Adsorption of Acetic Acid onto Activated Carbon from Barley Husks, Eggshells, and Silica Gel: Isotherm and Thermodynamic Analysis

Abstract

This study investigated the efficiency of three distinct low-cost adsorbents—activated carbon prepared from barley husks (ACB), eggshell powder (ESP), and commercial silica gel (SG)—for the removal of acetic acid from aqueous solutions. The research included optimizing the preparation conditions (e.g., carbonization temperature for ACB) and evaluating key operational parameters such as adsorbent dosage, contact time, initial acid concentration, and solution temperature. Experimental findings demonstrated that eggshell powder (ESP) exhibited the highest adsorption efficiency and capacity among the materials tested. The equilibrium contact time was consistently reached in approximately 30 minutes for all adsorbents. Kinetic analysis indicated that the adsorption data fit well with the Pseudo-Second-Order model. Thermodynamic analysis revealed that the process on ACB was endothermic (favorable at high temperatures), while it was exothermic (favorable at low temperatures) for both ESP and SG. Furthermore, the equilibrium data were successfully modeled using both the Langmuir and Freundlich isotherm models.