## 3 Results and Discussion
The photocatalytic activity of the samples was studied by detecting the UV-VIS spectra of MO dye after the photocatalytic degradation reaction under the same conditions. Figure 5a shows the UV-VIS absorption spectra of MO before (Co) and after photocatalytic degradation by FS-NT (0 and 2-5 mL) in pure MO solution. The results indicate that the photocatalytic effect was best when 3 mL of NH\({}_{4}\)OH was used as the nitrogen-doping source. Figure 5b shows UV-VIS absorption spectra of MO with an initial concentration of 10 mg L\({}^{-1}\) under different illumination times during the photocatalytic degradation of MO using a random batch of FS-NT (3 mL). Figure 5c shows the average degradation rate of MO degraded by three batches of FS-NT (0 and 2-5 mL), and the experimental results of the three different batches were averaged and standard errors were added. In a dark environment, dye in water was removed by adsorption, and the removal rates of MO by FS-NT (0 and 2-5 mL) were 10.05%, 9.34%, 10.91%, 8.33%, and 7.84%, respectively. The results showed that the average degradation rate of MO degraded by three different batches of FS-NT (3 mL) reached 95.53% \(\pm\) 0.53% within 32 min under irradiation conditions, and this degradation effect was better than that of other samples. The results suggest that proper non-metallic doping can improve the photocatalytic ability of TiO\({}_{2}\). The photocatalytic activity of some related materials for MO is presented in Table 1. Although there are differences in the materials [36; 37; 38], the photocatalytic degradation rate of FS-NT (3 mL) was commendable. The degradation effect of FS-NT (3 mL) in 32 min was favorable. In particular, the degradation rate was still 92% in recycling. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Initial Concentration of MO (mg/L)** & \multirow{2}{*}{**Light Source**} & **Amount of Catalyst per mL (mg)** & **Degradation Time (min)** & **Cyclic** \\  & & & **per mL (mg)** & **and Degradation Rate** & **Degradation Rate** \\ \hline ATT-SnO\({}_{2}\)-TiO\({}_{2}\) & 20 & High-pressure mercury lamp & 1 & 30 (99\%) & non \\ \hline ZnO/TiO\({}_{2}\) & 16 & High-pressure mercury lamp & 0.3 & 100 (98\%) & non \\ \hline Pt-TiO\({}_{2}\)/zeolite & 20 & High-pressure mercury lamp & 2 & 90 (99\%) & non \\ \hline FS-NT (3 mL) & 10 & High-pressure mercury lamp & 2 & 32 (95.53\% \(\pm\) 0.53\%) & 92\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The photocatalytic activity of related materials [36; 37; 38]. Figure 4: XPS spectra: N 1s of (**a**) FS-NT (0 mL) and (**b**) FS-NT (3 mL). Ti 2p of (**c**) FS-NT (0 mL) and (**d**) FS-NT (3 mL). O 1s of (**e**) FS-NT (0 mL) and (**f**) FS-NT (3 mL). The recovered FS-NT (0 and 3 mL) was used to degrade MO under the same experimental conditions. Figure 6 shows the photocatalytic activity of the recycled FS-NT (0 and 3 mL). The first to fifth cycle experiments corresponded to horizontal coordinates of 0-32 min, 32-64 min, 64-96 min, 96-128 min, and 128-160 min, respectively. The degradation rates of MO degraded by a batch of FS-NT (0 mL) recovered for the five cycles were 89.25%, 80.68%, 75.48%, 84.47%, and 86.30%, as shown in Figure 6a, respectively, and the average degradation rate was 83.24%. The degradation rates of MO degraded by a batch of FS-NT (3 mL) recovered for the five cycles were 94.44%, 91.92%, 91.91%, 90.09%, and 92.20%, as shown in Figure 6b, respectively, and the average degradation rate was 92.11% for the five cycles. The results indicate that the FS-NT (3 mL) photocatalyst exhibited better degradation performance through magnetic recovery. In the second, third, and fourth cycle experiments, the possible reason for the decrease in the degradation rate was the production of insoluble intermediates on the surface of the photocatalyst during the cyclic degradation process [18].