OICC Press Iranian Journal of Catalysis 2345-4865 15 3 2025 09 30 Green Synthesis and Characterization of NiO Nanoparticles with Enhanced Sonocatalytic Activity 10.57647/j.ijc.2025.1503.30 EN Safaa Ridah Shakor Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran Saeid Taghavi Fardood Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran Ali Naghipour Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran Journal Article 2025 09 30 The persistent nature and environmental toxicity of industrial dyes in wastewater necessitate the development of efficient and sustainable removal technologies, such as sonocatalysis. The sonocatalytic activity of the NiO nanoparticles (NPs) was studied for the degradation of Congo red dye (CR). NiO NPs were prepared via a green method. The obtained NiO NPs were characterized using XRD, BET, TEM, FESEM, EDX, and UV-Vis-DRS. The sonocatalytic efficiency of the NiO NPs was evaluated for the CR degradation. The results show that 95% of CR dye and 56% of total organic carbon (TOC) were removed within 30 min. Nevertheless, when a hydroxyl radical (•OH) scavenger t-butanol and hole (h+) scavenger (EDTA) were added it was observed that degradation efficiency reduced from 95% to 52% and 64% respectively, which revealed that •OH is the main oxidizing agents in this process. LC-MS analysis identified degradation products and enabled the proposal of a plausible sonocatalytic degradation pathway for Congo red dye. NiO NPs' reusability was evaluated using the same reaction conditions for five consecutive cycles. However, a slight loss of sonocatalytic efficiency was obtained, illustrating the stability and reusability of the nanoparticles. Highlights ·       Green synthesis of NiO NPs by Tragacanth gel ·       NiO NPs achieved 95% degradation of Congo Red (CR) dye and 56% TOC removal in 30 min. ·       BET analysis revealed synthesized NiO NPs with a large surface area of approximately 41.226 m²/g. ·       Degradation efficiency decreased significantly with •OH and hole scavengers, confirming the key role of •OH radicals. ·       NiO NPs demonstrated excellent stability and reusability, retaining high activity after five cycles.