Microwave-Assisted Synthesis of Fly Ash/Bamboo Leaf Ash-Based Geopolymer for Methylene-Blue Adsorption

Despite its significant economic contribution, the textile industry remains a major source of dye pollution due to extensive untreated wastewater discharge. This study introduced a facile microwave-assisted strategy for converting fly ash (FA) and bamboo leaf ash (BLA) into value-added porous geopolymer composites for the adsorption of methylene blue (MB) from aqueous solutions. By systematically varying the FA/BLA ratio, it reveals how BLA incorporation governs composite properties and organic-dye removal performance. As the BLA content increased from 0% (100FA) to 60% (40FA60BLA) in the geopolymer composition, both the BET surface area and BJH pore volume increased significantly. The sample 100FA showed a surface area of 24.4 m²/g and a pore volume of 0.019 cm³/g, whereas 40FA60BLA reached 54.6 m²/g and 0.045 cm³/g, respectively. The high silica content in BLA facilitated the formation of smaller pores in the geopolymer network, fitting the Langmuir isotherm model and achieving a maximum MB-adsorption capacity of 26.6 mg/g. Moreover, these geopolymers with the addition of BLA still gained above 50% of removal percentage of MB molecules after five consecutive cycles. Moreover, the incorporation of BLA also enhanced the treatment of real textile wastewater compared to those of FA geopolymer. These findings suggested that the incorporation of BLA into FA-based geopolymers provided an effective and sustainable strategy for dye removal in wastewater treatment while promoting the valorization of industrial by-product and agricultural waste.