Treatment Of Methylene Blue Simulation Dye Wastewater Solution By Dielectric Barrier Discharge

The textile industry can generate much wastewater containing various dyes with complex compositions,which is hard to be comprehensively degraded by traditional wastewater treatment technologies.In this thesis,methylene blue dye wastewater was degraded by atmospheric pressure plasma.Low-temperature plasma,as an advanced material preparation and treatment technology,has been developed rapidly in recent decades and is widely applied in dye wastewater treatment.Atmospheric pressure air DBD is widely studied due to its easy operation and stable discharge.A large number of active species such as oxygen atoms,ozone,hydrogen peroxide and hydroxyl groups will generate during the discharge process,which would effectively oxidize organic pollutant molecules into small molecules.The degradation process undergoes a series of reactions such as bond breaking,ring opening and conjoining,and finally degrades into aromatic compounds to degrade dye wastewater.In recent years,atmospheric pressure plasma has been improved in the degradation of dye wastewater,however,it still suffers from low energy utilization,low mineralization rate and unclear reaction mechanism,which greatly limits the practical applications in wastewater treatment.To improve the utilization rate of plasma,increase the stability of the reactor,and improve the energy utilization rate,a cylindrical double DBD reactor was used and dye wastewater was simulated by methylene blue solution.The thesis includes three main aspects:（a）the effect of basic discharge parameters on the methylene blue,（b）the effect of solution characteristics and additive synergistic technology on the degradation rate of methylene blue,and（c）the effect of reactor structure parameters on the degradation rate and mineralization rate of methylene blue.The results show that increasing the discharge voltage can significantly improve the degradation rate of methylene blue,while limited by the reactor lifetime and the stability of discharge,the input voltage was fixed at 24.4 k V.After scanning the experimental parameters,it was observed that when the solution flow rate was 118 ml/min and the aeration rate was 150m L/min,the highest degradation of methylene blue,and the degradation rate of methylene blue reached 75%after 60 min treatment.The mineralization degree reached 41.1%.Changing the pH value of the solution could effectively improve the degradation rate of methylene blue,and the degradation rate of methylene blue reached 92%and the mineralization rate reached 61.6%after 60 min process.Fenton reaction was formed to improve MB degradation by plasma at a small amount of Fe²⁺,while,a significant inhibition effect was observed at an excessive amount of Fe²⁺.The electrode structure has an effect on the degradation rate of methylene blue.The inner diameter of the dielectric tube greatly affects the degradation rate and discharge stability.The electrode mesh and size are positively correlated with the degradation rate.The 200-mesh copper electrode has the best degradation rate,which improved by 15%compared with that of the 20-mesh copper electrode.165 mm long electrode had the best degradation rate,which improved by 20%compared with that of the 72.5 mm electrode.And the highest energy utilization rate(9.37×10^-5 mg/J)was obtained at 145 mm electrode length.