## 2 Advanced Oxidation Processes
### Ozone-Based Technologies
#### 3.2.2 Catalytic and Photocatalytic Ozonation  
The performance of single ozonation can be enhanced using catalysts, radiation, and reagents, leading to higher degradation rates and reducing some disadvantages of this  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Pollutant** & \multicolumn{2}{c}{**Test**} & \multicolumn{2}{c}{**Results and**} & **Reference** \\  & \multicolumn{2}{c}{**Conditions**} & \multicolumn{2}{c}{**Conclusions**} & **Reference** \\  & & & & \\ \hline MP, EP, PP and BuP &  
technology. There are not many studies regarding the abatement of parabens by catalytic and photocatalytic ozonation. However, in general, the presence of catalysts and radiation plus catalyst seems to lead to better results. [PERSON] et al. [23] used photolytic and photocatalytic ozonation with TiO\({}_{2}\) to remove four parabens. The results showed 95% and 100% removal for photocatalytic ozonation and photolytic ozonation in 20 min, respectively. In fact, these results were higher than for single ozonation (82% degradation) in the same study. Furthermore, the same occurred in the study of [PERSON] et al. [28], who used ZnO as photocatalyst and had 47-52% degradation (pH = 9) in 60 min for single ozonation, while photolytic and photocatalytic ozonation led to 53-65% and 96-98% degradation, respectively. This behavior was also verified by [PERSON] et al. [26], who studied the degradation of a mixture of five parabens by ozonation and catalytic ozonation. The presence of catalyst required a lower ozone dose compared to single ozonation. Moreover, a treated solution with lower toxicity was achieved by the catalytic process. These results prove a clear improvement of ozonation when coupled with radiation and/or catalyst. However, in the study of [PERSON] et al. [23], the catalyst did not improve the parabens degradation, which can be related to the generation of radicals (OH or ozonide) or even to a negative interaction between the ozone and the catalyst. The same was reported in the study by [PERSON] et al. [102], in which they used photocatalytic and catalytic ozonation for the degradation of a parabens mixture in different water matrices using TiO\({}_{2}\)/NT and carried out toxicity assessment analysis using _Alliubirio fischeri_ bacteria and _Lepidium sativum_ seeds. The presence of catalyst only decreased the solutions' toxicity since the luminescence inhibition for _A. fischeri_ was lower and the germination index for _L. sativum_ was higher when the ozone was used with the catalyst. In addition, [PERSON] et al. [102] used UVA and sun as light sources. When sunlight was used, the objective was quickly achieved, but more ozone was consumed, while the use of UVA seemed to slightly enhance parabens degradation, although the difference was not as significant. Total parabens removal was achieved for TOD = 4.5 mg/L and TOD = 8.5 mg/L for UVA and sunlight, respectively, using an initial concentration of 1 mg/L. [PERSON] et al. [26] required TOD = 70 mg/L (Pt-TiO\({}_{2}\)) for the removal of 10 mg/L of each paraben (MP, EP, PP, BuP, and BeP) using catalytic ozonation, while the study of [PERSON] et al. [27] needed about 40 mg/L of TOD (Ag-TiO\({}_{2}\)) using photocatalytic ozonation for the same paraben's mixture and concentration. Both studies reached total removal of parabens. Furthermore, in the study of [PERSON] et al. [26], about 94 mg/L of TOD were necessary for catalytic ozonation using Ag-TiO\({}_{2}\), while in [PERSON] et al. 's [27] study, the presence of UVA led to a lower TOD of 40 mg/L using the same catalyst [27]. Moreover, in [PERSON] et al. 's [26] experiment, the best catalysts were Pd and Pt-TiO\({}_{2}\) in the catalytic experiments, while in the photocatalytic experiments of [PERSON] et al. [27], this was not verified, since the best catalysts were Ag and Pt-TiO\({}_{2}\)[27]. The catalyst's performance and behavior can be influenced by the photogenerated electrons and the generation of radicals.