High energy efficient degradation of toluene using a novel double dielectric barrier discharge reactor.

A double dielectric barrier discharge (DDBD) reactor was established to decompose toluene with high energy efficiency. Differences in discharge characteristics including visual images, voltage-current waveforms, Lissajous figures, and temperature variation, were determined between the DDBD and SDBD reactors. Removal efficiency, mineralization rate, CO2 selectivity, and energy yield were used to evaluate the toluene abatement performance of the two reactors. Compared to the SDBD reactor, the DDBD reactor exhibited more uniform and stable discharges due to a change in discharge mode. In addition, the DDBD reactor's dissipated power and reactor temperature (including the gas, barrier and ground electrode) were significantly lower than those in the SDBD reactor. At 22 - 24 kV, the DDBD reactor showed a higher toluene removal efficiency and mineralization rate, while at 14 -16 kV, the SDBD reactor exhibited higher respective value. The energy efficiency of the DDBD was 2.5-3 times that of the SDBD reactor, and the overall energy constant k(overall) of the DDBD reactor (1.47 mL/J) was significantly higher than that of the SDBD reactor (0.367 mL/J) as revealed by the kinetics study. Lastly, a plausible toluene degradation mechanism in the DDBD and SDBD reactors was proposed based on organic intermediates that formed during toluene decomposition.