Study Of Reactive Blue Degradation In Aqueous Solution By Nano Catalytic Double Dielectric Barrier Discharge

Organic wastewater pollution has become a serious environmental problem with the rapid development of industry, and dye wastewater is one of the key sourcs of typical refractory organic pollutants. Dielectric barrier discharge, one kind of technique which could produce free radicals in situ has become a promising technique to degrade dye wastewater. However, dielectric barrier discharge has some drawbacks, for example. long-time treatment, low utilization rate of active species and low energy efficiency. Based on those problems, to utilize effectively the different types energy generated from the DBD, different catalysts were tested in the DBD processes.This paper took reactive blue X-BR as the target pollutant, DBD plasma coupled with catalyst TiO2and nZVI were utilized to degrade the X-BR wastewater, the optimal condtions for the oxidative degradation were investigated, the degradation kinetics were analyzed. Moreover, TiO2and Fenton were combined tighter in DBD system to investigate the X-BR removal performance.. Several catalytic were compared, the results would be of a good foundation for the industrial application. The main results are summarized as following:(1)When nZVI absorbed X-BR alone, X-BR removal rate increased with the nZVI dosage increase, the overall reaction reached equilibrium after2hours. In the system that nZVI was the catalys, the optimum operation condtions are as the following:the voltage is65V, the current is0.92A, the reaction time was10min, and the optimum dosage of nZVI is0.5g/L. The reason of why there is an optimum concentration of nZVI is that the high concentration nZVI had an effect of inhibition for the X-BR degradation. This system performed general for the TOC degradation: the TOC removal rate was only as high as18%. nZVI has better catalytic effect than Fe2+.(2) Degradation of X-BR under different concentrations of nZVI dosage corresponded with the first order kinetic equation. With the increase of the initial concentration, the removal rate of X-BR decreased, but the absolute removal amount of the X-BR increased. After dosing of H2O2, the catalytic effect of nZVI was promoted, while the high concentration H2O2inhibited the catalytic effect. The addition of EDTA to nZVI can only weakly promote the degradation of X-BR’s. SO42-and Mn2+promoted the X-BR’s degradation during the initial reaction, while that inhibited the degradation in the latter reaction, especially with high concentration. Both EDTA and SO42-could promote the removal of TOC, while Mn2+inhibited the removal of TOC. Since nZVI had low reusing rate, and tended to agglomerate or form group easily, and are unstable during the reaction, nZVI could not be reused.(3)When TiO2absorbed X-BR alone, X-BR removal rate increased with the increase of the dosage. The overall reaction reached equilibrium after20minutes. For the system that TiO2was the catalyst of DBD, the optimum conditions were as following:the voltage was65V, the current was0.92A, the DBD reaction time was10min, and the best dosage TiO2was0.6g/L. At the same time, low concentration catalyst could promote the degradation of X-BR, while the high concentration catalyst had the inhibition effect on the degradation. After adding the catalyst, the removal rate of TOC reach up to20%.(4) Degradation of reactive brilliant blue X-BR under different concentrations of TiO2corresponded with the first order kinetic equation. With the increase of the initial concentration, the removal rate of X-BR decreased, but the absolute removal amount of the X-BR increased. With the increase of the initial input power, the catalytic effect of TiO2decreased. The addition of K2S2O8to nZVI can promote the catalytic degradation of X-BR and the best dosage K2S2O8was5mmol/L. CO32-、Cl-、SO42-、NO3-inhibited the X-BR’s degradation, the order of the inhibition was CO32->Cl->SO42->NO3-. TiO2could be reused.(5)After adding Fe2+during the reaction, Fenton systems were formed which catalyzed DBD with TiO2. When dosing low concentrations of Fe2+, it can promote the reaction, while the high concentration had the adverse effects. Fe3+has the same effect as Fe2+in the reaction. After adding metal ions including Fe2+, Fe3+, Cu2+and Mn2+, Fe2+played a good catalytic role to the reaction as well as Fe3+, while Cu2+and Mn2+had the opposite effects. The effects of these ions sequence were as the following:Fe3+> Fe2+> Mn2+> Cu2+;(6)By comparison, the catalytic effects sequence of the four catalytic systems was:DBD+TiO2+Fe3+> DBD+TiO2+Fe2+> DBD+TiO2> DBD+nZVI. It could be concluded from the three ionic (SO42-, NO3-and Cl-’) and UV-vis spectrum change during the reaction that the anthraquinone chromophore was firstly broken, then followed benzene, naphthalene ring, and triazine structure, but the structure change was not obvious. The better catalytic effects of these four systems, the more obvious the reduction of characteristic peak, and the higher concentration of ions (SO42-, NO3-and Cl-) were detected.