## 3 Results  
### Photolysis and Photocatalysis  
The photolytic degradation process of TMP is presented in Figure 2. The graph indicates that the complete degradation of TMP requires at least 5 h of irradiation with simulated solar radiation. However, when the photocatalytic film on the bottom of the reactor is introduced, the time required for complete degradation is reduced to fewer than 3 h, as shown in Figure 3.  
The results of our study confirm that TMP can be effectively degraded through photolysis, as previously stated in the study [10]. Moreover, it has been reported that TMP is highly resistant to hydrolysis (with a half-life of 1 year at 25 \({}^{\circ}\)C) and biodegradation (not susceptible to biodegradation). Therefore, in natural water environments, photolysis is the only effective process for eliminating TMP residuals, reducing its potential harmful impact on both humans and the environment [14].  
The photolytic degradation of TMP did not follow first-order kinetics. As depicted in Figure 2, there was only a slight decrease in TMP concentration during the initial 100 min, followed by a much faster degradation rate. This degradation profile suggests that there may be different degradation mechanisms present, with the initial degradation being slow due to the direct radiation exposure of the TMP solution. In the second part, a faster degradation occurs due to the formation of photoreactive degradation products that initiate autocatalytic decomposition [43]. To confirm this, the formation of TMP degradation products was monitored by observing the appearance of new chromatographic peaks during the photolysis experiments. It was observed that, as the TMP peak on the chromatograms decreased, two new peaks--degradation products (DP) 1 and 2--appeared and increased (Figure 4). As the experiment progressed, the peaks of DPs decreased, and one of them disappeared entirely up to 300 min, indicating that the degradation products  
Figure 3: Photocatalytic degradation of TMP.  
Figure 2: Photolytic degradation of TMP.  
formed from TMP are also photolytically degraded. As shown in Figure 4, the formation of TMP photodegradation products occurs in the second part of faster degradation of TMP, possibly due to the critical amount of photodegradation products formed, which then act photocatalytically.  
The formation and degradation of DP1 and DP2 (Figure 4 and Figure S2 in the Supplementary Material) was monitored through the increase/decrease of the chromatographic peak areas (\(A\)), which are proportional to their concentrations. Because there are no DP1 and DP2 standards it was not possible to convert the chromatographic peak areas into the corresponding concentrations.  
In order to elucidate the structures of the detected products of photolytic degradation, as well as to detect and elucidate the structures of the photocatalytic degradation products, HPLC-MS/MS analysis was performed. The tentative structures of TMP degradation products (Table 1) were proposed based on their retention times, _m/z_-values, and fragmentation patterns, obtained through the HPLC-MS/MS analysis. Mass spectra of TMP and its degradation products are shown in the Supplementary Material, Figure S3. In total, five degradation products were identified. All five were detected in the reaction solution from the photocatalytic experiments, while only DP1 and DP2 were identified during photolytic degradation. The identified DP1 and DP are the same degradation products identified by [PERSON] et al. [10] as photolytic degradation products under environmentally relevant conditions.