Design Of A Novel Non-equilibrium Plasma Reactor And Study On Its Degradation Of Methyl Orange

Non-equilibrium plasma-based water treatment technology is new technology integrating many kinds of advanced oxidation technologies. It could efficiently, rapidly and non-selectively degrade pollutants in water without secondary pollution, and has some other advantages. Therefore this technology shows good prospects for application. In present study, a novel non-equilibrium plasma-based water treatment reactor was designed. The reactor was made up of discharge part and a separate ozone aeration part. The two parts are connected by silicone tube so that water could be circulated by peristaltic pump between two parts and be treated by discharge and ozone alternately. Two paralleled porous titanium plates are used as electrodes in the pulsed discharge reactor and a20μm porous titanium aerator is installed in ozone aeration part. In this study, methyl orange (MO) solution was treated as simulated wastewater in the reactor. Effects of electrode gaps, voltages input into the reactor, pulse frequencies and different water quality on the MO removal efficiency, TOC mineralization rate and energy efficiency were discussed, as well as the catalytic effect of porous titanium electrode. From the above research, some conclusions could be drawn as follows:(1) After applying pulsed high voltage to electrodes, the electric discharge formed between two electrodes. Ozone was produced in gas phase, while active species such as hydroxyl radicals and hydrogen peroxide were generated in liquid phase. Active species directly react with MO, meanwhile, ozone was aerated into the solution to degrade MO in aeration part. Ozone could be made full use of and MO solution could be fully degraded by both discharge and aeration process, which improved the energy yield. Repeatability test showed that the operation of the reactor was stable, and the maximum error was only3.5%.(2) Electrode gap had some influences on MO removal efficiency. The smaller the electrode gap was, the higher the removal efficiency was when the gap varied from8-33mm. It was beneficial for removal efficiency when oxygen flow rate was0.18m3/h, and the best TOC mineralization rate was achieved at0.12m3/h. Meanwhile, the increase of either input voltage or pulse frequency could enhance the MO removal efficiency and TOC mineralization rate. The gas layer height and liquid layer height had significant influences on the degradation efficiency, while gas flow rate had no significant influence. The impact on MO removal in the reactor were:gas height> liquid layer height> gas flow rate.(3) Under the optimal configuration (LH=5mm, GH=3mm) of the reactor, after treating400mL MO solution (60mg/L) at30kV and100Hz for6minutes, the MO removal efficiency could reach95%. The increase in MO concentration could decrease the removal efficiency, but it could also reach95%after12minutes of discharge; the maximum energy yield was60.64g/(kWh).(4) The initial conductivity of solution had little influence on MO removal efficiency when the conductivity changed from50to600μS/cm. The increase in pH of MO solution could significantly restrain the degradation of MO. The removal efficiency under alkaline condition> neutral condition> acid condition. TOC mineralization rate enhanced with pH increasing. Moreover, the addition of H2O2could increase the TOC mineralization rate.(5) The treatment of acid chrome blue K in the reactor could achieve better removal efficiency than the removal of MO. After15minutes of discharge (30kV,100Hz), the removal efficiency of acid chrome blue K could almost be completely decomposed, and TOC mineralization rate could reach20%. General applicability in degrading pollutants could be found from the above case.(6) The catalytic experiment proved the formation of TiO2on porous titanium plate surface. The electrode could catalytically degrade MO under UV irradiation. Inference could be drawn that there may be synergetic combination of discharge and catalytic effect in the reactor.(7) In the reactor, there may be3aspects that affected the degradation of MO:high voltage discharge, ozone oxidation and photoelectric catalytic reactions. Thus, the MO molecules gradually become small molecules, and ultimately mineralized.