¹ Physics Department, Faculty of Science, Suez University, P.O. Box: 43221, Suez, Egypt.

² Physics Department, Faculty of Science, Islamic University of Madinah, Madinah 42351, Saudi Arabia.

* Correspondence: aashour_2000@iu.edu.sa

In this study, zinc oxide nanoparticles (ZnO NPs), reduced graphene oxide (RGO) nanosheets (NShs), and their hybrid ZnO/RGO nanocomposites (NCs) were synthesized using environmentally benign and sustainable routes. The prepared materials were systematically characterized and evaluated for their sonocatalytic performance toward methylene blue (MB) degradation. Structural and morphological analyses confirmed the formation of highly crystalline ZnO and the successful integration of RGO within the composite matrix. SEM observations revealed that ZnO NPs with sizes ranging from approximately 30 to 60 nm were uniformly anchored onto the folded and wrinkled surfaces of RGO NShs. Elemental purity was verified by EDX analysis, while FTIR and TGA results evidenced strong interfacial interactions and enhanced thermal stability in the ZnO/RGO NCs. Sonocatalytic experiments demonstrated a pronounced enhancement in MB degradation upon RGO incorporation. While pristine ZnO achieved only ~50% MB removal within 60 min, the ZnO/20% RGO NC exhibited superior activity, achieving over 90% degradation under identical conditions. Kinetic analysis revealed a substantial increase in the apparent rate constant, with ZnO/20% RGO showing the highest value (k = 0.051 min⁻¹), nearly three times that of pure ZnO (k = 0.018 min⁻¹). Correspondingly, the MB half-life was significantly reduced from 38.5 min for ZnO to 13.6 min for ZnO/20% RGO NC. The enhanced sonocatalytic performance is attributed to the synergistic effects of ultrasonic cavitation and the ZnO/RGO heterointerface, which promotes efficient charge separation, accelerates electron transport, and enhances reactive oxygen species generation. Reusability tests confirmed excellent stability, with ZnO/20% RGO NC retaining more than 95% of its initial efficiency after five consecutive cycles, whereas pristine ZnO suffered rapid deactivation. These results demonstrate that ZnO/RGO NCs with optimized RGO loading, particularly at 20%, represent robust, efficient, and sustainable sonocatalysts for wastewater remediation applications.