This study presents a catalyst-free dual-frequency ultrasound method for efficiently degrading methylene blue, a common pollutant in wastewater. The method uses two ultrasound frequencies to generate cavitation bubbles of different sizes, enhancing the degradation process. The research shows that dual-frequency ultrasound consistently outperforms single-frequency methods, with larger frequency differences leading to more effective degradation. Under identical acoustic power density conditions, dual frequencies of 20 and 80 kHz achieved a 91% degradation efficiency of methylene blue within 20 minutes. The study also highlights the role of cavitation bubbles in the degradation process, showing that dual frequencies improve bubble quality and enhance the production of reactive species like hydroxyl radicals (•OH) and hydrogen peroxide (H₂O₂), which contribute to the breakdown of methylene blue. The method is environmentally friendly and does not require additional catalysts or additives, making it a promising approach for wastewater treatment. The results demonstrate that dual-frequency ultrasound is an effective, efficient, and sustainable method for degrading methylene blue.This study presents a catalyst-free dual-frequency ultrasound method for efficiently degrading methylene blue, a common pollutant in wastewater. The method uses two ultrasound frequencies to generate cavitation bubbles of different sizes, enhancing the degradation process. The research shows that dual-frequency ultrasound consistently outperforms single-frequency methods, with larger frequency differences leading to more effective degradation. Under identical acoustic power density conditions, dual frequencies of 20 and 80 kHz achieved a 91% degradation efficiency of methylene blue within 20 minutes. The study also highlights the role of cavitation bubbles in the degradation process, showing that dual frequencies improve bubble quality and enhance the production of reactive species like hydroxyl radicals (•OH) and hydrogen peroxide (H₂O₂), which contribute to the breakdown of methylene blue. The method is environmentally friendly and does not require additional catalysts or additives, making it a promising approach for wastewater treatment. The results demonstrate that dual-frequency ultrasound is an effective, efficient, and sustainable method for degrading methylene blue.