<p>The rapid growth in dye production has led to widespread contamination of aquatic systems, posing serious risks to the environment and human health due to the persistence and toxicity of dye compounds. In this paper, the removal efficiency of an optimal activated carbon prepared from sawdust by chemical activation with H₃PO₄ phosphoric acid was investigated and discussed for cationic and anionic dyes. In fact, the adsorption capacity of an activated carbon prepared under optimal conditions in a previous study (impregnation ratio: 1.92, impregnation time: 6.02 h, heating rate: 20°C/min, activation temperature: 500°C, residence time: 30 min) was tested for the removal of methylene blue (MB, cationic dye), and methyl orange (MO, anionic dye). The influence of different batch parameters on the adsorption capacity of MB and MO was studied. Kinetic and adsorption isotherm modeling was carried out using pseudo-first order, pseudo-second order and intraparticle diffusion models, as well as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The results show that the adsorption kinetics were rapid (equilibrium is reached at 120 min for MO and 180 min for MB), the pseudo-second order model is suitable for describing the adsorption kinetics of both dyes, and that the adsorption process is controlled by various factors. Equilibrium data for MB adsorption are well fitted by the Langmuir model, while the Freundlich model provides a good fit for MO adsorption. The maximum adsorption capacity of the adsorbent used is 635.27 mg/g for MB and 392.89 mg/g for MO. The results obtained were discussed and compared with those of previous studies. Performance tests carried out on our material have demonstrated that it is a novel, cost-effective, and efficient adsorbent. The combined advantages of being derived from an abundant waste product and having a high affinity for both anionic and cationic dyes make it an innovative adsorbent.</p>