High-performance activated carbon from coconut shells for dye removal: study of isotherm and thermodynamics

This study investigates the production of high-performance activated carbon (AC) from coconut shells (CS) through acid and base activation processes, along with pre- and post-functionalization of the biochar, aiming to effectively remove dyes from aqueous solutions. The resulting AC exhibited outstanding adsorption capabilities, with the Langmuir model providing a good fit to the experimental data. Maximum adsorption capacities were observed at different temperatures: 805 mg g^-1 at 298 K, 904 mg g^-1 at 318 K, and 1000 mg g^-1 at 338 K for NaOH-activated AC, and 252 mg g^-1 at 298 K, 295 mg g^-1 at 318 K, and 305 mg g^-1 at 338 K for H₂SO₄-activated AC. The presence of active sites and functional groups on the surface of AC facilitated dye adsorption. The influence of various parameters, including adsorbent dosage, dye concentration, pH, and temperature, on the adsorption process were also examined, identifying the ideal conditions for dye removal. Thermodynamic analysis confirmed the endothermic nature of the adsorption process, with higher temperatures leading to increased adsorption capacities. Overall, the research highlights the potential of various activation routes for the production of high-value AC as a sustainable and effective adsorbent for dye removal from wastewater.