Study On The Degradation Of Bisphenol AF By Zinc Oxide And Zinc Oxide Activated Periodate Under Sunlight Driving

Exposure to endocrine disrupting substances in the environment have a great threat to the life safety for human beings and animals.In the past few decades,Bisphenol AF（BPAF）as a typical endocrine disrupting substance has potential toxic effect on the aqueous environment,affecting reproductive system and embryonic development.With application of BPAF in chemical industry manufacturing,higher content level of BPAF have been detected in environmental water aqueous and biological samples.Therefore,it is urgent to find a cost-effective method for removing BPAF from the aquatic environment.In this study,BPAF was selected as the substrate compound to explore the degradation efficiency and influencing factors of BPAF（Zn O dosage,IO₄^-concentration,BPAF concentration,initial p H and inorganic anions）by zinc oxide photocatalytic process（SLI/Zn O）and the light-driven zinc oxide activated periodate process（SLI/Zn O/IO₄^-）.Meanwhile,the pseudo first-order kinetic model was established to analyze the degradation kinetics of BPAF under different influencing factors.In addition,free radicals scavenging experiments,ESR spectrometry,photoluminescence spectrometry（PL）and liquid chromatography-mass spectrometry（LC-MS）were carried out to further reveal the degradation mechanism of BPAF by Zn O/IO₄^-system and SLI/Zn O/IO₄^-system.The main contents of this study are as follows:（1）The effects of different reaction parameters on the degradation efficiency of BPAF by SLI/Zn O system were investigated.The results showed that increasing the Zn O dosage and decreasing the BPAF concentration were favored to promote the target compound degradation,but the presence of higher dosage of catalyst would inhibit the photocatalytic activity.With the increase of p H value,the removal rate of BPAF increased.The addition of NO₃^-had little effect on the degradation of BPAF.The introduction of Cl^-in the water phase exhibited a dual effect on the degradation of BPAF,which BPAF degradation was suppressed at low concentration and promoted at high concentration.The CO₃^2-and H₂PO₄^-had a negative effect on the degradation of BPAF,and the inhibitory effect increased with the increasement of the anions concentration.The BPAF degradation under different reaction parameters followed pseudo-first-order kinetics reaction,and the reaction rate constant showed the same trend as the degradation efficiency of BPAF.Free radicals quenching experiments manifested that^·OH and O₂^·-were active free radicals responsible for the degradation of BPAF.（2）The effects of different reaction parameters on the degradation efficiency of BPAF by SLI/Zn O/IO₄^-system were investigated.The results showed that the increase of Zn O dose and IO₄^-concentration and the decrease of BPAF concentration had positive effects on the degradation of the target compounds.Weak acid solution（p H 5.5）and alkaline solution（p H9.0）were favored to accelerate the BPAF degradation.The presence of CO₃^2-and H₂PO₄^-in the solution could significantly inhibit the BPAF degradation in comparison to slight effect of NO₃^-.As the increase of Cl^-concentration level,the degradation efficiency of BPAF showed a trend of that that first increased and then decreased.Under the condition of different reaction parameters,the degradation kinetics of BPAF with the initial reaction time of 20min as the segment point was defined as two pseudo-first-order kinetic stages.The free radicals quenching experiments and ESR spectra show that the active oxygen species existing in the system were^·OH,O₂^·-and ¹O₂,of which^·OH was the dominant species.In addition,the existence of iodate radicals（IO₃^·）was confirmed by detecting the production of iodate（IO₃^-）in the solution.（3）The photosensitized degradation efficiency of BPAF via Vis/Zn O/IO₄^-system was evaluated.The degradation rate of BPAF was only 20.3%,indicating that SLI/Zn O/IO₄^-system mainly degrades BPAF through photocatalytic reaction.The photocatalytic reaction was mainly responsible for the degradation of BPAF in Vis/Zn O/IO₄^-system.The identified O₂^·-and ¹O₂ were main active species in the Vis/Zn O/IO₄^-system by free radicals quenching experiments.Combined with PL spectrum analysis,it can be seen that the addition of IO₄^-could effectively avoid the recombination of photo-generated carriers on the Zn O surface.The fewer content of BPAF may be excited by visible light irradiation and completed the electron injection process in the conduction band of Zn O.（4）The LC-MS was used to observed the transformation intermediates on the degradation process of BPAF.It can be reasonably concluded that BPAF may undergo periodate oxidation,electron delocalization,hydroxylation and ring-cleavage process,then transformed into small molecular compounds and eventually into CO₂ and H₂O.