## 3 Results and Discussion
### Study of the Kinetics of Acetamiprid Photo-Oxidation Using the Photoactive Micorparticles  
The effectiveness of polymers P1-P4 was evaluated in the photo-oxidation of Acetamiprid by monitoring the degradation of the pesticide, as described in Section 2.2 over time. The experiments were conducted at pH = 10 and control experiments carried out in the absence of light and without a photosensitizer, indicated no adsorption of Acetamiprid onto the polymers, nor any degradation of the compound through direct irradiation. The concentration of Acetamiprid was set at 0.1 ppm. The degradation of Acetamiprid was monitored using HPLC chromatography; the traditional UV-Vis method employed in previous studies [31; 59] cannot be applied in this case. Although the state of the art indicates that monitoring can also be carried out using 1H NMR and FTIR [40; 41], the HPLC approach was selected due to it is the most widely used in the literature. Irradiation used the 125 W Hg vapor lamp with the 0.1 M FeCl\({}_{3}\) filter to block wavelengths below 450 nm, preventing Acetamiprid photolysis and Rose Bengal UV degradation. The results obtained confirmed first-order kinetics in all cases for the degradation of Acetamiprid by singlet oxygen generated by Rose Bengal (Figure 4), as reported in the literature [49]. The kinetics of polymers P3 and P4, which are more hydrophilic, were superior to those of P2 and comparable to free RB. This confirms the successful incorporation of ethylenediamine and \(\gamma\)-gluconolactone through grafting into the polymeric matrix, enhancing the hydrophilicity of the microparticles; these results are consistent with prior research [31; 59]. The values for the first-order kinetics are shown in Table 1, with the observed rate constants (\(k_{obs}\)) derived from fitting the conversion data over time. Additionally, the final conversion rates achieved for Rose Bengal and photosensitizers P2-P4 at pH = 10 are also reported. Conversions exceeding 99% were achieved with RB, P3, and P4 within a time frame of approximately 300 min (Figure 5). Figure 4: First-order kinetics of Acetamiprid photo-oxidation over time (C) relative to the initial concentration (C\({}_{0}\)), for RB and P1–P4 (HPLC absorption maximum at 243 nm) at pH = 10. The influence of pH on the degradation kinetics of Acetamiprid was studied by assessing the Acetamiprid photo-oxidation in different pH scenarios. In this case, only polymers P3 and P4 were used, as they, as previously mentioned, exhibit higher performance than the nonpolar polymer P2. The effectiveness values of RB, P3, and P4 are presented in Table 2 in different pH reaction media. Figure 6 compares the degradation rates of Acetamiprid at different pH values. As observed, Acetamiprid degradation is considerably more efficient in high pH media, achieving in all cases degradation rates of above 99% after 300 min of reaction for pH = 10 and higher and degradation rates of above 90% for pH = 8. The degradation of Acetamiprid is more effective under mildly basic or basic conditions, suggesting that the photo-oxidation mechanism is more efficiently promoted in alkaline conditions, as will be discussed in detail later. \begin{table}
\begin{tabular}{c c c c} \hline
**Photosensitizer** & & **\% Degradation** & \(\mathbf{K_{obs}\ (min^{-1})}\) \\ \hline \multirow{2}{*}{RB} & Conversion (\%) & \textgreater{}99 & \multirow{2}{*}{0.0151} \\  & t (min) & 305 & \\ \hline \multirow{2}{*}{P2} & Conversion (\%) & 85 & \multirow{2}{*}{0.0054} \\  & t (min) & 350 & \\ \hline \multirow{2}{*}{P3} & Conversion (\%) & \textgreater{}99 & \multirow{2}{*}{0.0147} \\  & t (min) & 330 & \\ \hline \multirow{2}{*}{P4} & Conversion (\%) & \textgreater{}99 & \multirow{2}{*}{0.0148} \\  & t (min) & 325 & \\ \hline \end{tabular}
\end{table} 
Table 1: First-order constants and conversions for RB, P1, P2, P3, and P4 at pH = 10. Figure 5: Degradation ratio of Acetamiprid over time (C) relative to the initial concentration (C\({}_{0}\)), for RB and P1–P4 (HPLC absorption maximum at 243 nm) in pH = 10.