来源：ACS Publications
Siloxane and aluminol surfaces, ubiquitous in Earth’s system, regulate the adsorption of economically vital elements such as rare earth elements (REEs), yet their atomic-scale reactivity remains unclear. Using in situ atomic force microscopy (AFM), we directly probed atomic-scale reactivity of siloxane and aluminum surfaces for REEs (La, Y, and Yb) on illite and gibbsite. We reveal unexpectedly higher reactivity of siloxane over aluminol surface, with marked preference for heavy-REEs (Y, Yb) over light-REEs (La) in weak-acid environments (pH = 5.5–6.0). Atomic-scale imaging locates adsorption above SiO4 tetrahedra, contradicting the conventional hexatomic ring-centered model. Furthermore, we identify a hierarchical REE distribution on the Si-basal plane, providing a mechanistic basis for REE fractionation. Complementary density functional theory (DFT) simulations confirm negligible REE adsorption and pronounced reactivity on illite edge sites under protonated and deprotonated conditions, respectively. These findings challenge surface reactivity at mineral–water interfaces, offering novel insights into critical metals cycling in terrestrial and marine environments.