SONOPHOTOCHEMICAL OXIDATION OF ORGANIC CONTAMINANTS IN AQUEOUS SOLUTIONS USING PERSULFATE

Abstract

In present work, we have studied the kinetic fundamentals of sonophotochemical oxidation of emerging organic contaminants, atrazine and bisphenol A, in model aqueous solutions, simultaneously exposed to high-frequency ultrasound (US, 1.7 MHz) and ultraviolet light-emitting diodes (UV LEDs, 365 nm) in the absence and presence of persulfate (S2O82-) oxidant. Synergistic indices were calculated to assess a synergistic effect in the hybrid oxidation systems. It was found that the hybrid system {UV/US/S2O82-} exhibited the synergistic effect and was the most efficient for degrading bisphenol A in a raw: UV/US/S2O82- > UV/S2O82- > US/UV > US/S2O82- >> UV > US. In case of atrazine, no ultrasound effect was observed and the efficiencies of {UV/US/S2O82-} and {UV S2O82-} systems in terms of degradation rates were similar. In these oxidation systems, more than 90% of a contaminant was removed after 30 min treatment. Meanwhile, degradation rates for atrazine were higher than those wich were found for bisphenol A. This indicates a predomination of sulfate anion radicals, which react with bisphenol A rather slowly compared to atrazine. A synergism was also found under sonophotolysis of both contaminants without persulfate; however, this process requires a more prolonged irradiation time (~20% degraded in 40 min), hence, it is less energy-effective. The obtained results are promising for application of UV LEDs and high-frequency ultrasound in persulfate-based advanced oxidation processes to degrade organic contaminants in natural water and wastewater.