Oxidative Degradation Of Phenols With H₂O₂ Catalyzed By Iron Sulfides

Heterogeneous Fenton oxidation is widely used in the degradation of organic wastewater because of its recoverable catalyst,high efficiency and economy.Transition metal sulfide（TMs）has attracted extensive attention in heterogeneous Fenton-like oxidation due to its excellent conductivity,rich redox sites,excellent optical properties,outstanding mechanical stability and thermal stability.However,iron-based sulfides show good catalytic activity because of the synergistic effect between active component iron and electron donors.Among them,the content of Fe²⁺in the active center of the catalyst has an important influence on the catalytic performance.In this paper,the effects of conventional solvothermal method and microwave-assisted heating method on the catalytic performance of iron-based sulfide were compared,and the effects of sulfur source and iron source on the catalytic performance of iron-based sulfide and their possible mechanism were studied.The preparation of core-shell iron-based sulfide was studied,and Fe₃S₄@Si O₂ core-shell catalyst with high stability was constructed.Finally,the combined method of solvent thermal elution-catalytic reduction debromination（HDB）-catalytic oxidation was used to realize the harmless treatment of heavily polluted soil with tetrabromobisphenol A（TBBPA）.The main contents are as follows:（1）Iron-based sulfide catalysts were prepared by conventional solvothermal method and microwave-assisted solvothermal method respectively,and the effects of heating mode and preparation temperature on catalyst performance were compared.It was found that microwave-assisted solvothermal method was a mild,efficient and energy-saving method for preparing iron-based sulfide catalyst compared with conventional solvothermal methods.The catalyst characterization analysis（SEM,BET and XPS）showed that the catalytic performance and texture characteristics of iron-based sulfide prepared by this method were more excellent.By studying the influence laws and mechanism of preparation methods and conditions on catalytic performance,a preparation process of iron-based sulfide catalyst with mild conditions,high efficiency and energy saving was developed.Based on microwave-assisted solvent method,the effects of sulfur source and iron source precursors on the catalytic performance of iron-based sulfide catalyst were studied.The surface composition and microstructure of the prepared iron-based sulfide were characterized by SEM,TEM and XPS,and the relationship between sulfur species transformation and Fe（II）regeneration were clarified.At the same time,the possible mechanism of reactive oxygen species（ROS）production was expounded in detail by free radical quenching experiment and electron spin resonance（ESR）spectrum analysis.In addition,the effects of H₂O₂ dosage and initial p H on the degradation rate of phenol were studied.（2）Different types of supported iron-based sulfides were prepared,the effects of different preparation methods on the catalytic performance of supported iron-based sulfides were explored,and the effects of preparation methods and conditions on the matrix were clarified.Based on these,the optimal method for preparing Fe₃S₄@Si O₂core-shell catalyst-inverse emulsion method was defined.Furthermore,the activity and stability of Fe₃S₄@Si O₂ core-shell catalyst for catalyzing and activating H₂O₂ to degrade phenol were evaluated.It was found that the existence of Si O₂ microspheres in the core-shell structure could effectively reduce the loss of Fe₃S₄ during the catalytic oxidation reaction,thus improving the stability of Fe₃S₄ catalyst.Therefore,the material could effectively degrade phenol within 60 min and could be effectively reused for more than five times.At the same time,the system was applied to the removal of 2,4-dichlorophenol and methylene blue,and satisfactory treatment results were obtained.（3）In view of the heavily polluted soil of tetrabromobisphenol A（TBBPA）,TBBPA was eluted from its polluted soil by solvent thermal elution,and then debrominated by catalytic hydrogenation,and bisphenol A（BPA）was completely degraded by the wet oxidation system developed in the previous research.The results showed that polar solvents（especially methanol and ethanol）were more beneficial to elution and catalytic hydrogenation than nonpolar solvents for the extraction and catalytic hydrogenation of TBBPA from heavily polluted soil.Moreover,TBBPA could be completely hydrogenated to BPA in ethanol within 60 min;Furthermore,combined with catalytic oxidation,the mineralization of hydrogenation product BPA was realized,and BPA could be completely degraded within 12 min in the above oxidation system.On this basis,the combined degradation method of solvent thermal elution-catalytic hydrogenation-catalytic wet oxidation was constructed,and the harmless treatment of soil contaminated by TBBPA was realized.