## 3 Results and Discussion
### Photocatalytic Activity Assessment  
After the preparation of the supported catalysts, the photodegradation of SMX was investigated under UVA radiation to assess the photocatalytic oxidation performance of TiO\({}_{2}\)-Leca. However, powder TiO\({}_{2}\) was also tested as a catalyst for comparative purposes. Figure 3 shows SMX abatement during experiments using different loads of powder TiO\({}_{2}\) P25 (25, 50, and 100 mg/L). These amounts were selected to compare with the TiO\({}_{2}\) impregnation loads on the Leca surface. For example, 3.6%TiO\({}_{2}\)/Leca could impregnate  
Figure 2: (**a**) Effect of TiO\({}_{2}\) concentration in suspensions on the impregnation of Leca; (**b**) loss of TiO\({}_{2}\) mass for different TiO\({}_{2}\) loads in suspension. 22.03 mg of TiO\({}_{2}\)/g of Leca, meaning 10 g of Leca was available for 220.03 mg of TiO\({}_{2}\). The reactor used in the experiments works with 2 L of volume solution where the usage of 10 g of Leca represents a TiO\({}_{2}\) concentration of about 110 mg/L. An adsorption test of 15 min to the catalyst in dark conditions was performed before the photocatalytic oxidation test. During this period, it was possible to see an increase in the adsorption of the catalyst load. It did not exceed 20% of the SMX removal for the highest TiO\({}_{2}\) load. After this period, the removal of SMX was due to oxidation by photocatalysis. It was observed that after 30 min of irradiation of the SMX solution, 100% degradation was achieved regardless of the applied TiO\({}_{2}\) powder load in the range of 25-100 mg/L. However, the initial degradation rate increases with catalyst load, which can be explained by the increase of active sites available for the hydroxyl radical's production, allowing SMX efficient degradation [40]. [PERSON] et al. [41] applied 100 mg TiO\({}_{2}\)/L for the degradation of 100 mg/L of the SMX under UV light and reached about 40% of degradation for 2 h.  
Then, the photocatalytic efficiency of the prepared photocatalysts (3.6%TiO\({}_{2}\)/Leca, 5%TiO\({}_{2}\)/Leca, 10%TiO\({}_{2}\)/Leca) was investigated during the degradation of the SMX under UVA radiation. However, considering that 1%TiO\({}_{2}\)/Leca was the one with a lower load of impregnated TiO\({}_{2}\), its photoactivity was not evaluated in the SMX degradation tests. The process was initiated by testing the adsorption effect of the photocatalyst. For that, the catalyst was in contact with an aqueous solution of SMX during the first 15 min without any radiation source. Afterward, the UVA light source was turned on, irradiating the photocatalysts in contact with the SMX solution. The results presented in Figure 4 show that the SMX adsorption onto the catalyst surface is negligible since no reduction of SMX was verified until 0 min, contrary to what happens when TiO\({}_{2}\) is used as a powder (Figure 3). This indicates that the degradation can occur on the catalyst surface and/or liquid bulk by forming reactive species. Regarding the photocatalytic efficiency levels, they indicate degradation values ranging from 28, 43, to 78% for 2 h, with supported amounts of 86.6 mg/L (3.6%TiO\({}_{2}\)/Leca), 102.5 mg/L (5%TiO\({}_{2}\)/Leca) and 169.1 mg/L (10%TiO\({}_{2}\)/Leca). The 10%TiO\({}_{2}\)/Leca shows to be very effective in the degradation process of SMX, achieving about 78% of removal in 2 h. However, at the end of the experiments, a significant loss of TiO\({}_{2}\) (about 169.1 mg from 348 mg as the initial amount) from the surface of the support was observed in the reactor due to the friction between the particles causing erosion. This fact results from the densification in the TiO\({}_{2}\) coating on the ceramic support during the impregnations. Moreover, considering SMX removal and TiO\({}_{2}\) loss in aqueous media results, the most promising photocatalysts were those incorporated at 3.6 and 5%w/w. In this case, as the  
Figure 3: Degradation of SMX with TiO\({}_{2}\) P25, with loads of 25, 50, and 100 mg/L.