Abstract <p>The increasing contamination of surface and groundwater by pesticide residues, particularly from agricultural runoff, poses serious risks to human health, aquatic ecosystems, and long-term water security. In this context, the development of efficient, low-cost, and eco-friendly biosorbents derived from renewable waste materials is a crucial step toward sustainable environmental water treatment. In this study, chitin is extracted from shrimp waste and employed as a green and biodegradable biosorbent for the removal of malathion, a widely used organophosphorus pesticide, from aqueous solutions. The chitin material is characterized using FTIR, SEM, and XRD techniques, confirming its structural integrity and adsorption potential. Batch adsorption experiments are conducted to investigate the influence of temperature and initial malathion concentration, revealing an optimal adsorption capacity of 45.41 mg·g⁻¹ within 150 min. The adsorption process is best described by the Langmuir isotherm, pseudo-second-order kinetic, and Elovich models, indicating efficient and favorable adsorption behavior. Furthermore, computational modeling using DMol3 and molecular dynamics simulations provides insights into the adsorption mechanism, showing that physisorption predominates through dipole–dipole interactions and solvent reorganization effects. Overall, this study demonstrates the potential of shrimp waste-derived chitin as a sustainable and highly effective biosorbent for pesticide removal, offering a promising solution for addressing water pollution through green remediation strategies.</p> Graphical Abstract <p></p>