Adsorption is the surface ability of solid mater to bond with particles of gases or dissolved matter. This phenomenon is of great use in many separation processes, especially in the removal of industrial pollutants like heavy metals, pharmaceuticals, dyes and organic acids from wastewaters. This paper studies the adsorption of organic acids, acetic (CH3COOH) and formic (HCOOH). The study was performed in a column system with a fixed bed of granulated active carbon (GAC) with the height of 10 cm, and with a continuous flow of 21,9 ± 3,3 mL min^-1. First, the adsorption equilibrium of given acids was determined by the Freundlich isotherm model. Both acids showed similar affinity for adsorption. The results were shown by plotting the breakthrough curves that show the dependence of c/c0 to V/mL where c/c0 is the ratio of the solutions concentration before and after adsorption, and V/mL is the volume of the solution that passed through the column. The effect of concentration and particle shape was determined by comparing the breakthrough curves for the solution of the same acid with different concentrations, and by comparing both acids to each other at the same concentrations. The results showed that the speed of adsorption rises with the rise of concentration. At lower concentrations (c < 4 mol L^-1) the effect of molecular shape is also shown as acetic acid is adsorbed in less time than formic acid of the same concentration. At higher concentrations the effect of molecular shape is negligible compared to the effect of concentration.