## 2 Materials and Methods  
### Test Materials  
The materials essential for crafting Zr-EPEC particles encompass steel slag, fly ash, 525R common silicate cement, and a plant-based blowing agent. These materials are categorized into two groups: adsorption substrates and auxiliary components. Steel slag and fly ash serve as the principal substrates, while the auxiliary materials consist of a binder and a foaming agent. Specifically, 525R ordinary silicate cement is chosen as the binder, while the addition of a plant-based foaming agent enhances the material's specific surface area. These material selections have been thoughtfully made, drawing from prior research insights and considering key factors like material strength, porosity, and moldability.  
For this study, steel slag and fly ash were sourced from a steel plant and a power plant, respectively. Detailed physical properties of these materials are presented in Table 1, while Table 2 provides information on their chemical compositions, as analyzed through X-ray fluorescence (XRF). Additionally, Table 3 offers insights into the particle size distribution of both steel slag and fly ash.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name of Material** & **Density (g/cm\({}^{3}\))** & **Specific Surface Area (cm\({}^{2}\)/g)** & **Grain Size** & **Color** \\ \hline steel slag & 2.10 & 3633 & 70 mesh and above & sepia \\ coal ash & 2.91 & 580 & 100 mesh and above & pessimistic \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical properties of steel slag and fly ash.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Chemical Composition** & **Steel Slag** & **Coal Ash** \\ \hline CaO & 55.0 & 1.31 \\ Fe\({}_{2}\)O\({}_{3}\) & 21.5 & 4.39 \\ Al\({}_{2}\)O\({}_{3}\) & 1.51 & 45.9 \\ SiO\({}_{2}\) & 13.4 & 44.4 \\ MgO & 3.65 & 0.261 \\ MnO & 1.72 & 260 ppm \\ S\({}_{0}\) & 0.512 & 0.666 \\ V\({}_{2}\)O\({}_{5}\) & 0.417 & 0.380 ppm \\ TiO\({}_{2}\) & 0.296 & 1.26 \\ Na\({}_{2}\)O & 770 ppm & 940 ppm \\ ZnO & & 210 ppm \\ CuO & & 200 ppm \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical compositions of steel slag and fly ash.  
In the realm of material preparation, the binder plays a pivotal role in facilitating bonding and curing, ultimately enhancing the mechanical strength of the material. After careful consideration, 525R ordinary silicate cement was chosen as the most suitable binder. This decision stems from its advantageous attributes, including rapid maturation, robust compressive strength, broad applicability, and cost-effectiveness, all of which are elucidated in Table 4.  
Combined with the research results of the previous group, a plant-based foaming agent is still selected as the porogenic agent in the experiment [22]. This agent is characterized as a yellow-brown viscous liquid with a straightforward production process and cost-efficiency. Its primary merit lies in its remarkable compatibility with cement, facilitating reactions with calcium ions to generate insoluble salts. This reaction simultaneously renders the material's structure porous and loose within the foam while enhancing its stability, all without inducing secondary pollution.  
To enhance the phosphorus removal efficiency of the original EPRC material, this experiment introduced a modification utilizing zirconium chloride octahydrate (ZrOCl\({}_{2}\)-8H\({}_{2}\)O). ZrOCl\({}_{2}\)-8H\({}_{2}\)O is characterized as a white crystalline compound that readily dissolves in polar solvents such as water, ethanol, and ether. Its robust hydrolysis properties facilitate the conversion to zirconium hydroxide when exposed to aqueous environments. As a result, it is widely employed in adsorption and phosphorus removal processes.