Comparison of Moisture Sorption Isotherm Models and Desorption Kinetics of Silica-Impregnated Biochar Composite Desiccant

This study investigates the moisture sorption behavior and regeneration performance of a composite based on biomass-derived activated carbon (biochar) impregnated with silica (Na2SiO3) named AC/Si as desiccant. The composite was characterized by SEM and nitrogen adsorption analysis to evaluate structural changes after impregnation. Water vapor adsorption isotherms were fitted to five models (BET, Halsey, Henderson, Oswin, and Smith), with the Halsey model exhibiting the highest accuracy. Desorption kinetics were evaluated at 313–333 K using pseudo-first-order (PFO) and pseudo-second-order (PSO) models, with the PSO model providing a superior fit as evidenced by high R2 and low RMSE. The Arrhenius equation was employed to determine the activation energy (Ea) of the composite's desorption process, resulting in an Ea of 40.23 kJ/mol, which suggests efficient regeneration under moderate heating. These findings support the potential of AC/Si composites as energy-efficient, reusable desiccants for general-purpose moisture control.