The elimination of pollutants in water sources is a widely studied issue with the purpose of preserving the environment. In this work, the use of lemon peel (citrus lemon) as a bio-sorbent in the removal of Pb (II) and Ni (II) is studied, varying the temperature, adsorbent dose, and particle size. The materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis, to determine the bio adsorbent’s physicochemical properties. FTIR and EDS techniques confirmed the precipitation of ions on the adsorbent after the adsorption process. It was found that the optimal conditions according to the Response Surface Methodology (RSM) are: particle size for Ni (II) of 1 and 0.355 mm, adsorbent dose 0.077 g and 0.117 g, and temperatures of 34 and 45 ºC, for Pb (II) and Ni (II), respectively. The results reported that the Dubinin-Radushkevich isotherm and the pseudo-second-order model are more in line with the experimental data, suggesting that the adsorption process is driven by physisorption and occurs in multilayers. Thermodynamic parameters suggest that the process is exothermic for Ni (II) and endothermic for Pb (II), and irreversible. The binary study showed that there is no competition for active sites between the ions.