Insights into catalyst-free, highly effective degradation of pharmaceutical contaminant in aqueous solution by a dielectric barrier discharge system

The emerging pharmaceutical wastewater including non-steroidal anti-inflammatory drugs has posed a serious threat to the ecological environment and human health, and therefore effective treatment technologies are being urgently needed. Herein, a novel horizontal continuous-flow dielectric barrier discharge (DBD) system without catalyst was developed for the highly effective degradation of diclofenac in aqueous solution. The degradation efficiency of 10 mg/L diclofenac reached about 90% in 14 min, and the corresponding energy efficiency was 0.181 g/kWh. Furthermore, the treated water quality was evaluated in terms of TOC, BOD5/COD and toxicity. The biodegradability rapidly improved with the increasing of DBD treatment time as be expected, although the mineralization efficiency of diclofenac was still low. To gain insight into the degradation mechanism, short-lived transient and long-lived species have been identified during DBD process, in which transient species (·OH, ·O2–) were the major contribution to the oxidation of diclofenac. Furthermore, based on the intermediates identified by LC-MS, a possible degradation pathway of diclofenac by DBD system in aqueous solution was proposed. Therefore, the novel DBD reactor with horizontal continuous-flow appears to be more promising for the treatment of pharmaceutical wastewater in practical applications.