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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Halogen Bonding in Perfluoroalkyl Adsorption.
1Department of Civil, Environmental and Construction Engineering, Texas Tech University, Lubbock, Texas 79409, United States.
This study reveals halogen bonding as the key mechanism for removing per- and polyfluoroalkyl substances (PFAS), like PFOS and PFOA, from water. This finding aids in designing better materials for PFAS water purification.
Area of Science:
- Environmental Chemistry
- Materials Science
- Water Treatment
Background:
- Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants.
- Adsorption is a key technology for PFAS removal from water.
- A molecular-level mechanistic understanding for adsorbent selection is lacking.
Purpose of the Study:
- To identify the primary molecular mechanism driving perfluoroalkyl substance (PFAS) adsorption.
- To establish guidelines for the rational design and selection of PFAS adsorbents.
- To explore the role of electrostatic interactions and noncovalent bonding in PFAS adsorption.
Main Methods:
- A materiomic approach comparing electrostatic polarities of various materials.
- Novel interpretation of the Freundlich isotherm to elucidate adsorption mechanisms.
- Literature review of carbon, polymer, and mineral-based adsorbents for PFAS removal.
Main Results:
- Halogen bonding identified as the dominant mechanism for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption.
- Materials with high π electron density, lone electron pairs, and negative charges show favorable adsorption.
- Adsorption is consistent with Lewis acid-base interactions involving fluorine's σ-hole.
Conclusions:
- Halogen bonding is a critical, previously unappreciated, noncovalent interaction in PFAS adsorption.
- Understanding this mechanism facilitates the development of effective PFAS removal materials.
- This research provides a molecular basis for selecting and designing superior PFAS adsorbents.
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