Adsorption and desorption of phenol on activated carbon and a comparison of isotherm models

In this study, the potential of activated carbon for phenol adsorption from aqueous solution was studied. Batch kinetics and isotherm studies were carried out to evaluate the effect of contact time, initial concentration, and desorption characteristics of activated carbon. The equilibrium data in aqueous solutions was represented by the isotherm models. Desorption studies to recover the adsorbed phenol from activated carbon performed with NaOH solution. It is necessary to propose a suitable model to gain a better understanding on the mechanism of phenol desorption. For this purpose, pore diffusion and first-order kinetic models were compared. The diffusivity rate (D/r2) and first-order desorption rate (kD) constants were determined as 6.77 × 10−4 and 3.924 × 10−4 s−1, respectively. The two- and three-parameter in the adopted adsorption isotherm models were obtained using a non-linear regression with the help of MATLAB® package program. It was determined that best-fitted adsorption isotherm models were determined to be in the order: Langmiur > Toth > Redlich–Peterson > Freundlich isotherms.