# Dye Adsorbent Materials Based on Porous Ceramics from Glass Fiber-Reinforced Plastic and Clay
## 2 Materials and Methods  
### GFRP/Clay Ceramic Specimens Used for MB Dye Adsorption Tests  
Figure 1 shows the process used to prepare GFRP/clay ceramic specimens, which were used for the MB dye adsorption tests. Polyamide (PA) thermoplastic pellets (Renny, Mitsubishi Engineering-Plastics Co., Tokyo, Japan), which contain glass fibers at approximately 40% by mass, were used as a surrogate for waste GFRP. Scanning electron microscope (SEM, SU3500, Hitachi High-Technologies Corporation, Tokyo, Japan) images of the glass fibers are shown in Figure 1. The images show the residues after heating the 40% GF/GFRP pellets at 673 K. Based on these images, we estimated that the GFRP contains glass fibers with diameters of approximately 10 \(\upmu\)m and lengths of \(\sim\)1.0 mm. The clay used in this study was produced in Miyazaki, Japan, and is typically used in brick or tile manufacturing. The major minerals in the clay derive from the chlorite group. Figure 1: The manufacturing process of granular GFRP/clay ceramics for MB dye adsorption testing. Table 1 shows the inorganic chemical compositions of the GFRP and clay after firing at 1073 K. The inorganic chemical compositions were measured with an energy dispersive X-ray analyzer (EDX-720, Shimadzu Corporation, Kyoto, Japan) by using a fundamental parameter method. The type of the glass fibers included in GFRP is compatible with E glass type family within broad error bars. However, the glass fibers might include a contribution from another source (e.g., a CaCO\({}_{3}\) polymer filler) because CaO content is too high. Table 2 shows the manufacturing conditions of the GFRP/clay ceramic specimens. The GFRP/clay ceramic specimens were prepared with the following process. 1. Clay was crushed using a rotary mill (New Power Mill ABS-W, Osaka Chemical Co., Ltd., Osaka, Japan) and then sifted using a 0.3-mm mesh screen. 2. GFRP was also crushed in the rotary mill and then sifted with a 0.5 mm-mesh screen. Here, the maximum length of the glass fibers in GFRP, which were sifted with the 0.5 mm-mesh screen, was approximately 150 \(\upmu\)m [7]. 3. The crushed GFRP was mixed with the clay in the mass ratios listed in Table 2.
4. The GFRP and clay mixture was solidified by pressing into a mold at 10 MPa. The molded samples had a diameter of 74 mm and a thickness of 50-60 mm. 5. The molded samples were heated in an oxidizing or reducing atmosphere at a firing temperature of 1073 K in an electric furnace (KY-4N, Kyoei Electric Kilns Co., Ltd., Tajimi, Japan). The samples were then held at the firing temperature for 1 h and allowed to cool to room temperature in the furnace. For oxidative firing, samples were heated at 100 K h\({}^{-1}\) to the firing temperature. In reductive firing, the samples were heated at 400 K h\({}^{-1}\). 6. The produced GFRP/clay ceramics were then crushed with a hammer and selected to yield a predetermined particle size, as shown in Table 2. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Samples**} & **Mixing Ratio of** \\  & & **GFRP (Mass \%)** \\ \hline
1 & Clay & 0 \\
2 & 20\% GFRP/clay & 20 \\
3 & 40\% GFRP/clay & 40 \\
4 & 60\% GFRP/clay & 60 \\ \hline
5 & 20\% GFRP/clay & 20 \\
6 & 40\% GFRP/clay & 40 \\
7 & 60\% GFRP/clay & 60 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Manufacturing conditions for the granular ceramics. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Component**} & \multicolumn{2}{c}{**Raw Materials**} \\ \cline{2-3}  & **Clay (Mass \%)** & **40\% GF/GFRP (Mass \%)** \\ \hline SiO\({}_{2}\) & 65.8 & 54.9 \\ Al\({}_{2}\)O\({}_{3}\) & 21.9 & 16.3 \\ Fe\({}_{2}\)O\({}_{3}\) & 4.79 & 0.77 \\ K\({}_{2}\)O & 3.37 & 0.15 \\ MgO & 1.67 & - \\ CaO & 1.31 & 26.7 \\ TiO\({}_{2}\) & 0.87 & 0.56 \\ Others & 0.29 & 0.62 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Compositions of inorganic substances in the clay and GFRP.