Temperature-dependent waterbinding on potassiumbirnessite : A potential sorbent for atmospheric water harvesting

Abstract: The nanolayered manganese oxide birnessite (MnO2) is a naturally occurring mineralin soils and sediments. Its ability to capture and store water within its interlayers, andits great solar absorptivity, could be a part of the solution to global water shortage.Sorbent-based atmospheric water harvesting is a potential technology to increase thewater supply in arid areas. Fundamental studies on potential sorbents, such asbirnessite, is essential for further progress. To investigate how the nanometric waterfilms in birnessite act over a range of temperatures, Fourier Transform Infraredspectroscopy was used during 21-point adsorption/desorption isotherm cycles atconstant temperatures, from 30 to 80 °C. All spectra were analyzed and interpreted inthe computational environment of Matlab. The result showed that the water bindingin birnessite is temperature dependent, and it lose as much as half of its efficiency whenincreasing the temperature from 30 to 80 °C.