Study On The Catalytic Degradation Of Bisphenol A By Iron-porphyrin Complexes In Conjunction With Persulfates

Nowadays,water pollution is becoming a more and more serious issue.More and more non-degradable organic substances were detected in water.Thus,it is imperative to tackle the devastating water pollution issue.Persulfate?PS?advanced oxidation process has become a more and more attractive candidate method in recent years due to its facile reaction rate and high degradation efficiency.In addition,both peroxymonosulfate?PMS?and peroxodisulfate?PDS?are easy to store,pollution-free,stable,etc.As transition metal porphyrins derivatives,sodium ferric chlorophyllin?SFC?can react with persulfate to produce highly oxidative groups or intermediates,which have outstanding degradation performance of pollutants.In this paper,iron porphyrin complexes were used in the persulfate advanced oxidation process.By combining the properties of biomimetic catalytic activity of SFC and the properties of O-O bonds of PS,an SFC/PS system was constructed in order to study its synergistic degradation effects of organic pollutants.Bisphenol A?BPA?was used as the target pollutant to study the mechanism of BPA degradation by SFC/PMS system and analyze the SFC/PMS degradation process,degradation pathway and the recyclability of the residual precipitates.?1?Degradation effects of SFC/PDS system on MB and BPAThe degradation effects of SFC/PDS system were studied by selecting methylene blue?MB?and bisphenol A?BPA?as the target pollutant,respectively.The results showed that SFC/PDS system exhibited higher degradation performance of methylene blue than PDS or SFC alone.The MB degradation ratio was 79.5%and 80.4%after 5 min and 60 min reaction respectively at pH=7,stirring speed of 120 r/min,SFC concentration of 50?M,and PDS concentration of 250?M.BPA was insignificantly degraded in SFC/PDS system.The BPA degradation ratio was about 10%after 3 h reaction at pH=7,stirring speed of 120 r/min,SFC concentration of 60?M and PDS concentration of 300?M.?2?Degradation effects of SFC/PMS system on BPASFC/PMS system exhibited good degradation performance of BPA.The degradation efficiency was affected by SFC concentration,PMS concentration,initial pH of the solution,concentration of inorganic anions,etc.At the BPA/SFC/PMS molar ratio of 1:1:3 and pH=7,the degradation ratio was 99.2%after 60 min reaction.The BPA degradation performance was prominent at pH=3-11,especially pH=3 and pH=11.Thus,the limitation of a narrow range of pH in traditional Fe²⁺/PMS system was eliminated.BPA degradation was inhibited by NO₃^-,SO₄^2-and Cl^-to different extents,but promoted by HCO₃^-,especially CO₃^2-.The results showed that SFC/PMS system degraded BPA much better than SFC/PDS system,Fe²⁺/PMS system,Fe²⁺/PDS system,SMC/PMS system,SCC/PMS system,etc.The total PMS consumption was higher in acidic condition than alkaline condition,and the residual SFC concentration after reaction decreased with decreasing pH.During BPA degradation by SFC/PMS,the leaching of iron was insignificant.?3?Mechanism of BPA degradation by SFC/PMS systemRadical scavenging experiments and EPR tests showed that the main active species for BPA degradation in the system were singlet oxygen?¹O₂?and high-valent iron-oxo porphyrin species.Heterolysis of the O-O bond produced high-valent iron porphyrin?-cation radical(por^·+-Fe?IV?=O)during the reation.The products on BPA degradation were possibly C₁₄H₁₄O,C₁₄H₁₄O₂,C₈H₈O,C₉H₁₂ or C₉H₁₀.The residual precipitates during the reaction were analyzed.BPA was not degraded by the precipitates alone,but degraded after addition of PMS,which had certain cyclicity.