Dual-wavelength UV degradation of bisphenol A and bezafibrate in aqueous solution using excilamps (222, 282 nm) and LED (365 nm): yes or no synergy?

Dual-wavelength ultraviolet (DWUV) irradiation can lead to a synergistic effect in terms of accelerated degradation of emerging organic contaminants in aqueous media. This study compared the kinetics of single-wavelength and DWUV degradation of bisphenol A (BPA) and bezafibrate (BZF) in model aqueous solution using KrCl (222 nm), XeBr (282 nm) excilamps and LED (365 nm). Three novel dual combinations (222 + 282, 222 + 365 and 282 + 365 nm) were examined toward the potential synergy in direct photolysis and advanced oxidation processes (AOPs) using potassium persulfate and hydrogen peroxide. Kinetic comparison showed that the time- and fluence-based synergy did not occur in the dual combinations selected. Meanwhile, the single-wavelength UV treatment using KrCl excilamp was found to be highly efficient for degradation of target contaminants. At a given dosage of oxidants, the UV/S2O82- process exhibited higher performance than the UV/H2O2 one, attaining higher degradation rates and requiring lower UV fluences for 90% removal. This study demonstrates that the catalyst-free UV/S2O82- process using KrCl excilamp has a high potential for efficient removal of such organic contaminants from real waters with low turbidity.