Investigations in Synergism of Hybrid Advanced Oxidation Processes with Combinations of Sonolysis + Fenton Process + UV for Degradation of Bisphenol A

Abstract

Hybrid advanced oxidation processes (HAPOs) for degradation of recalcitrant organic pollutants have been extensively studied in recent literature. In this paper, we have presented a mechanistic investigation of hybrid advanced oxidation processes with combinations of sonolysis and Fenton process coupled with UV. Degradation of a ubiquitous pollutant, bisphenol A, discharged in environment with solid plastic waste has been used as the model reaction. Essentially, an attempt is made to explore synergy between the individual mechanisms of these processes. With conjectures of possible synergies, we have devised the experimental protocols with combination of sonolysis and Fenton process coupled with UV. It is revealed that techniques of sonolysis + Fe2+ and sono–Fenton have positive synergy while technique of Fenton process + UV has no synergy. The technique of sono–Fenton + UV has been found to have negative synergy. The rationales for positive synergy have been identified as conservation and/or regeneration of •OH radicals and increased probability of radical-pollutant interaction, while the absence of synergy is a consequence of low utilization of UV irradiation due to lesser fractional energy at absorption wavelength (254 nm) of H2O2. A probable cause for negative synergy is conjectured as hindrance to effective utilization of H2O2 through sonolysis and Fenton process route by UV irradiation. The highest mineralization, monitored through total organic carbon (TOC) of the solution, was obtained with the sono–Fenton process.