Adsorption is a method of separation between the solid phase and the particles in the gas or solution they adsorb. It is of great importance and application in industry, especially for wastewater treatment, removal of heavy metals, poisons, dyes and odors. During the adsorption, various sizes and parameters are studied, which can be tested via adsorption isotherms. The purpose of this paper was to perform the adsorption of formic acid. Adsorption was carried out using a granular activated carbon (GAC) column system at different heights of fixed bed and column diameter and constant flow rate. The default heights were 10, 15 and 20 cm, diameters 3 and 4 cm, and flow rate is 24.7 ± 3.9 mL min^-1. The test consisted of two parts. First, the adsorption balance of formic acid was described via the Freundlich isotherm and then the solution was passed through the column. The measurement results are presented through breakthrough curves describing the dependence of the ratio of the output and the inlet concentration of the solution (c/c0) on the volume of the leaked solution. The parameters of the Freundlich isotherm have shown a good affinity for adsorption. When comparing the acid breakdown curves of different GAC heights and different set concentrations, it is evident that adsorption is best at the highest coal level due to the larger number of pores within the layer and by increasing the concentration of the solution, the adsorption is faster.