Direct atomic-scale observation reveals rare earth element fractionation at mineral–water interfaces
7 affiliations
- 1State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- 2Guangdong research center for strategic metals and green utilization, Guangzhou 510640, China
- 3Guangdong Provincial Key Laboratory of Mineral Physics and Material, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- 4College of Earth and Planetary Sciences, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- 5Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- 6School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
- 7Zhejiang Key Laboratory of Environment and Health of New Pollutants, School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
Abstract
Clay minerals, ubiquitous across diverse geological systems, exert fundamental controls on critical geochemical processes, particularly through their adsorptive interactions with economically vital elements such as heavy rare earth elements (HREEs). The adsorption of HREEs onto clay surfaces is not only the key process that enriches these critical resources but also a potential archive for dating significant weathering events. However, the atomic-scale mechanisms governing the preferential adsorption and fractionation of rare earth elements (REEs) at mineral–water interfaces have remained poorly constrained. Here, employing in situ atomic-scale imaging via high-resolution atomic force microscopy, we systematically investigate the adsorption behaviors of light and heavy REEs (La, Y, Yb) onto key crystallographic planes—Si-basal, Al-basal, and edge terminations—of representative clay minerals (kaolinite, illite, mica) under environmentally relevant conditions (pH 4.8 to 6.4). We directly visualize and quantitatively reveal that Si-basal planes selectively enrich HREEs with pH-enhanced adsorption capacity, whereas Al-basal planes exhibit negligible REE adsorption below pH 5.8 but preferential HREE adsorption at pH 6.4. Integrating synchrotron X-ray absorption spectroscopy, we identify the adsorption mechanism of REE on Si-basal and Al-basal/edge planes as outer-sphere complexation and inner-sphere binding, respectively. Furthermore, we quantify the contributions of distinct planes via surface complexation modeling, revealing Si-dominated to Al- and edge-controlled adsorption with elevating pH. These atomic-scale findings not only resolve long-standing debates about clay mineral-mediated REE fractionation but also redefine fundamental paradigms of surface reactivity at silicate mineral–water interfaces, offering insights into the cycling and metallogeny of other critical metals in aqueous and sedimentary environments.
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BibTeX
@article{ran2026direct,
title = {{Direct atomic-scale observation reveals rare earth element fractionation at mineral–water interfaces}},
author = {Lingyu Ran and Gaofeng Wang and Jianxi Zhu and Bowen Ling and Jie Xu and Xiangwei Zhang and Xiaoliang Liang and Yongqiang Yang and Jingming Wei and Hongping He},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2026},
month = oct,
doi = {10.1073/pnas.2615180123},
url = {https://doi.org/10.1073/pnas.2615180123},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Direct atomic-scale observation reveals rare earth element fractionation at mineral–water interfaces
AU - Lingyu Ran
AU - Gaofeng Wang
AU - Jianxi Zhu
AU - Bowen Ling
AU - Jie Xu
AU - Xiangwei Zhang
AU - Xiaoliang Liang
AU - Yongqiang Yang
AU - Jingming Wei
AU - Hongping He
PY - 2026
DA - 2026/10/29
JO - Proceedings of the National Academy of Sciences of the United States of America
DO - 10.1073/pnas.2615180123
UR - https://doi.org/10.1073/pnas.2615180123
AB - Clay minerals, ubiquitous across diverse geological systems, exert fundamental controls on critical geochemical processes, particularly through their adsorptive interactions with economically vital elements such as heavy rare earth elements (HREEs). The adsorption of HREEs onto clay surfaces is not only the key process that enriches these critical resources but also a potential archive for dating significant weathering events. However, the atomic-scale mechanisms governing the preferential adsorption and fractionation of rare earth elements (REEs) at mineral–water interfaces have remained poorly constrained. Here, employing in situ atomic-scale imaging via high-resolution atomic force microscopy, we systematically investigate the adsorption behaviors of light and heavy REEs (La, Y, Yb) onto key crystallographic planes—Si-basal, Al-basal, and edge terminations—of representative clay minerals (kaolinite, illite, mica) under environmentally relevant conditions (pH 4.8 to 6.4). We directly visualize and quantitatively reveal that Si-basal planes selectively enrich HREEs with pH-enhanced adsorption capacity, whereas Al-basal planes exhibit negligible REE adsorption below pH 5.8 but preferential HREE adsorption at pH 6.4. Integrating synchrotron X-ray absorption spectroscopy, we identify the adsorption mechanism of REE on Si-basal and Al-basal/edge planes as outer-sphere complexation and inner-sphere binding, respectively. Furthermore, we quantify the contributions of distinct planes via surface complexation modeling, revealing Si-dominated to Al- and edge-controlled adsorption with elevating pH. These atomic-scale findings not only resolve long-standing debates about clay mineral-mediated REE fractionation but also redefine fundamental paradigms of surface reactivity at silicate mineral–water interfaces, offering insights into the cycling and metallogeny of other critical metals in aqueous and sedimentary environments.
SN - 0027-8424
SN - 1091-6490
ER -