Tunable effective diffusion of CO2 in aqueous foam

• 成果类型: Article
• 署名作者: Aprili, Cecile; Coupier, Gwennou; Lorenceau, Elise; Dollet, Benjamin
• 署名单位: Communaute Universite Grenoble Alpes; Universite Grenoble Alpes (UGA)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8689
• DOI: 10.1073/pnas.2504617122
• 发表日期: 2025-08-26
• 关键词: film permeability; gas; stabilization; absorption; SEPARATION; STABILITY; DYNAMICS

摘要

Aqueous foams are solid materials composed of gases and liquids, exhibiting a large gas/liquid surface area and enabling dynamic exchanges between their fluid components. The structure of binary-gas foams, whose bubbles consist of a mixture of two gases having different affinities with the liquid, thus offers real potential for the dynamic separation of these gases at low cost. In single-gas foams, the structure evolves under the effect of gas flow induced by Laplace pressure differences, arising from heterogeneities in bubble size. This leads to the well-documented Ostwald ripening. In addition to these capillary effects, the structure of binary-gas foams can evolve under the effect of gas flow induced by partial pressure differences, arising from heterogeneities in bubble composition. We experimentally investigate the shrinking of CO2-laden 2D foams exposed to air, observing a crust of tiny bubbles at the front. We derive a nonlinear diffusion model for the gas in the foam and propose a description of the whole foam as an effective, homogeneous medium, the key parameter being the gas permeability ratio across the foam's soap films (6=1 for CO2/air). The effective diffusivity of the gas in the foam emerges from the coupling between foam structure and gas transport across soap films. We extrapolate it for various permeability ratios and show that it can vary continuously between the diffusivity of the gas in the liquid and that of the gas in the atmosphere, enabling tunable gas retention and release by controlling the composition of the atmosphere.