## 2 Advanced Oxidation Processes
### Ozone-Based Technologies
#### 3.2.1 Single Ozonation  
The ozone molecule is known for being a powerful oxidant with very effective degradation results for organic molecules in wastewater treatment, despite having some drawbacks as poor mineralization. Besides wastewater treatment, this technology is also used for water disinfection. [PERSON] et al. [25] used ozonation to remove a mixture of five parabens. The authors achieved 99% parabens degradation in 12 min and 61% and 32% for COD and TOC removal in 3 h. As expected, while ozone was able to efficiently remove unsaturated molecules (such as the parabens), total mineralization was not possible to achieve. In fact, from the abatement of the parent molecules, saturated compounds were produced, which are refractory to further ozone oxidation. Furthermore, [PERSON] et al. [26] performed ozonation using the same mixture but with a concentration of 10 mg/L of each paraben, achieving total removal in 120 min. In fact, the results of ozonation should be analyzed as a function of transferred ozone dose (TOD), since this parameter allows one to understand \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{**Pollutant**} & \multicolumn{1}{c}{**Catalyst**} & \multicolumn{1}{c}{**Test**} & \multicolumn{1}{c}{**Results and**} & \multicolumn{1}{c}{**Reference**} \\ \hline \multirow{5}{*}{EP} & \multirow{5}{*}{N-TiO\({}_{2}\)} & \(\bullet\) & Solar simulator & (5\% UVA & \(\bullet\) & ZnO led to total removal in & \\  & & & and 0.1\% UVB). & \(\bullet\) & 20 min, while TiO\({}_{2}\) P25 led to & \\  & & & EP solution of 1 mg/L in & & about 90\% removal in 30 min, & \\  & & & ultrapure water. & & respectively. & \\  & & & & 250 mg/L of catalyst. & & \\ \hline \multirow{5}{*}{EP} & \multirow{5}{*}{N-TiO\({}_{2}\)} & \(\bullet\) & Solar simulator & \(\bullet\) & At best conditions, the EP & \\  & & & \(\bullet\) & Catalyst dose of 500 mg/L & & 34\% and 43\% for TiO\({}_{4}\)+Vis, & \\  & & & 300 ug/L of EP. & & N-TiO\({}_{2}\)+Vis, TiO\({}_{2}\)+Solar, and & \\  & & & & N-TiO\({}_{2}\)/Solar, respectively. & \\ \hline \multirow{5}{*}{EP} & \multirow{5}{*}{CuO\({}_{\star}\)/BiVO\({}_{4}\)} & \(\bullet\) & Solar simulator & \(\bullet\) & 97.6\% removal was achieved & \\  & & & 500 mg/L of EP & & in 60 min. & \\  & & & 500 mg/L of catalyst & & & \\ \hline \multirow{5}{*}{MP and pesticide} & \multirow{5}{*}{Fe\({}_{9}\)O\({}_{4}\)/BiVO\({}_{4}\)} & \(\bullet\) & 0.1 g/L of catalyst. & \(\bullet\) & MP removal: 74.98\% and & \\  & & & 5 mg/L MP solution & & 95.64\% in 2 h for & \\  & & & 5 mg/L MP solution & & Fe\({}_{9}\)O\({}_{4}\)/BiVO\({}_{4}\) and & \\  & & & Solar radiation. & & & \\  & & & 40–48\% UV and 40–43\% Vis & \(\bullet\) & MP removal of 40\% for TWN & \\  & & TNW & radiation. & & ( titanate nanowires) and 62\% & \\  & & Mn-TNW & \(\bullet\) & 133.3 mg/L of catalyst. & & (doped Mn) and TNW/Mn & \\  & & Mn/TNW & \(\bullet\) & 10 mg/L of MP in distilled & & (adsorbed Mn), respectively, & \\  & & & water. & & in 90 min. & \\ \hline \multirow{5}{*}{MP, EP, and PP} & \multirow{5}{*}{Fe ions} & \(\bullet\) & 350–410 nm radiation. & \(\bullet\) & Removal of EP and PP was & \\  & & & 5 mg/L of Fe for EP and PP, & & 40\% and 60\% in 90 min. & \\ \cline{1-1}  & & & and 25 mg/L of Fe for MP. & \(\bullet\) & MP removal was about 35\%. & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: \(Cont.\)the amount of ozone transferred to the reactional medium and it represents an important parameter for the economic evaluation using ozone [102]. [PERSON] et al. [23] treated a mixture of four parabens (MP, EP, PP, and BuP), achieving 82% removal in 20 min reaction. [PERSON] et al. [28] only achieved 47-52% removal for the best results. In fact, these results were obtained at pH = 9 and were higher than those reached for pH = 3 or pH = 5. This should be expected, since, in a basic medium, the generation of radicals is enhanced. This radical pathway is desired due to its higher performance when compared to direct ozone reaction at acidic pH [41]. [PERSON] et al.