Degradation of bisphenol A by combining ozone with UV and H₂O₂ in aqueous solutions: mechanism and optimization

A laboratory-scale study on the abatement of bisphenol A (BPA) was performed by combining O₃ with H₂O₂ and UV (O₃/H₂O₂/UV), an ozone-based advanced oxidation processes technique (AOP). This work aimed to (1) evaluate the removal of BPA with O₃/H₂O₂/UV, and to compare the degradation efficiency with other ozone-based AOPs (such as O₃ alone, O₃/H₂O₂, and O₃/UV), (2) structurally optimize BPA abatement by using a central composite design (CCD) for experimental design purposes and/or a response surface methodology to find the optimum, and (3) identify the degradation pathways, and main intermediate products, formed during BPA abatement with O₃/H₂O₂/UV. The degradation pathways of BPA degradation were revealed by O₃/H₂O₂/UV on the basis of evidences of intermediate generation. The effect of initial pH, ozone, and H₂O₂ dose during BPA abatement was studied in detail. By increasing each of these three parameters, an enhancement of the BPA degradation efficiency is mostly observed. BPA can be degraded completely when a sufficiently high ozone dose is applied. However, excess H₂O₂, as a scavenger of HO·, has a negative effect on BPA abatement, resulting in a decrease in the BPA’s degradation efficiency. For example, the removal decreased from 64 to 58% by enhancing the H₂O₂ initial dose from 0.5 to 0.75 mmol/L (at an initial pH and ozone dose of, respectively, 7 and 0.1 mg/L). The results confirmed that combining ozone with H₂O₂ and UV was a more efficient method than the other three ozone-based AOPs on the removal of BPA. Therefore, this method could be further applied for the treatment of real wastewaters containing BPA and other micropollutants.