Kinetic, equilibrium, and thermodynamic studies of adsorptive interactions of eosin-B on chemically treated orange peels

The present study investigated the adsorption of eosin B on the surface of powdered and chemically treated orange peels, along with this process’s condition optimizations, kinetics, and thermodynamics. The adsorbent dose (0.1–0.5 g), temperature (298, 303, 308, and 313 K), contact time (15–120 min), initial pH value (2–11) of the solution, and interfering salts (0.01 and 0.1 mol L−1) were all taken into consideration during the experiments. At all investigated temperatures and pH of 2, adsorption was more favourable. Although the Langmuir model might also represent the adsorption data, the Freundlich and Dubinin–Radushkevich (D–R) models provided a good description. The pseudo-second order kinetic model was followed during the adsorption process. The mechanics of the rate-controlling step were examined by applying the intra-particle diffusion-based mass transfer model to the experimental data. It was discovered that the only process that controlled the rate was intra-particle diffusion. The adsorption process appears to be spontaneous, and endothermic and involves van der Waals forces based on thermodynamic data.