Preparation And Application Of Attapulgite Clay-based Photo-fenton Catalyst

With the rapid development of China’s industry,the types of refractory organic pollutants flowing into the environment have increased sharply.The refractory organic pollutants have the characteristics of strong toxicity,complex composition,and difficulty in natural degradation.It will cause serious harm to the natural ecological environment and human health in my country,so the removal of refractory organic pollutants has become a hot research topic for scholars around the world.In this study,attapulgite was used as a carrier to support various metal oxides by impregnation method to obtain a composite heterogeneous photo-Fenton catalyst.The morphology,functional group,element morphology,specific surface area and pore size of the catalyst were characterized and analyzed.Using the screened catalyst with the best effect,the degradation of methylene blue（MB）simulated wastewater and2,4-D pesticide simulated wastewater were studied under the aid of UV light,the reaction system was optimized,and the reaction system was proposed.The degradation mechanism of the two pollutants,the degradation intermediates of 2,4-D were studied and discussed,and the possible degradation paths were speculated.The main contents of this research include the following aspects:（1）Using attapulgite as a carrier,Ti O₂and Fe₃O₄were supported by impregnation method to obtain a Ti O₂-Fe₃O₄/ATP catalyst.The catalyst with the best degradation effect was screened by changing the loading ratio of the two metal oxides.Through screening experiments,it was found that when the loading ratio of the two metal oxides was 1:1,the obtained catalyst exhibited the best catalytic performance among the catalysts of the same series.Using the prepared Ti O₂-Fe₃O₄/ATP catalyst,Cu O was loaded on its surface by ultrasonic impregnation method,and the effect of the addition amount of Cu O and the calcination temperature of the catalyst on the catalytic performance of the material was investigated.When the temperature is400℃,the catalyst has the best catalytic effect.Through the analysis of catalyst morphology,elements and functional groups,it was found that metals such as Ti O₂,Fe₃O₄,and Cu O were successfully loaded on the surface of attapulgite mainly by physical adsorption,and the loading of various metal oxides made attapulgite interlaced with each other.With more pore structure,attapulgite maintains the original crystal structure.In addition,the weight loss of the catalyst was 1.7%,indicating that the catalyst has good thermal stability.（2）The prepared Ti O₂-Fe₃O₄-Cu O/ATP catalysts were used to degrade the simulated wastewater containing MB dyes and the simulated wastewater with 2,4-D pesticides,respectively.The effects of temperature,H₂O₂addition,p H,catalyst dosage,and initial concentration of organic pollutants on the degradation experiments were investigated.The study found that when the p H was 2,the amount of H₂O₂was5 m L/L,the temperature was 60°C,and the dosage of the catalyst was 1 g/L,the degradation of MB by the catalyst for 100 min under the assistance of UV light tended to be stable.And the degradation rate reaches more than 99%,and the removal rate of MB can still reach more than 63%after being reused for 5 times.When 2,4-D was used as the target pollutant,when the p H value was 2,the amount of H₂O₂was 5m L/L,the temperature was 50°C,and the dosage of catalyst was 2 g/L,under the assistance of UV light The catalyst degrades 2,4-D pesticide wastewater for 180 min,and the degradation rate reaches more than 96%.After use,it is recycled and reused by magnets.After 5 times of recycling,the removal rate of 2,4-D can still reach 96%.more than 55%.（3）The prepared Ti O₂-Fe₃O₄/ATP was used to support Ni O by ultrasonic impregnation method,and the effect of its loading ratio and catalyst calcination temperature on the catalytic performance of the material was investigated.The results show that the catalyst has the best catalytic effect when the loading ratio is 4%and the calcination temperature is 500℃.The analysis of catalyst morphology and elements and functional groups showed that metals such as Ti O₂,Fe₃O₄,and Ni O were successfully loaded on the surface of attapulgite by physical adsorption,and the loading of various metal oxides made attapulgite interlaced and formed more pore structure,it maintains the original crystal structure of attapulgite.The weight loss of the catalyst was 1.2%,which indicated that the catalyst had good thermal stability.The catalyst was used to study the degradation of MB dye simulated wastewater and2,4-D pesticide simulated wastewater,respectively.The effects of temperature,H₂O₂addition,p H,catalyst dosage,and initial concentration of organic pollutants on the degradation effect were investigated.The study found that when the p H was 2,the amount of H₂O₂was 5 m L/L,the temperature was 60°C,and the dosage of the catalyst was 1 g/L,the catalyst tended to be stable for MB degradation for 100 min under the assistance of UV light.The degradation rate is over 99%,and the removal rate of MB can still reach over 70%after 5 times of reuse.When 2,4-D was used as the target pollutant,when the p H value was 2,the amount of H₂O₂was 5 m L/L,the temperature was 50°C,and the dosage of catalyst was 2 g/L,under the assistance of ultraviolet light,the The degradation of 2,4-D pesticide wastewater by the catalyst for180 min tends to be stable and the degradation rate reaches more than 90%.After use,it is recycled and reused by magnets.After 5 times of recycling,the removal rate of2,4-D can still reach 50%above,indicating that the catalyst has a certain stability.（4）The degradation mechanisms of the heterogeneous catalysts Ti O₂-Fe₃O₄-Cu O/ATP and Ti O₂-Fe₃O₄-Ni O/ATP were studied,and the effects of ultraviolet light and hydrogen peroxide on the catalytic effects of the two catalysts were discussed respectively.The amount of free radicals and photogenerated holes generated in the two photo-Fenton systems was detected,and it was proved that both systems belong to the photo-Fenton catalytic system.The possible degradation mechanisms of the two target pollutants by the photo-Fenton catalytic system were proposed,and the degradation intermediates of 2,4-D were analyzed by HPLC-MS and their possible degradation pathways were speculated.It has certain reference value for the future treatment of organic pollutants.