Ultrasonic Degradation of Endocrine Disrupting Compounds in Seawater and Brackish Water

Abstract

In this study, a series of experiments was conducted on the relative degradation of commonly known endocrine-disrupting com- pounds such as bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) in a single-component aqueous solution using 28 and 580 kHz ultrasonic reactors. The experiments were conducted with three different types of model water: deionized water (DI), synthetic brack- ish water (SBW), and synthetic seawater (SSW) at pH 4, 7.5, and 11 in the presence of inert glass beads and humic acids. Significantly higher sonochemical degradation (93-97% for BPA) occurred at 580 kHz than at 28 kHz (43-61% for BPA), regardless of water type. A slightly higher degradation was observed for EE2 compared to that of BPA. The degradation rate of BPA and EE2 in DI water, SBW, and SSW after 30 min of ultrasound irradiation at 580 kHz increased slightly with the increase in pH from 4 (0.073-0.091 min-1 for BPA and 0.081-0.094 min -1 for EE2) to 7.5 (0.087-0.114 min -1 for BPA and 0.092-0.124 min -1 for EE2). In contrast, significant degradation was ob - served at pH 11 (0.149-0.221 min-1 for BPA and 0.147-0.228 min-1 for EE2). For the given frequencies of 28 and 580 kHz, the degradation rate increased in the presence of glass beads (0.1 mm and 25 g) for both BPA and EE2: 0.018-0.107 min -1 without beads and 0.052-0.142 min-1 with beads for BPA; 0.021-0.111 min-1 without beads and 0.054-0.136 min-1 with beads for EE2. A slight increase in degradation of both BPA and EE2 was found as the concentration of dissolved organic carbon (DOC, humic acids) increased in both SBW and SSW: 0.107-0.115 min-1 in SBW and 0.087-0.101 min-1 in SSW for BPA; 0.111-0.111 min-1 in SWB and 0.092-0.105 min-1 in SSW for EE2. After 30 min of sonicating the humic acid solution, DOC removal varied depending on the water type: 27% (3 mg L -1 ) and 7% (10 mg L -1 ) in SBW and 7% (3 mg L-1) and 4% (10 mg L-1) in SSW.