# Dye Adsorbent Materials Based on Porous Ceramics from Glass Fiber-Reinforced Plastic and Clay
## 3 Results and Discussion
### MB Dye Adsorption Ability of the GFRP/Clay Ceramics  
Figure 8 shows the reduction rate in the MB dye concentration for each granular ceramic specimen. The reduction rate for the MB dye concentration increased as the MB solution stirring speed increased for all ceramic types. These results confirmed that the agitation of the MB solution increased the ceramic's ability to adsorb MB. [PERSON] et al. (2016) have reported on the adsorption phenomena of activated carbon and liquid-phase phenol, indicating that phenol adsorption initially occurs mainly on the outer surface of an activated carbon body, followed by the inside of the body over longer periods of time. Furthermore, they reported that the film coefficient of material transfer between the activated carbon body and liquid-phase phenol, at an early stage, is proportional to the stirring speed of the liquid. Similarly, based on the adsorption phenomena of the activated carbon and liquid-phase phenol, we suggest that agitation of the MB solution accelerates MB dye movement to the outer surface and inside of the ceramic body, which promotes MB dye adsorption to the ceramic. Figure 7: Ceramic pore-size distributions. By comparing the rate of the decrease in the MB concentration for each ceramic, the reductively fired 60% GFRP/clay ceramic possessed the highest MB dye adsorption ability and that of the oxidatively fired 60% GFRP/clay ceramic was the lowest. The rate of decrease in the MB concentration for the reductively fired GFRP/clay ceramics slightly increased with an increase in the GFRP mixing ratio. Furthermore, to investigate the influence that glass fibers have on the MB dye adsorption ability for the GFRP/clay ceramics, we performed MB dye adsorption testing of the glass fiber, which was prepared by heating 40% GF/GFRP pellets in an oxidizing atmosphere at 673 K.  
Figure 9 shows a microscope image of the glass fibers and the temporal change in MB solution absorbance. Here, the absorbance value of the MB solution was 2.3, which corresponds to an MB dye concentration of \(1\times 10^{-4}\) mol/L. The increase in absorbance of the MB solution indicates an increase in the turbidity of the solution. Figure 8: The reduction rate of the MB dye concentration for various GFRP/clay ceramics. (**a**) Oxidatively fired GFRP/clay ceramics. (**b**) Reductively fired GFRP/clay ceramics. Figure 9: Microscope image of the glass fibers and the changes in absorbance for the MB solution. This result indicates that the MB dye was not adsorbed by glass fibers because the absorbance of the MB solution did not decrease over time. Hence, the components that adsorbed the MB dye were the clay and carbide in the GFRP/clay ceramic. Furthermore, we assume that carbide adsorbed a larger amount of MB dye than the clay because the MB concentration reduction rate for the reductively fired ceramics was higher than that of the clay ceramic. Based on the above experimental results, we can summarize the MB dye adsorption characteristics of the ceramics as follows. 1. The MB dye adsorption ability of the oxidatively fired 60% GFRP/clay ceramic was the lowest due to it having the largest glass fiber content, which had no ability to adsorb MB dye. In addition, this ceramic possessed the smallest specific surface area, as shown in Table 3.
2. In contrast, the MB dye adsorption ability of the reductively fired 60% GFRP/clay ceramic was the highest. We attribute this result to the ceramic because it contains a larger carbide proportion, a comparatively high specific surface area, and high porosity; however, this ceramic also contained the joint-largest glass fiber content. We suggest that the high specific surface area of the ceramic promoted the physical adsorption of the MB dye via Van der Waals forces. The high porosity facilitated MB dye movement into the ceramic body. The clay component adsorbed MB dye via both cation exchange and physical adsorption through Van der Waals forces [12]. For the carbide component, physical adsorption is likely the main adsorption mechanism [15].