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Preparation of Carbon Nanosheets at Room Temperature
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Methyl-Cyclohexane Methanol (MCHM) Isomer-Dependent Binding on Amorphous Carbon Surfaces
1Department of Chemistry, The University of Memphis, Memphis, TN 38152, USA.
Molecules (Basel, Switzerland)
|July 2, 2021
Summary
Methyl-cyclohexane methanol (MCHM) isomer binding to activated carbon, influenced by water temperature, explains its unexpected release from filters after a chemical spill. This research highlights interfacial chemistry's role in water treatment.
Area of Science:
- Environmental Chemistry
- Surface Science
- Water Treatment Technologies
Background:
- A 2014 chemical spill released over 10,000 gallons of methyl-cyclohexane methanol (MCHM) into West Virginia's Elk River.
- Initial water treatment using granulated activated carbon (GAC) failed to immediately remove MCHM, and it was later detected leaching from filters.
- Over 300,000 residents experienced prolonged disruption of clean water services due to the MCHM contamination.
Purpose of the Study:
- To investigate the hypothesis that preferential adsorption of MCHM isomers and seasonal water temperature variations explain the observed MCHM release from GAC filters.
- To understand the interfacial chemistry governing MCHM interactions with activated carbon for improved water treatment strategies.
Main Methods:
- Calculated intermolecular potentials between ovalene and MCHM isomers (cis- and trans-).
- Compared physisorption potentials of MCHM isomers onto an amorphous carbon model using molecular mechanics (MM).
- Applied semi-empirical and density functional theory (DFT) to predict isomer binding strengths.
- Utilized Arrhenius kinetics to correlate binding energies with observed environmental behavior under varying water temperatures.
Main Results:
- MM simulations predicted stronger binding of the trans-MCHM isomer compared to the cis-isomer onto an amorphous carbon surface.
- DFT calculations corroborated the preferential binding of the trans-isomer to both planar and amorphous carbon surfaces.
- Predicted binding energy differences, when combined with seasonal temperature variations, provide a kinetic explanation for MCHM leaching from GAC filters.
Conclusions:
- The study demonstrates preferential adsorption of the trans-MCHM isomer onto activated carbon filter media.
- Seasonal temperature fluctuations, acting on differential isomer binding energies, explain the delayed release of MCHM from GAC filters.
- Detailed interfacial chemistry investigations are crucial for understanding and mitigating the impacts of chemical spills on water treatment systems.
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