Evaluation of Traditional and Vacuum-Regenerable Sorbents Exposed to a Multi-Gas Contaminant Mixture in the Trace Contaminant Control Unit

The efficient removal of trace contaminants generated by crewmember’s metabolic processes from the ventilation loop of the Exploration Portable Life Support System (xPLSS) is critical for the health and safety of astronauts. Currently, acid-impregnated activated carbon (Ammonasorb II), a non-regenerable sorbent, is used in the Trace Contaminant Control (TCC) system. This limits the TCC operational service life and can add significant logistical hurdles to spacecraft missions. New regenerable sorbents, such as XploSafe’s nanoporous silica-based sorbent, can considerably expand the operational capabilities of the TCC. To evaluate potential sorbents, XploSafe developed a TCC test-bed apparatus, which is used to directly compare the trace contaminant removal capabilities of regenerable and non-regenerable sorbents under operational conditions. The tested sorbents are placed inside a model TCC cartridge and exposed to a recirculating closed-loop system at a sub-atmospheric pressure of 4.3 psia and flow rate of 6 ACFM. A multi-gas stream of nine priority NASA contaminants (including ammonia, methyl mercaptan, and formaldehyde) is injected into the recirculation loop at established source rates. Contaminant concentrations inside the recirculation loop are monitored in real time using a combination of sensors and by periodically sampling a fixed volume of the circulating gas stream. The sampled gas is analyzed by a thermal desorption unit connected to a gas chromatograph-mass spectrometer to precisely quantify the analytes within the sample. Ammonasorb II and XploSafe sorbent are individually exposed to a trace contaminant multi-gas stream for over 150 and 24 hours, respectively. In addition, a vacuum regeneration cycle is incorporated with a pressure swing at a set time interval to evaluate the effectiveness of the XploSafe sorbent with regeneration. The results show that sorbents can be evaluated under realistic conditions. With regeneration, XploSafe's sorbent could significantly increase extravehicular activity.