The effects of the surface oxidation of activated carbon, the solution pH and the temperature on adsorption of ibuprofen

A commercial microporous–mesoporous granular activated carbon was modified by oxidation with either H2O2 in the presence or absence of ultrasonic irradiation, or NaOCl or by a thermal treatment under nitrogen flow. Raw and modified materials were characterized by N2 adsorption–desorption measurements at 77 K, Boehm titrations, pH measurements and X-ray photoelectron spectroscopy. Ibuprofen adsorption kinetic and isotherm studies were carried out at pH 3 and 7 on raw and modified materials. The thermodynamic parameters of adsorption were calculated from the isotherms obtained at 298, 313 and 328 K. The pore size distribution of carbon loaded with ibuprofen brought out that adsorption occurred preferentially into the ultramicropores. The adsorption of ibuprofen on pristine activated carbon was found endothermic, spontaneous (ΔG° = −1.1 kJ mol−1), and promoted at acidic pH through dispersive interactions. All explored oxidative treatments led mainly to the formation of carbonyl groups and in a less extent to lactonic and carboxylic groups. This then helped to enhance the adsorption uptake while decreasing adsorption Gibbs energy (notably −7.3 kJ mol−1 after sonication in H2O2). The decrease of the adsorption capacity after bleaching was attributed to the presence of phenolic groups.