Enhancing oil adsorption capacity via gamma irradiation: A green approach for coconut shell powder and coconut shell-derived activated carbon

• Coconut shell powder (CS-P) and activated carbon (CS-AC) were assessed as oil sorbents. • CS-P and CS-AC were gamma-irradiated with varying doses of 0–40 kGy. • Oil adsorption capacities of CS-P and CS-AC increased with increasing gamma doses. • CS-AC exhibited higher adsorption capacity than CS-P under the same oil and gamma dose. • Gamma irradiation served as a green modification method for CS-AC and CS-P. . Oil pollution remains a critical threat to aquatic and terrestrial environments, requiring efficient, low-cost, and eco-friendly remediation strategies. This study investigated the use of coconut shell-derived activated carbon (CS-AC) and raw coconut shell powder (CS-P) as sustainable oil sorbents, with surface properties modified using gamma irradiation at doses ranging from 0 to 40 kGy. Three oils with varying viscosities, namely diesel, vegetable oil, and engine oil, were used to assess adsorption performance. Comprehensive characterizations including SEM-EDS, BET, FTIR, XRD, and TGA were conducted to evaluate the structural and chemical changes induced by gamma irradiation. The results showed that gamma irradiation led to increased surface polarity through the formation or the enhancement of oxygen-containing functional groups, which enhanced oil–sorbent interactions. The maximum oil adsorption capacities were obtained at 40 kGy for both materials, with CS-AC exhibiting substantially higher performance due to its well-developed porous structure and higher surface area. Additionally, adsorption kinetics followed the pseudo-first-order (PFO) model, indicating physisorption as the dominant mechanism, supported by strong linear fits. Intraparticle diffusion (IPD) analysis further suggested a two-stage adsorption process for CS-AC, with rapid initial diffusion into pores followed by slower surface adsorption, while CS-P exhibited primarily surface-controlled kinetics throughout. Overall, gamma irradiation proved to be a simple, green, and effective method for enhancing oil adsorption properties of coconut-based sorbents, making them promising candidates for oil spill remediation and broader environmental applications involving contaminant removal.