# Chlorobenzene Removal Using DBD Coupled with CuO/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) Catalyst
## 2 Experimental Section
### Experimental Setup
After standing for 5 min, a few drops of the starch solution was added into the absorption solution as an indicator, and the sodium thiosulfate standard solution with a concentration of 0.02 mol/L was used to titrate the absorption solution. The byproducts of chlorobenzene degradation after single plasma treatment and plasma catalysis treatment with an applied voltage of 4.2 kV, flow rates of 3 L-min\({}^{-1}\) and SED of 950 J-L\({}^{-1}\) were analyzed by a gas chromatography-mass spectrometer (GC-MS). To exclude the extra effect of catalyst (adsorption effect, etc.) on chlorobenzene removal, the experiment was carried out after the catalyst bed reached adsorption equilibrium (the concentration of chlorobenzene remains steady after passing through the reactor). The effect of temperature is negligible since the control experiment carried out at 105 \({}^{\circ}\)C (the highest temperature detected during the experiment) shows that there is no significant degradation of chlorobenzene without discharge. In this work, discharge power and gas flow rate, the most important process parameters for plasma discharge, were selected as input parameters, while chlorobenzene removal efficiency and CO2 selectivity were selected as response parameters. The input parameters were standardized by z-score. To ensure the comparability between the action coefficients:  
\[\text{x}_{\text{i}}=\frac{\text{X}_{\text{i}}\ -\ \overline{\text{X}}}{\sigma} \tag{6}\]  
where xi is the standardized value of the ith variable, Xi is the real value of the ith variable, \(\overline{\text{X}}\) is the average value of data, and \(\sigma\) is the standard deviation of the data. The standardized and real values of the selected plasma processing parameters were given in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{5}{c}{**Parameters**} \\ \hline Flow Rate (L/min) & 1 & 2 & 3 & 4 & 5 \\ \hline x\({}_{1}\) & \(-1.46\) & \(-0.73\) & 0 & 0.73 & 1.46 \\ \hline Discharge Power (W) & 37.5 & 44.3 & 55 & 60 & 67.5 \\ \hline x\({}_{2}\) & \(-1.28\) & \(-0.73\) & 0.15 & 0.56 & 1.17 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Schematic diagram of the DBD reactor. The chosen process parameters and their standardized values. In this study, a second-order polynomial response equation was established to correlate the relationship between independent plasma operation variables and responses variables:  
\[\text{Y}=\beta_{0}+\beta_{1}\text{x}_{1}+\beta_{2}\text{x}_{2}+\beta_{11}\text{ x}_{1}{}^{2}+\beta_{22}\text{x}_{2}{}^{2}+\beta_{12}\text{x}_{1}\text{x}_{2}+\varepsilon \tag{7}\]  
where Y is the response, x1, x2 are the standardized variables, \(\varepsilon\) is the error, \(\beta_{0}\) is a constant, \(\beta_{1}\), \(\beta_{2}\) are linear coefficients of two variables, \(\beta_{11}\), \(\beta_{22}\) are quadratic coefficients of two variables, and \(\beta_{12}\) are interaction coefficients of two variables, respectively. To estimate the quality of fit and the significance of chosen parameters, the analysis of variance was performed, including the Fisher's F-test and the calculation of correlation coefficient (R2) for the generated models [52].