## 5 Coupling Copper-Based Catalyst/PMS Systems with Other Advanced Oxidation Techniques  
To form a combined AOP system, numerous AOPs, such as ozonation, ultrasonic irradiation, UV-Vis irradiation, and MW irradiation, have been integrated with copper-based catalyst/PMS systems. However, the intricacy of the reaction system increases with the addition of extra AOPs. On the other hand, the combined systems offer numerous potential benefits, including the synergistic improvement of organic contaminant degradation rates and improved PMS efficacy for pollutant elimination. Nevertheless, before incorporating further AOPs, two crucial factors need to be considered: first, the influence of incorporating additional AOPs on the catalyst's stability to prevent the early release of metal ions, and second, the additional treatment costs arising from the intricate setup, maintenance, and operation.  
The amalgamated system that merges UV-Vis irradiation with a copper-based catalyst/PMS system has garnered the most extensive investigation. Diverse catalysts like copper nanoparticles [200], carbon-based Cu-Fe oxide [201], and \(Co_{0.5}Cu_{0.5}Fe_{2}O_{4}\) magnetic nanoparticles [202] have been devised for activating PMS under UV-Vis irradiation. Generally, PMS can undergo activation through three feasible activation pathways in the copper-based catalyst/PMS/UV-Vis system: direct activation by UV irradiation, redox-based activation, and heterogeneous photocatalytic activation. While the combined impact appears to offer a hopeful outlook for future utilization, the advancement of the hybrid copper-based heterogeneous catalyst/PMS/UV-Vis system's catalyst is currently at an early stage. There remains a need for the creation of new catalysts to progress this field. Itis imperative for the catalyst to serve a dual function as both a photocatalyst and a PMS activator to effectively harness the collaborative influence.  
The mixed configuration involving a disparate copper-based catalyst/PMS/ozone system has been the subject of prior examination, utilizing magnetic copper ferrite nanoparticles as the catalyst [203]. The introduction of ozone can augment the production of responsive radicals within the reaction environment, as ozone also has the capability to set PMS in motion, generating both \(SO_{4}^{\bullet-}\) and \(HO^{\bullet}\)[204]. A highly favorable condition is necessary to avert the self-scavenging reactions of different ROS.  
Other combination systems using either ultrasonic [205] or MW [206] irradiation with copper-bases heterogeneous catalyst/PMS procedures have also been documented to yield a beneficial impact on the speed of contaminant elimination, attributed to the enhanced dynamics within the reaction environment. As an example, apart from expediting the cleansing of the catalyst's surface to enable redox reactions, US irradiation induces the formation of cavitation bubbles in the water. Upon their implosion, these bubbles lead to the creation of \(SO_{4}^{\bullet-}\) and \(HO^{\bullet}\) through the activation of PMS and the pyrolysis of water [207]. The MW irradiation raises the temperature of the water and generates localized high-temperature regions on the catalyst surface, thereby expediting the activation of PMS and facilitating faster redox reactions. Nevertheless, as the reactivity within the reaction system intensifies, it becomes crucial to consider the steadiness of the catalyst to avoid the untimely release of metal ions through dissolution.