Two-Step Adsorption of PtCl62- Complexes at a Charged Langmuir Monolayer: Role of Hydration and Ion Correlations

Ahmet Uysal; William Rock; Baofu Qiao; Wei Bu; Binhua Lin

doi:10.1021/acs.jpcc.7b09350

Two-Step Adsorption of PtCl₆^2- Complexes at a Charged Langmuir Monolayer: Role of Hydration and Ion Correlations

Ahmet Uysal^*, William Rock, Baofu Qiao, Wei Bu, Binhua Lin

^*Corresponding author for this work

The Center for Computation and Theory of Soft Material

Research output: Contribution to journal › Article › peer-review

27 Scopus citations

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 PtCl₆^2- 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)
Pages (from-to)	25377-25383
Number of pages	7
Journal	Journal of Physical Chemistry C
Volume	121
Issue number	45
DOIs	https://doi.org/10.1021/acs.jpcc.7b09350
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

Access to Document

10.1021/acs.jpcc.7b09350

Cite this

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title = "Two-Step Adsorption of PtCl62- Complexes at a Charged Langmuir Monolayer: Role of Hydration and Ion Correlations",

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.",

author = "Ahmet Uysal and William Rock and Baofu Qiao and Wei Bu and Binhua Lin",

note = "Funding Information: 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. Publisher Copyright: {\textcopyright} 2017 American Chemical Society.",

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AU - Bu, Wei

AU - Lin, Binhua

N1 - Funding Information: 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. Publisher Copyright: © 2017 American Chemical Society.

PY - 2017/11/16

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N2 - 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.

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