Micro hollow cathode excited dielectric barrier discharge (DBD) plasma bubble and the application in organic wastewater treatment

A novel micro hollow cathode excited DBD plasma bubbling reactor was designed to improve the organic wastewater treatment efficiency. Both the discharge process as well as the mass transfer can be enhanced synchronously. The key of the discharge reactor is the micron-sized channels in the dielectric medium. On the one hand, the plasma bubbles were generated when the plasma activated gas flowing through the micro-channels, which can enhance the mass transfer between plasma and water. More importantly, the discharge inception criterion was reduced and the discharge intensity was enhanced because of the “micro hollow cathode effect” and “plasma electrode effect” of the micro-channels. P-chlorophenol was chosen as the target organic contaminant to facilitate comparison with other plasma water treatment researches. Influence factors including discharge voltage, gas flow rate, p-chlorophenol concentration, initial pH value, salinity and micro-channel quantity were explored. After 30 min treatment, the maximum p-chlorophenol removal as well as the dechlorination ratio reached over 99%. The energy efficiency of p-chlorophenol removal increased with the micro-channel quantity. It is 276.94 mg/kWh for a single micro-channel but 6820.13 mg/kWh for 20 micro-channels. From the results of this study, the micro hollow cathode excited DBD plasma is of significance favorable for the treatment of organic wastewater.