Oscillating Electric Field Effects on Adsorption of the Methane-Water System on Kaolinite Surface

摘要

A quantitative understanding of oscillating electric field effects on adsorption of the methane-water system on kaolinite surfaces is vital for enhancing methane desorption and forecasting gas production. We have performed nonequilibrium molecular dynamics simulations to investigate the adsorption behaviors of methane-water on the kaolinite (0 0 1) surface applying oscillating electric fields in the frequency range of 0-100 GHz and amplitudes of 0-0.25 V/angstrom. The simulated results demonstrate that water will preferentially adsorb onto the surface, forming a water layer and preventing the adsorption of methane and thus leading to the reduced adsorption of methane. The applied oscillating electric fields contribute to a thicker water layer and a smaller amount of adsorbed methane for the water-methane system on kaolinite surfaces. Furthermore, higher oscillating frequency and stronger intensity of the applied electric fields facilitate the desorption of methane. These phenomena associate with the fact that the applied oscillating fields reduce hydrogen bond amounts on the interface of kaolinite, and higher frequencies or stronger intensities further break hydrogen bonds. Meanwhile, the interaction energy of water-kaolinite and the self-diffusion coefficient of water increase with the frequency and intensity of the applied electric fields. This study helps us to understand the mechanism of how oscillating electric fields affect the adsorption behaviors of the methane-water system on kaolinite surfaces and is of applicable importance to boost gas production.