STUDY ON THE ADSORPTION CAPACITY OF DIRECT RED 79 DYE ON ACTIVATED CARBON PREPARED FROM LONGAN SEEDS

Abstract

In this study, activated carbon was successfully synthesized from longan seeds (ACLS), using NaOH as the activating. The resulting ACLS exhibited a porous structure characterized by a specific surface area of 678.5 m²/g. Investigations into the factors influencing the adsorption of Direct Red 79 (DR79) dye by ACLS using the static adsorption method revealed the following: the optimal adsorption pH was found to be 3.0; the adsorption equilibrium was reached within 150 minutes at room temperature (25±1⁰C). As the temperature increases within the studied range of 298 to 318K, the adsorption efficiency increases, with determined values of ΔG^o < 0; ΔH^o = 24.003 kJ/mol, indicating a spontaneous and endothermic process. The adsorption process of DR79 by ACLS was investigated using the Langmuir, Freundlich, Temkin, and Elovich adsorption isotherm models. Among these, the Langmuir isotherm model provided the best description of the DR79 adsorption. The maximum adsorption capacity of DR79 onto ACLS, as determined by this model, was 684.93 mg/g at 298K.