Equilibrium, Thermodynamics, and Regeneration and Reuse of Biosorbents Developed from Pelletized Agricultural Residues for Gas Dehydration

Abstract

Adsorption process is among the most feasible approaches to gas dehydration in the industry to achieve high-purity products. Developing low-cost and novel bio-based adsorbents from agricultural by-products has recently received growing attention. Canola meal and oat hull with specified compositions have demonstrated a promising potential for the selective removal of water vapor and possess considerable water uptake capacities compared to commercial desiccants. The biosorbents were densified to form pellets of similar size and shape with controlled sorption capacity and physical properties for industrial usage. The current research focuses on sorption equilibrium isotherm and thermodynamics, as well as sorption–desorption and reusability of biosorbent pellets. The experimental water sorption equilibrium data obtained at 25 °C and 101.3 kPa showed a type II isotherm and were successfully modeled by the GAB and Redhead isotherms; however, data obtained at 35 and 45 °C and 101.3 kPa demonstrated a linear isotherm. The water uptake by the biosorbent pellets was exothermic and physisorption, mainly due to the hydrogen bonds formed between water molecules and hydrophilic functional groups on the surface. The pellets were stable over 50 sorption–desorption cycles inside the pressure swing adsorption column without detectable changes in their structure.