Rising global energy demands necessitate cleaner fuel technologies due to stringent environmental regulations. Emerging techniques like oxidative desulfurization and denitrogenation offer advantages over traditional hydrotreatment, selectively oxidizing sulfur and nitrogen compounds without damaging hydrocarbon structures. This research employs nano-crystalline silver dichromate-geopolymer composites catalysts prepared by direct precipitation, sonochemical, surfactant-assisted and surfactant assisted sonochemical routes for oxidizing sulfur and nitrogen compounds in fuel oil. Surfactant assisted preparation aided in generating catalysts with controlled size, while sonochemical synthesis facilitated uniform dispersion of the particles. The uniform dispersion, controlled particle size, and low agglomeration along with unclogged pores aided the sonochemically prepared catalyst in demonstrating superior catalytic performance over other counterparts in individual sulfur oxidation tests. In contrast, due to the high rate of oxidation and high affinity to occupy active sites, the catalyst prepared by surfactant assisted sonochemical route performed better than its sonochemical counterpart in individual nitrogen compound oxidation tests. The prepared catalysts were thoroughly characterized by different analytical characterization techniques. Single component oxidation resulted in 80.86 and 98.94% conversion of sulfur and nitrogen, while simultaneous oxidation resulted in 58.41% sulfur oxidation and 95.69% nitrogen conversion. Due to the cavitation effect, efficient mixing and a high local temperature and pressure created due to the introduction of ultrasound, the conversion rose to 88.02 and 98.02% for sulfur and nitrogen, respectively. Post oxidation, the oxidation products were removed by extraction, leading to 100% removal of nitrogen and 85% removal of sulfur. The proposed mechanism suggested the oxidation of both the compounds to occur through the formation of active Cr(VI)-peroxo species.