Effect of Temperature on the Adsorption of Water in Porous Carbons

Journal Article · Sat Oct 01 04:00:00 EDT 2005 · Langmuir

DOI:https://doi.org/10.1021/la051120t· OSTI ID:1003554

Striolo, A. ^[1]; Gubbins, K. E. ^[2]; Gruszkiewicz, Miroslaw S. ^[3]; Cole, David R. ^[3]; Simonson, J. Michael ^[3]; Chialvo, Ariel A. ^[3]; Cummings, Peter T. ^[3]; Burchell, Timothy D. ^[3]; More, Karren Leslie ^[3]

---

1. Vanderbilt Univ., Nashville, TN (United States)
2. North Carolina State Univ., Raleigh, NC (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

We report experimental and simulation studies to investigate the effect of temperature on the adsorption isotherms for water in carbons. Adsorption isotherms are measured by a gravimetric technique in carbon-fiber monoliths at 378 and 423 K and studied by molecular simulation in ideal carbon pores in the temperature range 298-600 K. Experimental adsorption isotherms show a gradual water uptake, as the pressure increases, and narrow adsorption-desorption hysteresis loops. In contrast, simulated adsorption isotherms at room temperature are characterized by negligible uptake at low pressures, sudden and complete pore filling once a threshold pressure is reached, and wide adsorption-desorption hysteresis loops. As the temperature increases, the relative pressure at which pore filling occurs increases and the size of the hysteresis loop decreases. Experimental adsorption-desorption hysteresis loops are narrower than those from simulation. Discrepancies between simulation and experimental results are attributed to heterogeneities in chemical composition, pore connectivity, and nonuniform pore-size distribution, which are not accounted for in the simulation model. The hysteresis phase diagram for confined water is obtained by recording the pressure-density conditions that bound the simulated hysteresis loop at each temperature. We find that the hysteresis critical temperature, i.e., the lowest temperature at which no hysteresis is detected, can be hundreds of degrees lower than the vapor-liquid critical temperature for bulk model water. The properties of confined water are discussed with the aid of simulation snapshots and by analyzing the structure of the confined fluid.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1003554
• Journal Information: Langmuir, Journal Name: Langmuir Journal Issue: 21 Vol. 21; ISSN 0743-7463
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE