In this work, the equilibrium of the sorption process of copper(II) ions on crushed peanut shell of the size class of particles with a diameter of 200 to 250 µm was investigated. The experiments were carried out in batch reactors, using a suspension prepared from 1 g of crushed peanut shell and copper(II)chloride solutions of different initial concentrations. The suspensions were mixed in a water bath at a constant temperature of 30 °C and a speed of 150 rpm. Samples were taken from the suspensions every 24 hours for 72 hours to determine if equilibrium had been reached. The samples were filtered and analysed with a UV/VIS spectrophotometer. The experimental data obtained were analysed using the Jovanović, Freundlich, Hill and Redlich-Peterson adsorption isotherms. By comparing the experimental data with the selected adsorption isotherms and the calculated RMSE values, it was found that the Hill isotherm best fits the obtained experimental data. It was also found that the sorption efficiency decreases with increasing initial concentration of the copper(II) ion solution. The equilibrium state was reached after 72 hours in all systems tested. It was found that for solutions with initial concentrations greater than 6.496 mmol/dm 3 , the equilibrium amount of copper(II) ions sorbed onto the crushed peanut shell was about 0.21 mmol/g and did not depend on the initial concentration of the solution.