Equilibrium, kinetic and thermodynamic studies on the adsorption of phenol onto chitin

The adsorption of phenol onto chitin, a naturally occurring material was studied as a function of initial pH, temperature and initial phenol concentration. The highest phenol adsorption capacity was determined as 21.5 mg g−1 for 300 mg dm−3 initial phenol concentration at pH 1.0 and 40 °C. Adsorption data were well described by the Freundlich Model, although they could be modeled by the Langmuir equation. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second-order kinetic model provided the best correlation of the experimental data compared to the pseudo-first-order model. The thermodynamic constants of the adsorption process; ΔG°, ΔH° and ΔS° were evaluated as -19.4 kJ mol−1 (at 40 °C), 10.2 kJ mol−1 and 0.093 kJ mol−1 K−1, respectively. These showed that adsorption of phenol on chitin was endothermic and spontaneous.