Highly efficient degradation of bisphenol A with persulfate activated by vacuum-ultraviolet/ultraviolet light (VUV/UV): Experiments and theoretical calculations

Abstract

Enhanced degradation and mineralization of bisphenol A (BPA) known as a typical endocrine disrupting chemical (EDC) in VUV/UV-activated persulfate process (VUV/UV/PS) were investigated. The pseudo-first-order reaction rate constant and total organic carbon (TOC) removal ratio of BPA in this process were 1.75 and 1.70 times of those in UV-activated PS process (UV/PS), respectively. The excitation-emission matrix (EEM) fluorescence spectroscopy of reaction solution at different time clearly indicated the change of BPA and its intermediates during the reaction process. The significant interactive effects of three important operating parameters including the initial concentration of BPA, the initial concentration of PS and the initial pH of solution on BPA degradation efficiency were evaluated and optimized by using central composite design (CCD) of response surface methodology (RSM). At the optimum experimental conditions (i.e., 30 mg/L BPA, 1.25 mM PS and at pH 9), the maximum degradation efficiency of BPA at 2 min was up to 92.2%. Sulfate radicals (SO4•-) were the dominant reaction activate species for BPA degradation. Based on the analysis of liquid chromatograph-mass spectrometry (LC/MS), gas chromatograph-mass spectrometry (GC/MS) and Fourier transform infrared spectroscopy (FTIR) of the reaction mixture and density function theory (DFT) calculation, it was proposed that BPA degradation was mainly caused by SO4•--induced hydroxylation reaction, HO• addition and β-scission of C–C bond. Moreover, the electrical energy consumption of BPA degradation in VUV/UV/PS process was less. Additionally, BPA in real water samples could also be effectively degraded at lower treatment costs in this process. Hence, the present study demonstrates that VUV/UV activation of PS is a highly efficient and economical alternative to remove BPA in real water matrices..