Study On α-Fe₂O₃ Crystal Plane Control And Its Catalytic Degradation Properties In Heterogeneous Photofenton

The traditional Fenton oxidation technology has the following defects:narrow p H application range,low H₂O₂ utilization rate,and difficulty in recycling of iron ions to produce secondary pollution.To overcome these defects,a heterogeneous Fenton has been developed on this basis.The main feature of the heterogeneous Fenton reaction is that the iron-containing solid phase catalyst replaces Fe²⁺in the homogeneous reaction,Thus,the two-phase advantage can separate the catalyst from the reaction solution and achieve recycling.Moreover,due to the immobilization of iron ions,the narrow p H range in reaction,a large amount of iron sludge is generated during the reaction,and the secondary pollution caused can be solved to a certain extent.However,due to the solid-liquid two-phase mass transfer resistance,the heterogeneous Fenton catalytic activity is greatly reduced.Currently,numerous studies have shown that by controlling the growth of the catalyst crystal to achieve the exposure of its specific crystal plane,the catalytic activity can be greatly improved.However,most studies have focused on the high exposure of high-energy crystal planes,and rarely consider the interactions and effects between different crystal planes.On this basis,this topic proposes the preparation of highly active catalystα-Fe₂O₃ with{110}/{113}crystal plane exposure,and studies its degradation characteristics in heterogeneous photo-Fenton reaction system,and explores its catalytic oxidation degradation mechanism.When the reaction volume is 30m L,the precursor concentration Fe Cl₃·6H₂O is33mmol/L,and the dosage of Fe Cl₃·6H₂O,Na H₂PO₄,Na F is 1:1:15,Using hydrothermal method to react at 180°C for 24h,α-Fe₂O₃ catalyst with high catalytic activity was prepared.The performance test experiment shows that the removal rate of MO can reach about 95%in 60 minutes.Material characterization and experimental data show that the{110}/{113}crystal plane is effectively exposed on the catalyst surface and has a synergistic effect at a specific exposure ratio.Since light can promote the Fe³⁺/Fe²⁺cycle,this topic constructs a heterogeneous photo-Fenton reaction system,when the initial concentration of MO is 40mg/L,the optimal reaction conditions are initial p H=5,the amount of H₂O₂ is 20mmol/L,and the dosage of catalyst is 200mg/L,UV dose is 57.6J/cm2,temperature is 25°C±2.With the optimal reaction factors,the removal rates of MO were 42.93%,85.14%,and 97.83%for 20 minutes,40 minutes,and 60 minutes respectively.After the catalyst is used three times repeatedly,the removal rate of MO can be kept above 80%after 60 minutes of reaction.It will reach a stable state after the second use,and the maximum dissolution of iron ions in the second use only accounted for 3.58%of the iron content in the amount of catalyst,it shows that the catalyst has a certain degree of reuse stability.By analyzing the changes of H₂O₂ during the reaction and free radical suppression experiments,it was certified that in this experiment system,·OH and h⁺play an important role in degradation.Its catalytic oxidation mechanism is a combination of heterogeneous Fenton,photocatalysis and homogeneous Fenton.