From Waste to Water Remediation: Fly Ash-Derived Hectorite for Dye and Heavy Metal Removal

Transforming industrial solid waste into functional materials is a central challenge in sustainable chemistry. Here, we report a green steam-assisted method for synthesizing mesoporous hectorite using silica extracted from coal fly ash. The synthesis proceeds under mild conditions (473.15 K, 24 h) without generating liquid waste, distinguishing it from conventional hydrothermal routes. By optimizing precursor ratio, temperature, and time, we obtain a well-ordered layered structure with approximately 4 nm mesopores and a high specific surface area (54 m²/g). The resulting hectorite exhibits exceptional adsorption capacities toward Crystal Violet (657.8 mg/g) and Cu²⁺ (82.47 mg/g), with rapid kinetics (10 min) and stable reusability over five cycles. Mechanistic studies reveal synergistic adsorption involving ion exchange, electrostatic attraction, and surface complexation, while kinetic and thermodynamic analyses confirm spontaneous, endothermic chemisorption. This work establishes a closed-loop, waste-to-resource strategy that integrates fly ash valorization, green synthesis of layered silicates, and high-performance water remediation.