## 3 Results and Discussion
### Engineering Implications  
This study provides an in-depth examination of the influence of different photocatalyst dosages on the adsorption and breakdown of TCH in aqueous solutions, aiming to establish a robust theoretical basis to guide the practical application of photocatalytic technology in real-world applications. Photocatalyst dosages of 0.1 g/L, 0.2 g/L, 0.3 g/L, and 0.4 g/L were tested under various conditions (Figure S5). The results demonstrated that under simulated sunlight, the degradation of TCH was rapid, with degradation rates of 69.93%, 80.96%, 84.79%, and 87.41%, respectively, within 60 min. Notably, although increasing the catalyst dosage initially resulted in a significant improvement in TCH removal efficiency, this improvement plateaued after the dosage reached 0.2 g/L. This finding is crucial for optimizing the choice of catalyst dosage in practical applications.  
Further analysis, employing a pseudo-first-order kinetic approach, determined the k-values (rate constants) as 0.0192 min\({}^{-1}\), 0.0474 min\({}^{-1}\), 0.0372 min\({}^{-1}\), and 0.0421 min\({}^{-1}\) for the respective dosages. The results indicate that using 0.2 g/L achieves an optimal balance between reaction rate and cost-effectiveness. Additionally, the impact of initial pH on the degradation performance of CdS/g-C\({}_{3}\)N\({}_{4}\) composites is presented in Supplementary Figure S6, highlighting the optimal pH range for TCH degradation. Unlike other studies, this research not only optimizes catalyst dosage through detailed kinetic analysis but also provides practical operational parameters, offering significant guidance for real-world applications.  
Given the global increase in antibiotic usage--estimated at 63,000 to 240,000 tons per year--efficient wastewater treatment has become an environmental priority [55]. Our study demonstrates that only 200 g of CdS/g-C\({}_{3}\)N\({}_{4}\) photocatalyst is needed to treat one cubic meter of TCH wastewater. This method is simple to operate, economically advantageous, and superior to conventional treatment methods, such as the UV/ZnO/Sulfite (UZS) advanced oxidation process, which costs approximately $0.82 per cubic meter [56]. Thus, the use of CdS/g-C\({}_{3}\)N\({}_{4}\) photocatalyst represents a cost-effective and highly effective approach for wastewater treatment, with promising application potential.  
Moreover, to assess the broad applicability of this composite photocatalyst, methylene blue was selected as a representative dye for degradation experiments. The degradation effect is shown in Figure S7. The findings verified that the CdS/g-C\({}_{3}\)N\({}_{4}\) composite demonstrates excellent photocatalytic degradation effects on both antibiotic and dye wastewater.  
Figure 12: Schematic diagram of CdS/g-C\({}_{3}\)N\({}_{4}\)-2 photocatalytic mechanism.  
Unlike numerous existing studies that concentrate on individual pollutant types, this research explores the photocatalyst's versatility, confirming its multifunctionality and broad applicability. Future research should focus on pilot-scale or even full-scale production experiments to further verify the feasibility and stability of this system.