Waste‐Based Ceramic Adsorbent: A Sustainable Approach for Methylene Blue Dye Removal

A waste‐based geopolymer adsorbent with an improved mesopore structure was developed for the removal of Methylene blue dye. The synergistic potential of clay, fly ash, and GGBS as combined raw materials in geopolymer systems for cationic dye removal remains understudied, and this work addresses this gap by evaluating their integrated performance. These precursors impart a negative surface charge, enabling cationic dye adsorption, and using raw kaolin instead of metakaolin avoids energy‐intensive calcination. XRF, XRD, IR spectroscopy, Zeta potential, BET, and EDX characterizations were employed to study the physicochemical properties of the developed geopolymer. It exhibits an increase in specific surface area from 1 m 2 /g to 13.5 m 2 /g and an increase in pore volume from 0.002 cm 3 /g to 0.026 cm 3 /g compared to the raw fly ash. The adsorbents B‐3 and B‐4 exhibited excellent dye removal efficiency of above 95% for 10‐50 mg/L initial dye concentration and more than 80% efficacy at all concentrations. The experimentally determined maximum adsorption capacity was 21.12 mg/g for B‐4 (4 g/L dosage). Kinetic studies fit best to the pseudo‐first‐order model as well as pseudo‐second‐order model, while adsorption isotherm studies fit best to the Langmuir isotherm model, indicating synergistic physisorption and chemisorption with monolayer adsorption.