## 2 Advanced Oxidation Processes
### Sonochemical Methods
#### 3.1.2. Parabens Abatement by Photocatalysis  
The presence of catalysts should improve the degradation of parabens, particularly when UVA radiation is used since it seems that this kind of light poorly removes parabens when only light is applied. With this, it is expected to obtain better results when UVA photocatalysis is used. [PERSON] et al. [91] used doped TiO\({}_{2}\) catalysts and pure TiO\({}_{2}\) to remove methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BuP), and benzylparaben (BeP) by UVA photocatalysis, reaching parabens degradation values higher than 15%. In fact, this was higher than the results obtained by the photolysis of the same mixture, which proves their good catalyst effect. [PERSON] et al. [7] removed MP using photocatalysis with UV radiation catalyzed with TiO\({}_{2}\) P25, reaching 94% degradation after 120 min, and [PERSON] et al. [32] achieved 85% degradation of BeP. In both works, photocatalysis was clearly better than photolysis. [PERSON] et al. [3] used TiO\({}_{2}\) catalysts (P25 and Vlp-7000) for the degradation of six CECs, including MP and EP. Results showed that P25 is the most efficient catalyst, with degradations higher than 65%, and for which has the best dose of 200 mg/L and whose pH efficiency is in the order 7 \(>\) 5.5 \(>\) 8.5. Moreover, the experiments using a pilot installation led to good results regarding the pollutants removal as well. Better degradation was achieved in the presence of catalyst as well. Comparing these results to the photolysis results presented in Section 3.1.1, the presence of catalyst seems to show an obvious improvement in parabens abatement. The studies of [PERSON] et al. [91], [PERSON] et al. [7], and [PERSON] et al. [32] used UVA radiation, while [PERSON] et al. [3] applied sunlight instead. The presence of UVA light (also present in the solar spectrum) is important, since this radiation is the only one able to activate the TiO\({}_{2}\) catalyst due to the high bandgap that is associated with this material. In fact, if its bandgap is reduced, then the more efficient use of visible radiation or solar light should be possible, which could decrease the operational costs of this technology. With this, several studies using doped TiO\({}_{2}\) catalyst or also other catalysts are also discussed. [PERSON] and [PERSON] [92] used TiO\({}_{2}\) catalyst to remove EP through photocatalysis, using simulated solar radiation in laboratory experiments and sunlight for experiments at pilot scale. The use of catalyst under lab conditions led to 63.1% removal in 120 min reaction, with the application of 0.95 g/L of catalyst and initial EP concentration of 1 mg/L. Regarding the pilot-scale experiment, 45.88% degradation was achieved after 6 h, using the same experimental conditions, but a higher volume (100 L). The authors also used hydrogen peroxide with TiO\({}_{2}\), resulting in a better EP removal performance using the best operational conditions, achieving 96.9% removal in 2 h and 81.38% in 6 h, for laboratory and pilot-scale experiments, respectively. [PERSON] et al. [96] achieved better results, reaching almost total removal in 20 min using ZnO, while TiO\({}_{2}\) P25 led to about 90%