Improving the adsorption kinetics of ibuprofen on an activated carbon fabric through ultrasound irradiation: Simulation and experimental studies

Abstract

In order to override the slow adsorption kinetics of micropollutants on an activated carbon fabric (ACF) in water medium, different mixing modes, i.e. orbital stirring (250 rpm), low frequency ultrasonic irradiation with either a 20 kHz probe (volumic power: 80 W/L) or a 38 kHz bath (10 W/L), were compared to promote the adsorption of ibuprofen (4 ppm initial concentration).The used ACF is formed of wowen braids made of three yarns (∼300 µm diameter), each of them being composed of microporous fiber bundles (12.6 µm diameter) and its texture was accurately characterized. The adsorption kinetics were studied in buffered phosphate solution (pH 7.5) on a disk, braids or fiber from the fabric and were simulated by a volume diffusion model. The fitted values of the external mass transfer and the volume diffusion coefficients have demonstrated the limitation of the adsorption kinetics under stirring on the fabric disks and braids by the diffusion step within the yarn in the inter-fiber macroporosity.The 20 kHz sonication coupled to the adsorption on ACF led to the degradation of ibuprofen by OH° radicals issued from water sonolysis but without damaging further the fabric. The low power irradiation at 38 kHz allowed a sharp acceleration of the adsorption kinetics with respect to the one obtained through orbital stirring. This is explained by a fast mobility of the ibuprofen owing to the presence of standing waves and absence of harsh cavitation as compared to 20 kHz probe system, and confirmed by a fitted diffusion coefficient higher than the one of molecular ibuprofen and of two order of magnitude than in stirring conditions.