## 3 Results and Discussion
### Experimental Study with Simulated and Direct Solar Irradiance on IWWTP Samples  
After conducting optimization experiments to determine the optimal irradiation distance for the simulated sunlight lamp, the results indicate that a photocatalyst saturation effect occurs at a distance of less than approximately 8 cm from the light source. These \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Method** & **Characteristics** & **\% Degradation** & **t (min)** & **pH** & **Reference** \\ \hline TiO\({}_{2}\) & Heterogeneous & \textgreater{}99 & 1600 & 3 & [41; 43] \\ Fenton & Homogeneous & \textgreater{}99 & 40 & 3 & [43; 66] \\ Fenton & Homogeneous, wastewater & \textgreater{}99 & 90 & 3 & [43; 66] \\ Photo-Fenton & Homogeneous & \textgreater{}99 & 10 & 2.8 & [43; 72] \\ Photo-Fenton & Heterogeneous & \textgreater{}99 & 60 & 3 & [43; 45] \\ Photo-Fenton & Heterogeneous & 78 & 240 & 9 & [43; 45] \\ Fenton & Homogeneous, wastewater & \textgreater{}99 & 60 & 3 & [46] \\ Photo-Fenton & Homogeneous, wastewater & \textgreater{}99 & 30 & 3 & [46] \\ Fenton & Heterogeneous & \textgreater{}99 & 60 & 3 & [71] \\ Fenton & Heterogeneous & 30 & 60 & 8 & [71] \\ \hline Singlet Oxygen & Heterogeneous, wastewater & 94 & 360 & 7.5–8 & This study \\ Singlet Oxygen & Heterogeneous, wastewater & \textgreater{}99 & 300 & 10 & This study \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of different Acetamiprid degradation techniques in different pH media. Figure 9: Scheme of the conversions achieved in successive reaction cycles of Acetamiprid photo-oxidation (IWWTP sample 1; pH = 10; reaction time per cycle = 300 min), using polymer P4 as the photosensitizer. Cycle 2 was conducted without irradiation. laboratory-scale experiments demonstrate that beyond this distance, an increase in the reaction time is required to achieve over 99% Acetamiprid removal. As shown in Figure 10, when exceeding the photocatalyst saturation distance limit at approximately 8 cm, the reduced light intensity lowers the kinetic constant and drastically increases the time required to achieve more than 99% conversion of Acetamiprid. This suggests that the optimal distance for conducting experiments with simulated sunlight in the laboratory is less than 8 cm, where the full energy emitted by the lamp is effectively utilized. The results obtained for the reaction time as a function of distance fit well with a second-order polynomial regression model. The regression can be justified considering that the irradiance varies inversely with the square of the distance from the emitting source. Regarding the experiments with direct solar irradiation, these were conducted similarly to those with simulated sunlight, using the P3 and P4 polymers, sample 5 of wastewater from the IWWTP at pH = 10, and the FeCl3 filter. Table 5 presents the results of the photo-oxidation experiments of Acetamiprid conducted under solar irradiation during different times of the year in Murcia, with the average solar irradiation values recorded during the reaction time. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Date** & **Solar Irradiation** & **Photosensitizer** & **Time to \textgreater{}99\% Degradation** & **Kobs (min\({}^{-1}\))** \\ \hline
27 June & 7.72 kWh/m\({}^{2}\) & P3 & 585 min & 0.007872 \\  & & P4 & 582 min & 0.007913 \\ \hline
18 July & 7.33 kWh/m\({}^{2}\) & P3 & 614 min & 0.007494 \\  & & P4 & 613 min & 0.007513 \\ \hline
8 August & 7.16 kWh/m\({}^{2}\) & P3 & 627 min & 0.007340 \\  & & P4 & 625 min & 0.007368 \\ \hline
12 September & 6.49 kWh/m\({}^{2}\) & P3 & 678 min & 0.006790 \\  & & P4 & 677 min & 0.006802 \\ \hline
17 October & 5.21 kWh/m\({}^{2}\) & P3 & 775 min & 0.005941 \\  & & P4 & 775 min & 0.005941 \\ \hline
14 November & 3.35 kWh/m\({}^{2}\) & P3 & 916 min & 0.005027 \\  & & P4 & 915 min & 0.005033 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Photocatalytic Acetamiprid degradation kinetic results under different solar irradiation values.