Dye Adsorption Mechanism of Glass Fiber-Reinforced Plastic/Clay Ceramics and Influencing Factors

Abstract

The effective reuse of waste glass fiber-reinforced plastic (GFRP) is desired. We previously produced porous ceramics by firing mixtures of crushed GFRP and clay in a reducing atmosphere and demonstrated their applicability as adsorbents for the removal of basic dyes from dyeing wastewater. However, the primary influencing factors and the dye adsorption mechanism have not been fully elucidated, and the adsorption of acidic and direct dyes has not been clarified. In this study, adsorption tests were conducted, and the effects of the firing atmosphere, specific surface area, type of dye, and individual components were comprehensively investigated. The results showed that reductively fired ceramics containing plastic carbide residue adsorbed basic dye very well but did not adsorb acidic dye well. The clay structure was the primary factor for the dye adsorption rather than the GFRP carbide. The mechanism for the basic dye adsorption appears to have been an increase in specific surface area due to the plastic carbide residue in the ceramic structure, which increased the ion exchange between the clay minerals and the dye. By adjusting the pH of the aqueous solution, the GFRP/clay ceramic also adsorbed considerable amounts of direct dye, so the mechanism was determined to be ion exchange with the calcium component of the glass fibers.

Porous Ceramics Adsorbents Based on Glass Fiber-Reinforced Plastics for NOx and SOx Removal

“…Table 1 presents the inorganic chemical compositions of GFRP, clay and Bora [ 14 , 15 ]. Their compositions were measured by an energy dispersive X-ray analyzer (EDX-720, Shimadzu Corporation, Kyoto, Japan) using a fundamental parameter method after firing at 1073 K.…”

“…Figure 1 shows the manufacturing process of the GFRP/clay ceramic samples. The sample manufacturing procedure was as follows [ 14 , 15 ]: The clay was crushed using a rotary mill (New Power Mill ABS-W, Osaka Chemical Co., Ltd., Osaka, Japan) and was then sifted using a 0.3 mm mesh screen. GFRPs were also crushed using the same rotary mill and were then sifted using a 0.5 mm mesh screen.…”

“…Figure 2 shows examples of microscope (SZX10, Olympus Corporation, Tokyo, Japan) images of the samples [ 14 , 15 ]. The reductively fired GFRP/clay ceramic samples were black owing to the plastic carbide residues.…”

“…Table 2 presents the inorganic chemical compositions of the samples [ 14 , 15 ]. The GFRP/clay ceramics had greater CaO contents than the clay ceramic, and the ratio of CaO to the total mass of the ceramics increased with the GFRP mixing ratio because of the increase in the glass fiber content.…”

“…However, ceramics produced by firing the mixture of GFRPs and clay powders under a reducing atmosphere contain a small amount of plastic carbide residue with the glass fibers. Consequently, these ceramics exhibit higher specific surface area than those produced under an oxidizing atmosphere [ 14 , 15 ]. Because of the high specific surface area and porosity of the ceramics as well as the high ion exchange function of the clay [ 16 , 17 , 18 , 19 ], this type of ceramics was studied as a dye adsorbent material to remove pigments from dye-contaminated wastewater [ 14 , 15 ].…”