Production of Hydroxyl Free Radical, the Main Mechanism for Removing Steroid Hormones by Ultrasound

Background: One of the new methods for elimination or destruction of estrogen hormones is ultrasound irradiation. The aim of this study was to determine the main mechanism of steroid hormones removal by ultrasound. Methods: In this study, estrogen (E1) and 17 beta-estradiol (E2) were irradiated with ultrasound at different frequencies, powers, and exposure times in two cases: with and without butyl alcohol in a batch-mode cylindrical reactor made of Plexiglas in the amount of one liter. Residual concentrations of hormones were measured by solid phase extraction and gas chromatography-mass chromatography (GC-MS). Results: The result showed that ultrasound has high ability to remove hormones E1 and E2 (between 56.3% and 79.2%). Also, after adding butyl alcohol which is a free radical scavenger, the removal efficiency of ultrasound in both hormones was greatly reduced but didn’t reach to zero, so the main mechanism of hormones removal was hydroxyl free radical production. Conclusions: Due to the high efficiency of ultrasound for the removal as well as defects in other removal methods, more studies about optimization of the effective parameters on it, and technical and economical comparison with other removal methods are needed.