The adsorption process of phenol onto activated carbon particles in suspension is modeled with a 2 3 full factorial design. In an earlier study, the optimal operating conditions of temperature, agitation, and pH of the phenol solution were determined. In this present study, the values of these parameters remain constant and equal to their optimum values (T = (30 +/- 1) degrees C, omega = 400 rpm, and pH = 3). The aim of this article is to find a simple and reliable relation between the three independent variables (the particle diameter, the amount of activated carbon, and the initial concentration of phenol) and the response which is the percent removal of phenol that has been described by a polynomial model. Exploration of the model shows that for adsorption from solutions containing a low initial concentration of phenol the use of a low concentration suspension of powder activated carbon or high concentration Suspension of granular activated carbon is advised. Whereas for the adsorption from solutions containing a high initial concentration of phenol, the use of a high quantity of carbon of any particle size is Suggested. The results obtained show that there are critical values for those parameters which divide the studied intervals into two zones where the evolution of the adsorptive quantity is different.