acids (citric and oxalic acids), and total REE concentration conditions. Increasing electrolyte concentration inhibits REE adsorption at pH 7, suggesting that ion exchange contributes to adsorption at these pH values. DIC affects adsorption above pH 7−8 by forming strong aqueous complexes with heavy REEs. Citric acid decreases REE adsorption via aqueous complexation of REEs at pH 5 but does not affect adsorption at pH 5. The surface complexation model captures the main adsorption trends with two mechanisms: ion exchange on basal planes at pH ∼6 and inner-sphere surface complexation to edge sites at pH ∼6. Equilibrium constants for surface complexation increase in the order of Yb Dy Nd, indicating a higher strength of adsorption for heavy REEs. This study demonstrates how water chemistry conditions control the adsorption mechanisms that may determine the mobility of REEs in subsurface environments rich in kaolinite.

• Research Organization: Washington University in St. Louis
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
• DOE Contract Number: SC0022213
• OSTI ID: 2570438
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
Rare earth elements
clay
critical minerals
kaolinite
surface complexation modeling