Sustainable valorization of Salacca zalacca leaves into MoO₃-loaded biogenic silica for efficient oxidative desulfurization of dibenzothiophene

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Transitioning to ultra-low-sulfur fuels requires efficient strategies to remove refractory sulfur compounds from petroleum streams. Conventional hydrodesulfurization remains energy-intensive and is often ineffective toward aromatic sulfur species such as dibenzothiophene (DBT). In this work, MoO₃ supported on biogenic silica derived from Salacca zalacca leaves (MoO₃/BS) was prepared by spray impregnation, representing a previously unexplored application of Salacca zalacca -derived silica as a support for oxidative desulfurization (ODS). XRF analysis showed a high SiO₂ purity of 99.55%, while MoO₃/BS exhibited a total acidity of 0.09 mmol NH₃ g⁻¹ , a specific surface area of 15.06 m² g⁻¹ , and an average pore diameter of 3.67 nm. RSM–CCD identified 45.20 min, an O/S molar ratio of 10.16, and a catalyst dosage of 1.58 wt% as the optimum conditions, with a predicted DBT removal of 92.19%. Experimental verification at the numerical optimum yielded 92.15% apparent DBT removal, corresponding to a deviation of only 0.04 %age points. Control experiments indicated contributions from both adsorption and Mo-mediated peroxide oxidation. Notably, DBT removal decreased progressively to 84.22% after five cycles, accompanied by substantial Mo loss, indicating active-phase loss as a key limitation. Altogether, this work demonstrates a route for valorizing Salacca zalacca leaf waste into a functional silica support for Mo-based ODS, providing a basis for further evaluation in more complex and realistic fuel systems.