In view of climate change, seawater desalination is of concern to mankind, as the most difficult step in water treatment is the isolation of NaCl from seawater. The methods currently used to disable seawater remain costly, so it is important to understand and improve other methods for reducing the cost of seawater filtration. An atomic-scale computational study of NaCl and H₂O adsorption on graphite and graphene is presented, with the aim of estimating the ability of graphite-graphene to remove NaCl from seawater to obtain drinking water. The calculations are based on Density Functional Theory (DFT), using the Grid-based Projector-Augmented Wave (GPAW) approach, Atomistic Simulation Environment (ASE), and Quantum ESPRESSO methods. The main results of our work are the optimization of H₂O and NaCl molecule energies and densities of molecular states, and the calculation of the optimal adsorption distance of these molecules on the adsorbent (graphite-graphene). The observed changes in adsorption energies and density of states of the adsorbent could be exploited in the perspective of seawater filter applications. Our results could contribute to the optimization of potential seawater filter applications. The present work provides interesting information to the theoretical and experimental communities working in this field of research. It opens up the debate on the adsorption of H₂O and NaCl molecules on graphite and graphene.