Fast Kinetics Biosourced Carbon-Based Sorbents for Atmospheric Water Harvesting

Sorbent-based atmospheric water harvesting methods are emerging as promising techniques to address current and future water stress challenges. Recent advancements in sorbent design have shifted focus toward achieving both rapid sorption kinetics and high steady-state water uptake. Herein, daily water yields reaching 42, 15, 11, and 6.5 L<middle dot>kg-1<middle dot>day-1 are reported, respectively, at 95, 60, 30 and 10% relative humidity at 30 degrees C by employing activated, biosourced carbon-based sorbents. The specific dynamic vapor sorption performances of these biobased nanoporous sponges, Bio-NPS, were discussed as a function of their processing conditions, structures, and chemical compositions. The theoretical model proposed by Do et al. was applied to better understand the sorption mechanisms of water in different porous carbon media. The oxidation of hardwood charcoals using KOH at temperatures below 500 degrees C produced microporous sorbents rich in oxygen (18 atom %) and hydrophilic functions with a small specific surface. Type V water-sorption isotherms were obtained with no hysteresis. A moderate maximum water uptake (0.35 g<middle dot>g-1 of sorbent at 95% relative humidity) was attained, with fast water sorption kinetics. At higher processing temperatures, sorbents presented a higher specific surface (2748 m2<middle dot>g-1 for the sorbent processed at 900 degrees C) with reduced oxygen amount and hydrophilic functions. A higher maximum water uptake was obtained, reaching 1.3 g<middle dot>g-1 at 95% relative humidity, but cycles were slower. Through Bio-NPS, a significant step demonstrating effective, sustainable, and robust water production performances across a wide range of conditions has been achieved, alongside low-environmental-impact and sustainable synthesis.