Preliminary characterization of carbon dioxide transfer in a hollow fiber membrane module as a possible solution for gas–liquid transfer in microgravity conditions

Abstract In microgravity, one of the major challenge encountered in biological life support systems (BLSS) is the gas–liquid transfer with, for instance, the necessity to provide CO 2 (carbon source, pH control) and to recover the evolved O 2 in photobioreactors used as atmosphere bioregenerative systems. This paper describes first the development of a system enabling the accurate characterization of the mass transfer limiting step for a PTFE membrane module used as a possible efficient solution to the microgravity gas–liquid transfer. This original technical apparatus, together with a technical assessment of membrane permeability to different gases, is associated with a balance model, determining thus completely the CO 2 mass transfer problem between phases. First results are given and discussed for the CO 2 mass transfer coefficient k L CO 2 obtained in case of absorption experiments at pH 8 using the hollow fiber membrane module. The consistency of the proposed method, based on a gas and liquid phase balances verifying carbon conservation enables a very accurate determination of the k L CO 2 value as a main limiting step of the whole process. Nevertheless, further experiments are still needed to demonstrate that the proposed method could serve in the future as reference method for mass transfer coefficient determination if using membrane modules for BLSS in reduced or microgravity conditions.