Transient spark dielectric barrier post-discharge plasma reactor with a liquid electrode for dye degradation: A primary study

TL;DR

This study addresses dye-laden textile wastewater treatment using a novel transient spark dielectric barrier discharge (DBD) reactor with a liquid electrode. The authors design and optimize a post-discharge DBD system, evaluate multiple operating parameters with crystal violet as a model dye, and validate performance on additional dyes; kinetics reveal pseudo-first-order behavior with $\ln(C_t/C_0) = -k t$ and rate constants ranging from approximately $0.4$ to $0.8$ min$^{-1}$ depending on flow and concentration. They measure dissolved ozone in reactive gases via iodometric titration and argue that ozone, along with secondary ROS such as $\dot{OH}$ and $H_2O_2$, drives rapid oxidative degradation, achieving >98% removal in minutes across dyes. The work demonstrates the potential of a low-frequency, liquid-electrode DBD reactor for rapid dye mineralization at lab scale, with practical implications for textile wastewater treatment and a path toward integrating additional oxidation steps to reach complete mineralization.

Abstract

The potential application of non-thermal plasma in treating textile industrial wastewater motivates researchers to develop innovative techniques at a laboratory scale to achieve the goal of wastewater mineralization. In line with this objective, a dielectric barrier post-discharge plasma reactor with a liquid electrode has been built for the study of synthetic dye degradation. The plasma reactor was optimized by altering various operating conditions to achieve a higher degradation efficiency at given discharge conditions. The reaction kinetics of crystal violet degradation were studied, and the same plasma reactor was tested for other synthetic dyes (wastewater model samples). The results suggest that the proposed dielectric barrier post-discharge plasma reactor may offer a promising solution for treating dye effluents from the textile industry.

Figures (15)

• Figure 1: Schematic diagram of post-dielectric barrier discharge plasma reactor for degrading synthetic dyes (model wastewater samples).
• Figure 2: (a) Voltage and corresponding current waveforms at 50 Hz input signal. (b) Voltage and corresponding current waveforms at microsecond time scale (zoom view of the green dotted area in Fig.\ref{['fig:fig2a']}(a)). (c) Instantaneous power waveforms corresponding voltage and current signals in Fig.\ref{['fig:fig2']}(b).
• Figure 3: Variation of degradation time for CV (at which dye degraded $>$ 98 %) with changing conductivity of cathode liquid electrode. Volume of dye solution was 500 ml, dye concentration was 40 mg/L, gas flow rate was 400 cc/min, and dye solution temperature was 27° C.
• Figure 4: Variation of degradation time (at which dye degraded $>$ 98 %) with different oxygen flow rates at two different CV dye concentrations, 10 mg/L and 20 mg/L. The volume of dye solution, Magnetic stirrer speed and temperature of the solution were 500 ml, 400 RPM, and 26.4° C, respectively.
• Figure 5: Variation of degradation time for CV and MO dye solutions (at which dye degraded $>$ 98 %) with different stirrer speeds (RPM). Volume of dye solution was 500 ml, dye concentration was 40 mg/L, gas flow rate was 400 cc/min, and the dye solution temperature was 28° C.