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Control of carbon dioxide (CO2) is crucial for all crew inhabited space-flight missions. Air revitalization requires safe and reliable CO2 extraction systems characterized by small volume, low mass, low rate of energy use, minimal use of consumables, and little or no crew time for operation and maintenance. Current designs are relatively costly to operate due to consumable usage rates (e.g., LiOH), high mass and/or volume (solid amines), and/or high energy costs associated with regeneration of CO2 adsorption capacity (e.g., metal oxide). Our work focuses on the development of a highly efficient enzyme catalyzed, Carbonic Anhydrase based liquid membrane biomimetic reactor. We report here on the use of aqueous chemistry modeling to guide the design of new liquid membrane compositions. We examine the effects of these new solutions on enzyme activity and on the solubility of other gases in the mix.

The technologies for processing respiratory gases to support humans and plants and to provide material for regeneration of oxygen in Advanced Life Support applications remain far from optimal. Here we report on our ongoing efforts to develop an enzyme-based, hybrid, facilitated transport bioreactor for the efficient capture of CO2 from dilute respiratory gas streams. In this paper, we examine four different cases with respect to maintaining a driving force for removal of CO2 from respiratory gas.

Carbon dioxide (CO2) control is crucial for crew inhabited space-flight. Existing systems suffer from high consumable usage rates (e.g., LiOH), high mass and/or volume, and/or high energy costs associated with regeneration of CO2 adsorption capacity (e.g., metal oxide). Any new technology must be safe, reliable and have low EMS - small volume, low mass, low rate of energy use, minimal use of consumables, and little need for crew time for operation and maintenance. Our enzyme catalyzed contained liquid membrane facilitated transport reactor/separator for the selective capture of carbon dioxide (CO2) from mixed gas streams satisfies these requirements. The liquid membrane is held in place by hydrophobic microporous polypropylene membranes. This continuous process design is ideally suited to CO2 concentrations ranging from 0.035% to 1% or even higher. The system is stable and can accept feed or sweep gases independent of relative humidity.

Carbon dioxide (CO2) management is critical for all life forms and certainly for all human space-flight missions. CO2 must be extracted and removed or recycled safely, reliably, and rapidly while maintaining CO2 levels within allowable limits independent of crew activity. In view of ESM considerations the system should minimize mass, volume, energy and crew maintenance. Such considerations favor regenerable systems. Our efforts in this direction are focused on a contained liquid membrane design enzyme catalyzed by carbonic anhydrase that exhibits high permeance, ca. 5*10−7 molesCO2/m2 s Pa, very high selectivity vs. nitrogen and is non-responsive to a wide variety of VOCs. Over the last year we have addressed five issues: scale-up, integrated water management, enzyme immobilization, system modeling, and process engineering design. We have developed a membrane element (10 cm × 10 cm × 0.67 cm) capable of removing 0.09 kg/d CO2 from a 0.5% feed stream.