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Updated: May 17, 2025
06:31
Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device
Published on: March 18, 2020
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Optically Triggered Nucleation Eliminates Hydration Hysteresis in Swelling Minerals
Yuntian Teng1,2, Cheng Chen2, Liange Zheng1
1Lawrence Berkeley National Laboratory, CA, 1 Cyclotron Rd, Berkeley 94720, California, United States.
Summary
Hydration hysteresis in porous materials is driven by metastable phase transitions. Visible light can control these transitions, making both branches of the hysteresis loop reversible and impacting soil contaminant mobility.
Area of Science:
- Materials Science
- Physical Chemistry
- Environmental Science
Background:
- Hydration hysteresis is common in porous solids, but the metastability of its branches is debated.
- Understanding hysteresis mechanisms is crucial for predicting water-sorbent interactions.
Purpose of the Study:
- To investigate the metastability of hydration hysteresis branches in smectites.
- To explore the role of optical activation in controlling hydration states.
Main Methods:
- Isothermal, isobaric hydration calorimetry.
- In situ Raman spectroscopy.
- Optical activation using continuous-wave laser illumination.
Main Results:
- Both endothermic and exothermic phase transitions were optically activated, confirming metastability of both branches.
- A net free energy difference of +15 kJ/mol of water was observed.
- Hysteresis vanished under laser illumination, with reversible sorption energy of 5R per water molecule.
- Raman spectra indicated hydrogen bonding screens interlayer charge, weakening interactions and releasing heat.
Conclusions:
- Water sorption hysteresis arises from interfacial phase transitions promoted by visible light.
- Optical control of hydration states has implications for sorbent behavior, including carbon and contaminants in soils.
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