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Title: Two-Step Adsorption of PtCl 6 2– Complexes at a Charged Langmuir Monolayer: Role of Hydration and Ion Correlations

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. Here, we studied the adsorption of PtCl 6 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.
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [2]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
  2. Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Published Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 45; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1408257
Alternate Identifier(s):
OSTI ID: 1421788