<p>Water quality is essential for human health, environmental stability, and sustainable development. However, increasing contamination by persistent pollutants such as polycyclic aromatic hydrocarbons (PAHs) pose serious ecological and health risks. In this study, a hydrophobic cellulose-based adsorbent was developed for the removal of PAHs, with a focus on naphthalene, from aqueous solutions. For the first time, cellulose was extracted from bell pepper stem fibers using a liquefaction method, followed by bleaching and surface modification with stearoyl chloride to enhance hydrophobicity and adsorption performance. The optimum adsorbent dosage was found to be 1.25&#xa0;g/L. Adsorption equilibrium data fit well with the Freundlich isotherm model, suggesting a heterogeneous surface with multilayer adsorption characteristics. Kinetic studies followed a pseudo-second-order (PSO) model, indicating chemisorption. The modified cellulose demonstrated effective surface adsorption and allowed facile desorption using ethanol. The adsorbent also showed high performance across a wide pH range, from acidic to basic conditions. Importantly, it retained strong adsorption efficiency after five consecutive regeneration cycles, highlighting its reusability. In addition to naphthalene, the material was effective in removing anthracene, phenanthrene, and pyrene. These results suggest that the stearoyl cellulose adsorbent offers a promising, sustainable solution for the removal of hazardous PAHs from contaminated water systems.</p> Graphical abstract <p></p>