Research On The Device Of Gas-liquid Hybrid Discharge Degrading Azo Dye Wastewater And Decolorization

With the rapid development of dye industry, the variety and quantity of dyes are increasing, which result in the problem of dye wastewater pollution was intensified, and it has become one of the main source of water pollution. As making up the largest part of the dye industry, because of its colority, complex composition, difficulty to degrade, traditional methods such as adsorption, flocculation, and biological oxidation is often difficult to achieve complete purification. Recently, the Pulsed high-voltage electrical Discharge Plasma (DPD) as a new technique of wastewater treatment, DPD has advantageous of high efficiency, nonselective, no secondary pollution, has been received more and more attention. The experiment installation of gas-liquid pulsed discharge was designed and established, the typical azo-dye structure of methyl orange (MO) was chosen as research object, the technological parameters of reactor, performance of reactor, degradation process by DPD was investigated. The results are as following:Gas-liquid pulsed discharge reactor was processed and established, the optimum experimental conditions was determined by comparing a pseudo-first-order rate constant (k) of degradation and energy efficiency (G50%) with different structural parameters. The five stainless steel needles with spacing 17mm, which was encased a perforated resin plate with the needle tip protruding 2 mm, are used as the discharge anode. Electrode gap was 10mm, and oxygen flow rate was 0.18m3/h. The grounding electrode was a stainless steel wire mesh with mesh size of 1.0 mm (diameter 47 mm). In order to enhance the utilization of active species, the five-layer stainless steel wire mesh with distance of 15 mm was set above the anode.The decolorization rate of MO could be improved significantly by increasing the input voltage and pulse frequency, taking into account the capacity of power supply, the peak voltage was 42kV and pulse frequency was 120Hz. The rate constant k decreases with increasing the initial concentration of MO, initial conductivity and the hydroxyl radical scavenger, However, k increases with the increase of pH, it means that alkaline solution was favorable for MO decolorization.Repetition of experiments showed that the stable performance of the gas-liquid pulsed discharge reactor. Compared with other literature, the energy efficiency G50%for MO degradation was 0.61×10-9mol/J in this study, and it could be further improved in the process of scaling-up. The present DPD system was an effective technology for the treatment of MO solutions, The degradation was almost completed within 12 min with 25 mg/L MO and approximately 41% of the initial CODcr was removed within 30 min treatment, the results indicated that MO decolorization was a fast process, whereas mineralization was attained after a long period of time.According to the change of pH value and conductivity, the change tendency of NO2-,NO3-concentration and the analysis of UV-Vis spectrogram in MO degradation process, the possible degradation pathway was concluded:the MO molecule was cracked firstly, and then decomposed into smaller formic acid with the effect of many active species, finally, it could be further complete mineralized to SO42-, NO3-, CO2, H2O and other inorganic ions and molecules.