Study On The Degradation And Mechanism Of Bisphenol Compounds By Vacuum Ultraviolet /ultraviolet Light Activated Persulfate

Bisphenol A（BPA）is one kind of important industrial raw materials and is also a well-known endocrine disrupting chemical（EDCs）with bioaccumulation and low dose effect,which posed a serious threat to human health.In recent years,although other bisphenol compounds（BPs）including bisphenol B（BPB）,bisphenol F（BPF）,bisphenol S（BPS）and bisphenol AF（BPAF）are used extensively as the substitutes for BPA,they have also arisen some concerns.This was because they were frequently detected in different water bodies and have potential toxicity.Moreover,they are resistance to the traditional wastewater treatment methods.Therefore,developing an effective method to remove BPA and its substitutes in water are necessary for the safe of drinking water and human health.Advanced oxidation process based on sulfate radicals（SR-AOPs）can degrade refractory organic contaminants.It has been reported that vacuum ultraviolet/ultraviolet（VUV/UV）can efficiently activate persulfate（PS）for generating sulfate radicals.However,BPA and its substitutes degradation in VUV/UV activated PS（VUV/UV/PS）has not been reported.Therefore,BPA degradation in vacuum ultraviolet/ultraviolet activated persulfate process（VUV/UV/PS）and effects of various factors on BPA degradation were investigated in the study.Based on the DFT calculation and identified intermediates,possible BPA degradation mechanisms were proposed.Moreover,degradations of BPB,BPF,BPS and BPAF in VUV/UV/PS process were also investigated.Meanwhile,the main reactive species were identified.Based on results of DFT calculation and the analysis of intermediates,degradation pathways of BPs were proposed.Finally,the degradation and mineralization of BPA and its substitutes in VUV/UV/PS process were compared.The main results obtained are as follows:（1）VUV/UV can efficiently activate PS lead to high degradation and mineralization efficiencies of BPA,and the degradation rate of BPA in VUV/UV/PS process was 1.182 min^-1 which was 7 times than that under the irradiation of VUV/UV.The higher BPA concentration,the slower degradation of BPA.While increasing PS concentration promoted BPA degradation.When p H was 11.12,the degradation rate of BPA was as high as 0.47 min^-1.The presence of Cl^-and SO₄^2-accelerated BPA degradation,while BPA degradation was inhibited in VUV/UV/PS process with 100m M Cl^-.HCO₃^-at 1 m M and 10 m M exhibited a negative effect on BPA degradation,but a positive effect was observed at 100 m M HCO₃^-.The presence of NO₃^-and natural organic matters were not.Although BPA degradation efficiencies in river water and tap water were lower than that in ultrapure water,BPA were completely removed within 20min in river water and tap water.SO₄^·-was the dominant radical for BPA degradation in VUV/UV/PS process.Based on the analysis of liquid chromatograph-mass spectrometry（LC/MS）,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 andβ-scission of C-C bond.（2）VUV/UV/PS process can efficiently degrade BPB,BPF,BPS and BPAF.SO₄^·-was the dominant radicals for BPB,BPF and BPAF degradation,while HO·was main reactive species for BPS degradation.According to DFT calculation,the benzene ring and hydroxyl group were the reaction sites of BPB,BPF,BPS and BPAF.Based on the analysis of DFT calculation and identified intermediates,three degradation pathways of BPB,BPF,BPS and BPAF were proposed,including hydroxylation,β-scission and self-coupling of phx BPs.Besides,BPB and BPF can be oxidized via H abstraction,BPS and BPAF can be degraded via de-hydroxylation.（3）The degradation order of five BPs in VUV/UV/PS process was BPAF>BPB>BPA>BPF>BPS due to their different central groups.Above 80%of mineralization of BPA and its substitutes in VUV/UV/PS were achieved at 120 min.