## 3 Results
### DCF Degradation in Aqueous Solution by EB Irradiation after Nanobubbling Process  
Low concentrations of DCF were easily decomposed under EB irradiation (Figure 2). Almost 100% of the DCF was decomposed at 0.5 kGy when the DCF initial concentration was 10 mg/L; thus, a higher initial concentration of DCF was selected to determine the effect of nanobubbling. The degradation of DCF was studied after nanobubbling pretreatment followed by EB irradiation for a solution with an initial DCF concentration of 125 mg/L. The DCF solution was first nanobubbled for 30 min, followed by EB irradiation. After 30 min of nanobubbling, about 16% of the DCF was removed from the aqueous solution due to the reaction of OH radicals, which were generated by with nanobubbling process, with DCF (Equation (4)). With an increasing adsorbed dose, the concentrations of e\({}_{\text{aq}}^{-}\) and OH radicals also increased. The removal efficiency of DCF was improved under EB irradiation with or without nanobubbling pretreatment. At a 5.0 kGy absorbed dose, the concentration of OH radicals generated by EB irradiation was much higher than that generated through the nanobubbling process. Approximately 99% and 96% of the DCF were efficiently removed under EB irradiation with and without the nanobubbling pretreatment, respectively (Figure 4). The inorganic ions products (Cl\({}^{-}\), NH\({}_{4}\)\({}^{+}\)) from the DCF degradation in the aqueous solution are presented in Figures 5 and 6, respectively. The concentrations of Cl\({}^{-}\) and NH\({}_{4}\)\({}^{+}\) (shown as Cl and N, respectively) increased with increasing dose, i.e., with the decrease in DCF concentration. Cl\({}^{-}\) was generated due to the dissociated electron capture reaction of hydrated electron with DCF (Equation (4)). These results are in agreement with those reported by [PERSON] et al. [21]. Based on the calculation of mass balance, at a 5 kGy absorbed dose, about 53% and 49% of Cl (equivalent to 2 Cl atoms) were released from DCF degradation under EB irradiation with and without the nanobubbling pretreatment (Table 1). \begin{table}
\begin{tabular}{c c c} \hline \hline  & **EB (5 kGy)** & **Nano + EB (5 kGy)** \\ \hline DCF & 96\% & 99\% \\ Cl\({}^{-}\) & 53\% & 49\% \\ NH\({}_{4}^{+}\) & 29\% & 35\% \\ CO\({}_{2}\) & \textless{}1\% & \textless{}1\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: DCF degradation (%) and formation of its main inorganic products (%) in water under electron-beam irradiation at 5 kGy, with (Nano + EB) and without (EB) nanobubble pretreatment ([DCF]\({}_{0}\) = 125 mg/L). Figure 3: Concentration of DCF and dissolved O\({}_{2}\) vs. nanobubbling time ([DCF]\({}_{0}\) = 10 mg/L). Figure 4: DCF removal efficiency in aqueous solution under electron-beam irradiation with (Nano + EB) and without nanobubbling pretreatment (EB) ([DCF]\({}_{0}\) = 125 mg/L). Figure 5: Variation in Cl\({}^{-}\) concentration with the absorbed dose for DCF degradation under electron-beam irradiation with (Nano + EB) and without nanobubble pretreatment (EB) ([DCF]\({}_{0}\) = 125 mg/L). Figure 6: Variation in N concentration with the adsorbed dose for DCF degradation under electron-beam irradiation with (Nano + EB) and without nanobubble pretreatment (EB) ([DCF]\({}_{0}\) = 125 mg/L). For both processes, CO2 formation was less than 1% and NH4+ formation was about 29% and 35%, respectively, under EB irradiation alone and EB irradiation together with the nano-bubbling pretreatment, respectively (Table 1). Moreover, the dissolved CO2 and carbonic salts seemed to increase with the absorbed dose (Figure 7). From the analysis of the total carbon (TC) and inorganic carbon (IC) present in the samples before and after treatment at different doses (Figures 7 and 8), it was possible to conclude that the total organic carbon (TOC) for both processes, measured by subtracting IC from TC, increased until 2 kGy, with the values remaining relatively stable at higher absorbed doses.