Innovative water-based dynamic liquid bubble membrane generation device for gas/vapour separation

Gas and vapour separation by membrane technology has become a promising method because of its high energy efficiency and low capital investment. Here, we demonstrate a proof of concept of the design of a new type of liquid membrane called the “dynamic liquid bubble membrane” (DLBM) connected by plateau borders. The DLBM is composed of a network of bubbles formed by passing a gaseous mixture through water containing a surfactant. The bubble network serves as a membrane to selectively separate the gases/vapours of mixtures according to the different solubilities of the gases in the bubble liquid. To the best of our knowledge, this type of liquid foam has not been described previously. The effects of key experimental factors, such as the surfactant concentration in the water of the membrane solution and the bubble velocity (controlled by the slope of the device) of the DLBM, on the CO2/CH4 separation performance were investigated. The retentate gas (CH4) remained over 99.9 % for the high CH4 concentration injection mixture (>66.7 % CH4). Then, O2/CO2 was used to simulate the fluid of the alveolar lining during the full in-breath process. We found that carbon dioxide transferred outside the bubble film, while oxygen was retained inside the bubble. This finding supports a further understanding of the CO2 transport mechanism of alveoli. We further demonstrated that the thickness of the bubble film was closely correlated to mass transfer resistance theory, while the gas selectivity was completely unaffected. This innovative DLBM generation device is a highly attractive and promising prototype for designing a green and highly efficient gas/vapour separation membrane technology.