Preparation And Properties Of Potassium Ferrite Photofenton Catalyst

As a result of the deterioration of the ecological environment,the life of human beings and plants and animals has been greatly affected.The harm caused by various environmental problems has seriously affected the normal life of human beings.Especially the pollution of water resources,which has caused various degrees of harm and even extinction.The polluted wastewater contains a large number of organic substances,after long-term ingestion into the human body,will cause a variety of diseases,and even lead to the occurrence of cancer.It can cause various diseases and even cause cancer.Because these dyes contain various chromogenic groups,they have the characteristics of complex composition,stable structure,high concentration,dark color and strong toxicity.They attracted the interest of various experts and scholars.Methylene blue as a dye is widely used in various textile,printing,dyeing,biotechnology and other industries.Because high concentration of methylene blue solution can cause poisoning and death of animals in water.Crystal violet is widely used as a biological dye,which is extremely toxic to microorganisms in water and causes long-term adverse effects on the water environment.Rhodamine B solution has strong fluorescence and is widely used in various printing and dyeing industries.However,rhodamine B dye wastewater has a strong toxicity,causing different degrees of damage to human organs and even carcinogenic.Therefore,it is very important to choose a suitable treatment method to degrade dyes in wastewater.Heterogeneous photo-Fenton oxidation has been widely used in the treatment of dye wastewater as an efficient degradation technology.Compared with the traditional homogeneous Fenton reaction,it makes up for the disadvantages of strict reaction conditions,excessive use of hydrogen peroxide,large amount of iron sludge formation,and the inability to recycle of the catalyst in the homogeneous Fenton reaction.Moreover,under the light condition,a large number of extra hydroxyl active species will be generated in the reaction system and used for the degradation of the dye,which greatly improves the catalytic performance of the catalyst.Based on the various previous studies,we successfully synthesized potassium ferrite?K₂Fe₄O₇?crystals with different scales by using hydrothermal method in this paper.The degradation and mechanism of methylene blue,crystal violet and rhodamine B dyes were systematically studied by using these crystal materials as heterogeneous photofenton catalysts with simulating visible light.Our specific research contents are as follows:?1?In this paper,different sizes of potassium ferrite catalysts were synthesized by hydrothermal synthesis.After continuously adjusting the hydrothermal reaction conditions,a catalyst KFO-20 with large specific surface and narrow band gap was successfully prepared.The particle size distribution of this catalyst is about 20?m.It has a regular hexagon,a smooth surface,and a large specific surface area of 63.79m²/g,which provides more active sites for the catalytic reaction and accelerates the efficiency of the catalytic reaction.The KFO-20 catalyst has a very narrow band gap value of 1.44eV,it can absorb ultraviolet light in the range of 300-420 nm and visible light in the wide range of 420-700 nm.The generation of photo-generated electron-hole pairs adds a large number of additional hydroxyl species to the reaction and enhances the effect of the catalytic reaction.The structure,morphology and size of the synthesized photo-Fenton catalyst K₂Fe₄O₇?KFO?were characterized in detail by various techniques and methods.?2?In this experiment,30 mg/L KFO-20 was used as the photo-Fenton catalyst,20 mg/L methylene blue solution was used as the reaction substrate,10 mM hydrogen peroxide was used as the oxidant,and the visible light radiation was added to form an Heterogeneous photo-Fenton system for the degradation of methylene blue.Among them,the synergism between the catalyst,hydrogen peroxide and visible light makes the degradation rate of methylene blue reach 100%in 35 minutes and the degradation rate of methylene blue can still reach 83%after KFO-20 catalyst is used four times under the same condition,suggesting that it had good chemical stability.In addition,the degradation rates of crystal violet and rhodamine B dyes were 92%and 48%under the same conditions,indicating that the KFO-20 catalyst has excellent universal applicability.We explored the contribution of various active species to the degradation process of methylene blue through the Trapping Experiments.It was found that the hydroxyl radical was the most important active species in this experiment and played a key role in the degradation of methylene blue.Photogenerated holes and photogenerated electrons also played a role in the degradation of methylene blue in this experiment.Combining the results of the Trapping Experiments with the results of the TOC,we proposed the photo-Fenton catalytic mechanism of KFO.