<p>This paper describes an integrated experimental and theoretical examination into the synthesis of low-cost activated carbon (AC) obtained from date-pit wastes for the effective removal of methylene blue (MB) from aqueous solutions. The AC was manufactured using chemical activation with phosphoric acid (H₃PO₄) in different amounts to enhance surface properties. The best conditions for carbonization were found to be 600 °C for 2 h, after a rigorous assessment of key synthesis factors. Under these circumstances, the resultant AC demonstrated significant carbonization yield and remarkable adsorption efficiency, removing up to 99.71% of the MB. Batch adsorption tests were carried out to determine the impact of pH, contact duration, adsorbent dosage, and starting dye concentration on performance. X-ray diffraction (XRD) was used for structural characterization, which confirmed the material's amorphous and porous characteristics. Further, density functional theory (DFT) and molecular dynamics (MD) simulations were used to investigate the molecular interactions between MB and the AC surface, shedding light on the adsorption process. Theoretical findings confirmed actual data, emphasizing the importance of electrostatic and π-π interactions in dye adsorption. This combined method highlights the promising potential of bio-based activated carbon in environmental remediation, notably for sustainable wastewater treatment employing plentiful agricultural waste.</p>