Adsorption kinetics of phenol and 3-nitrophenol from aqueous solutions on conventional and novel carbons.

Carbonaceous adsorbents prepared from olive stones biomass and novolac resin, as well as a commercial activated carbon for comparison reasons, have been examined for the removal of phenol and 3-nitrophenol from aqueous solutions. All carbonaceous adsorbents have been characterized by SEM-EDAX analysis and mercury porosimetry. The experimental data were examined according to the following kinetic models: pseudo first order, pseudo second order, Natarajan and Khalaf, Elovich, power function equations and intraparticle diffusion. By plotting the amount of adsorbate (phenol or 3-nitrophenol) adsorbed per unit mass of adsorbent b(t), versus the square root of time, four regions can be distinguished (A, B, C and D). By applying all the previously described models it is concluded that: (a) the intraparticle diffusion model is valid for the B and C region, whereas macropore diffusion and mesopore diffusion, respectively, take place. The pore diffusion coefficient, D for each carbonaceous material was calculated and indicated that the adsorption is controlled by diffusion, (b) the power model for the adsorption of phenol on each of the three carbonaceous materials is acceptable only for the C region and (c) the pseudo second order for the adsorption of 3-nitrophenol on each of the three carbonaceous materials is acceptable for the C region.