Employing ionomer-based membrane pair technology to extract water from brine

Closing the water loop on long duration spaceflight missions is a key aspect of reducing mission mass and logistics support for orbiting facilities and interplanetary spacecraft. At present, no single practical process exists that is capable of extracting purified water from the wastewater stream in a single step. Recently, the use of synthetic membranes has shown promise in simplifying water purification systems. To build on this work, Paragon Space Development Corporation® (Paragon) researched the use of a microporous-ionomer membrane pair, or ionomer water processor (IWP), under a Phase I NASA SBIR to improve the robustness and effectiveness of membrane-based water/brine separation processes. The microporous membrane prevents liquid wastewater from direct contact with the ionomer, a condition that would reduce the effectiveness of the ionomer. A test rig was built and used to test the brine dewatering capabilities of the ionomer-microporous membrane pair. The hydrophobic side of an ionomer-microporous membrane pair was exposed to both liquid and vapor pretreated urine ersatz brine. The water vapor that transported across the membrane was collected as condensate and sent to a lab for analyses. While still not a singlestep solution to water recovery, prominent findings suggest that a brine dewatering system based on ionomer-microporous membrane pair technology shows great potential to reduce the complexity of water recovery systems. Of note: (1) the membrane pair can function in both liquid-contact and vapor-contact modes, which is important for zero-gravity operation, (2) the membrane pair was shown to prevent 98%-99% of brine stock TOCs and up to 99.8% of ammonium from entering the product stream (permeate), (3) near-complete drying of the brine can be accomplished with this technology, (4) temperatures to drive permeation are consistent with ECLSS waste heat, and (5) permeation rates suggest reasonable unit size can be designed.