Mass transfer and equilibrium modelings of phenol adsorption on activated carbon from olive stone

Abstract

Activated carbon was produced from olive stones by chemical activation using ZnCl2 at 20 % w/w for 12 h. Pyrolysis was performed at 700 °C for 2 h in a quartz tubular reactor. The adsorbent was characterized using SEM, XRD, FTIR, N2 adsorption-desorption isotherms, and the BJH. The images showed the presence of voids on the surface of the activated carbon. Diffractograms revealed a material of reduced crystallinity containing predominantly short-range ordering. BET surface area was 667 m2 g −1, and total pore volume was 0.318 m2 g −1. The equilibrium study showed that a higher temperature intensified the phenol adsorption capacity, and the highest value was around 120 mg g−1. Besides, the Freundlich isotherm was the more suitable to represent the equilibrium data. The thermodynamic study indicated that phenol adsorption onto activated carbon produced was spontaneous, favorable, endothermic, and entropy-controlled. According to physical statistics interpretation, the dual layer with one energy site was the most suitable model for describing the adsorption equilibrium. The concentration decay for the phenol showed that the initial phenol concentration direct affects the experimental data profile. Concerning the estimated mass transfer parameters and statistical parameters for the PVSDM, it was found that the external mass transfer and surface diffusion increased with the initial concentration. This trend indicates that the extremal mass transfer affected the adsorption kinetics.