Microwave driven vapor harvesting with common sorbent materials.

Water shortage is a present problem across the world that is anticipated to worsen with a warming climate and growing population. In places where other sources are unreliable, harvesting it directly from the atmosphere is an appealing option. One practical strategy makes use of sorbent materials, whose uptake and release of vapor can be cycled to drive moisture from low to high concentration, thus enabling condensation above the ambient due point. The efficiency of such devices depends on the magnitude and reversibility of the vapor uptake of the sorbent as well as the efficiency of the thermal cycling mechanism. We present a method by which brief exposure to microwave radiation is used to desorb vapor from the sorbent without degrading it, in a custom setup to characterize the performance of sorbent candidates as pertains to their use in concentrating vapor for harvesting. We characterize the performance of ubiquitous and benign material, paper towel, with varying amounts of impregnated hygroscopic salt to demonstrate the method and gain an understanding of the parameters driving performance.