## 2 Cu-Based Catalyst-Activated PMS Processes
### Zero-Valent Copper  
ZVCu finds applications in a wide range of industries, including agriculture [48], catalysis [49], medical sectors [50], and environmental remediation [51]. ZVCu has been valuable for its contributions to pollution abatement initiatives. It is considered a favorable option for the remediation of wastewaters and manufacturing discharge [52; 53; 54]. This is correlated with the potential of ZVCu to produce electrons, ionic species (Cu(I) and \begin{table}
\begin{tabular}{c c c c c} \hline
**Catalyst** & **Contaminant** & **Reactive Species** & **Efficiency** & **Ref.** \\ \hline ZVCu & & & & \\ \hline Nanoscale ZVCu & Benzoic acid (BA) & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 100\% in 10 min & [27] \\ ZVCu & 2,4-DCP & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 56.7\% of TOC in 120 min. & [28] \\ ZVCu & NPX & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 91.0\% in 30 min & [29] \\ Copper oxide & & & & \\ \hline CuO & Iopamidol & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 100\% in 15 min & [30] \\ CuO & Phenol & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 65\% in 60 min & [31] \\ CuO & BPA & \(\text{IO}_{2}^{\bullet-},\text{SO}_{4}^{\bullet-}\) & 100\% in 20 min & [32] \\ Cu\({}_{2}\)O & BPA & Surface-activated PMS & 100\% in 120 min & [33] \\ CuO & AO7 & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 95.38\% in 15 min & [34] \\ Spongelike porous CuO & AO7 & \(\text{SO}_{4}^{\bullet-}\) & 85\% in 60 min & [35] \\ Copper ferrite & & & & \\ \hline \(CuFe_{2}O_{4}\) & TBBPA & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 99\% in 30 min & [36] \\ \(CuFe_{2}O_{4}\) & ATZ & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & \textgreater{}98\% in 15 min & [37] \\ \(CuFe_{2}O_{4}\) & BPA & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 95.2\% in 60 min & [38] \\ \(CuFe_{2}O_{4}\) & Norfloxacin & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & \textgreater{}90\% in 120 min & [39] \\ \(CuFe_{2}O_{4}\) & Iopromide & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & \textgreater{}100\% in 10 min & [40] \\ \(CuFeO_{2}\) & Sulfadiazine (SDZ) & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 86\% in 12 min & [41] \\ \(CuFeO_{2}\) & Orange I & \(\text{SO}_{4}^{\bullet-},H\text{O}^{\bullet}\) & 77.8–79.3\% in 30 min & [42] \\ \hline \end{tabular}
\end{table} 
Table 1: ZVCu, copper oxide, and copper ferrite catalysts for the degradation of organic pollutants by PMS activation. Cu(II)), and hydroxides/oxides near the metal surface throughout oxidation-reduction processes [55; 56]. To eliminate pollutants near the metal surface, both reductive and oxidative processes are employed. The layer covering the ZVCu surface, composed of Cu oxides/hydroxides, enhances the degradation process through adsorption. However, there are certain pollutants that cannot be efficiently degraded using only ZVCu. For this reason, adding an oxidizing agent and even using irradiation sources are some of the substitutes implemented to improve the effectiveness of the ZVCu. On the other hand, PMS is a potent oxidizing agent. It is characterized by high stability, relatively low cost, and excellent aqueous solubility. Because of its non-symmetrical arrangement, which makes it more easily activated by an assortment of catalysts, PMS has attracted increasing interest as a substitute for hydrogen peroxide (\(H_{2}O_{2}\)) and peroxdyisulfate (\(S_{2}O_{8}^{2-}\)). Additionally, activating PMS offers multiple advantages such as moderate reaction parameters and the preclusion of subsequent pollution [57], and it is currently regarded as an outstanding option for the degradation of persistent organic compounds. Despite the pros, there are some shortcomings associated with the rate of reactions between PMS and organic pollutants at room temperature, requiring activation to expedite the procedure [58]. For this reason, there are many methods used.