Removal of Diethyl Phthalate from Aqueous Media by Adsorption on Different Activated Carbons: Kinetic and Isotherm Studies

The adsorption of diethyl phthalate (DEP) was studied on four activated carbons (ACs) with different chemical and microporous properties. The kinetic results showed that the non-linear form of the pseudo-second order kinetic model provided the best parameters. Results further showed that the DEP adsorption kinetics is favored by ACs which have a ratio of a specific microporous surface to a specific external surface that is relatively low. Besides, an increase in temperature induced an increase in the rate constant k(2), but the adsorption capacity is temperature independent. Two models, (Langmuir (linear and non-linear forms) and Dubinin-Radushkevich-Kaganer (DRK)), were tested from experimental data. While the Langmuir model provided the best correlation on all the ACs studied. The surface occupied, calculated with the Langmuir parameter obtained by the non-linear form, evidenced the importance of the external surface and the mean pore size. The results show that the non-electrostatic interactions are predominant in the DEP adsorption and are essentially due to dispersion and hydrophobic interactions (for L27 and X17). In the case of F22 and S21 the DEP adsorption is only due to dispersion interaction. A comparison of the thermogravimetric analysis of the ACs washed and saturated shows that the DEP is totally desorbed between 300 and 500 degrees C with a characteristic peak.