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چکیده
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In this study, CdO and NiO nanoparticles were synthesized via green method and characterized using XRD, BET, TEM, FESEM, EDX, DRS, and EDX-Mapping techniques. FESEM results showed that the CdO nanoparticles had a spherical morphology. The average size of the nanoparticles was approximately 30 nm based on TEM image. BET analysis revealed a specific surface area of 28.28 m²/g. The band gap energy of the CdO nanoparticles was calculated to be 1.98 eV. The sonocatalytic activity of the CdO nanoparticles was evaluated for the degradation of Direct Red 31 dye, achieving a degradation efficiency of 97% and 74% total organic carbon (TOC) removal within 20 min. Radical scavenger experiments indicated that hydroxyl radicals (•OH) play a dominant role in the degradation mechanism. The degradation by-products and proposed mechanism were confirmed by LC-MS analysis. NiO nanoparticles with a cubic structure were synthesized. FESEM images showed spherical morphology. The average particle size was determined to be 25 nm by TEM. BET analysis showed a specific surface area of about 41.226 m2/g. The band gap of the nanoparticles was calculated to be 2.51 eV using DRS. Their sonocatalytic efficiency was tested for the degradation of Congo red dye, resulting in 95% dye removal and 56% TOC reduction within 30 min. The addition of hydroxyl radical scavenger (t-butanol) and hole scavenger (EDTA) reduced degradation efficiency from 95% to 52% and 64%, respectively, indicating the critical role of •OH radicals in this process. LC-MS analysis identified degradation products and supported a possible sonocatalytic degradation pathway for Congo red dye. Reusability tests over five cycles demonstrated the stability and recyclability of CdO and NiO nanoparticles, with only a slight decrease in sonocatalytic efficiency observed.
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