Study On Treatment Of Aromatic Compounds In Printing And Dyeing Wastewater By Fenton Oxidation

Printing and dyeing wastewater is a kind of industrial wastewater that is difficult to degrade,not only has high colour,complex organic matter,more salts,lower biochemical activity and stronger alkalinity,but also has huge discharge.Worse still,dyeing wastewater contains some heavy metals,which pose a great danger to our environment and human health.Therefore,the search for efficient degradation methods for dyeing wastewater is an important issue in our fine chemical and environmental protection business.In this study,a new Fenton-like system,i.e.Cu²⁺/Cl^-/H₂O₂ system,was constructed for the characteristics of high alkalinity,heavy metal ions and high salt content of printing and dyeing wastewater.In this paper,the construction method of this Fenton-like system,the evaluation criteria and influencing factors of catalytic activity,the degradation mechanism,the generation and detection of active species are systematically studied,hoping to provide some new ideas for the degradation treatment of dye wastewater.The main conclusions of this thesis are as follows:（1）The dye can be effectively decomposed by the Cu²⁺/Cl^-/H₂O₂-like Fenton system,and the system requires the combined action of Cu²⁺,Cl^-and H₂O₂ to work well.A Fenton-like system consisting of 4 mmol/L Cu²⁺,8 g/L Cl^-and 0.12 mol/L H₂O₂ resulted in 83.50%degradation of 20 mg/L methylene blue（MB）in 15 min;and the system allowed almost complete decolourisation of methyl orange（MO）and malachite green（MG）in 30 min.In the presence of some common printing and dyeing auxiliaries such as oxalic acid（OA）,citric acid（CA）and ethylenediaminetetraacetic acid（EDTA）,the system still showed strong catalytic activity.（2）In the Cu²⁺/Cl^-/H₂O₂ type Fenton system,both hydroxyl radicals and high-valent copper active species work together.About 46.35%of the methylene blue was degraded by the hydroxyl radicals and the valence of the copper ions was changed during the reaction.About 7%of the high-priced copper participated in the degradation of the dye.By calculating the interaction and reaction kinetics among different species in the system,it was inferred that the copper species that played the main role in the system was in the form of Cu Cl⁺.（3）MgO₂ was prepared by direct and indirect methods as a substitute for H₂O₂ and analysed for its active oxygen content and purity.The MgO₂ in the Cu²⁺/Cl^-/MgO₂-based Fenton system not only failed to enhance the catalytic activity of the system towards the dye,but also reduced the catalytic degradation of the dye due to its difficulty in decomposing under highly alkaline conditions,and the system was not suitable for the treatment of dye wastewater.