Preparation and characterization of activated charcoal from a plant mixture and its use in the adsorption of methyl orange dye from aqueous solutions, a chemical and thermodynamic study

Water pollution from industrial effluents, particularly those containing synthetic dyes, poses a serious environmental and health threat due to their toxicity, persistence, and resistance to conventional treatment methods. Developing sustainable and cost-effective adsorbents is therefore of great importance. In this work, nano-activated carbon was synthesized from a mixture of wormwood and acacia seed pods and evaluated for the removal of orange dye from aqueous solutions. The adsorbent showed high efficiency, achieving 95% removal within 40 minutes. The effects of contact time, temperature, and adsorbent dosage were systematically investigated. Kinetic analysis indicated that the adsorption process followed the pseudo- second-order model, while thermodynamic results confirmed that the process was endothermic and spontaneous at all studied temperatures, as shown by negative Gibbs free energy values. Positive entropy changes suggested increased randomness at the solid–solution interface, and equilibrium data fitted well to the Freundlich model, indicating heterogeneous multilayer adsorption. Overall, the findings demonstrate that the adsorption mechanism is mainly physical in nature and highlight the potential of this green-synthesized nano-activated carbon as an efficient and eco-friendly material for treating dye-contaminated wastewater.