Abstract
Mineral-water interfacial reactions are central to chemical processes that control the fate of nutrients and contaminants in natural environments. Mineral surfaces commonly have complex structures and compositions whose impact on interfacial reactivity is poorly understood. Here, we investigated the effects of surface heterogeneities on Rb+ sorption at the quartz (101)-10 mM RbCl solution interface at pH 9.8 using in situ high-resolution X-ray reflectivity. Two surface locales (i.e., Spots A and B) having distinct interfacial structures were chosen: Spot A was characterized by its low defect density (≤20% topmost Si vacancies) and Rb+ adsorption occurred predominantly as an inner-sphere complex. In comparison, Spot B had a higher defect density (∼50% vacancies) and was covered with poorly crystalline SiO2. A substantially larger Rb+ uptake (i.e., 7-times higher coverage) was observed on this defective surface where Rb+ incorporated in the vacancy sites (confirmed by density functional tight binding-based molecular dynamics simulations) or adsorbed directly on the disordered film. These results provide a direct quantification of how surface heterogeneity influences the geochemical behavior of mineral-water interfaces, in particular highlighting the important role of chemical and structural defects on the sorbate speciation and coverage at silicate mineral surfaces.
| Original language | English |
|---|---|
| Pages (from-to) | 17372-17386 |
| Number of pages | 15 |
| Journal | Journal of Physical Chemistry C |
| Volume | 128 |
| Issue number | 41 |
| DOIs | |
| State | Published - Oct 17 2024 |
Funding
This material is based upon work supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Geosciences program. This work utilized resources of the Advanced Photon Source (APS), a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357 and the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. DOE under contract no. DE-AC05-00OR22725. The X-ray reflectivity data were collected at beamline 33-ID-D, APS. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under contract no. DE-AC02-06CH11357. The U.S. Government retains for itself and others acting on its behalf a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly by or on behalf of the Government.