Kinetic Modelling of Naphthalenesulphonic Acid Adsorption from Aqueous Solution onto Untreated and Ozonated Activated Carbons

Abstract

The adsorption rate of 1-naphthalenesulphonic (NS), 1,5-naphthalenedisulphonic (NDS) and 1,3,6-naphthalenetrisulphonic (NTS) acids onto activated carbon (AC) was studied in this work. In addition, the effect of oxidizing the AC with ozone on the rate of adsorption was investigated. The adsorption equilibrium data as well as the concentration decay data for the naphthalenesulphonic acids (NSAs) were obtained in a batch adsorber. The Freundlich, Langmuir and Prausnitz–Radke isotherms were fitted to the experimental adsorption equilibrium data when it was found that the Prausnitz–Radke isotherm gave the best fit. The experimental concentration decay data were interpreted via a diffusional model which considered the adsorption rate at a surface site, external mass transport and intraparticle diffusion. The results revealed that intraparticle diffusion was the controlling mechanism in the diffusional model and that this model predicted the experimental data satisfactorily. The effective diffusion coefficients of the NSAs could be estimated using the tortuosity factor equation together with tortuosity factors for the ACs ranging from 3.7 to 5.5.