# Dye Adsorbent Materials Based on Porous Ceramics from Glass Fiber-Reinforced Plastic and Clay
## 3 Results and Discussion  
### Preliminary Experiments  
In this study, granular ceramics were used as adsorbents to remove the MB dyes. We considered that ceramics with smaller particle sizes have an increased MB dye adsorption ability due to a larger ceramic surface area [13]. However, when we excessively reduced the particle size of the ceramic, the ceramic particles themselves increased the turbidity of the aqueous solution due to fine ceramic particle floatation in the aqueous solution. Such fine particles floating in the aqueous solution require an additional step for removal. Hence, we limited the minimum ceramic particle size. We first examined  
Figure 5: A schematic diagram of the MB dye adsorption test based on the granular GFRP/clay ceramic specimens. the relationship between ceramic particle size and water turbidity by performing a preliminary experiment and determined the appropriate GFRP/clay ceramic particle size. Figure 6 shows the turbidity and pH of the aqueous solution after 1 and 60 min when 50 mL of distilled water, which contained 1 g of ceramics with particle sizes of 0.1-0.3 and 0.3-0.5 mm, was stirred in at 150 rpm. Here, Kaolin was used for calibrating the turbidity of the aqueous solution, and the turbidity was measured with a drainage analyzer based on the Testing Methods for Industrial Water of Japanese Industrial Standard JIS K0101: 1998. Figure 6: (a) Turbidity and (b) pH in mixtures of distilled water containing ceramics with particle sizes in the range of 0.1–0.3 mm and 0.3–0.5 mm, stirred at 150 rpm. The turbidity of the water, in which the clay ceramic without glass fibers and the 20% GFRP/clay ceramic fired oxidatively or reductively were soaked, was higher than others. Comparing water turbidity, in which GFRP/clay ceramics were soaked, the turbidity decreased with an increasing GFRP mixing ratio. These results indicate that the clay ceramic component increased the turbidity of water. Clay is hydrophilic, whereas glass fibers and carbide are hydrophobic. The hydrophilic nature of the substances contained in water markedly affects its turbidity. When using ceramics with particle sizes in the range of 0.1-0.3 mm, all ceramic types formed turbid mixtures, and for particles in the range of 0.3-0.5 mm, certain ceramic types caused turbidity. Ceramics with particles of 0.5 mm or larger did not cause turbidity in the water (turbidity data not shown). Based on the above results, granular ceramics with a particle size of 0.5-1.0 mm or larger were used for the MB dye adsorption tests. The pH value of water, in which the clay ceramics without glass fibers were soaked, was weakly acidic, and that of water, in which oxidatively fired GFRP/clay ceramic was soaked, was alkali. The alkalinity of the water raised as the GFRP mixing ratio was increased. We attribute the alkalinity of the water to the dissolution of the calcium component in the glass fibers into the water, which decreased the concentration of hydrogen ions. The pH of the water, in which reductively fired GFRP/clay ceramic was soaked, was weakly alkali. The alkalinity of the water was slightly lower than that of the oxidatively fired GFRP/clay ceramic. Apparent Porosities, Specific Surface Areas, and Carbide Contents of the GFRP/Clay Ceramic Specimens  
Table 4 lists the apparent porosities, specific surface areas, and carbon contents of the GFRP/clay ceramics. Here, as mentioned earlier, for the apparent porosities of the ceramics, the values which were measured by using a mercury intrusion technique are listed, and for the specific surface areas, the values which were measured by using a gas adsorption method are listed. The clay ceramic had a porosity of approximately 32%, whereas the GFRP/clay ceramics had porosities in the range of 38-66%. The porosities of the GFRP/clay ceramics increased nearly linearly with an increasing GFRP mixing ratio [7]. We attribute this result to increases in the amount of resin as the GFRP mixing ratio was increased.