## 3 Results and Discussion  
### Comparison of Zr-EPRC Preparation Methods  
#### 3.1.1 Comparison of Modification Methods  
As illustrated in Figure 2, the adsorption capacity of all three groups of Zr-EPRC particles for phosphorus surpasses that of the original EPRC particles, demonstrating a significant enhancement in the phosphorus removal efficiency through the introduction of a zirconium oxychloride octahydrate modification. This enhancement can be attributed to the loading process in which zirconium oxychloride octahydrate becomes attached to the adsorbent material in the form of zirconium oxide or zirconium hydroxide, thereby creating a zirconium-based adsorbent. The substantial specific surface area of amorphous-hydrated zirconium oxide, coupled with the rapid exchange between the hydroxyl group in the zirconium tetramer and the phosphate ions in water, results in a considerable increase in both the rate and capacity of phosphate adsorption. This optimization of adsorption leads to improved phosphorus removal performance compared to the original EPRC particles.  
Figure 2 reveals that the modification of the substrate to enhance phosphorus removal is more effective when compared to the direct modification of EPRC particles (No. 1 Zr-EPRC particles). Both No. 2 and No. 3 Zr-EPRC particles exhibit significantly better phosphorus removal effects than No. 1 Zr-EPRC particles. This is attributed to the fact that in the case of the direct modification of EPRC particles, zirconium ions can only adhere to the outermost layers of the material, resulting in weaker attachment in terms of quantity and stability compared to substrate modification. Furthermore, when comparing the two groups of particles modified using substrate methods, the adsorption effectiveness of No. 3 is slightly superior to that of No. 2, although the overall difference is not substantial.  
Table 5 provides an overview of the state of the four groups of particles following the completion of static phosphorus ion adsorption. After the adsorption process is complete for the original EPRC particles and the No. 1 and No. 3 Zr-EPRC particles, the residual liquid remains clear, the particles remain intact, and there are no anomalies. In contrast, after the adsorption process of No. 2 Zr-EPRC particles is completed, the residual liquid exhibits slight turbidity, and there are indications of detachment on the surface of the adsorbent material, accompanied by slight chalkiness. This phenomenon may be attributed to the high iron content in the steel slag, creating an environment that is conducive to the formation of a zirconium-iron modifier, which significantly increases the roughness of the substrate's surface. This, in turn, may not be conducive to subsequent cement adhesion. However, increasing the amount of cement blending could potentially lead to a reduction in the adsorption effectiveness.  
In summary, among the three modification methods, both No. 2 and No. 3 Zr-EPRC particles exhibit superior modification effects compared to the No. 1 particles. However, it is worth noting that the No. 2 Zr-EPRC particles face greater challenges during the granulation process. Therefore, the approach of separately modifying the substrate and then granulating it, as demonstrated in the No. 3 particles, was selected for the preparation of Zr-EPRC particles. This method will serve as the focus of subsequent experiments and investigations.