In this thesis, the equilibrium of copper ion sorption on dried and milled peanut shell particles with diameter between 100 and 200 µm was investigated. The experiments were carried out in five batch reactors, in suspensions of 1 g of milled peanut shells and 0.2 L of copper(II) chloride dihydrate solution of different initial concentrations. The prepared suspensions were mixed under isothermal conditions (T = 27 °C) and at a speed of 200 rpm. Suspension samples were sampled and analyzed with a UV/VIS spectrophotometer at defined time intervals during 96 hours to verify if an equilibrium state had been established in the systems investigated. The obtained experimental data were analyzed by Langmuir, Freundlich and Sips isotherms. The analysis of the agreement of the experimental data with the adsorption isotherms and the values of the calculated RMSE parameter revealed that the Langmuir isotherm shows the best agreement with the experimental data and that the sorption efficiency decreases with the initial concentration of the copper(II) chloride dihydrate increase. In all systems tested, equilibrium state was reached after 24 hours; the amount of copper ions retained on milled peanut shells in equilibrium is independent of the initial concentrations of the solutions and is about 0.20 mmol/g, except for the lowest concentration used.