Effect of water occupancy on the excess adsorption of methane in montmorillonites

L Wang and DB Wang and CH Cai and N Li and L Zhang and ML Yang, JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING, 80, 103393 (2020).

DOI: 10.1016/j.jngse.2020.103393

Excess adsorption is usually used to measure the adsorption capacity for methane in porous clays and to compare with experiments. The commonly used definition of excess adsorption neglects water-occupied volume in moist clays. Such approximation leads to negative excess adsorption for nanoporous adsorbents with high water content, which is unphysical and deviates from experiments. Based on Monte-Carlo and molecular dynamics computations on montmorillonites with various slit apertures, a modified definition is proposed for the excess adsorption of methane in the nanoslit systems by taking the water-occupied volume into account. The modified model produces positive excess adsorption values that match better with the available observations.

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