Investigation On H₂O₂ Formation In Water By High Pulsed Discharge

Lots of reactive species, UV radiation, shock waves can be generated by high pulse discharge, and they can decompose toxic organic pollutants into small molecules and sterilize microorganisms efficiently. This technology has been widely focused and studied, because it has many advantages; for instance, degrading the organic pollutants in suit, no need to join other chemical compounds, no secondary pollution. At present, there are many studies about degrading pollutants successfully by high pulsed discharge plasma. However, high pulsed discharge is a complex physical and chemical reaction process, and the mechanism about formation active species has not been studied very clearly. The formation of active species is very important for degrading the poulltutants and sterilization, especially H2O2, and it is very impotant to study the formation mechanism of H2O2.In the present study, needles-plate reactor was used to investigate the formation of H2O2 by gas discharge, liquid discharge and gas-liquid discharge. The influence factors include electrical parameters, structure parameters and gas liquid parameters. Analysing the experimental results, the following conclusions can be got:(1) The effects of peak voltage on formation H2O2 by three discharge processes have been investigated. Higher pulse energy can generate more H2O2, and when the peak voltage was 18 kV, the formation rate of H2O2 by liquid discharge was 0.11 mg/min which was the highest rate. The highest energy efficiency was 5.9×10-5 mg/J by gas discharge.(2) When the peak voltage was the same, decreasing the electrods gap can promote the formation of H2O2 and improve energy efficiency in the three discharge forms.(3) Solution conductivity was also an important factor in influencing discharge. Different results got by the three discharge processes. The formation of H2O2 was not influenced obviously by solution conductivity in gas discharge and gas-liquid discharge processes. But the formation of H2O2 was affected obviously by solution conductivity in liquid discharge process. As the solution conductivity increasing, the formation rate of H2O2 increased firstly and then decreased, and when the conductivity was 66μs/cm, the formation rate of H2O2 was the highest.(4) The optimum air flow rate was 1.6 L/min in gas discharge process, and if the air flow rate was higher than 1.6 L/min, the H2O2 would not increase. Oxygen was more favor than air for the formation of H2O2 in gas-liquid discharge process. (5) The acid and neutral conditions were in favor of the formation of H2O2, in gas discharge process.