A three-dimensional mass transfer model (pore volume and surface diffusion model, PVSDM 3D) was applied to elucidate the ibuprofen adsorption on standard (SAC) and ultrasound modified (USAC) activated carbons. Experimental isotherms and kinetic curves were constructed at pH 2.0 and 298 K. The results revealed that USAC presented higher values of surface area, pore diameter, pore volume and void fraction than SAC, demonstrating that the ultrasonic modification was efficient to improve the characteristics of activated carbon. The adsorption capacities obtained using USAC carbon were around 25% higher in relation to the obtained using SAC carbon. For both adsorbents, the Redlich-Peterson model was able to predict the isotherm data. At pH of 2.0, dispersive interactions pi-pi and donor-acceptor interactions between the aromatic ring of ibuprofen and carbonyl groups of the activated carbons occurred. The concentration decay curves obtained with USAC required less time to reach equilibrium due to its modification of textural properties. The application of PVSDM 3D model evidenced that the D s (surface diffusion coefficient) values for USAC were around 1.7 folds greater than those obtained by SAC, besides it was corroborated that the magnitude of total intraparticular flux is a function of time and position inside the particle. It was verified that the ibuprofen molecule diffuses exclusively by surface diffusion and that the diffusion in the pore volume can be neglected. The D-s values ranged from 1.8 x 10(-9) to 33.6 x 10(-9) cm(2) s(-1).