Preparation Of SiO₂-coated Nano Zero-valent Iron And Decolorization Of Dye Wastewater

In the past few decades,as the economic development brought greater pressure on the environment and the environment capacity of water has gradually become smaller,wastewater treatment and improvement of water bodies has become an urgent task.With the increase in population and industrialization,dye-related products are also increasing,and dyes have become inseparable from our lives.Due to its teratogenic and mutagenic effects,dye wastewater is also highly contaminated with the color of water,and therefore has great harm to the environment and human body.In recent years,nano-zero-valent iron has gradually become a new tool for treating sewage,and it has been widely recognized for its economical availability and no secondary pollution.However,studies have found that because the size of the material is nanoscale,the specific surface area is large and the activity is strong,so that it is easy to agglomerate and is easily oxidized.When nZVI removes pollutants,hydroxide precipitates on the surface of the nZVI,which hinders the reaction of the nZVI materials inside,resulting in low pollutant removal efficiency.Due to the above limitations,it is necessary to modify the nZVI so that it can be better applied.Based on the above reasons,this study mainly studied the preparation and characterization of nZVI and its modified materials,and was applied to the treatment of dye wastewater.This study uses liquid phase reduction method to prepare nZVI material,and then use SiO₂ coating on nZVI surface to prepare modified SiO₂-nZVI material by St?ber hydrolysis method.Transmission electron microscopy of the two reductants showed that the SiO₂-nZVI material had obvious core-shell chain structure on the surface,and the outer layer was evenly coated with a SiO₂ mesh transparent film,which was superior to the nZVIwith uneven grain size.According to FT-IR,the characteristic absorption peaks of O-H and SiO₂ are contained in the infrared spectrum of SiO₂-nZVI material,and the modified nZVI has good oxidation resistance and can remain relatively stable in the air.Through XRD analysis of the material,it is found that the coated nZVI particle size becomes smaller,and the SiO₂ cladding layer is an amorphous structure.The effect of the dosage of SiO₂-nZVI material,the initial concentration of the dyestuff,and the initial pH of the solution on the removal rate of the dyestuff was investigated.It was found that the dosing amount of the SiO₂-nZVI material was 4.5 mmol/L.The initial concentration of 200mg/L,the initial pH value of the solution 5.5,the highest dye removal rate,can reach 95%or more.Decolorization and degradation experiments were performed on the three major dyes of azo,anthraquinoneand triphenylmethane,and the differences in degradation rates of different dyes were analyzed and compared.In-depth analysis of the process of SiO₂-nZVI dye wastewater treatment,inspect the degradation of the system during the degradation of the nature of the SiO₂-nZVI degradation dye wastewater mechanism.By analyzing the products of SiO₂-nZVI degradation of dyes and a series of kinetic experiments,the mechanism of degradation of dyes by SiO₂-nZVI materials was further analyzed,and it was found that SiO₂-nZVI materials degrading dyes met the pseudo first order dynamics law.