## 3 Results
### Catalytic Activity of CoSN@C
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Catalysts** & \(k\)**/(min\({}^{-1}\))** & \(R^{2}\) \\ \hline CoSN@C & 1.852 & 0.99 \\ CoN@C & 0.442 & 0.98 \\ SN@C & 0.122 & 0.99 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RhB degradation kinetics fitted by the pseudo-first-order reaction. Figure 3: Comparison of degradation performance in different system (**a**); adsorption process of CoSN@C (**b**); the calculated pseudo-first-order rate constants (\(k\)) for RhB degradation (**c**); and TOC removal in the CoSN@C + PMS and CoSN@C system (**d**). \(\mathrm{L}^{-1}\), the degradation rates of RhB were 3.64%, 90.10%, 100%, and 100%, respectively. The degradation efficiency increases with the increase in catalyst dosage due to the increased number of catalytic sites and the probability of contact between active sites and PMS. Considering economic reasons, the optimal dosage of catalyst and PMS was determined to be 0.05 mg \(\mathrm{L}^{-1}\) and 1 mM, respectively. Figure 4c shows, when the reaction temperatures were 15 \({}^{\circ}\)C, 25 \({}^{\circ}\)C and 35 \({}^{\circ}\)C, the degradation rates of RhB for 4 min were 92.08%, 99.92%, and 100.00%, corresponding to the degradation reaction rate constants (\(k\)) of 0.65 min\({}^{-1}\), 1.85 min\({}^{-1}\), and 2.83 min\({}^{-1}\), respectively, and the degradation rates accelerated with the increase in reaction temperature. Figure 3d shows the effect of pH change from 3.0 to 11.0 on the degradation of RhB by CoSN@C + PMS system. The catalyst is effective under acidic conditions when the pH is 3-5. The degradation rate of RhB can reach 99.9% at 4 min. Furthermore, it becomes less effective under alkaline conditions, which may have been due to a large number of hydroxide ions (HO) in the solution making the surface of CoSN@C material hydroxylated, thus affecting the adsorption of PMS on the surface of the material, which is not conducive to PMS catalytic activation [38]. In addition, PMS undergoes autolysis at higher pH through a non-radical pathway, which also decreases the degradation rate of RhB [39,40]. Therefore, the CoSN@C-PMS catalytic system has the best catalytic effect between pH 3 and 5. Various inorganic anions in the actual water body influence the activation performance of the catalyst. Common inorganic anions such as \(\mathrm{Cl}^{-}\), \(\mathrm{NO}_{3}{}^{-}\), \(\mathrm{HCO}_{3}{}^{-}\), and \(\mathrm{H}_{2}\mathrm{PO}_{3}{}^{-}\) in aqueous humor were chosen to examine the influence of their presence on the catalytic activation of PMS for RhB degradation (Figure 5). When \(\mathrm{H}_{2}\mathrm{PO}_{3}{}^{-}\) was added to the solution, a significant enhancement of the catalytic system's ability to degrade RhB was observed, and the rate of RhB degradation was close to 100% after 1-2 min of reaction. It may be the dissociation of \(\mathrm{H}_{2}\mathrm{PO}_{3}{}^{-}\) in solution releasing \(\mathrm{HPO}_{3}{}^{-}\), and nucleophilic attack on PMS, enhancing the generation of \(\mathrm{SO}_{4}{}^{-}\) and \(\mathrm{{}^{1}O}_{2}\) to improve degradation [41,42]. In contrast, after adding \(\mathrm{Cl}^{-}\) and \(\mathrm{NO}_{3}{}^{-}\), the RhB degradation rate after 4 min reaction was 97.85 and 99.33%, respectively, with less effect. The addition of \(\mathrm{HCO}_{3}{}^{-}\) decreased the RhB degradation rate to 71.5%, which significantly inhibited RhB degradation, most likely due to the reaction  
Figure 4: Effects of some operating parameters on the degradation phenol by CoSN@C + PMS system: (**a**) PMS dosage; (**b**) catalyst loading; (**c**) temperature; and (**d**) initial pH. of HCO\({}_{3}\)- with singlet oxygen and free radicals to form carbonate radicals with deficient activity [29; 43].