Abstract
Anion exchange at positively charged interfaces plays an important role in a variety of physical and chemical processes. However, the molecular-scale details of these processes, especially with heavy and large anionic complexes, are not well-understood. We studied the adsorption of PtCl62- anionic complexes to floating DPTAP monolayers in the presence of excess Cl- as a function of the bulk chlorometalate concentration. This system aims to simulate the industrial conditions for heavy metal separations with solvent extraction. In situ X-ray scattering and fluorescence measurements, which are element and depth sensitive, show that the chlorometalate ions only adsorb in the diffuse layer at lower concentrations, while they adsorb predominantly in the Stern layer at higher concentrations. The response of DPTAP molecules to the adsorbed ions is determined independently by grazing incidence X-ray diffraction and supports this picture. Molecular dynamics simulations further elucidate the nanoscale structure of the interfacial complexes. The results suggest that ion hydration and ion-ion correlations play a key role in the competitive adsorption process.
Original language | English (US) |
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Pages (from-to) | 25377-25383 |
Number of pages | 7 |
Journal | Journal of Physical Chemistry C |
Volume | 121 |
Issue number | 45 |
DOIs | |
State | Published - Nov 16 2017 |
Funding
We thank Lynda Soderholm for her valuable comments on the manuscript. We also thank Sang Soo Lee for fruitful discussions. This work was supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Chemical Sciences, Geosciences, and Biosciences, Heavy Element Chemistry, under contract DE-AC02-06CH11357. The synchrotron X-ray experiments were done at ChemMatCARS, Sector 15-ID-C of the Advanced Photon Source at Argonne National Laboratory. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Basic Energy Science, under contract DE-AC02-06CH11357. Chem-MatCARS was supported by NSF/CHE-1346572. The MD simulations were done at the computing resources provided on Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- General Energy
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films