A Synergistic Treatment Process Of Dielectric Barrier Discharge/Photocatalysts/Micro-Aeration For Coking Wastewater

Wastewater treatment by DBD is an advanced and combined oxidation technology which capable of the photo-, electro- and chemical-oxidation. It has the advantages of extensive application and advanced treatment effect therefore became attractive in recent years. It was taken as a more and more important environment-friendly technology. Micro-aeration is a most effective method to improve the transfer efficiency of DO from air to water.This study uses all the three methods (dielectric barrier discharge/ photocatalysis/micro-aeration) at the same time to treat high strength organic water. The active species (O3、·OH)and ultraviolet light (produced by the plasma discharge) degrade organic matter synergetically. The micro-aeration improves the transfer efficiency of 03、·OH and provides bubble for the plasma discharge in water at the same time.The physical and chemical effects of plasma discharge to the organic matter in the wastewater are fully developed by the dielectric barrier discharge/photocatalysis/micro-aeration technology.The plasma wastewater treatment technology mainly uses the chemical effect during the plasma discharge process at present other than the physical effect. Moreover, there are still some drawbacks for this technology such as long treatment time, insufficient utilization of reactive species. This paper set up a continuos dynamic dielectric barrier discharge/ photocatalysis/micro-aeration installation to treat coking wastewater synergetically with all the three methods.The main conclusions are:1. The design and optimization of a dynamic dielectric barrier discharge/photocatalysis/micro-aeration reactor for the treatment of coking wastewater. A cylindrical dielectric barrier discharge device and the micro-aeration membrane were installed at the bottom of the reactor. The liquid inside the reactor acts as the low voltage electrode of the dielectric barrier discharge. It should be the most effective dielectric barrier discharge/photocatalysis/micro-aeration wastewater treatment facility.2. This study optimized the parameters that influencing the treatment effect,including the discharge parameters and the wastewater treatment process parameters. It focused on the analysis of the influence of discharge voltage,discharge time, the initial concentration of the solution and the aeration rate on the degradation of phenol. The response surface method was adopted to optimize the design of discharge voltage, discharge time, the initial concentration of the solution and the aeration rate for the degradation of phenol on the basis of Single factor experiments. The results showed that optimal configuration for the phenol degradation was: the discharge voltage of 34.7kV,the discharge time of 29.71 min, initial concentration of 40.41 mg·L-1 and aeration rate of 150.38mL·min-1. The degradation rate of phenol was 74.28% in this condition.3. The TiO2-nanotubes were prepared with hydrothermal method. The TiO2 was doped with N to modify its property. The N-doped TiO2, nanotube photocatalysis was prepared by hydrothermal-impregnation method and sol-gel hydrothermal method.① Hydrothermal-impregnation method. The N-TNTS was prepared by the impregnation method in which TiO2 nanotube prepared by the hydrothermal method was taken as raw material and the NH4F was taken as nitrogen source. ② Sol-gel hydrothermal method. First the N-doped TiO2 was prepared by the sol-gel hydrothermal method in which the butyl phthalate was taken as the titanium source and NH4F as nitrogen source. Then The N-TNTS was prepared by the hydrothermal method from N-doped TiO2. The characterizations of synthesized Ti02 nanotube and the modified TiO2 nanotube were analyzed by XRD, TEM and UV-Vis RDS methods to check the influence of different preparation conditions on the microstructure, crystal formation and photocatalytic activity.4. The phenol solution was chosen to simulate the coking wastewater. The phenol degradation effects were checked at different discharge voltage,discharge time, initial phenol solution concentration and catalyst of respectively the dielectric barrier discharge/photocatalysts/micro-aeration method, the dielectric barrier discharge/photocatalysts method and the dielectric barrier discharge /micro-aeration method.The results indicated that: the degradation efficiency was the highest when using the dielectric barrier discharge/photocatalysts/micro-aeration method and the degradation rate was 96.7% when the initial phenol solution concentration was 50mg/L, the discharge voltage was 35kV and discharge time was 20 min. The maximum phenol degradation rate was 75.4% for the dielectric barrier discharge/photocatalysts method, 68.9% for the dielectric barrier discharge /micro-aeration method and 52.8% for the dielectric barrier discharge method.The degradation mechanism of the dielectric barrier discharge/photocatalysts/micro-aeration method was analyzed on the basis of the experiment results: It was a comprehensive result of multiple degradation approach which typically includes the UV decomposition, ·OH, 03, 03/UV, H2O2/UV, Ti02/03/UV, TiO2/ UV etc.The experimental results demonstrate that effect of removal was best and the rate of removal was fastest when DBD/photocatalysts/micro-aertion were used in treatmet process at same time.