Sonochemical Degradation of the Anticancer Pharmaceutical Anastrozole Using Low-Frequency Ultrasound: Kinetic and Mechanistic Study

Anastrozole (ANZ), a pharmaceutical classified as an endocrine disruptor (EDC), is widely used in the prevention and treatment of breast cancer. Due to its chemical stability, ANZ, like other EDCs, is excreted largely unmetabolized and has been detected at low concentrations in surface water, groundwater, and wastewater effluents. The persistence of such compounds raises environmental and public health concerns, as conventional physicochemical and biological wastewater treatment methods are often ineffective in removing them.

Advanced oxidation processes (AOPs) have gained attention as efficient and environmentally friendly alternatives for degrading recalcitrant pollutants in wastewater.

In this study, the sonochemical degradation of ANZ was investigated for the first time using low-frequency ultrasound. Experiments were conducted in a double-walled batch reactor at a power density of 71 W/L and a temperature of 20 °C, maintained through water circulation. The reactor volume was 200 mL, and ANZ concentrations were monitored using High-Performance Liquid Chromatography (HPLC).

The impact of ultrasonic intensity was assessed, showing that increased power density enhanced ANZ degradation. Higher initial ANZ concentrations were found to decrease the apparent rate constant. The effect of pH was also studied; acidic conditions slightly favored degradation, while alkaline conditions slightly hindered it.

Mechanistic analysis revealed that ANZ degradation occurred predominantly at the bubble–liquid interface and inside cavitation bubbles. The process was further tested in both synthetic and real wastewater matrices. Results indicated satisfactory performance, with only a minor reduction in efficiency observed in real wastewater, likely due to the presence of bicarbonate ions acting as radical scavengers. These findings highlight the potential of sonochemical treatment as a viable method for removing persistent pharmaceutical contaminants from wastewater.