Sonophotolytic degradation of estriol at various ultraviolet wavelength in aqueous solution

This study investigated degradation of the hormone estriol by sonolysis, photolysis and sonophotolysis at various UV wavelengths. Degradation was determined with UVA (365 nm), UVC (254 nm), or VUV (185 nm) irradiation and/or ultrasound exposure (283 kHz). The pseudo-first order degradation rate constants were in the order of 10 ^-1 to 10 ^-4 min ^-1 depending on the processes. The dominant reaction mechanism of estriol in sonolysis was estimated as hydroxyl radical reaction by the addition of tert-butanol (t-BuOH), which is a common hydroxyl radical scavenger. Photolytic and sonophotolytic estriol degradation rate also were high at shortest UV wavelength (VUV) due to the higher energy of photons, higher molar absorption coefficient of estriol and increased hydroxyl radical generation from the homolysis of water. Small synergistic effects were observed for sonophotolytic degradation with UVA and UVC irradiation. No synergy was observed for sonophotolysis with VUV irradiation.