Adsorption trapping of Acid Orange 61(AO61) dye in aqueous phase using activated carbon derived from almond shells

This study evaluates the efficiency of NaCl-modified almond shell biomass as a low-cost adsorbent for the removal of Acid Orange 61 (AO61) from aqueous solutions. Adsorption experiments were performed in batch mode, and the influence of key operating parameters was systematically investigated, including adsorbent dose (1 to 6 g/L), initial dye concentration (30 to 150 mg/L), pH (2.5 to 8), and temperature (293 to 323 K). The results showed that the highest adsorption efficiency was obtained at pH close to 8, with an initial dye concentration of 30 mg/L and a temperature of 293 K. The adsorption process was relatively rapid, reaching 85% removal within 90 minutes. The equilibrium data were well described by the Langmuir isotherm model, with a maximum adsorption capacity of 130.63 mg/g. Kinetic analysis indicated that the adsorption follows a pseudo-second-order model, indicating that the adsorption kinetics were best described by the pseudo-second-order model. Thermodynamic parameters (?G?, ?H?, and ?S?) confirmed that the process is spontaneous and endothermic. These findings demonstrate that activated almond shell biomass is an efficient and environmentally friendly low-cost adsorbent for the removal of Acid Orange 61 from contaminated water, offering a sustainable approach for the valorization of agricultural waste.