Senior Oxidation Degradation Of Methylene Blue Dye Wastewater

With the vigorous development of printing and dyeing industry in our country,the amount of wastewater emission from printing and dyeing excesses 1700,000,000 m³ per year.The dye in wastewater absorbs the ray then reduces the transparency of the water,which would influence the species and microorganism in water in combination with visual pollution and environmental damage. Characterized by complex chemical toxic components,lots of biorefractory organic compounds and enormous kinds of dye products,dye wastewater is difficult to be effectively treated and biodegraded. Advanced Oxidation Processes(AOPs) is the technical key points in treatment of wastewater.It is widely accepted that the mechanism of AOPs is the free radical oxidation mechanism.AOPs employ composite oxidant,irradiation,electricity or catalyst to produce kinds of strong oxydants(·OH,HO₂·,O₂^-).Expecially·OH,it can degrade any organic pollutements to CO₂,H₂O or mineral salt. Methylene blue(MB) dye wastewater will be treated by AOPs in this article.The first part of this thesis is to degrade methylene blue with AOPs which employ oxygen dissolved in the water as oxydant and use CuO-MoO₃-P₂O₅ as catalyst.CuO-MoO₃-P₂O₅ is charactered by X-ray diffraction(XRD),Fourier Transform Infrared Spectrometer(FT-IR),X-ray Photoelectron Spectroscopy(XPS) and Scanning Electron Microscopy(SEM).MB is adopted to investigate the catalytic activity of CuO-MoO₃-P₂O₅ in AOPs.XPS shows that CuO-MoO₃-P₂O₅ after reaction has two valence(n_Cu2O:n_CuO=40.14:59.86).Compared to 100%Cu²⁺ in CuO-MoO₃-P₂O₅ before reaction,it can be concluded that Cu element involves in the degradation. Catalyst activity experiments show that CuO-MoO₃-P₂O₅ is the good catalyst to degrade MB.The sceond part of this thesis is to degrade MB with AOPs which employ oxygen dissolved in the water as oxydant and use FeOx-MoO₃-P₂O₅(x=1 or 1.5) as catalyst.The crystal size of FeOx-MoO₃-P₂O₅(x=1 or 1.5) is evaluated by XRD.The metal valence in FeOx-MoO₃-P₂O₅(x=1 or 1.5) is tested by XPS.XRD reveals that the crystal size of Fe₂O₃-MoO₃-P₂O₅(0%starch,w/w) is 93.26 nm,while 25.396 nm for FeOx-MoO₃-P₂O₅(25%starch,w/w).It shows that the crystal size becomes small with increasing its content in starch dosage.Effects of experimental conditions including pH,the initial concentration of methylene blue,the amount of catalysts and temperature were investigated with the help of the Taguchi method and the orthogonal design of experimental parameters.An analysis of variance(ANOVA) reveals that concentration was the most significant parameter affecting the decoloration.The change of the catalysts dose has an insignificant effect on the decoloration.The third part of this thesis is that adding Fe modified kaolin catalyst on the basis of three-dimensional electrode is to generate lots of intermediate oxidative species which accelerate the degradation of methylene blue dye wastewater.Current density and the initial pH are tested to find the optimal parameter combination.Experimental results show that the solution of the initial pH affect the degradation efficiency.COD degradation rate decline in high pH.