Preparation Of Fe-La-Al/MMT And CWPO Degradation Of Methylene Blue

According to statistics,about 40%of the world’s textiles are produced and supplied by China,resulting in a large amount of printing and dyeing wastewater.The components of dye wastewater are complex and toxic,so it is difficult to achieve ideal degradation effect by traditional technology.In this paper,Iron-lanthanum-aluminum/pillar montmorillonite（Fe-La-Al/MMT）catalyst was prepared by cation exchange method,and catalytic wet hydrogen peroxide oxidation（CWPO）technology was used to treat methylene blue simulated dye wastewater.The purpose was to develop a new heterogeneous catalyst for the degradation of organic pollutants.The effects of preparation method,Fe/La molar ratio,active metal loading（AML）,ultrasonic time and calcination temperature on Fe-La-Al/MMT catalyst were investigated.SEM,XRD,N₂ adsorption/desorption,FT-IR,DR UV-Vis,TG and other technology on the catalyst characterization.The activity and stability of the catalyst were evaluated by the degradation rate,COD removal rate and Fe leaching of CWPO degradation of methylene blue wastewater.The results showed that when the molar ratio of Fe/La was 7/3,the AML value was 6%,the ultrasonic time was 60 min,and the calcination temperature was 500℃for 2 h,the Fe-La-Al/MMT（U）catalyst prepared by ultrasonic assisted method had high crystallinity,regular crystal form,large specific surface area（148 m²/g）and interlayer spacing（1.759 nm）.The catalyst had the best effect on the treatment of methylene blue by CWPO.After 120 min of reaction,the degradation rate was 99.85%,and the COD removal rate was 74.48%,which was 4.37%higher than that of the traditional method.In addition,the preparation cycle of the catalyst can be shortened by 75%and the water consumption can be reduced by 50%by using ultrasonic assisted method.The optimized catalyst was used to treat methylene blue wastewater by CWPO to screen out the suitable process conditions.The results showed that when the dosage of catalyst was 0.5g/L,the initial p H was 4.07,the dosage of H₂O₂ was 28 mmol/L,and the reaction temperature was 60℃,the COD removal rate of methylene blue was 74.48%,and the Fe leaching was only 0.6815 mg/L.In addition,the COD removal rate of methylene blue over Fe-La-Al/MMT（U）catalyst was only reduced by 11.3%after five cycle experiments,indicating that the catalyst had good activity and stability.The mechanism of CWPO degradation of methylene blue was discussed.It was confirmed that the main active group in the reaction system was HO·.The pseudo-first order and semi-empirical Fermi equations were used as models to study the kinetics of CWPO degradation of methylene blue,and the changes of methylene blue concentration at different temperatures were fitted.The results show that the Fermi equation has a higher coincidence degree and can describe the degradation process of methylene blue more accurately.