Atmospheric water sorption kinetics of a biomass-derived sorbent: a preliminary study

This study aims to investigate the atmospheric water sorption kinetics of a CaCl₂ salt-impregnated sorbent derived from waste sugarcane biomass under real-time semi-arid to semi-humid conditions. The samples prepared by impregnating highly porous activated carbon prepared from waste sugarcane bagasse in different salt concentrations of CaCl₂ was initially screened based on its water uptake and sorption kinetics. Subsequently, the screened sorbent underwent further characterization to assess its textural properties, surface morphology, thermal stability, functional groups, and density. Under low relative humidity (RH) conditions ranging from 30 to 50%, the sorbent exhibited commendable water uptake ranging between 0.71 and 0.95 g/g, coupled with rapid adsorption and desorption kinetics. The sorbent also demonstrated operational stability over 10 adsorption–desorption cycles. The experimental water uptake data was also fitted using the Linear Driving Force (LDF) model to determine the sorption rate constant and resulted in a very good agreement with the model. Furthermore, at 60 °C, more than 80% desorption was attained, indicating the feasibility of solar-assisted operation. This study highlights the potential of sorbents derived from waste biomass for sustainable AWH applications.