The Dye Wastewater Treated By Ozone, Microwave, Catalytic Oxidation And Combined Process

Dyeing wastewater is characterized by high COD concentration, heavy chroma, high salt content, strong toxicity, complicated ingredients and poor biodegradability, which has posed a serious threat to the water environment of China. The control of dyeing wastewater is imminent. The reason for an urgent need to explore an efficient technology to treat dyeing wastewater is that the traditional methods have many shortcomings, such as high cost of processing, the large amount of sludge and secondary pollution. The article takes reactive red X-3B as a model pollutant, by comparing the performance of ozonation, microwave catalytic oxidation and ozone-microwave catalytic oxidation process, poses the feasibility of microwave catalytic oxidation and ozone-microwave catalytic oxidation process, discusses the factors, degradation mechanism and kinetics, studies catalyst preparation.In the ozonation dyeing wastewater system, ozone can decolourize the reactive red X-3B dyeing wastewater rapidly but can’t degrade the organic compounds in water very well. The results show that15min is the most appropriate reaction time;9.99mg/min is the appropriate ozone intake quantity;8℃is the suitable temperature and alkaline conditions are more conducive than acidic conditions to the removal of the TOC. Lower concentration of the substrate (i.e., lower initial dye concentration) can obtain higher removal efficiency. Compared to the ozonation process, microwave catalytic oxidation and ozone-microwave catalytic oxidation process get a higher TOC removal and reactions are affected by the amount of catalyst, microwave irradiation time and irradiation power. The optimal condition based on univariate analysis test is that the catalyst dosage is150g/L, microwave irradiating for3min and the irradiation power is560W.The2-3mm Al2O3is chosen as carrier which is loaded by MnO2as the active component on the surface through ultrasonic impregnating. The optimal condition concluded from orthogonal test is that impregnating solution concentration is1.0mol/L, the immersion time is48h and ultrasonic impregnating for30min, and then the impregnated Al2O3is calcined at400℃for4h. At last, the catalysts are characterized by adopting SEM and BET.Degradation mechanism, degradation pathways and reaction kinetics, are studied in this article. The results show that ozonation process is due to direct oxidation and indirect oxidation. The-N=N-chromophore, triazine ring and naphthalene ring are destroyed by ozonation, and the small molecules are directly oxidized to carbon dioxide and water. Microwave catalytic oxidation reaction and ozone-microwave catalytic oxidation reaction rely on the strong oxidizing of·OH to oxidize dye molecules into carbon dioxide and water, and there are no accumulation of intermediate products. Ozonation alone is accorded with the secondary reaction dynamics, microwave catalytic oxidation and ozone-microwave catalytic oxidation process are in line with the first-order kinetics.This study indicated that microwave catalytic oxidation and ozone-microwave catalytic oxidation process have great significance to the treatment of dyeing wastewater.