Removal Of Dyes By Preparation Of Mn/Fe Substituted Polyoxometalates/hydrotalcite

China's developed textile industry has brought considerable economic benefits while also aggravating environmental pollution.Their discharge has brought serious environmental and human health problems,so the treatment of printing and dyeing wastewater is imminent.LDHs can synthesize different kinds of composite materials by varying the types of interlaminar anions and endow them with different properties,so as to obtain a new class of materials with different functions.In this paper,different intercalated proportions of Fe and Mn substituted Keggin polyoxometalates/LDHs composites?PFe W/LDHs and PMn W/LDHs?were synthesized by anion exchange method,and their structures were characterized.The removal effects of anion dyes,cation dyes and mixed dyes were investigated by using these two composites.The XRD and FT-IR results showed that PFe W and PMn W were successfully inserted into the layers of LDHs.It was found from BET test that both catalysts were mesoporous materials.Combining with SEM characterization,it was found that both catalysts had typical hydrotalcite plate slit and fissure lamellar structure.Through the characterization of TG-DTA,it could be known that both catalysts had good thermal stability during catalytic degradation in aqueous solution.In the degradation experiments of PFe W/LDHs?1:2?and PMn W/LDHs?1:2?on acid red27?AR27?,the removal rate of AR27 under different conditions was compared.The effects of hydrogen peroxide concentration,initial p H value and reaction temperature on the degradation process were investigated.The cyclic stability and catalytic degradation mechanism of PFe W/LDHs?1:2?and PMn W/LDHs?1:2?were studied.The experimental results showed that PFe W/LDHs?1:2?and PMn W/LDHs?1:2?had high catalytic activity.After four times of cyclic reaction,the two catalysts still had high catalytic activity,and the crystal shape and surface morphology of the catalysts did not change.After the reaction,only a small amount of manganese ions were leached out,indicating that the two catalysts had high stability and recyclability.The process of degradation mainly depended on the formation of·OH and·OOH radicals.The experiments also proved that Mn²⁺and Mn³⁺,Fe²⁺and Fe³⁺promoted the Fenton reaction by mutual transformation,and element W was involved in the degradation reaction.This study also proved that PFe W/LDHs and PMn W/LDHs with different intercalation ratios had different surface electrical properties,indicate that with the increase of PFe W or PMn W between the layers of the subject LDHs,the charge of the hydrotalcite laminate would be significantly reduced.The surface electrical properties of the composites could be adjusted by changing the intercalation amount of the object to adapt to the treatment of different types of dyes.In this study,the mixed catalysts with the intercalation ratio of 2:1 and 1:2 could achieve a very significant effect on the treatment of mixed dye wastewater with anion and cation dyes.Above mentioned,this study not only enriched the theory of hydrotalcite intercalation,but also had a certain application prospect for the treatment of real dye wastewater.