M88/PS/Vis system for degradation of bisphenol A: Environmental factors, degradation pathways, and toxicity evaluation

In this study, we synthesized a typical iron-based metal-organic framework, MIL-88B (Fe), and constructed a MIL-88B (Fe)/persulfate/visible light (M88/PS/Vis) system for photocatalytic degradation of bisphenol A (BPA) in aqueous solution. The removal efficiency, environmental factors, and degradation mechanism and pathways were explored. The results showed that there were synergistic effects in the M88/PS/Vis system: BPA (10 mg/L) could be removed completely within 25 min with 0.6 g/L M88 and 2 mM PS under visible light, while the removal rates with individual M88/Vis or M88/PS was only 26.0% and 34.1%, respectively. In addition, the BPA degradation rate in the M88/PS/Vis system (0.107 min(-1)) was 4.7 times higher than that in the M88/PS system (0.023 min(-1)) and 8.9 times higher than that in the M88/Vis system (0.012 min(-1)), respectively. Additionally, environmental factors could strongly impact the degradation of BPA in the studied system in which O-2(center dot-) and SO4 center dot- played a dominant role. More importantly, risk assessment in the BPA/M88/PS/Vis system was, for the first time, estimated in our study via the ecological structure activity relationships program at three trophic levels and Cell Counting Kit-8 method. Although there were some intermediates with higher biological toxicity than BPA and increased the toxicity of solution, most intermediates were one or more level less toxic than BPA. In most cases, the toxicity of solutions were lower than the initial samples, which demonstrated the effectiveness of M88/PS/Vis system in the reduction of toxicity of BPA, and the toxicity hazard in general could be effectively avoided by prolonging the duration of light exposure. This research provides a profound understanding of the potential application of PS activation by photocatalyst for both BPA removal and toxicity shift under visible light.