Molecular mechanism of electrostatic field-enhanced water vapour absorption at the gas-solution Interface

FS Fan and YG Yin and GY Xu and WH Chen and CN Markides, INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER, 169, 109610 (2025).

DOI: 10.1016/j.icheatmasstransfer.2025.109610

Gas-solution mass transfer is critical in industrial manufacturing, chemical processing, and indoor humidity control. Liquid desiccant dehumidification (LDD) systems offer energy-efficient, environmentally friendly humidity control by utilising low-grade heat and avoiding conventional refrigerants, but their performance is limited by low interfacial vapour absorption. Interfacial transport-absorption, reflection, and release-is governed by structural properties, providing a molecular-level perspective for performance enhancement. This study proposes active control of water vapour transport at the LiBr solution vapour-liquid interface using an external electrostatic field (E-field) applied along the mass transfer direction to induce interfacial polarisation. Molecular dynamics (MD) simulations show that the E-field increases net absorption, with positive fields more effective than negative ones. Both polarities enhance absorption by reorienting water dipoles, disrupting hydrogen-bond (H-bond) networks, and promoting diffusion. Reflection and release are highly polarity-dependent: positive fields enrich Li+ at the interface, strengthening hydration, trapping water, and suppressing release; negative fields deplete Li+ and accumulate Br-, weakening hydration, and facilitating release. These findings provide a molecular framework for enhancing interfacial mass transfer through external field modification to improve dehumidification and may also guide optimisation of other gas-liquid processes involving polar molecules.

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