<p>The presence of heavy metal ions in water bodies poses a threat to human health because of their toxicity and bioaccumulative effects. This work aimed to explore the production and application of graphene oxide (GO) and agar-based bionanocomposite as an adsorbent for the removal of copper (Cu²⁺) and lead (Pb²⁺) ions from water in single-component and binary systems. The addition of 20 wt% GO increased the adsorption capacity up to 13 times for Cu²⁺ and 3 times for Pb²⁺, attributed to GO’s high surface area and abundant oxygen functional groups. Characterization analysis revealed a material with a disordered structure, and oxygen functional groups on its surface that favor the adsorption of cationic compounds. The adsorbent showed the highest adsorption capacity at pH = 5 for both metals. The kinetic evolution showed that adsorption equilibrium was reached within 60&#xa0;min. Fick’s law equation and QDF model provided a good fit to the experimental data. The adsorption equilibrium is well described by the Freundlich isotherm model for Pb²⁺ and the Anti-Langmuir isotherm model for Cu²⁺. The maximum adsorption capacities assessed experimentally were 48.22 mg·g^-1 for Pb²⁺ and 33.10 mg·g^-1 for Cu²⁺. Regeneration exhibited an average recovery of 92.75% (Cu²⁺) and 94.25% (Pb²⁺) over four adsorption-desorption cycles, with a sudden small decrease observed in the final cycle. In an equimolar binary system, the adsorption capacities decreased, which indicates competitive adsorption in the system, with Pb²⁺ being favored.</p> Graphical Abstract <p></p>