The Catalytic Activation Mechanism Of FeOCl In Photo-Fenton And Photo-Fenton-like Systems

In this dissertation,the application of iron oxychloride?FeOCl?in photo-Fenton and photo-Fenton-like oxidation was studied.The·OH and SO₄^·-were produced by heterogeneous reaction and the organic pollutants in water were degraded.FeOCl was prepared by a partial thermal decomposition method and characterized by a series of characterizations.From the characterization results of XRD,SEM and BET,FeOCl presents nanoflakes and the specific surface area was 14.4m2/g,FeOCl had the highest purity and crystallinity when crystallized at250°C;it was confirmed by XPS.The elemental composition in FeOCl is Fe,O,Cl;combined with UV-DRS and VB XPS analysis,FeOCl is a narrow bandgap catalyst?Eg=1.78eV?and can respond to visible light.The different catalytic systems of FeOCl and the effects of catalysts,oxidants,pH and other factors were studied.Combining electron paramagnetic resonance?EPR?qualitative and fluorescence methods,the generation rate of free radicals,the influence of visible light intensity and the catalytic synergy efficiency were quantitatively analyzed.The Fe???/Fe???changes on the surface of FeOCl were catalyzed by the qualitative and semi-quantitative analysis of EPR and XPS.The catalytic activation mechanism of FeOCl in photo-Fenton and light-like Fenton systems was proposed.The specific content is as follows:a)In the FeOCl/H₂O₂/Vis system,the condition-optimized contaminant RhB can be completely degraded in 45 min with a small amount of H₂O₂?10 mg/L?,and the reaction rate is 0.08969 min^-1.The EPR and terephthalic acid fluorescence spectrophotometry were used to qualitatively and quantitatively study the·OH generation of Fe OCl catalysts in the Photo-Fenton system.The generation rate of·OH was 6.0×10^-4S^-1.The XPS characterization of the solid before and after the reaction shows that during the reaction,Fe???is reduced to Fe???on the surface of the FeOCl catalyst,and the visible light intensity is changed by the EPR to measure the change in the amount of OH generated in the Fenton system,indicating the generation of OH.The quantity increases with the increase of light intensity;b)In the FeOCl/SPC/Vis system,RhB can be completely degraded within 45 min under condition optimization,and the reaction rate is 0.07675 min^-1.A qualitative study of the formation of·OH in FeOCl/SPC/Vis system was carried out using EPR for FeOCl catalysts.It was shown that compared with FeOCl/SPC system,Fe OCl/SPC/Vis system generates more·OH;the FeOCl catalyst was characterized by XPS analysis before and after the reaction.During the reaction,the Fe???surface of the FeOCl catalyst was reduced to Fe???,and the relative content ratio of Fe???/Fe???increased from 0.31 to 0.66.c)In the FeOCl/PS/Vis system,RhB can be completely degraded within 45 min under conditions optimized with a reaction rate of 0.07197 min^-1.The EPR test results show that·OH is predominant in the early stage of the reaction,and the amount of SO4·-generated gradually increases with the increase of reaction time.The free radical inhibition experiment proves that,with h+,SO4·-is the main free radical in the system;The recombination rate of photogenerated electron holes of FeOCl is higher,and PS can act as a photoelectron trapping agent to suppress the recombination rate of photogenerated electron holes and improve the degradation rate and reaction rate;the Fe???/Fe surface is characterized by XPS before and after reaction.The proportion of???increased from 0.25 to 0.68 and 0.48,respectively,demonstrating that visible light promotes electron transfer and is beneficial to the reduction of Fe???;...