Study On The Degradation Of Perfluorooctanoic Acid By Persulfate With Iron-porphyrin Loaded Biochar As Catalyst

Pentadecafluorooctanoic acid（PFOA）is one of the highest detection rates of perfluorinated compounds in the environment.It has been detected in the atmosphere,water and soil,even in organisms.PFOA has neurotoxicity,regeneration toxicity,immunotoxicity and other toxicity.It is bioaccumulative and difficult to be naturally degraded.The pollution problem of PFOA has seriously threatened the ec ological environment and human health,and it is a brook no delay task to develop an effective technology to degrade PFOA.Herein,inspired by biomimetic materials,a preeminent heterogeneous catalyst,iron-porphyrin loaded biochar（Fe（TPFPP）/BC）was constructed to activate persulfate.for PFOA degradation.Moreover,the existence of persistent free radicals（PFRs）on biochar could transfer electrons to iron-porphyrin and persulfate to directly or indirectly speed up the generation of SO ₄^-·and HO·.By introducing ascorbic acid（AA）as an electronic circulation agent to maintain the concentration of PFRs,the Fe（TPFPP）/BC-PS-AA system was constructed to degrade the target pollution of PFOA.The optimal conditions for the degradation of PFOA by the system and the influence of environmental factors on the degradation effect of PFOA were investigated.The degradation process of PFOA and the reaction mechanism of the system were proposed as well.The results show that the Fe（TPFPP）/BC-PS-AA system can efficiently and rapidly degrade PFOA,and Fe（TPFPP）/BC can efficiently activate persulfate.The system could degrade 75.90%PFOA in 30 min,even reaching 90.88%with increasing reaction time.The degradation effect of PFOA in Fe（TPFPP）/BC-PS-AA system is far higher than that of Fe（TPFPP）/BC-AA system and PS-AA system alone.And the degradation rates are increased by 1.33 times and 2.99 times,respectively.The degradation effect of PFOA in the system under acidic conditions is better than alkaline conditions.Within the p H range of 1-3,the system has the best degradation effect on PFOA.The original p H of the system is within this range,and the system does not need to adjust the p H.The coexisting impurities(Cl^-and CO₃^2-)in the environment have shown different degrees of inhibition on the degradation of PFOA.Among them,the inhibitory effect of CO₃^2-on the degradation effect of PFOA is stronger than that of Cl^-.In the PFOA degradation process,SO₄^-·is the main radical,and HO·act as the auxiliary radical.Under the existence of SO ₄^-·and HO·,PFOA is defluorinated and decarbonized step by step,until it is completely mineralized into CO₂ and F^-.