# Dye Adsorbent Materials Based on Porous Ceramics from Glass Fiber-Reinforced Plastic and Clay
## 1 Introduction  
Glass fiber-reinforced plastic (GFRP) is used in various products, such as automobile parts and small ships, due to its light weight and high strength properties. Currently, however, most GFRP waste is sent to landfills because it is difficult to recycle with existing recycling technologies [1, 2]. Fine glass fiber dust and leachates from this process may cause serious health and environmental damage [3]. To reduce this environmental burden, the development of an effective technique to dispose of waste GFRP is desirable.  
Hence, previous studies have produced porous glass fiber-reinforced ceramics by mixing crushed waste GFRP with clay and then firing the resulting mixture to generate GFRP/clay ceramics [4, 5, 6, 7]. Such ceramics are highly water permeable and strong; therefore, we have used these ceramics as a filtering material for turbid water treatment [6]. The ceramic filtering materials can remove various sizes of suspended matter in turbid water and ceramics with different pore size distributions are producible by adjusting the mixing ratio of GFRP with clay, the particle size of crushed GFRP, and the ceramic firing temperature. However, at present, GFRP/clay ceramic filtering materials are not able to easily remove nanometer-sized suspended particles and the purification of wastewater containing harmful substances remains challenging, which results in a need for ceramics that have an improved purification ability.  
Currently, clothing fibers and leather goods are dyed during manufacturing processes. As a result, factories produce a large amount of dye wastewater. The dye wastewater must be purified by the proper treatment methods to avoid adverse environmental effects at the discharge site. Activated carbon treatments [8; 9] and [PERSON]'s reagent-based methods [10; 11] are mainly used to purify dye wastewater. However, activated carbon treatments are expensive and approaches using [PERSON]'s reagent also require additional treatments to remove sludge produced during the purification process.  
GFRP/clay ceramics are porous clay-based ceramics. Clay minerals have excellent absorbability for dyes [12]. If GFRP/clay ceramics were used as dye adsorbents, it might be possible to effectively use waste GFRP to address issues involved with current dye wastewater treatments. In this study, we investigate the possibility of using GFRP/clay ceramics as adsorbent materials to remove dyes from wastewater effluent.  
First, various specimens were fabricated by adjusting the mixing ratio of clay and crushed 40% GF/GFRP, as well as the firing atmosphere. We examined the apparent porosity, specific surface area, and carbon content of the ceramic as factors that are likely to influence the dye adsorption ability. Next, we performed adsorption tests with methylene blue (MB) dye with several types of GFRP/clay ceramics by modifying the MB solution stirring speed. Decreases in the MB dye concentration were compared with that of a ceramic produced from only clay (i.e., a clay ceramic). Based on these results, we evaluated the MB dye adsorption ability of the GFRP/clay ceramics and investigated the mechanisms that occur during MB dye adsorption.